RadioI[VOLT AUTO Contro TRACTOR BATTERY Electrics Bob Kopski NEW Electric club Les Adams president Adams Electronics supplier Electric need wrote tell new all-Electric club has formed northwestern Chicago IL area Elec tric Model Fliers Chicago EMF Chicago presently comprised about 20 modelers has sole interest further advancement Electricpowered flight Les tells number growing steadily AMA member interested should contact either Larry Sperling 312 303-5165 Les Adams 312 364-0660 after 600 pm CST Electric interests welcome Scale Pattern Sailplanesanything Les vice-president group himself very capable Electric modeler club planning Electric fly-in sometime during 1986 info will announced later Watch column particulars Heres wishing best guys EMF Chicago makes second all-Electric club know ofthe other ing SPARKS Houston TX other such Electric groups please let know Ill pass word along column Basic Electricity past several stallments continuing mini-series have discussed multimeters rather exten sively particular familiar moving-needle analog multimeter has examined considerable detail plans month make transition discussion digital multimeters DMMs However reviewing past columns realized 2 1-OHM 10 WATT RESISTORS IN PINT OF COLD WATER MULTIMETER ON 10 AMP RANGE ST LEADS MOOEL AIRPLANE WHEEL COLLAR 4 PLACES MAY BE REMOVED ONCE CIRCUIT CURRENT IS READ LEADS CONNECTED TOGETHER TO CLOSE CIRCUIT 15 PIECES OFMULTIMETER SET WIRE 4 LONGON 250 MILLIVOLT RANGE SHUNT NICHROMgJ WIRE BUNDLE HIGH-CURRENT SHUNT CALIBRATION CIRCUIT Calibrating shunt using two-meter test setup Drawing gives circuit details Analog muitimeter set 10-amp scale digital multlmeter DMM 200 millivolt scale Circuit current case 53 amps dictates shunt adjusted obtain 53 millivolts pint cool water gets pretty warm after few minutes run ning two 1-ohm 10-watt resistors dissipating about 80 watts Constructing high-current shunt L wiring harness can custom-made f needsbut keep connector-wIre length minimum Shunt wires cut five-foot length nichrome foam-cutting wire Wheel collars screws must brass completed shuntor sampling resistorassembly R 15 shunt wires four inches long 50 Model Aviation some things practical nature promised early have grown long overdue So month well take look simple accessory can easily make expand usefulness multimetereither analog digital although analog type will used example easily-constructed device will allow measure very large currents other wise beyond range multime ters future column well see make simple device double useful voltage ranges DMMs accessory shown nothing special external currentmeter SHUNT Youll remember multimeters have several internal select able shunt resistors allow measure current over very wide range Normally lowest current range analog multimeters about 50 microamps millionths ampere 200 microamps DMMs highest ranges usually 10 amps two amps respectively Thus multimeter very useful instrument often cant used measure motor current because latter often exceeds 10 amps special shunt shown will extend capability multimeters upward 25 amperes friends will cover nearly Electric modeling interests world shunt pictured consists small bundle short nichrome wire Continued page 130 Single-meter method calibrating shunt 1 Meter first used ammeter current recorded Meter removed recon nected voltmeter set 250 scale portion circuit used current test closed Note two-meter setup voltmeter reading 53 Voltmeter connected inner pair wheel collars shunt Using shunt R Kopekis Astro cobalt 25 turns 9 x 6 nylon prop Battery dozen 12 Ah cells routed through speed control Note shunt jumper wires inserted motor power wiring motor current can measured Muitimeter shows 155 indicating motor drawing 155 amps Shunt needed because multimeter circuits cant handle large currents Hotativ Horn Ak Acm 7J&W LAIZOs 8 GAS MOSEL Il4odL j 9Ec0O 8REA5ER 1941 BROOKLYN DODGER 56 Cabin EWEST* Retail $52 95**INTRODUCTORY PRICE* $3900 1938 Record Breaker 96 $6956 1939 Zipper 54$5356 1938 Kloud King 63 $4236 1941 Brigiclier 36 $8076 1941 Super Ouaker 76 $7276 1940 So Long 50$3036 1936 Buccaneer 94 $5996 1938 Clipper MKI 7254156 1937 Dallaire 198 $75 16 1935 Miss America 64 $7196 1941 Playboy Sr 60 $5116 1941 Playboy Jr 54 $3116 1938 Powerhouse 84 $5356 1940 Sailplane 78 $6476 1938 Trenton Terror 72 $4070 1940 Ranger 46$3196 1939 Korda Wake 44 $1916 l939Mercury 72 6 kits qualify SAM events FF & K/c feature highest quality machine cut & sanded parts Superior Competition sheet strip wood wire & window material Plans orig PP hut isodela easily convertible Sch K/C KITS Sailplanes Electric power Gas Hobby Horn SENSOAR Glider 78 5s] $1860 Midway Model GNOME K/C Hand Launch Glider$2400 Jolly Models FLINGER K/C HLG 58 Span $2400 Midway Model PAST EDDIE Aerobatic /05 Elec$19 50 Jolly Models ELECTRICUS Electric Glider 05s$3259 Leisure PLAYBOY SR 67 Gear 05 Elect $3000 Astro ASTRO SPORT 37 Direct 05 Elect $2250 Leisure WASP 37 Direct 05 Electrics $2250 Midway ULTRA MK IV 86 Geared 04 EP $3900 Midway PLYING QUAKER 016 00 854 stroke $6476 Oks/Midway DENNY JR 72 Alum Camel $6396 Oks/Midway BUZZARD BOMBSHELL 73$5196 FULL LINE OP ELECTRIC SYSTEMS t Parts AvaIl SHIPPING & HANDLING 04 Page CATALOGUE Up $000 add $159$200 PP/Sat Class $001 $2009 add $225A copy will sent $2001 $4506 add $300 freewhen requested-$4501 ts $7000 add $350 order over $7000 add $006HOBBY HORN CA Addressees add 6$ tax15173 Moran St [A] Send MO Visa/MCI#EapIPO Boa 2212 Check [allow up 30Westistinster Ca 92684 days CK clearance] 7141 8938311 COD Eaact Charges plus $158 Hdl [Cash Only]lAW Hrs [718] DAVE ROBELENS PRONTO AND SUPER PRONTO HIGH QUALITY 48 SPAN KIT FOR 09 TO 25 ENGINES FEATURES 10w Wil desIgn high wing stability excelent inverted perfomiance Gentleforfhenovice orftre expert versatle perfmarEe 46 hour npid-f ire assembly beginner Precision machine-cut 516 balsa plywond spnice Rofed full size plarw showing complete wing Step-by-step irIsucbons easy assembly Finned mate landing gear Exceptonal small field perfonnance May flown 1 3 clunnels Tested recommended aperoved PJC Mndeler Magazine Medel Aviaton -July 1984 r Johnnie Casburns Month Only Super Lucky Fly H Super Lucky Fly II 45 65 List 995Special. $8995 Little Super Lucky Fly II 35 45 LIST. $11995SPECIAL. $8495 Prices Subject Change Without Notice rwi HeW $3995 Pwiw NeW $4995 w *r m yat dsbtur net stuck d5 er order dIrect post pad delivery Virginia residents add 45/a sales tax TIDEWATER HOBBY ENTERPRISES [3 Route 1 Box 241D Lanexa vrgnia 23089 Phone 804 966-5092 2 lage Pre-finished wing ready join Wing covered 1/64 plywood Easy build/Easy fly Excellent Plans Lots Hardware Accessories Johnnie Casburn Manufacturing Co 571 5-5E E Rosedale Fort Worth TX 76112 Day 817/451-7537 t 817/572-1452 April 198651 SAILPLANE LAUNCH EQUIPMENT FOR EVERY S PORT WINCH source QUIET FLIGHT supplies hi-starts accessories electric motors & reducers batteries chutes braided nylon line tow line drums more. VISA MASTERCARD DAVEY 1Pm lE CoRPoRATmN ONE WOOD LANEMALVERNPA19355 215644-6772 SEND SASE FOR INFO Engines/Wilson Continued page 127 tion maintain constant down pressure piston Plastigage mashed out too wide clearance too close thicker shim combination shims shouldbe used Plastigage mashed out wide enough clearance too great thinner shim no shim should used clear ance correct clean off Plastigage piston head reassemble head engine gasket used backplate put place mount backplate engine Tighten screws previously described Rotate crankshaft sure crankpin and/or connecting rod rubbing backplate binding detected tighten propeller crankshaft hold ward doesnt cure problem remove frontplate Using wood block protect crankshaft tap back crankshaft center hammer sure crankshaft rear bearing fully seated forwardmost position Reassemble engine try again crankshaft bearings fully seated should no contact backplate fully-assembled engine turns feels free except case new ABC engine may bind top stroke screw fresh glow plug reassemble carburetor engine 0-ring hold down carburetor against 0-ring tight ening screws nut hold place overhauling procedures have finished engine can broken using same procedures new information article applies generally two-cycle front-intake RC engines conventional constructions Other types engines require somewhat different procedures have better way tasks please write let know Walt Wilson 3000 Persimmon Dr St Charles MO 63301 Addresses companies products mentioned GatorRC Products 3713 Pompano Dr Pensacola FL 32504 K&B Manufacturing 12152 Woodruff Ave Downey CA 90241 Marvel Oil Company Inc Port Ches ter NY 10573 Sealed Power Corp Plastigage 100 Terrace Plaza Muskegon MI 49443 RC Soaring/Pruss Continued page 49 next two years may also thank outgoing officers served two terms four years Warren Plohr LSF/334 Presi dent Larry Jolly LSF/3579 Vice-Presi dent Ken Bates LSF/604 Secretary Cal Sobczynski LSF/2487 Treasurer During 1985 seven gents names added Level V list bringing total up 46 Earle Latimer LSF/31 19 Lansing MI Terry Edmonds LSF/463 Iowa City IA Dale Harber LSF/1880 Yoder IN Charron Smith LSF/4093 Grand MI Richard Ransom LSF/4747 lonia MI Thomas Dickey LSF/3816 Gaithersburg MD Robert Schow LSF/166 Vienna VA Congratulations As column closing out word received Larry Jolly representing USA won first place South Africa flying first International F3H Cross-Country event ever held Larry flying original design Comet Details later article Larry himself Until next month good lift Dan Pruss 131 E Pennington Ln Plainfield IL 60544 RC Electrics/Kopski Continued page 51 lengths nichrome Because nichrome has relatively stable resistance temperature variation copper other conductive wire could used task temperature coefficient copper -many metals around plus % minus 5o per 100 C Thus value shunresistance would vary quite noticeably ambient internal temperature thereby rendering such metals useless purposes later wire used readily available modelers foam-cutting wire RC Modeler PO Box 487 Sierra Madre CA 91024 Cost $225 five-foot length postpaid As received wire measured little over three ohms sug gest confirm yours just sure information given di rectly applicable Ill try give sufficient detail just case can ac commodate somewhat different resist ances few words now before get how-to nittygritty Youll recall discussion last month about ohmmeter function multimeter measure resistance five-foot length nichrome wire set meter selector switch lowest resistance range short test leads together carefully zero ohms adjustment knob until meter pointer rests 0 ohms scale Its often good practice tape meter face gently fingertip sure needle has reached its true resting position connect test leads end nichrome wire Make sure leads make tight contactboth zeroing operation connection What should get 3 33 ohms 130 Model Aviation POW OM RETRIEVER HOBBY HAMMER $Q~ APPROXLENGTH7/Extra Tip INCLUDES$125 ONE STEEL AND ONE BRASS TIP Send check Money Order M &WMODELS PO Box 6627 Huntington Beach CA 92615 Add 150 Post & Hand Rae add 6% tax nave DMM results should same although latter case may have some test lead resistance subtract total reading Just short DMM leads together tightly note reading subtract test-lead resistance wire plus test leads value RCM wire significantly different three-ohm example value would expect itto read apply principles anyway Back shunt What need measure very large motor currents very-low-resistance sampling resistor known stable value sampling resistor connected series motor leads motor current flows through Being small resistance flowing current develops small voltage drop resistor Since multimeters have low voltage scale 200 250 millivolts 02 025 volts very convenient have shunt resistor value such voltage values developed across 20 25 amps flowing respectively earlier les sons can determine resistance needed applying Ohms Law R R resistance ohms V voltage volts current amps So R 20 25 0 ohm 10 milliohms Remember value Well need later calibration shunt get such very tiny resistance three ohms worth nichrome foam-cutting wire three per five feet 50V100 ohm per inch would need piece wire fifth inch long Impractical course Far practical parallel small bundle reasonable-length pieces wire will produce total resistance equal individual piece resistance divided number pieces shunt pictured made just way particular used 15 pieces four inches long Thus resistance bundle 1/15 x 4 x 005 02 ohms divided 15 133 hundredths ohm 133 milliohms clearly close tobut high side ofthe 10 milli ohms want go over size value Read have used multimeter measure resistances few ohms have no doubt discovered important make tight test lead contact shunt resistors such making 1/100 ohm tight electrical contact isnt good enough reason pic tured shunt configured fourterminal device has two current ter minals two voltage terminals outermost connections four-inchlong resistance wire bundle current contacts connecting points current under test enters leaves shunt ie circuit current flows through outermost connec tions two inner contacts tap off some voltage drop along length shunt sampling resistor inner tap points low-voltage scale multimeter will connected effect total 00133-ohm shunt slightly too long inner voltage pickoff points shorten shunt just right value 10 milliohms worth current-sampling resistance Begin assembly shunt first cutting 15 four-inch lengths wire Straighten out kinks bends easily done rolling wires individually between two pieces wood Bundle pieces slip four 5A2-in brass wheel col lars less setscrews over Position wheel collars approximately shown keeping outermost ones just inside very ends wire bundle Select four 6-32 brass machine screws grind ends smooth slightly rounded least deburred screws will hold wheel collars must compress wire bundles tightly important screw ends cut through wire pieces screws tightened very important Assemble flat washer No 6 solder lug another flat washer spring lockwasher 6-32 hex nut order loosely onto two screws thread screws two outer wheel collars Make sure wires neatly bundled collars about / inch inside bundle ends tighten screws Tighten un til wire bundle squeezed tight end holding screwdriver screw slot use small wrench pliers run nut up against washers solder lugs Its easy tempting use wire bundle handle help things alongbut dont screws must loosened collars Hold tighten screw/nut combina tiondont let screw work loose collar doesnt work just right first time start over get right Believe methis far difficult describe Install screws two inner wheel collars tighten gently collars spaced about eigth inch outer collar exact spacing inner collars will determined during calibration shunt shunt assembly can now fitted wire connections choice Mine outfitted short harness hav ing Molex connectors end positive leads connector soldered shunt solder lugs con nector negative leads straight through small Molex connectors same kind used Astro other motor/battery wiring harnesses assembly shown easily inserted Continued page 134 April 1986 131 OPS 80 Fan Enamel Needle Bearing Rod New OPS 80 warmed over 65 has needle bearing rod new 80 case larger by-pass exhaust area slide valve carb fits old 65 mounts 0PS 80 produces 455 HP 21000 RPM Order today local hobby shop S6iSPO4 Comkeio#t mftoz4 %ee PO Box 26247 e New Orleans LA 70186 S 504 242-5967 DALLAI RE SPORTSTER SPECI FICATIONS Wing Span 72 Inches Wing Chord 11 Inches Power 21-30 Engine Radio 3 Channels KIT INCLUDES Full size rolled plans Easy-to-follow instructions Machine cut sanded parts Necessary hardware 4g OLD TIMER Rt 1 Box 180 a MS 38754 Telephone 601 247-3578 PRODUCTS earn tuc flICPCflhaMfl mnnra Fm Complete Line Exhaust Systems * Tuned Pipes led Tuned Pipes * Headers uri Mufflers * Expansion Mufflers copter Ball Mufflers Specialized Exhaust Systems Un*urpassd Wfl ~hi b Pedomance RC Electrics/Kopski Continued page 131 directly motor circuit planes Thus motor current flows through assembly causes small propor tionate voltage drop appear between inner voltage-tap wheel collars voltage direct representation actual motor current Now comes fun part calibrating homemade shunt case calibrat ing means adjusting spacing between two innermost wheel collars specific voltage appears specific current flowing through shunt Calibration can done using single multimeter can done easily using two multimeters An accom panying photo illustrates two-meter method text will describe singlemeter method Note second meter connected read tap voltage can either DMM pictured another analog instrument Calibration done configuring test circuit containing shunt several amperes flowing through measuring current normal multimeter cur rent scale measuring again using low-voltage multimeter setting read shunt voltage calibration circuit simple consists two resistors some hookup wire clip leads Power circuit best sup plied car battery similar DC source can supply several amperes sever al minutes steadily used tractor bat tery field boxin warm work shop since December 27 its cold southeastern PA two resistors Radio Shack oneohm 10-watt ones Catalog No 271-13 1 wired series making twoohm 20-watt resistor power-dissipa tion rating resistors increased significantly immersing jar water pictured Fill pint jar cold water plunk resistors leaving wire leads emerging being sure resistor bodies fully covered water resistor pair connected series multimeter 12-volt battery resulting current should fall somewhere between five six amps almost 12 volts being dropped across two-ohm resistor assembly since much voltage loss wiring meter shunt means two-ohm resistors dissipating lots power Specifically P V/R P power watts V nominal battery voltage R resistance ohms So P 2/2 2 atts should now clear 20-watt resistor set immersed water attempt test resistors free air Back calibration procedure Take particular note circuit current reading get relates shunt voltage reading found next step Wait several minutes settle out reading tends drift Mine 53 amps Now remove multimeter/current meter circuitbut reclose circuit two-ohm resistor-set shunt remain series 12-volt battery Set multimeter its lowest voltage rangeusually 025 volts analog multimetersand meter test leads proper jacks ones used current measurement previously made connect meter innermost wheel collar connections shunt should get voltage reading around 50 millivoltsabout full-scale deflection Adjust spacing innermost collars until voltage reading reflects refer back calculated desired resistance shunt circuit current measured previ ously case desired shunt volt age 53 millivolts 0053 volts Snug up inner collar screws Thats shunt calibrated shunt calibration factor 10 per amp 53 amps circuit current produced 53 x 10 53 millivolts voltage shunt taps actual circuit current may different calibration fac tor will same because force way adjusting wheel collars calibration described above reas onably good some error inherent single-meter procedure because circuit current will change slightly up ward current meter removed reconfigured measure shunt voltage procedure can made somewhat betterand easierif two multimeters used series circuit constantly monitor cur rent used voltmeter watch shunt voltage inner wheel collar spacing set However error first approach small onemeter method perfectly adequate use high currents shunt will get hot can such tiny resistance / ohm get hot Recall earlier lessons suppose shunt measuring 25 amps Thus P R P power watts current amperes R resistance ohms So P 25 x 133/100 100 watts typical nite lite medium-size Christmas tree lamp rated about seven watts know hot gets dont just grab onto see second thought dontyoull burn fingers Well shunt metal somewhat larger surface area lamp has thermal mass its slower reach full temperature its hot its hot cause damage Further likely run much current long periods Shunt powerand thus shunt temperaturedrops rapidly lower current case shunt 134 Model Aviation ONLY $4995 GOITIOIIII TIllS PROF/LE0COMBAThRAT WIDE & NARROW WEDGE 15 -- 6 Capacities UNIFLOW & STIIDD Cuutrn hail huh Ingredients Fof detailed brochure50C stamps/check oni CAROLINA-TAFFINDER 8345 Delhi Road charleston Hgts SC 29418 803-563-7169 made common metal like copper aluminum shunt heat would direct ly affect shunt resistance thus voltage readingin some cases grossly Hence use vastly stable nichrome metal actual use power lost shunt power avallable motor Looking another way voltage drop shunt voltage denied motor Thus youre likely notice small drop motors rpm shunt installed motor circuit effect will pronounced systems fewer cells Shunt voltage drop smaller percentage voltage bat teries made up large numbers cells readers having DMM highest scale being two amps calibration circuit current would have set value less two amps no particular problem just substitute single 10-ohm 10-watt resistor Radio Shack 271-132 two-ohm set shown circuit current will around 12 amps shunt voltage will around 12 millivolts low value course pushing practical meter limits resulting shunt calibration may prove less accurate obtained higher calibra tion-circuit current meter ac curacy next month Nevertheless principles mentioned analog meter calibration hold case well resulting shunt DMM combination have measurement capability up 20 amps since DMMs typically have low voltage range 200 millivolts Late news SPARKS all-electric club Houston TX has announced Sec ond Spring Fun-Fly April 12-13 event will held Petrosky Ele mentary School its AMA-sanctioned AMA license required enter will offer competitive opportunity low-key basis information con tact Contest Director Eddie Thomas Houston SPARKS 1427 Ashwood Dr Sugar Land TX 77478 713/491-3375 Just mention name youll get extrafine service Thats month Hope helps whove asking meas ure large currents Any comment question may sent author SASE please Bob Kopski 25 West End Dr Lans dale PA 19446 Oh Silent Spring Flights please hurry RC Old-Timers/Mathews Continued page 53 featured series photos December 1985 column has come home roost Dick Lyons now living Camarillo CA formerly Chicago IL sent some photos took model years ago unbeknown Harry Scatena Dick following explanation photos column set bell ringing after much headscratching remembered seen model years ago contest Gary IN fact seemed remember taking some pictures time After much searching through old albums found enclosed photos young modelers attracted very unusual modelas can see crowd photos contest Gary called Little Nationals annual af fair few years before war WW II local department store sponsor attracted very large turn out attended 1939 1940 dont recall year photos taken also have photos Carl Goldberg flying early Interceptor Jim Cahill Dick Obarski among modeling notables meet have mentioned old Gary IN con test previous columns pointing out degree participation non-modeling business fraternal groups sort makes fellow wonder sort sponsorship no longer exists doesnt Also note Harry Scatena some what well-dressed contemporary flying-attire standardsbut about helper suit yet have situation Harry Scatena will see first time photos taken him pusher almost 50 years ago about matter time Dick Lyons another comment letter enjoy col umneven mostly RC Well now guess Ive out Free Flight its pure form long readers have forgotten Im Free Flighter retrieving problems became agony de-feet moved Wichita Greensburg donated over 100 Free Flight trophies local SAM Society Antique Modelers 56 chapter kept National Grand Champion trophies Among Junior firsts Rubber Scale Gas Scale A-l Nordic A-2 Nordic FAL Power B Gas C Gas plus another 40 nd-place lower trophies bird dogs grew up left rely RC solve retrieving spirit still willingbut flesh weak Im Help Help need pictures Free Flight models designed after 1942that nostalgia era detect very con siderable interest among readers Continued page 139 April1986 135 Well time around may take cake folks fascinating old pusher designed built Harry Scatena
Edition: Model Aviation - 1986/04
Page Numbers: 50, 51, 130, 131, 134, 135
RadioI[VOLT AUTO Contro TRACTOR BATTERY Electrics Bob Kopski NEW Electric club Les Adams president Adams Electronics supplier Electric need wrote tell new all-Electric club has formed northwestern Chicago IL area Elec tric Model Fliers Chicago EMF Chicago presently comprised about 20 modelers has sole interest further advancement Electricpowered flight Les tells number growing steadily AMA member interested should contact either Larry Sperling 312 303-5165 Les Adams 312 364-0660 after 600 pm CST Electric interests welcome Scale Pattern Sailplanesanything Les vice-president group himself very capable Electric modeler club planning Electric fly-in sometime during 1986 info will announced later Watch column particulars Heres wishing best guys EMF Chicago makes second all-Electric club know ofthe other ing SPARKS Houston TX other such Electric groups please let know Ill pass word along column Basic Electricity past several stallments continuing mini-series have discussed multimeters rather exten sively particular familiar moving-needle analog multimeter has examined considerable detail plans month make transition discussion digital multimeters DMMs However reviewing past columns realized 2 1-OHM 10 WATT RESISTORS IN PINT OF COLD WATER MULTIMETER ON 10 AMP RANGE ST LEADS MOOEL AIRPLANE WHEEL COLLAR 4 PLACES MAY BE REMOVED ONCE CIRCUIT CURRENT IS READ LEADS CONNECTED TOGETHER TO CLOSE CIRCUIT 15 PIECES OFMULTIMETER SET WIRE 4 LONGON 250 MILLIVOLT RANGE SHUNT NICHROMgJ WIRE BUNDLE HIGH-CURRENT SHUNT CALIBRATION CIRCUIT Calibrating shunt using two-meter test setup Drawing gives circuit details Analog muitimeter set 10-amp scale digital multlmeter DMM 200 millivolt scale Circuit current case 53 amps dictates shunt adjusted obtain 53 millivolts pint cool water gets pretty warm after few minutes run ning two 1-ohm 10-watt resistors dissipating about 80 watts Constructing high-current shunt L wiring harness can custom-made f needsbut keep connector-wIre length minimum Shunt wires cut five-foot length nichrome foam-cutting wire Wheel collars screws must brass completed shuntor sampling resistorassembly R 15 shunt wires four inches long 50 Model Aviation some things practical nature promised early have grown long overdue So month well take look simple accessory can easily make expand usefulness multimetereither analog digital although analog type will used example easily-constructed device will allow measure very large currents other wise beyond range multime ters future column well see make simple device double useful voltage ranges DMMs accessory shown nothing special external currentmeter SHUNT Youll remember multimeters have several internal select able shunt resistors allow measure current over very wide range Normally lowest current range analog multimeters about 50 microamps millionths ampere 200 microamps DMMs highest ranges usually 10 amps two amps respectively Thus multimeter very useful instrument often cant used measure motor current because latter often exceeds 10 amps special shunt shown will extend capability multimeters upward 25 amperes friends will cover nearly Electric modeling interests world shunt pictured consists small bundle short nichrome wire Continued page 130 Single-meter method calibrating shunt 1 Meter first used ammeter current recorded Meter removed recon nected voltmeter set 250 scale portion circuit used current test closed Note two-meter setup voltmeter reading 53 Voltmeter connected inner pair wheel collars shunt Using shunt R Kopekis Astro cobalt 25 turns 9 x 6 nylon prop Battery dozen 12 Ah cells routed through speed control Note shunt jumper wires inserted motor power wiring motor current can measured Muitimeter shows 155 indicating motor drawing 155 amps Shunt needed because multimeter circuits cant handle large currents Hotativ Horn Ak Acm 7J&W LAIZOs 8 GAS MOSEL Il4odL j 9Ec0O 8REA5ER 1941 BROOKLYN DODGER 56 Cabin EWEST* Retail $52 95**INTRODUCTORY PRICE* $3900 1938 Record Breaker 96 $6956 1939 Zipper 54$5356 1938 Kloud King 63 $4236 1941 Brigiclier 36 $8076 1941 Super Ouaker 76 $7276 1940 So Long 50$3036 1936 Buccaneer 94 $5996 1938 Clipper MKI 7254156 1937 Dallaire 198 $75 16 1935 Miss America 64 $7196 1941 Playboy Sr 60 $5116 1941 Playboy Jr 54 $3116 1938 Powerhouse 84 $5356 1940 Sailplane 78 $6476 1938 Trenton Terror 72 $4070 1940 Ranger 46$3196 1939 Korda Wake 44 $1916 l939Mercury 72 6 kits qualify SAM events FF & K/c feature highest quality machine cut & sanded parts Superior Competition sheet strip wood wire & window material Plans orig PP hut isodela easily convertible Sch K/C KITS Sailplanes Electric power Gas Hobby Horn SENSOAR Glider 78 5s] $1860 Midway Model GNOME K/C Hand Launch Glider$2400 Jolly Models FLINGER K/C HLG 58 Span $2400 Midway Model PAST EDDIE Aerobatic /05 Elec$19 50 Jolly Models ELECTRICUS Electric Glider 05s$3259 Leisure PLAYBOY SR 67 Gear 05 Elect $3000 Astro ASTRO SPORT 37 Direct 05 Elect $2250 Leisure WASP 37 Direct 05 Electrics $2250 Midway ULTRA MK IV 86 Geared 04 EP $3900 Midway PLYING QUAKER 016 00 854 stroke $6476 Oks/Midway DENNY JR 72 Alum Camel $6396 Oks/Midway BUZZARD BOMBSHELL 73$5196 FULL LINE OP ELECTRIC SYSTEMS t Parts AvaIl SHIPPING & HANDLING 04 Page CATALOGUE Up $000 add $159$200 PP/Sat Class $001 $2009 add $225A copy will sent $2001 $4506 add $300 freewhen requested-$4501 ts $7000 add $350 order over $7000 add $006HOBBY HORN CA Addressees add 6$ tax15173 Moran St [A] Send MO Visa/MCI#EapIPO Boa 2212 Check [allow up 30Westistinster Ca 92684 days CK clearance] 7141 8938311 COD Eaact Charges plus $158 Hdl [Cash Only]lAW Hrs [718] DAVE ROBELENS PRONTO AND SUPER PRONTO HIGH QUALITY 48 SPAN KIT FOR 09 TO 25 ENGINES FEATURES 10w Wil desIgn high wing stability excelent inverted perfomiance Gentleforfhenovice orftre expert versatle perfmarEe 46 hour npid-f ire assembly beginner Precision machine-cut 516 balsa plywond spnice Rofed full size plarw showing complete wing Step-by-step irIsucbons easy assembly Finned mate landing gear Exceptonal small field perfonnance May flown 1 3 clunnels Tested recommended aperoved PJC Mndeler Magazine Medel Aviaton -July 1984 r Johnnie Casburns Month Only Super Lucky Fly H Super Lucky Fly II 45 65 List 995Special. $8995 Little Super Lucky Fly II 35 45 LIST. $11995SPECIAL. $8495 Prices Subject Change Without Notice rwi HeW $3995 Pwiw NeW $4995 w *r m yat dsbtur net stuck d5 er order dIrect post pad delivery Virginia residents add 45/a sales tax TIDEWATER HOBBY ENTERPRISES [3 Route 1 Box 241D Lanexa vrgnia 23089 Phone 804 966-5092 2 lage Pre-finished wing ready join Wing covered 1/64 plywood Easy build/Easy fly Excellent Plans Lots Hardware Accessories Johnnie Casburn Manufacturing Co 571 5-5E E Rosedale Fort Worth TX 76112 Day 817/451-7537 t 817/572-1452 April 198651 SAILPLANE LAUNCH EQUIPMENT FOR EVERY S PORT WINCH source QUIET FLIGHT supplies hi-starts accessories electric motors & reducers batteries chutes braided nylon line tow line drums more. VISA MASTERCARD DAVEY 1Pm lE CoRPoRATmN ONE WOOD LANEMALVERNPA19355 215644-6772 SEND SASE FOR INFO Engines/Wilson Continued page 127 tion maintain constant down pressure piston Plastigage mashed out too wide clearance too close thicker shim combination shims shouldbe used Plastigage mashed out wide enough clearance too great thinner shim no shim should used clear ance correct clean off Plastigage piston head reassemble head engine gasket used backplate put place mount backplate engine Tighten screws previously described Rotate crankshaft sure crankpin and/or connecting rod rubbing backplate binding detected tighten propeller crankshaft hold ward doesnt cure problem remove frontplate Using wood block protect crankshaft tap back crankshaft center hammer sure crankshaft rear bearing fully seated forwardmost position Reassemble engine try again crankshaft bearings fully seated should no contact backplate fully-assembled engine turns feels free except case new ABC engine may bind top stroke screw fresh glow plug reassemble carburetor engine 0-ring hold down carburetor against 0-ring tight ening screws nut hold place overhauling procedures have finished engine can broken using same procedures new information article applies generally two-cycle front-intake RC engines conventional constructions Other types engines require somewhat different procedures have better way tasks please write let know Walt Wilson 3000 Persimmon Dr St Charles MO 63301 Addresses companies products mentioned GatorRC Products 3713 Pompano Dr Pensacola FL 32504 K&B Manufacturing 12152 Woodruff Ave Downey CA 90241 Marvel Oil Company Inc Port Ches ter NY 10573 Sealed Power Corp Plastigage 100 Terrace Plaza Muskegon MI 49443 RC Soaring/Pruss Continued page 49 next two years may also thank outgoing officers served two terms four years Warren Plohr LSF/334 Presi dent Larry Jolly LSF/3579 Vice-Presi dent Ken Bates LSF/604 Secretary Cal Sobczynski LSF/2487 Treasurer During 1985 seven gents names added Level V list bringing total up 46 Earle Latimer LSF/31 19 Lansing MI Terry Edmonds LSF/463 Iowa City IA Dale Harber LSF/1880 Yoder IN Charron Smith LSF/4093 Grand MI Richard Ransom LSF/4747 lonia MI Thomas Dickey LSF/3816 Gaithersburg MD Robert Schow LSF/166 Vienna VA Congratulations As column closing out word received Larry Jolly representing USA won first place South Africa flying first International F3H Cross-Country event ever held Larry flying original design Comet Details later article Larry himself Until next month good lift Dan Pruss 131 E Pennington Ln Plainfield IL 60544 RC Electrics/Kopski Continued page 51 lengths nichrome Because nichrome has relatively stable resistance temperature variation copper other conductive wire could used task temperature coefficient copper -many metals around plus % minus 5o per 100 C Thus value shunresistance would vary quite noticeably ambient internal temperature thereby rendering such metals useless purposes later wire used readily available modelers foam-cutting wire RC Modeler PO Box 487 Sierra Madre CA 91024 Cost $225 five-foot length postpaid As received wire measured little over three ohms sug gest confirm yours just sure information given di rectly applicable Ill try give sufficient detail just case can ac commodate somewhat different resist ances few words now before get how-to nittygritty Youll recall discussion last month about ohmmeter function multimeter measure resistance five-foot length nichrome wire set meter selector switch lowest resistance range short test leads together carefully zero ohms adjustment knob until meter pointer rests 0 ohms scale Its often good practice tape meter face gently fingertip sure needle has reached its true resting position connect test leads end nichrome wire Make sure leads make tight contactboth zeroing operation connection What should get 3 33 ohms 130 Model Aviation POW OM RETRIEVER HOBBY HAMMER $Q~ APPROXLENGTH7/Extra Tip INCLUDES$125 ONE STEEL AND ONE BRASS TIP Send check Money Order M &WMODELS PO Box 6627 Huntington Beach CA 92615 Add 150 Post & Hand Rae add 6% tax nave DMM results should same although latter case may have some test lead resistance subtract total reading Just short DMM leads together tightly note reading subtract test-lead resistance wire plus test leads value RCM wire significantly different three-ohm example value would expect itto read apply principles anyway Back shunt What need measure very large motor currents very-low-resistance sampling resistor known stable value sampling resistor connected series motor leads motor current flows through Being small resistance flowing current develops small voltage drop resistor Since multimeters have low voltage scale 200 250 millivolts 02 025 volts very convenient have shunt resistor value such voltage values developed across 20 25 amps flowing respectively earlier les sons can determine resistance needed applying Ohms Law R R resistance ohms V voltage volts current amps So R 20 25 0 ohm 10 milliohms Remember value Well need later calibration shunt get such very tiny resistance three ohms worth nichrome foam-cutting wire three per five feet 50V100 ohm per inch would need piece wire fifth inch long Impractical course Far practical parallel small bundle reasonable-length pieces wire will produce total resistance equal individual piece resistance divided number pieces shunt pictured made just way particular used 15 pieces four inches long Thus resistance bundle 1/15 x 4 x 005 02 ohms divided 15 133 hundredths ohm 133 milliohms clearly close tobut high side ofthe 10 milli ohms want go over size value Read have used multimeter measure resistances few ohms have no doubt discovered important make tight test lead contact shunt resistors such making 1/100 ohm tight electrical contact isnt good enough reason pic tured shunt configured fourterminal device has two current ter minals two voltage terminals outermost connections four-inchlong resistance wire bundle current contacts connecting points current under test enters leaves shunt ie circuit current flows through outermost connec tions two inner contacts tap off some voltage drop along length shunt sampling resistor inner tap points low-voltage scale multimeter will connected effect total 00133-ohm shunt slightly too long inner voltage pickoff points shorten shunt just right value 10 milliohms worth current-sampling resistance Begin assembly shunt first cutting 15 four-inch lengths wire Straighten out kinks bends easily done rolling wires individually between two pieces wood Bundle pieces slip four 5A2-in brass wheel col lars less setscrews over Position wheel collars approximately shown keeping outermost ones just inside very ends wire bundle Select four 6-32 brass machine screws grind ends smooth slightly rounded least deburred screws will hold wheel collars must compress wire bundles tightly important screw ends cut through wire pieces screws tightened very important Assemble flat washer No 6 solder lug another flat washer spring lockwasher 6-32 hex nut order loosely onto two screws thread screws two outer wheel collars Make sure wires neatly bundled collars about / inch inside bundle ends tighten screws Tighten un til wire bundle squeezed tight end holding screwdriver screw slot use small wrench pliers run nut up against washers solder lugs Its easy tempting use wire bundle handle help things alongbut dont screws must loosened collars Hold tighten screw/nut combina tiondont let screw work loose collar doesnt work just right first time start over get right Believe methis far difficult describe Install screws two inner wheel collars tighten gently collars spaced about eigth inch outer collar exact spacing inner collars will determined during calibration shunt shunt assembly can now fitted wire connections choice Mine outfitted short harness hav ing Molex connectors end positive leads connector soldered shunt solder lugs con nector negative leads straight through small Molex connectors same kind used Astro other motor/battery wiring harnesses assembly shown easily inserted Continued page 134 April 1986 131 OPS 80 Fan Enamel Needle Bearing Rod New OPS 80 warmed over 65 has needle bearing rod new 80 case larger by-pass exhaust area slide valve carb fits old 65 mounts 0PS 80 produces 455 HP 21000 RPM Order today local hobby shop S6iSPO4 Comkeio#t mftoz4 %ee PO Box 26247 e New Orleans LA 70186 S 504 242-5967 DALLAI RE SPORTSTER SPECI FICATIONS Wing Span 72 Inches Wing Chord 11 Inches Power 21-30 Engine Radio 3 Channels KIT INCLUDES Full size rolled plans Easy-to-follow instructions Machine cut sanded parts Necessary hardware 4g OLD TIMER Rt 1 Box 180 a MS 38754 Telephone 601 247-3578 PRODUCTS earn tuc flICPCflhaMfl mnnra Fm Complete Line Exhaust Systems * Tuned Pipes led Tuned Pipes * Headers uri Mufflers * Expansion Mufflers copter Ball Mufflers Specialized Exhaust Systems Un*urpassd Wfl ~hi b Pedomance RC Electrics/Kopski Continued page 131 directly motor circuit planes Thus motor current flows through assembly causes small propor tionate voltage drop appear between inner voltage-tap wheel collars voltage direct representation actual motor current Now comes fun part calibrating homemade shunt case calibrat ing means adjusting spacing between two innermost wheel collars specific voltage appears specific current flowing through shunt Calibration can done using single multimeter can done easily using two multimeters An accom panying photo illustrates two-meter method text will describe singlemeter method Note second meter connected read tap voltage can either DMM pictured another analog instrument Calibration done configuring test circuit containing shunt several amperes flowing through measuring current normal multimeter cur rent scale measuring again using low-voltage multimeter setting read shunt voltage calibration circuit simple consists two resistors some hookup wire clip leads Power circuit best sup plied car battery similar DC source can supply several amperes sever al minutes steadily used tractor bat tery field boxin warm work shop since December 27 its cold southeastern PA two resistors Radio Shack oneohm 10-watt ones Catalog No 271-13 1 wired series making twoohm 20-watt resistor power-dissipa tion rating resistors increased significantly immersing jar water pictured Fill pint jar cold water plunk resistors leaving wire leads emerging being sure resistor bodies fully covered water resistor pair connected series multimeter 12-volt battery resulting current should fall somewhere between five six amps almost 12 volts being dropped across two-ohm resistor assembly since much voltage loss wiring meter shunt means two-ohm resistors dissipating lots power Specifically P V/R P power watts V nominal battery voltage R resistance ohms So P 2/2 2 atts should now clear 20-watt resistor set immersed water attempt test resistors free air Back calibration procedure Take particular note circuit current reading get relates shunt voltage reading found next step Wait several minutes settle out reading tends drift Mine 53 amps Now remove multimeter/current meter circuitbut reclose circuit two-ohm resistor-set shunt remain series 12-volt battery Set multimeter its lowest voltage rangeusually 025 volts analog multimetersand meter test leads proper jacks ones used current measurement previously made connect meter innermost wheel collar connections shunt should get voltage reading around 50 millivoltsabout full-scale deflection Adjust spacing innermost collars until voltage reading reflects refer back calculated desired resistance shunt circuit current measured previ ously case desired shunt volt age 53 millivolts 0053 volts Snug up inner collar screws Thats shunt calibrated shunt calibration factor 10 per amp 53 amps circuit current produced 53 x 10 53 millivolts voltage shunt taps actual circuit current may different calibration fac tor will same because force way adjusting wheel collars calibration described above reas onably good some error inherent single-meter procedure because circuit current will change slightly up ward current meter removed reconfigured measure shunt voltage procedure can made somewhat betterand easierif two multimeters used series circuit constantly monitor cur rent used voltmeter watch shunt voltage inner wheel collar spacing set However error first approach small onemeter method perfectly adequate use high currents shunt will get hot can such tiny resistance / ohm get hot Recall earlier lessons suppose shunt measuring 25 amps Thus P R P power watts current amperes R resistance ohms So P 25 x 133/100 100 watts typical nite lite medium-size Christmas tree lamp rated about seven watts know hot gets dont just grab onto see second thought dontyoull burn fingers Well shunt metal somewhat larger surface area lamp has thermal mass its slower reach full temperature its hot its hot cause damage Further likely run much current long periods Shunt powerand thus shunt temperaturedrops rapidly lower current case shunt 134 Model Aviation ONLY $4995 GOITIOIIII TIllS PROF/LE0COMBAThRAT WIDE & NARROW WEDGE 15 -- 6 Capacities UNIFLOW & STIIDD Cuutrn hail huh Ingredients Fof detailed brochure50C stamps/check oni CAROLINA-TAFFINDER 8345 Delhi Road charleston Hgts SC 29418 803-563-7169 made common metal like copper aluminum shunt heat would direct ly affect shunt resistance thus voltage readingin some cases grossly Hence use vastly stable nichrome metal actual use power lost shunt power avallable motor Looking another way voltage drop shunt voltage denied motor Thus youre likely notice small drop motors rpm shunt installed motor circuit effect will pronounced systems fewer cells Shunt voltage drop smaller percentage voltage bat teries made up large numbers cells readers having DMM highest scale being two amps calibration circuit current would have set value less two amps no particular problem just substitute single 10-ohm 10-watt resistor Radio Shack 271-132 two-ohm set shown circuit current will around 12 amps shunt voltage will around 12 millivolts low value course pushing practical meter limits resulting shunt calibration may prove less accurate obtained higher calibra tion-circuit current meter ac curacy next month Nevertheless principles mentioned analog meter calibration hold case well resulting shunt DMM combination have measurement capability up 20 amps since DMMs typically have low voltage range 200 millivolts Late news SPARKS all-electric club Houston TX has announced Sec ond Spring Fun-Fly April 12-13 event will held Petrosky Ele mentary School its AMA-sanctioned AMA license required enter will offer competitive opportunity low-key basis information con tact Contest Director Eddie Thomas Houston SPARKS 1427 Ashwood Dr Sugar Land TX 77478 713/491-3375 Just mention name youll get extrafine service Thats month Hope helps whove asking meas ure large currents Any comment question may sent author SASE please Bob Kopski 25 West End Dr Lans dale PA 19446 Oh Silent Spring Flights please hurry RC Old-Timers/Mathews Continued page 53 featured series photos December 1985 column has come home roost Dick Lyons now living Camarillo CA formerly Chicago IL sent some photos took model years ago unbeknown Harry Scatena Dick following explanation photos column set bell ringing after much headscratching remembered seen model years ago contest Gary IN fact seemed remember taking some pictures time After much searching through old albums found enclosed photos young modelers attracted very unusual modelas can see crowd photos contest Gary called Little Nationals annual af fair few years before war WW II local department store sponsor attracted very large turn out attended 1939 1940 dont recall year photos taken also have photos Carl Goldberg flying early Interceptor Jim Cahill Dick Obarski among modeling notables meet have mentioned old Gary IN con test previous columns pointing out degree participation non-modeling business fraternal groups sort makes fellow wonder sort sponsorship no longer exists doesnt Also note Harry Scatena some what well-dressed contemporary flying-attire standardsbut about helper suit yet have situation Harry Scatena will see first time photos taken him pusher almost 50 years ago about matter time Dick Lyons another comment letter enjoy col umneven mostly RC Well now guess Ive out Free Flight its pure form long readers have forgotten Im Free Flighter retrieving problems became agony de-feet moved Wichita Greensburg donated over 100 Free Flight trophies local SAM Society Antique Modelers 56 chapter kept National Grand Champion trophies Among Junior firsts Rubber Scale Gas Scale A-l Nordic A-2 Nordic FAL Power B Gas C Gas plus another 40 nd-place lower trophies bird dogs grew up left rely RC solve retrieving spirit still willingbut flesh weak Im Help Help need pictures Free Flight models designed after 1942that nostalgia era detect very con siderable interest among readers Continued page 139 April1986 135 Well time around may take cake folks fascinating old pusher designed built Harry Scatena
Edition: Model Aviation - 1986/04
Page Numbers: 50, 51, 130, 131, 134, 135
RadioI[VOLT AUTO Contro TRACTOR BATTERY Electrics Bob Kopski NEW Electric club Les Adams president Adams Electronics supplier Electric need wrote tell new all-Electric club has formed northwestern Chicago IL area Elec tric Model Fliers Chicago EMF Chicago presently comprised about 20 modelers has sole interest further advancement Electricpowered flight Les tells number growing steadily AMA member interested should contact either Larry Sperling 312 303-5165 Les Adams 312 364-0660 after 600 pm CST Electric interests welcome Scale Pattern Sailplanesanything Les vice-president group himself very capable Electric modeler club planning Electric fly-in sometime during 1986 info will announced later Watch column particulars Heres wishing best guys EMF Chicago makes second all-Electric club know ofthe other ing SPARKS Houston TX other such Electric groups please let know Ill pass word along column Basic Electricity past several stallments continuing mini-series have discussed multimeters rather exten sively particular familiar moving-needle analog multimeter has examined considerable detail plans month make transition discussion digital multimeters DMMs However reviewing past columns realized 2 1-OHM 10 WATT RESISTORS IN PINT OF COLD WATER MULTIMETER ON 10 AMP RANGE ST LEADS MOOEL AIRPLANE WHEEL COLLAR 4 PLACES MAY BE REMOVED ONCE CIRCUIT CURRENT IS READ LEADS CONNECTED TOGETHER TO CLOSE CIRCUIT 15 PIECES OFMULTIMETER SET WIRE 4 LONGON 250 MILLIVOLT RANGE SHUNT NICHROMgJ WIRE BUNDLE HIGH-CURRENT SHUNT CALIBRATION CIRCUIT Calibrating shunt using two-meter test setup Drawing gives circuit details Analog muitimeter set 10-amp scale digital multlmeter DMM 200 millivolt scale Circuit current case 53 amps dictates shunt adjusted obtain 53 millivolts pint cool water gets pretty warm after few minutes run ning two 1-ohm 10-watt resistors dissipating about 80 watts Constructing high-current shunt L wiring harness can custom-made f needsbut keep connector-wIre length minimum Shunt wires cut five-foot length nichrome foam-cutting wire Wheel collars screws must brass completed shuntor sampling resistorassembly R 15 shunt wires four inches long 50 Model Aviation some things practical nature promised early have grown long overdue So month well take look simple accessory can easily make expand usefulness multimetereither analog digital although analog type will used example easily-constructed device will allow measure very large currents other wise beyond range multime ters future column well see make simple device double useful voltage ranges DMMs accessory shown nothing special external currentmeter SHUNT Youll remember multimeters have several internal select able shunt resistors allow measure current over very wide range Normally lowest current range analog multimeters about 50 microamps millionths ampere 200 microamps DMMs highest ranges usually 10 amps two amps respectively Thus multimeter very useful instrument often cant used measure motor current because latter often exceeds 10 amps special shunt shown will extend capability multimeters upward 25 amperes friends will cover nearly Electric modeling interests world shunt pictured consists small bundle short nichrome wire Continued page 130 Single-meter method calibrating shunt 1 Meter first used ammeter current recorded Meter removed recon nected voltmeter set 250 scale portion circuit used current test closed Note two-meter setup voltmeter reading 53 Voltmeter connected inner pair wheel collars shunt Using shunt R Kopekis Astro cobalt 25 turns 9 x 6 nylon prop Battery dozen 12 Ah cells routed through speed control Note shunt jumper wires inserted motor power wiring motor current can measured Muitimeter shows 155 indicating motor drawing 155 amps Shunt needed because multimeter circuits cant handle large currents Hotativ Horn Ak Acm 7J&W LAIZOs 8 GAS MOSEL Il4odL j 9Ec0O 8REA5ER 1941 BROOKLYN DODGER 56 Cabin EWEST* Retail $52 95**INTRODUCTORY PRICE* $3900 1938 Record Breaker 96 $6956 1939 Zipper 54$5356 1938 Kloud King 63 $4236 1941 Brigiclier 36 $8076 1941 Super Ouaker 76 $7276 1940 So Long 50$3036 1936 Buccaneer 94 $5996 1938 Clipper MKI 7254156 1937 Dallaire 198 $75 16 1935 Miss America 64 $7196 1941 Playboy Sr 60 $5116 1941 Playboy Jr 54 $3116 1938 Powerhouse 84 $5356 1940 Sailplane 78 $6476 1938 Trenton Terror 72 $4070 1940 Ranger 46$3196 1939 Korda Wake 44 $1916 l939Mercury 72 6 kits qualify SAM events FF & K/c feature highest quality machine cut & sanded parts Superior Competition sheet strip wood wire & window material Plans orig PP hut isodela easily convertible Sch K/C KITS Sailplanes Electric power Gas Hobby Horn SENSOAR Glider 78 5s] $1860 Midway Model GNOME K/C Hand Launch Glider$2400 Jolly Models FLINGER K/C HLG 58 Span $2400 Midway Model PAST EDDIE Aerobatic /05 Elec$19 50 Jolly Models ELECTRICUS Electric Glider 05s$3259 Leisure PLAYBOY SR 67 Gear 05 Elect $3000 Astro ASTRO SPORT 37 Direct 05 Elect $2250 Leisure WASP 37 Direct 05 Electrics $2250 Midway ULTRA MK IV 86 Geared 04 EP $3900 Midway PLYING QUAKER 016 00 854 stroke $6476 Oks/Midway DENNY JR 72 Alum Camel $6396 Oks/Midway BUZZARD BOMBSHELL 73$5196 FULL LINE OP ELECTRIC SYSTEMS t Parts AvaIl SHIPPING & HANDLING 04 Page CATALOGUE Up $000 add $159$200 PP/Sat Class $001 $2009 add $225A copy will sent $2001 $4506 add $300 freewhen requested-$4501 ts $7000 add $350 order over $7000 add $006HOBBY HORN CA Addressees add 6$ tax15173 Moran St [A] Send MO Visa/MCI#EapIPO Boa 2212 Check [allow up 30Westistinster Ca 92684 days CK clearance] 7141 8938311 COD Eaact Charges plus $158 Hdl [Cash Only]lAW Hrs [718] DAVE ROBELENS PRONTO AND SUPER PRONTO HIGH QUALITY 48 SPAN KIT FOR 09 TO 25 ENGINES FEATURES 10w Wil desIgn high wing stability excelent inverted perfomiance Gentleforfhenovice orftre expert versatle perfmarEe 46 hour npid-f ire assembly beginner Precision machine-cut 516 balsa plywond spnice Rofed full size plarw showing complete wing Step-by-step irIsucbons easy assembly Finned mate landing gear Exceptonal small field perfonnance May flown 1 3 clunnels Tested recommended aperoved PJC Mndeler Magazine Medel Aviaton -July 1984 r Johnnie Casburns Month Only Super Lucky Fly H Super Lucky Fly II 45 65 List 995Special. $8995 Little Super Lucky Fly II 35 45 LIST. $11995SPECIAL. $8495 Prices Subject Change Without Notice rwi HeW $3995 Pwiw NeW $4995 w *r m yat dsbtur net stuck d5 er order dIrect post pad delivery Virginia residents add 45/a sales tax TIDEWATER HOBBY ENTERPRISES [3 Route 1 Box 241D Lanexa vrgnia 23089 Phone 804 966-5092 2 lage Pre-finished wing ready join Wing covered 1/64 plywood Easy build/Easy fly Excellent Plans Lots Hardware Accessories Johnnie Casburn Manufacturing Co 571 5-5E E Rosedale Fort Worth TX 76112 Day 817/451-7537 t 817/572-1452 April 198651 SAILPLANE LAUNCH EQUIPMENT FOR EVERY S PORT WINCH source QUIET FLIGHT supplies hi-starts accessories electric motors & reducers batteries chutes braided nylon line tow line drums more. VISA MASTERCARD DAVEY 1Pm lE CoRPoRATmN ONE WOOD LANEMALVERNPA19355 215644-6772 SEND SASE FOR INFO Engines/Wilson Continued page 127 tion maintain constant down pressure piston Plastigage mashed out too wide clearance too close thicker shim combination shims shouldbe used Plastigage mashed out wide enough clearance too great thinner shim no shim should used clear ance correct clean off Plastigage piston head reassemble head engine gasket used backplate put place mount backplate engine Tighten screws previously described Rotate crankshaft sure crankpin and/or connecting rod rubbing backplate binding detected tighten propeller crankshaft hold ward doesnt cure problem remove frontplate Using wood block protect crankshaft tap back crankshaft center hammer sure crankshaft rear bearing fully seated forwardmost position Reassemble engine try again crankshaft bearings fully seated should no contact backplate fully-assembled engine turns feels free except case new ABC engine may bind top stroke screw fresh glow plug reassemble carburetor engine 0-ring hold down carburetor against 0-ring tight ening screws nut hold place overhauling procedures have finished engine can broken using same procedures new information article applies generally two-cycle front-intake RC engines conventional constructions Other types engines require somewhat different procedures have better way tasks please write let know Walt Wilson 3000 Persimmon Dr St Charles MO 63301 Addresses companies products mentioned GatorRC Products 3713 Pompano Dr Pensacola FL 32504 K&B Manufacturing 12152 Woodruff Ave Downey CA 90241 Marvel Oil Company Inc Port Ches ter NY 10573 Sealed Power Corp Plastigage 100 Terrace Plaza Muskegon MI 49443 RC Soaring/Pruss Continued page 49 next two years may also thank outgoing officers served two terms four years Warren Plohr LSF/334 Presi dent Larry Jolly LSF/3579 Vice-Presi dent Ken Bates LSF/604 Secretary Cal Sobczynski LSF/2487 Treasurer During 1985 seven gents names added Level V list bringing total up 46 Earle Latimer LSF/31 19 Lansing MI Terry Edmonds LSF/463 Iowa City IA Dale Harber LSF/1880 Yoder IN Charron Smith LSF/4093 Grand MI Richard Ransom LSF/4747 lonia MI Thomas Dickey LSF/3816 Gaithersburg MD Robert Schow LSF/166 Vienna VA Congratulations As column closing out word received Larry Jolly representing USA won first place South Africa flying first International F3H Cross-Country event ever held Larry flying original design Comet Details later article Larry himself Until next month good lift Dan Pruss 131 E Pennington Ln Plainfield IL 60544 RC Electrics/Kopski Continued page 51 lengths nichrome Because nichrome has relatively stable resistance temperature variation copper other conductive wire could used task temperature coefficient copper -many metals around plus % minus 5o per 100 C Thus value shunresistance would vary quite noticeably ambient internal temperature thereby rendering such metals useless purposes later wire used readily available modelers foam-cutting wire RC Modeler PO Box 487 Sierra Madre CA 91024 Cost $225 five-foot length postpaid As received wire measured little over three ohms sug gest confirm yours just sure information given di rectly applicable Ill try give sufficient detail just case can ac commodate somewhat different resist ances few words now before get how-to nittygritty Youll recall discussion last month about ohmmeter function multimeter measure resistance five-foot length nichrome wire set meter selector switch lowest resistance range short test leads together carefully zero ohms adjustment knob until meter pointer rests 0 ohms scale Its often good practice tape meter face gently fingertip sure needle has reached its true resting position connect test leads end nichrome wire Make sure leads make tight contactboth zeroing operation connection What should get 3 33 ohms 130 Model Aviation POW OM RETRIEVER HOBBY HAMMER $Q~ APPROXLENGTH7/Extra Tip INCLUDES$125 ONE STEEL AND ONE BRASS TIP Send check Money Order M &WMODELS PO Box 6627 Huntington Beach CA 92615 Add 150 Post & Hand Rae add 6% tax nave DMM results should same although latter case may have some test lead resistance subtract total reading Just short DMM leads together tightly note reading subtract test-lead resistance wire plus test leads value RCM wire significantly different three-ohm example value would expect itto read apply principles anyway Back shunt What need measure very large motor currents very-low-resistance sampling resistor known stable value sampling resistor connected series motor leads motor current flows through Being small resistance flowing current develops small voltage drop resistor Since multimeters have low voltage scale 200 250 millivolts 02 025 volts very convenient have shunt resistor value such voltage values developed across 20 25 amps flowing respectively earlier les sons can determine resistance needed applying Ohms Law R R resistance ohms V voltage volts current amps So R 20 25 0 ohm 10 milliohms Remember value Well need later calibration shunt get such very tiny resistance three ohms worth nichrome foam-cutting wire three per five feet 50V100 ohm per inch would need piece wire fifth inch long Impractical course Far practical parallel small bundle reasonable-length pieces wire will produce total resistance equal individual piece resistance divided number pieces shunt pictured made just way particular used 15 pieces four inches long Thus resistance bundle 1/15 x 4 x 005 02 ohms divided 15 133 hundredths ohm 133 milliohms clearly close tobut high side ofthe 10 milli ohms want go over size value Read have used multimeter measure resistances few ohms have no doubt discovered important make tight test lead contact shunt resistors such making 1/100 ohm tight electrical contact isnt good enough reason pic tured shunt configured fourterminal device has two current ter minals two voltage terminals outermost connections four-inchlong resistance wire bundle current contacts connecting points current under test enters leaves shunt ie circuit current flows through outermost connec tions two inner contacts tap off some voltage drop along length shunt sampling resistor inner tap points low-voltage scale multimeter will connected effect total 00133-ohm shunt slightly too long inner voltage pickoff points shorten shunt just right value 10 milliohms worth current-sampling resistance Begin assembly shunt first cutting 15 four-inch lengths wire Straighten out kinks bends easily done rolling wires individually between two pieces wood Bundle pieces slip four 5A2-in brass wheel col lars less setscrews over Position wheel collars approximately shown keeping outermost ones just inside very ends wire bundle Select four 6-32 brass machine screws grind ends smooth slightly rounded least deburred screws will hold wheel collars must compress wire bundles tightly important screw ends cut through wire pieces screws tightened very important Assemble flat washer No 6 solder lug another flat washer spring lockwasher 6-32 hex nut order loosely onto two screws thread screws two outer wheel collars Make sure wires neatly bundled collars about / inch inside bundle ends tighten screws Tighten un til wire bundle squeezed tight end holding screwdriver screw slot use small wrench pliers run nut up against washers solder lugs Its easy tempting use wire bundle handle help things alongbut dont screws must loosened collars Hold tighten screw/nut combina tiondont let screw work loose collar doesnt work just right first time start over get right Believe methis far difficult describe Install screws two inner wheel collars tighten gently collars spaced about eigth inch outer collar exact spacing inner collars will determined during calibration shunt shunt assembly can now fitted wire connections choice Mine outfitted short harness hav ing Molex connectors end positive leads connector soldered shunt solder lugs con nector negative leads straight through small Molex connectors same kind used Astro other motor/battery wiring harnesses assembly shown easily inserted Continued page 134 April 1986 131 OPS 80 Fan Enamel Needle Bearing Rod New OPS 80 warmed over 65 has needle bearing rod new 80 case larger by-pass exhaust area slide valve carb fits old 65 mounts 0PS 80 produces 455 HP 21000 RPM Order today local hobby shop S6iSPO4 Comkeio#t mftoz4 %ee PO Box 26247 e New Orleans LA 70186 S 504 242-5967 DALLAI RE SPORTSTER SPECI FICATIONS Wing Span 72 Inches Wing Chord 11 Inches Power 21-30 Engine Radio 3 Channels KIT INCLUDES Full size rolled plans Easy-to-follow instructions Machine cut sanded parts Necessary hardware 4g OLD TIMER Rt 1 Box 180 a MS 38754 Telephone 601 247-3578 PRODUCTS earn tuc flICPCflhaMfl mnnra Fm Complete Line Exhaust Systems * Tuned Pipes led Tuned Pipes * Headers uri Mufflers * Expansion Mufflers copter Ball Mufflers Specialized Exhaust Systems Un*urpassd Wfl ~hi b Pedomance RC Electrics/Kopski Continued page 131 directly motor circuit planes Thus motor current flows through assembly causes small propor tionate voltage drop appear between inner voltage-tap wheel collars voltage direct representation actual motor current Now comes fun part calibrating homemade shunt case calibrat ing means adjusting spacing between two innermost wheel collars specific voltage appears specific current flowing through shunt Calibration can done using single multimeter can done easily using two multimeters An accom panying photo illustrates two-meter method text will describe singlemeter method Note second meter connected read tap voltage can either DMM pictured another analog instrument Calibration done configuring test circuit containing shunt several amperes flowing through measuring current normal multimeter cur rent scale measuring again using low-voltage multimeter setting read shunt voltage calibration circuit simple consists two resistors some hookup wire clip leads Power circuit best sup plied car battery similar DC source can supply several amperes sever al minutes steadily used tractor bat tery field boxin warm work shop since December 27 its cold southeastern PA two resistors Radio Shack oneohm 10-watt ones Catalog No 271-13 1 wired series making twoohm 20-watt resistor power-dissipa tion rating resistors increased significantly immersing jar water pictured Fill pint jar cold water plunk resistors leaving wire leads emerging being sure resistor bodies fully covered water resistor pair connected series multimeter 12-volt battery resulting current should fall somewhere between five six amps almost 12 volts being dropped across two-ohm resistor assembly since much voltage loss wiring meter shunt means two-ohm resistors dissipating lots power Specifically P V/R P power watts V nominal battery voltage R resistance ohms So P 2/2 2 atts should now clear 20-watt resistor set immersed water attempt test resistors free air Back calibration procedure Take particular note circuit current reading get relates shunt voltage reading found next step Wait several minutes settle out reading tends drift Mine 53 amps Now remove multimeter/current meter circuitbut reclose circuit two-ohm resistor-set shunt remain series 12-volt battery Set multimeter its lowest voltage rangeusually 025 volts analog multimetersand meter test leads proper jacks ones used current measurement previously made connect meter innermost wheel collar connections shunt should get voltage reading around 50 millivoltsabout full-scale deflection Adjust spacing innermost collars until voltage reading reflects refer back calculated desired resistance shunt circuit current measured previ ously case desired shunt volt age 53 millivolts 0053 volts Snug up inner collar screws Thats shunt calibrated shunt calibration factor 10 per amp 53 amps circuit current produced 53 x 10 53 millivolts voltage shunt taps actual circuit current may different calibration fac tor will same because force way adjusting wheel collars calibration described above reas onably good some error inherent single-meter procedure because circuit current will change slightly up ward current meter removed reconfigured measure shunt voltage procedure can made somewhat betterand easierif two multimeters used series circuit constantly monitor cur rent used voltmeter watch shunt voltage inner wheel collar spacing set However error first approach small onemeter method perfectly adequate use high currents shunt will get hot can such tiny resistance / ohm get hot Recall earlier lessons suppose shunt measuring 25 amps Thus P R P power watts current amperes R resistance ohms So P 25 x 133/100 100 watts typical nite lite medium-size Christmas tree lamp rated about seven watts know hot gets dont just grab onto see second thought dontyoull burn fingers Well shunt metal somewhat larger surface area lamp has thermal mass its slower reach full temperature its hot its hot cause damage Further likely run much current long periods Shunt powerand thus shunt temperaturedrops rapidly lower current case shunt 134 Model Aviation ONLY $4995 GOITIOIIII TIllS PROF/LE0COMBAThRAT WIDE & NARROW WEDGE 15 -- 6 Capacities UNIFLOW & STIIDD Cuutrn hail huh Ingredients Fof detailed brochure50C stamps/check oni CAROLINA-TAFFINDER 8345 Delhi Road charleston Hgts SC 29418 803-563-7169 made common metal like copper aluminum shunt heat would direct ly affect shunt resistance thus voltage readingin some cases grossly Hence use vastly stable nichrome metal actual use power lost shunt power avallable motor Looking another way voltage drop shunt voltage denied motor Thus youre likely notice small drop motors rpm shunt installed motor circuit effect will pronounced systems fewer cells Shunt voltage drop smaller percentage voltage bat teries made up large numbers cells readers having DMM highest scale being two amps calibration circuit current would have set value less two amps no particular problem just substitute single 10-ohm 10-watt resistor Radio Shack 271-132 two-ohm set shown circuit current will around 12 amps shunt voltage will around 12 millivolts low value course pushing practical meter limits resulting shunt calibration may prove less accurate obtained higher calibra tion-circuit current meter ac curacy next month Nevertheless principles mentioned analog meter calibration hold case well resulting shunt DMM combination have measurement capability up 20 amps since DMMs typically have low voltage range 200 millivolts Late news SPARKS all-electric club Houston TX has announced Sec ond Spring Fun-Fly April 12-13 event will held Petrosky Ele mentary School its AMA-sanctioned AMA license required enter will offer competitive opportunity low-key basis information con tact Contest Director Eddie Thomas Houston SPARKS 1427 Ashwood Dr Sugar Land TX 77478 713/491-3375 Just mention name youll get extrafine service Thats month Hope helps whove asking meas ure large currents Any comment question may sent author SASE please Bob Kopski 25 West End Dr Lans dale PA 19446 Oh Silent Spring Flights please hurry RC Old-Timers/Mathews Continued page 53 featured series photos December 1985 column has come home roost Dick Lyons now living Camarillo CA formerly Chicago IL sent some photos took model years ago unbeknown Harry Scatena Dick following explanation photos column set bell ringing after much headscratching remembered seen model years ago contest Gary IN fact seemed remember taking some pictures time After much searching through old albums found enclosed photos young modelers attracted very unusual modelas can see crowd photos contest Gary called Little Nationals annual af fair few years before war WW II local department store sponsor attracted very large turn out attended 1939 1940 dont recall year photos taken also have photos Carl Goldberg flying early Interceptor Jim Cahill Dick Obarski among modeling notables meet have mentioned old Gary IN con test previous columns pointing out degree participation non-modeling business fraternal groups sort makes fellow wonder sort sponsorship no longer exists doesnt Also note Harry Scatena some what well-dressed contemporary flying-attire standardsbut about helper suit yet have situation Harry Scatena will see first time photos taken him pusher almost 50 years ago about matter time Dick Lyons another comment letter enjoy col umneven mostly RC Well now guess Ive out Free Flight its pure form long readers have forgotten Im Free Flighter retrieving problems became agony de-feet moved Wichita Greensburg donated over 100 Free Flight trophies local SAM Society Antique Modelers 56 chapter kept National Grand Champion trophies Among Junior firsts Rubber Scale Gas Scale A-l Nordic A-2 Nordic FAL Power B Gas C Gas plus another 40 nd-place lower trophies bird dogs grew up left rely RC solve retrieving spirit still willingbut flesh weak Im Help Help need pictures Free Flight models designed after 1942that nostalgia era detect very con siderable interest among readers Continued page 139 April1986 135 Well time around may take cake folks fascinating old pusher designed built Harry Scatena
Edition: Model Aviation - 1986/04
Page Numbers: 50, 51, 130, 131, 134, 135
RadioI[VOLT AUTO Contro TRACTOR BATTERY Electrics Bob Kopski NEW Electric club Les Adams president Adams Electronics supplier Electric need wrote tell new all-Electric club has formed northwestern Chicago IL area Elec tric Model Fliers Chicago EMF Chicago presently comprised about 20 modelers has sole interest further advancement Electricpowered flight Les tells number growing steadily AMA member interested should contact either Larry Sperling 312 303-5165 Les Adams 312 364-0660 after 600 pm CST Electric interests welcome Scale Pattern Sailplanesanything Les vice-president group himself very capable Electric modeler club planning Electric fly-in sometime during 1986 info will announced later Watch column particulars Heres wishing best guys EMF Chicago makes second all-Electric club know ofthe other ing SPARKS Houston TX other such Electric groups please let know Ill pass word along column Basic Electricity past several stallments continuing mini-series have discussed multimeters rather exten sively particular familiar moving-needle analog multimeter has examined considerable detail plans month make transition discussion digital multimeters DMMs However reviewing past columns realized 2 1-OHM 10 WATT RESISTORS IN PINT OF COLD WATER MULTIMETER ON 10 AMP RANGE ST LEADS MOOEL AIRPLANE WHEEL COLLAR 4 PLACES MAY BE REMOVED ONCE CIRCUIT CURRENT IS READ LEADS CONNECTED TOGETHER TO CLOSE CIRCUIT 15 PIECES OFMULTIMETER SET WIRE 4 LONGON 250 MILLIVOLT RANGE SHUNT NICHROMgJ WIRE BUNDLE HIGH-CURRENT SHUNT CALIBRATION CIRCUIT Calibrating shunt using two-meter test setup Drawing gives circuit details Analog muitimeter set 10-amp scale digital multlmeter DMM 200 millivolt scale Circuit current case 53 amps dictates shunt adjusted obtain 53 millivolts pint cool water gets pretty warm after few minutes run ning two 1-ohm 10-watt resistors dissipating about 80 watts Constructing high-current shunt L wiring harness can custom-made f needsbut keep connector-wIre length minimum Shunt wires cut five-foot length nichrome foam-cutting wire Wheel collars screws must brass completed shuntor sampling resistorassembly R 15 shunt wires four inches long 50 Model Aviation some things practical nature promised early have grown long overdue So month well take look simple accessory can easily make expand usefulness multimetereither analog digital although analog type will used example easily-constructed device will allow measure very large currents other wise beyond range multime ters future column well see make simple device double useful voltage ranges DMMs accessory shown nothing special external currentmeter SHUNT Youll remember multimeters have several internal select able shunt resistors allow measure current over very wide range Normally lowest current range analog multimeters about 50 microamps millionths ampere 200 microamps DMMs highest ranges usually 10 amps two amps respectively Thus multimeter very useful instrument often cant used measure motor current because latter often exceeds 10 amps special shunt shown will extend capability multimeters upward 25 amperes friends will cover nearly Electric modeling interests world shunt pictured consists small bundle short nichrome wire Continued page 130 Single-meter method calibrating shunt 1 Meter first used ammeter current recorded Meter removed recon nected voltmeter set 250 scale portion circuit used current test closed Note two-meter setup voltmeter reading 53 Voltmeter connected inner pair wheel collars shunt Using shunt R Kopekis Astro cobalt 25 turns 9 x 6 nylon prop Battery dozen 12 Ah cells routed through speed control Note shunt jumper wires inserted motor power wiring motor current can measured Muitimeter shows 155 indicating motor drawing 155 amps Shunt needed because multimeter circuits cant handle large currents Hotativ Horn Ak Acm 7J&W LAIZOs 8 GAS MOSEL Il4odL j 9Ec0O 8REA5ER 1941 BROOKLYN DODGER 56 Cabin EWEST* Retail $52 95**INTRODUCTORY PRICE* $3900 1938 Record Breaker 96 $6956 1939 Zipper 54$5356 1938 Kloud King 63 $4236 1941 Brigiclier 36 $8076 1941 Super Ouaker 76 $7276 1940 So Long 50$3036 1936 Buccaneer 94 $5996 1938 Clipper MKI 7254156 1937 Dallaire 198 $75 16 1935 Miss America 64 $7196 1941 Playboy Sr 60 $5116 1941 Playboy Jr 54 $3116 1938 Powerhouse 84 $5356 1940 Sailplane 78 $6476 1938 Trenton Terror 72 $4070 1940 Ranger 46$3196 1939 Korda Wake 44 $1916 l939Mercury 72 6 kits qualify SAM events FF & K/c feature highest quality machine cut & sanded parts Superior Competition sheet strip wood wire & window material Plans orig PP hut isodela easily convertible Sch K/C KITS Sailplanes Electric power Gas Hobby Horn SENSOAR Glider 78 5s] $1860 Midway Model GNOME K/C Hand Launch Glider$2400 Jolly Models FLINGER K/C HLG 58 Span $2400 Midway Model PAST EDDIE Aerobatic /05 Elec$19 50 Jolly Models ELECTRICUS Electric Glider 05s$3259 Leisure PLAYBOY SR 67 Gear 05 Elect $3000 Astro ASTRO SPORT 37 Direct 05 Elect $2250 Leisure WASP 37 Direct 05 Electrics $2250 Midway ULTRA MK IV 86 Geared 04 EP $3900 Midway PLYING QUAKER 016 00 854 stroke $6476 Oks/Midway DENNY JR 72 Alum Camel $6396 Oks/Midway BUZZARD BOMBSHELL 73$5196 FULL LINE OP ELECTRIC SYSTEMS t Parts AvaIl SHIPPING & HANDLING 04 Page CATALOGUE Up $000 add $159$200 PP/Sat Class $001 $2009 add $225A copy will sent $2001 $4506 add $300 freewhen requested-$4501 ts $7000 add $350 order over $7000 add $006HOBBY HORN CA Addressees add 6$ tax15173 Moran St [A] Send MO Visa/MCI#EapIPO Boa 2212 Check [allow up 30Westistinster Ca 92684 days CK clearance] 7141 8938311 COD Eaact Charges plus $158 Hdl [Cash Only]lAW Hrs [718] DAVE ROBELENS PRONTO AND SUPER PRONTO HIGH QUALITY 48 SPAN KIT FOR 09 TO 25 ENGINES FEATURES 10w Wil desIgn high wing stability excelent inverted perfomiance Gentleforfhenovice orftre expert versatle perfmarEe 46 hour npid-f ire assembly beginner Precision machine-cut 516 balsa plywond spnice Rofed full size plarw showing complete wing Step-by-step irIsucbons easy assembly Finned mate landing gear Exceptonal small field perfonnance May flown 1 3 clunnels Tested recommended aperoved PJC Mndeler Magazine Medel Aviaton -July 1984 r Johnnie Casburns Month Only Super Lucky Fly H Super Lucky Fly II 45 65 List 995Special. $8995 Little Super Lucky Fly II 35 45 LIST. $11995SPECIAL. $8495 Prices Subject Change Without Notice rwi HeW $3995 Pwiw NeW $4995 w *r m yat dsbtur net stuck d5 er order dIrect post pad delivery Virginia residents add 45/a sales tax TIDEWATER HOBBY ENTERPRISES [3 Route 1 Box 241D Lanexa vrgnia 23089 Phone 804 966-5092 2 lage Pre-finished wing ready join Wing covered 1/64 plywood Easy build/Easy fly Excellent Plans Lots Hardware Accessories Johnnie Casburn Manufacturing Co 571 5-5E E Rosedale Fort Worth TX 76112 Day 817/451-7537 t 817/572-1452 April 198651 SAILPLANE LAUNCH EQUIPMENT FOR EVERY S PORT WINCH source QUIET FLIGHT supplies hi-starts accessories electric motors & reducers batteries chutes braided nylon line tow line drums more. VISA MASTERCARD DAVEY 1Pm lE CoRPoRATmN ONE WOOD LANEMALVERNPA19355 215644-6772 SEND SASE FOR INFO Engines/Wilson Continued page 127 tion maintain constant down pressure piston Plastigage mashed out too wide clearance too close thicker shim combination shims shouldbe used Plastigage mashed out wide enough clearance too great thinner shim no shim should used clear ance correct clean off Plastigage piston head reassemble head engine gasket used backplate put place mount backplate engine Tighten screws previously described Rotate crankshaft sure crankpin and/or connecting rod rubbing backplate binding detected tighten propeller crankshaft hold ward doesnt cure problem remove frontplate Using wood block protect crankshaft tap back crankshaft center hammer sure crankshaft rear bearing fully seated forwardmost position Reassemble engine try again crankshaft bearings fully seated should no contact backplate fully-assembled engine turns feels free except case new ABC engine may bind top stroke screw fresh glow plug reassemble carburetor engine 0-ring hold down carburetor against 0-ring tight ening screws nut hold place overhauling procedures have finished engine can broken using same procedures new information article applies generally two-cycle front-intake RC engines conventional constructions Other types engines require somewhat different procedures have better way tasks please write let know Walt Wilson 3000 Persimmon Dr St Charles MO 63301 Addresses companies products mentioned GatorRC Products 3713 Pompano Dr Pensacola FL 32504 K&B Manufacturing 12152 Woodruff Ave Downey CA 90241 Marvel Oil Company Inc Port Ches ter NY 10573 Sealed Power Corp Plastigage 100 Terrace Plaza Muskegon MI 49443 RC Soaring/Pruss Continued page 49 next two years may also thank outgoing officers served two terms four years Warren Plohr LSF/334 Presi dent Larry Jolly LSF/3579 Vice-Presi dent Ken Bates LSF/604 Secretary Cal Sobczynski LSF/2487 Treasurer During 1985 seven gents names added Level V list bringing total up 46 Earle Latimer LSF/31 19 Lansing MI Terry Edmonds LSF/463 Iowa City IA Dale Harber LSF/1880 Yoder IN Charron Smith LSF/4093 Grand MI Richard Ransom LSF/4747 lonia MI Thomas Dickey LSF/3816 Gaithersburg MD Robert Schow LSF/166 Vienna VA Congratulations As column closing out word received Larry Jolly representing USA won first place South Africa flying first International F3H Cross-Country event ever held Larry flying original design Comet Details later article Larry himself Until next month good lift Dan Pruss 131 E Pennington Ln Plainfield IL 60544 RC Electrics/Kopski Continued page 51 lengths nichrome Because nichrome has relatively stable resistance temperature variation copper other conductive wire could used task temperature coefficient copper -many metals around plus % minus 5o per 100 C Thus value shunresistance would vary quite noticeably ambient internal temperature thereby rendering such metals useless purposes later wire used readily available modelers foam-cutting wire RC Modeler PO Box 487 Sierra Madre CA 91024 Cost $225 five-foot length postpaid As received wire measured little over three ohms sug gest confirm yours just sure information given di rectly applicable Ill try give sufficient detail just case can ac commodate somewhat different resist ances few words now before get how-to nittygritty Youll recall discussion last month about ohmmeter function multimeter measure resistance five-foot length nichrome wire set meter selector switch lowest resistance range short test leads together carefully zero ohms adjustment knob until meter pointer rests 0 ohms scale Its often good practice tape meter face gently fingertip sure needle has reached its true resting position connect test leads end nichrome wire Make sure leads make tight contactboth zeroing operation connection What should get 3 33 ohms 130 Model Aviation POW OM RETRIEVER HOBBY HAMMER $Q~ APPROXLENGTH7/Extra Tip INCLUDES$125 ONE STEEL AND ONE BRASS TIP Send check Money Order M &WMODELS PO Box 6627 Huntington Beach CA 92615 Add 150 Post & Hand Rae add 6% tax nave DMM results should same although latter case may have some test lead resistance subtract total reading Just short DMM leads together tightly note reading subtract test-lead resistance wire plus test leads value RCM wire significantly different three-ohm example value would expect itto read apply principles anyway Back shunt What need measure very large motor currents very-low-resistance sampling resistor known stable value sampling resistor connected series motor leads motor current flows through Being small resistance flowing current develops small voltage drop resistor Since multimeters have low voltage scale 200 250 millivolts 02 025 volts very convenient have shunt resistor value such voltage values developed across 20 25 amps flowing respectively earlier les sons can determine resistance needed applying Ohms Law R R resistance ohms V voltage volts current amps So R 20 25 0 ohm 10 milliohms Remember value Well need later calibration shunt get such very tiny resistance three ohms worth nichrome foam-cutting wire three per five feet 50V100 ohm per inch would need piece wire fifth inch long Impractical course Far practical parallel small bundle reasonable-length pieces wire will produce total resistance equal individual piece resistance divided number pieces shunt pictured made just way particular used 15 pieces four inches long Thus resistance bundle 1/15 x 4 x 005 02 ohms divided 15 133 hundredths ohm 133 milliohms clearly close tobut high side ofthe 10 milli ohms want go over size value Read have used multimeter measure resistances few ohms have no doubt discovered important make tight test lead contact shunt resistors such making 1/100 ohm tight electrical contact isnt good enough reason pic tured shunt configured fourterminal device has two current ter minals two voltage terminals outermost connections four-inchlong resistance wire bundle current contacts connecting points current under test enters leaves shunt ie circuit current flows through outermost connec tions two inner contacts tap off some voltage drop along length shunt sampling resistor inner tap points low-voltage scale multimeter will connected effect total 00133-ohm shunt slightly too long inner voltage pickoff points shorten shunt just right value 10 milliohms worth current-sampling resistance Begin assembly shunt first cutting 15 four-inch lengths wire Straighten out kinks bends easily done rolling wires individually between two pieces wood Bundle pieces slip four 5A2-in brass wheel col lars less setscrews over Position wheel collars approximately shown keeping outermost ones just inside very ends wire bundle Select four 6-32 brass machine screws grind ends smooth slightly rounded least deburred screws will hold wheel collars must compress wire bundles tightly important screw ends cut through wire pieces screws tightened very important Assemble flat washer No 6 solder lug another flat washer spring lockwasher 6-32 hex nut order loosely onto two screws thread screws two outer wheel collars Make sure wires neatly bundled collars about / inch inside bundle ends tighten screws Tighten un til wire bundle squeezed tight end holding screwdriver screw slot use small wrench pliers run nut up against washers solder lugs Its easy tempting use wire bundle handle help things alongbut dont screws must loosened collars Hold tighten screw/nut combina tiondont let screw work loose collar doesnt work just right first time start over get right Believe methis far difficult describe Install screws two inner wheel collars tighten gently collars spaced about eigth inch outer collar exact spacing inner collars will determined during calibration shunt shunt assembly can now fitted wire connections choice Mine outfitted short harness hav ing Molex connectors end positive leads connector soldered shunt solder lugs con nector negative leads straight through small Molex connectors same kind used Astro other motor/battery wiring harnesses assembly shown easily inserted Continued page 134 April 1986 131 OPS 80 Fan Enamel Needle Bearing Rod New OPS 80 warmed over 65 has needle bearing rod new 80 case larger by-pass exhaust area slide valve carb fits old 65 mounts 0PS 80 produces 455 HP 21000 RPM Order today local hobby shop S6iSPO4 Comkeio#t mftoz4 %ee PO Box 26247 e New Orleans LA 70186 S 504 242-5967 DALLAI RE SPORTSTER SPECI FICATIONS Wing Span 72 Inches Wing Chord 11 Inches Power 21-30 Engine Radio 3 Channels KIT INCLUDES Full size rolled plans Easy-to-follow instructions Machine cut sanded parts Necessary hardware 4g OLD TIMER Rt 1 Box 180 a MS 38754 Telephone 601 247-3578 PRODUCTS earn tuc flICPCflhaMfl mnnra Fm Complete Line Exhaust Systems * Tuned Pipes led Tuned Pipes * Headers uri Mufflers * Expansion Mufflers copter Ball Mufflers Specialized Exhaust Systems Un*urpassd Wfl ~hi b Pedomance RC Electrics/Kopski Continued page 131 directly motor circuit planes Thus motor current flows through assembly causes small propor tionate voltage drop appear between inner voltage-tap wheel collars voltage direct representation actual motor current Now comes fun part calibrating homemade shunt case calibrat ing means adjusting spacing between two innermost wheel collars specific voltage appears specific current flowing through shunt Calibration can done using single multimeter can done easily using two multimeters An accom panying photo illustrates two-meter method text will describe singlemeter method Note second meter connected read tap voltage can either DMM pictured another analog instrument Calibration done configuring test circuit containing shunt several amperes flowing through measuring current normal multimeter cur rent scale measuring again using low-voltage multimeter setting read shunt voltage calibration circuit simple consists two resistors some hookup wire clip leads Power circuit best sup plied car battery similar DC source can supply several amperes sever al minutes steadily used tractor bat tery field boxin warm work shop since December 27 its cold southeastern PA two resistors Radio Shack oneohm 10-watt ones Catalog No 271-13 1 wired series making twoohm 20-watt resistor power-dissipa tion rating resistors increased significantly immersing jar water pictured Fill pint jar cold water plunk resistors leaving wire leads emerging being sure resistor bodies fully covered water resistor pair connected series multimeter 12-volt battery resulting current should fall somewhere between five six amps almost 12 volts being dropped across two-ohm resistor assembly since much voltage loss wiring meter shunt means two-ohm resistors dissipating lots power Specifically P V/R P power watts V nominal battery voltage R resistance ohms So P 2/2 2 atts should now clear 20-watt resistor set immersed water attempt test resistors free air Back calibration procedure Take particular note circuit current reading get relates shunt voltage reading found next step Wait several minutes settle out reading tends drift Mine 53 amps Now remove multimeter/current meter circuitbut reclose circuit two-ohm resistor-set shunt remain series 12-volt battery Set multimeter its lowest voltage rangeusually 025 volts analog multimetersand meter test leads proper jacks ones used current measurement previously made connect meter innermost wheel collar connections shunt should get voltage reading around 50 millivoltsabout full-scale deflection Adjust spacing innermost collars until voltage reading reflects refer back calculated desired resistance shunt circuit current measured previ ously case desired shunt volt age 53 millivolts 0053 volts Snug up inner collar screws Thats shunt calibrated shunt calibration factor 10 per amp 53 amps circuit current produced 53 x 10 53 millivolts voltage shunt taps actual circuit current may different calibration fac tor will same because force way adjusting wheel collars calibration described above reas onably good some error inherent single-meter procedure because circuit current will change slightly up ward current meter removed reconfigured measure shunt voltage procedure can made somewhat betterand easierif two multimeters used series circuit constantly monitor cur rent used voltmeter watch shunt voltage inner wheel collar spacing set However error first approach small onemeter method perfectly adequate use high currents shunt will get hot can such tiny resistance / ohm get hot Recall earlier lessons suppose shunt measuring 25 amps Thus P R P power watts current amperes R resistance ohms So P 25 x 133/100 100 watts typical nite lite medium-size Christmas tree lamp rated about seven watts know hot gets dont just grab onto see second thought dontyoull burn fingers Well shunt metal somewhat larger surface area lamp has thermal mass its slower reach full temperature its hot its hot cause damage Further likely run much current long periods Shunt powerand thus shunt temperaturedrops rapidly lower current case shunt 134 Model Aviation ONLY $4995 GOITIOIIII TIllS PROF/LE0COMBAThRAT WIDE & NARROW WEDGE 15 -- 6 Capacities UNIFLOW & STIIDD Cuutrn hail huh Ingredients Fof detailed brochure50C stamps/check oni CAROLINA-TAFFINDER 8345 Delhi Road charleston Hgts SC 29418 803-563-7169 made common metal like copper aluminum shunt heat would direct ly affect shunt resistance thus voltage readingin some cases grossly Hence use vastly stable nichrome metal actual use power lost shunt power avallable motor Looking another way voltage drop shunt voltage denied motor Thus youre likely notice small drop motors rpm shunt installed motor circuit effect will pronounced systems fewer cells Shunt voltage drop smaller percentage voltage bat teries made up large numbers cells readers having DMM highest scale being two amps calibration circuit current would have set value less two amps no particular problem just substitute single 10-ohm 10-watt resistor Radio Shack 271-132 two-ohm set shown circuit current will around 12 amps shunt voltage will around 12 millivolts low value course pushing practical meter limits resulting shunt calibration may prove less accurate obtained higher calibra tion-circuit current meter ac curacy next month Nevertheless principles mentioned analog meter calibration hold case well resulting shunt DMM combination have measurement capability up 20 amps since DMMs typically have low voltage range 200 millivolts Late news SPARKS all-electric club Houston TX has announced Sec ond Spring Fun-Fly April 12-13 event will held Petrosky Ele mentary School its AMA-sanctioned AMA license required enter will offer competitive opportunity low-key basis information con tact Contest Director Eddie Thomas Houston SPARKS 1427 Ashwood Dr Sugar Land TX 77478 713/491-3375 Just mention name youll get extrafine service Thats month Hope helps whove asking meas ure large currents Any comment question may sent author SASE please Bob Kopski 25 West End Dr Lans dale PA 19446 Oh Silent Spring Flights please hurry RC Old-Timers/Mathews Continued page 53 featured series photos December 1985 column has come home roost Dick Lyons now living Camarillo CA formerly Chicago IL sent some photos took model years ago unbeknown Harry Scatena Dick following explanation photos column set bell ringing after much headscratching remembered seen model years ago contest Gary IN fact seemed remember taking some pictures time After much searching through old albums found enclosed photos young modelers attracted very unusual modelas can see crowd photos contest Gary called Little Nationals annual af fair few years before war WW II local department store sponsor attracted very large turn out attended 1939 1940 dont recall year photos taken also have photos Carl Goldberg flying early Interceptor Jim Cahill Dick Obarski among modeling notables meet have mentioned old Gary IN con test previous columns pointing out degree participation non-modeling business fraternal groups sort makes fellow wonder sort sponsorship no longer exists doesnt Also note Harry Scatena some what well-dressed contemporary flying-attire standardsbut about helper suit yet have situation Harry Scatena will see first time photos taken him pusher almost 50 years ago about matter time Dick Lyons another comment letter enjoy col umneven mostly RC Well now guess Ive out Free Flight its pure form long readers have forgotten Im Free Flighter retrieving problems became agony de-feet moved Wichita Greensburg donated over 100 Free Flight trophies local SAM Society Antique Modelers 56 chapter kept National Grand Champion trophies Among Junior firsts Rubber Scale Gas Scale A-l Nordic A-2 Nordic FAL Power B Gas C Gas plus another 40 nd-place lower trophies bird dogs grew up left rely RC solve retrieving spirit still willingbut flesh weak Im Help Help need pictures Free Flight models designed after 1942that nostalgia era detect very con siderable interest among readers Continued page 139 April1986 135 Well time around may take cake folks fascinating old pusher designed built Harry Scatena
Edition: Model Aviation - 1986/04
Page Numbers: 50, 51, 130, 131, 134, 135
RadioI[VOLT AUTO Contro TRACTOR BATTERY Electrics Bob Kopski NEW Electric club Les Adams president Adams Electronics supplier Electric need wrote tell new all-Electric club has formed northwestern Chicago IL area Elec tric Model Fliers Chicago EMF Chicago presently comprised about 20 modelers has sole interest further advancement Electricpowered flight Les tells number growing steadily AMA member interested should contact either Larry Sperling 312 303-5165 Les Adams 312 364-0660 after 600 pm CST Electric interests welcome Scale Pattern Sailplanesanything Les vice-president group himself very capable Electric modeler club planning Electric fly-in sometime during 1986 info will announced later Watch column particulars Heres wishing best guys EMF Chicago makes second all-Electric club know ofthe other ing SPARKS Houston TX other such Electric groups please let know Ill pass word along column Basic Electricity past several stallments continuing mini-series have discussed multimeters rather exten sively particular familiar moving-needle analog multimeter has examined considerable detail plans month make transition discussion digital multimeters DMMs However reviewing past columns realized 2 1-OHM 10 WATT RESISTORS IN PINT OF COLD WATER MULTIMETER ON 10 AMP RANGE ST LEADS MOOEL AIRPLANE WHEEL COLLAR 4 PLACES MAY BE REMOVED ONCE CIRCUIT CURRENT IS READ LEADS CONNECTED TOGETHER TO CLOSE CIRCUIT 15 PIECES OFMULTIMETER SET WIRE 4 LONGON 250 MILLIVOLT RANGE SHUNT NICHROMgJ WIRE BUNDLE HIGH-CURRENT SHUNT CALIBRATION CIRCUIT Calibrating shunt using two-meter test setup Drawing gives circuit details Analog muitimeter set 10-amp scale digital multlmeter DMM 200 millivolt scale Circuit current case 53 amps dictates shunt adjusted obtain 53 millivolts pint cool water gets pretty warm after few minutes run ning two 1-ohm 10-watt resistors dissipating about 80 watts Constructing high-current shunt L wiring harness can custom-made f needsbut keep connector-wIre length minimum Shunt wires cut five-foot length nichrome foam-cutting wire Wheel collars screws must brass completed shuntor sampling resistorassembly R 15 shunt wires four inches long 50 Model Aviation some things practical nature promised early have grown long overdue So month well take look simple accessory can easily make expand usefulness multimetereither analog digital although analog type will used example easily-constructed device will allow measure very large currents other wise beyond range multime ters future column well see make simple device double useful voltage ranges DMMs accessory shown nothing special external currentmeter SHUNT Youll remember multimeters have several internal select able shunt resistors allow measure current over very wide range Normally lowest current range analog multimeters about 50 microamps millionths ampere 200 microamps DMMs highest ranges usually 10 amps two amps respectively Thus multimeter very useful instrument often cant used measure motor current because latter often exceeds 10 amps special shunt shown will extend capability multimeters upward 25 amperes friends will cover nearly Electric modeling interests world shunt pictured consists small bundle short nichrome wire Continued page 130 Single-meter method calibrating shunt 1 Meter first used ammeter current recorded Meter removed recon nected voltmeter set 250 scale portion circuit used current test closed Note two-meter setup voltmeter reading 53 Voltmeter connected inner pair wheel collars shunt Using shunt R Kopekis Astro cobalt 25 turns 9 x 6 nylon prop Battery dozen 12 Ah cells routed through speed control Note shunt jumper wires inserted motor power wiring motor current can measured Muitimeter shows 155 indicating motor drawing 155 amps Shunt needed because multimeter circuits cant handle large currents Hotativ Horn Ak Acm 7J&W LAIZOs 8 GAS MOSEL Il4odL j 9Ec0O 8REA5ER 1941 BROOKLYN DODGER 56 Cabin EWEST* Retail $52 95**INTRODUCTORY PRICE* $3900 1938 Record Breaker 96 $6956 1939 Zipper 54$5356 1938 Kloud King 63 $4236 1941 Brigiclier 36 $8076 1941 Super Ouaker 76 $7276 1940 So Long 50$3036 1936 Buccaneer 94 $5996 1938 Clipper MKI 7254156 1937 Dallaire 198 $75 16 1935 Miss America 64 $7196 1941 Playboy Sr 60 $5116 1941 Playboy Jr 54 $3116 1938 Powerhouse 84 $5356 1940 Sailplane 78 $6476 1938 Trenton Terror 72 $4070 1940 Ranger 46$3196 1939 Korda Wake 44 $1916 l939Mercury 72 6 kits qualify SAM events FF & K/c feature highest quality machine cut & sanded parts Superior Competition sheet strip wood wire & window material Plans orig PP hut isodela easily convertible Sch K/C KITS Sailplanes Electric power Gas Hobby Horn SENSOAR Glider 78 5s] $1860 Midway Model GNOME K/C Hand Launch Glider$2400 Jolly Models FLINGER K/C HLG 58 Span $2400 Midway Model PAST EDDIE Aerobatic /05 Elec$19 50 Jolly Models ELECTRICUS Electric Glider 05s$3259 Leisure PLAYBOY SR 67 Gear 05 Elect $3000 Astro ASTRO SPORT 37 Direct 05 Elect $2250 Leisure WASP 37 Direct 05 Electrics $2250 Midway ULTRA MK IV 86 Geared 04 EP $3900 Midway PLYING QUAKER 016 00 854 stroke $6476 Oks/Midway DENNY JR 72 Alum Camel $6396 Oks/Midway BUZZARD BOMBSHELL 73$5196 FULL LINE OP ELECTRIC SYSTEMS t Parts AvaIl SHIPPING & HANDLING 04 Page CATALOGUE Up $000 add $159$200 PP/Sat Class $001 $2009 add $225A copy will sent $2001 $4506 add $300 freewhen requested-$4501 ts $7000 add $350 order over $7000 add $006HOBBY HORN CA Addressees add 6$ tax15173 Moran St [A] Send MO Visa/MCI#EapIPO Boa 2212 Check [allow up 30Westistinster Ca 92684 days CK clearance] 7141 8938311 COD Eaact Charges plus $158 Hdl [Cash Only]lAW Hrs [718] DAVE ROBELENS PRONTO AND SUPER PRONTO HIGH QUALITY 48 SPAN KIT FOR 09 TO 25 ENGINES FEATURES 10w Wil desIgn high wing stability excelent inverted perfomiance Gentleforfhenovice orftre expert versatle perfmarEe 46 hour npid-f ire assembly beginner Precision machine-cut 516 balsa plywond spnice Rofed full size plarw showing complete wing Step-by-step irIsucbons easy assembly Finned mate landing gear Exceptonal small field perfonnance May flown 1 3 clunnels Tested recommended aperoved PJC Mndeler Magazine Medel Aviaton -July 1984 r Johnnie Casburns Month Only Super Lucky Fly H Super Lucky Fly II 45 65 List 995Special. $8995 Little Super Lucky Fly II 35 45 LIST. $11995SPECIAL. $8495 Prices Subject Change Without Notice rwi HeW $3995 Pwiw NeW $4995 w *r m yat dsbtur net stuck d5 er order dIrect post pad delivery Virginia residents add 45/a sales tax TIDEWATER HOBBY ENTERPRISES [3 Route 1 Box 241D Lanexa vrgnia 23089 Phone 804 966-5092 2 lage Pre-finished wing ready join Wing covered 1/64 plywood Easy build/Easy fly Excellent Plans Lots Hardware Accessories Johnnie Casburn Manufacturing Co 571 5-5E E Rosedale Fort Worth TX 76112 Day 817/451-7537 t 817/572-1452 April 198651 SAILPLANE LAUNCH EQUIPMENT FOR EVERY S PORT WINCH source QUIET FLIGHT supplies hi-starts accessories electric motors & reducers batteries chutes braided nylon line tow line drums more. VISA MASTERCARD DAVEY 1Pm lE CoRPoRATmN ONE WOOD LANEMALVERNPA19355 215644-6772 SEND SASE FOR INFO Engines/Wilson Continued page 127 tion maintain constant down pressure piston Plastigage mashed out too wide clearance too close thicker shim combination shims shouldbe used Plastigage mashed out wide enough clearance too great thinner shim no shim should used clear ance correct clean off Plastigage piston head reassemble head engine gasket used backplate put place mount backplate engine Tighten screws previously described Rotate crankshaft sure crankpin and/or connecting rod rubbing backplate binding detected tighten propeller crankshaft hold ward doesnt cure problem remove frontplate Using wood block protect crankshaft tap back crankshaft center hammer sure crankshaft rear bearing fully seated forwardmost position Reassemble engine try again crankshaft bearings fully seated should no contact backplate fully-assembled engine turns feels free except case new ABC engine may bind top stroke screw fresh glow plug reassemble carburetor engine 0-ring hold down carburetor against 0-ring tight ening screws nut hold place overhauling procedures have finished engine can broken using same procedures new information article applies generally two-cycle front-intake RC engines conventional constructions Other types engines require somewhat different procedures have better way tasks please write let know Walt Wilson 3000 Persimmon Dr St Charles MO 63301 Addresses companies products mentioned GatorRC Products 3713 Pompano Dr Pensacola FL 32504 K&B Manufacturing 12152 Woodruff Ave Downey CA 90241 Marvel Oil Company Inc Port Ches ter NY 10573 Sealed Power Corp Plastigage 100 Terrace Plaza Muskegon MI 49443 RC Soaring/Pruss Continued page 49 next two years may also thank outgoing officers served two terms four years Warren Plohr LSF/334 Presi dent Larry Jolly LSF/3579 Vice-Presi dent Ken Bates LSF/604 Secretary Cal Sobczynski LSF/2487 Treasurer During 1985 seven gents names added Level V list bringing total up 46 Earle Latimer LSF/31 19 Lansing MI Terry Edmonds LSF/463 Iowa City IA Dale Harber LSF/1880 Yoder IN Charron Smith LSF/4093 Grand MI Richard Ransom LSF/4747 lonia MI Thomas Dickey LSF/3816 Gaithersburg MD Robert Schow LSF/166 Vienna VA Congratulations As column closing out word received Larry Jolly representing USA won first place South Africa flying first International F3H Cross-Country event ever held Larry flying original design Comet Details later article Larry himself Until next month good lift Dan Pruss 131 E Pennington Ln Plainfield IL 60544 RC Electrics/Kopski Continued page 51 lengths nichrome Because nichrome has relatively stable resistance temperature variation copper other conductive wire could used task temperature coefficient copper -many metals around plus % minus 5o per 100 C Thus value shunresistance would vary quite noticeably ambient internal temperature thereby rendering such metals useless purposes later wire used readily available modelers foam-cutting wire RC Modeler PO Box 487 Sierra Madre CA 91024 Cost $225 five-foot length postpaid As received wire measured little over three ohms sug gest confirm yours just sure information given di rectly applicable Ill try give sufficient detail just case can ac commodate somewhat different resist ances few words now before get how-to nittygritty Youll recall discussion last month about ohmmeter function multimeter measure resistance five-foot length nichrome wire set meter selector switch lowest resistance range short test leads together carefully zero ohms adjustment knob until meter pointer rests 0 ohms scale Its often good practice tape meter face gently fingertip sure needle has reached its true resting position connect test leads end nichrome wire Make sure leads make tight contactboth zeroing operation connection What should get 3 33 ohms 130 Model Aviation POW OM RETRIEVER HOBBY HAMMER $Q~ APPROXLENGTH7/Extra Tip INCLUDES$125 ONE STEEL AND ONE BRASS TIP Send check Money Order M &WMODELS PO Box 6627 Huntington Beach CA 92615 Add 150 Post & Hand Rae add 6% tax nave DMM results should same although latter case may have some test lead resistance subtract total reading Just short DMM leads together tightly note reading subtract test-lead resistance wire plus test leads value RCM wire significantly different three-ohm example value would expect itto read apply principles anyway Back shunt What need measure very large motor currents very-low-resistance sampling resistor known stable value sampling resistor connected series motor leads motor current flows through Being small resistance flowing current develops small voltage drop resistor Since multimeters have low voltage scale 200 250 millivolts 02 025 volts very convenient have shunt resistor value such voltage values developed across 20 25 amps flowing respectively earlier les sons can determine resistance needed applying Ohms Law R R resistance ohms V voltage volts current amps So R 20 25 0 ohm 10 milliohms Remember value Well need later calibration shunt get such very tiny resistance three ohms worth nichrome foam-cutting wire three per five feet 50V100 ohm per inch would need piece wire fifth inch long Impractical course Far practical parallel small bundle reasonable-length pieces wire will produce total resistance equal individual piece resistance divided number pieces shunt pictured made just way particular used 15 pieces four inches long Thus resistance bundle 1/15 x 4 x 005 02 ohms divided 15 133 hundredths ohm 133 milliohms clearly close tobut high side ofthe 10 milli ohms want go over size value Read have used multimeter measure resistances few ohms have no doubt discovered important make tight test lead contact shunt resistors such making 1/100 ohm tight electrical contact isnt good enough reason pic tured shunt configured fourterminal device has two current ter minals two voltage terminals outermost connections four-inchlong resistance wire bundle current contacts connecting points current under test enters leaves shunt ie circuit current flows through outermost connec tions two inner contacts tap off some voltage drop along length shunt sampling resistor inner tap points low-voltage scale multimeter will connected effect total 00133-ohm shunt slightly too long inner voltage pickoff points shorten shunt just right value 10 milliohms worth current-sampling resistance Begin assembly shunt first cutting 15 four-inch lengths wire Straighten out kinks bends easily done rolling wires individually between two pieces wood Bundle pieces slip four 5A2-in brass wheel col lars less setscrews over Position wheel collars approximately shown keeping outermost ones just inside very ends wire bundle Select four 6-32 brass machine screws grind ends smooth slightly rounded least deburred screws will hold wheel collars must compress wire bundles tightly important screw ends cut through wire pieces screws tightened very important Assemble flat washer No 6 solder lug another flat washer spring lockwasher 6-32 hex nut order loosely onto two screws thread screws two outer wheel collars Make sure wires neatly bundled collars about / inch inside bundle ends tighten screws Tighten un til wire bundle squeezed tight end holding screwdriver screw slot use small wrench pliers run nut up against washers solder lugs Its easy tempting use wire bundle handle help things alongbut dont screws must loosened collars Hold tighten screw/nut combina tiondont let screw work loose collar doesnt work just right first time start over get right Believe methis far difficult describe Install screws two inner wheel collars tighten gently collars spaced about eigth inch outer collar exact spacing inner collars will determined during calibration shunt shunt assembly can now fitted wire connections choice Mine outfitted short harness hav ing Molex connectors end positive leads connector soldered shunt solder lugs con nector negative leads straight through small Molex connectors same kind used Astro other motor/battery wiring harnesses assembly shown easily inserted Continued page 134 April 1986 131 OPS 80 Fan Enamel Needle Bearing Rod New OPS 80 warmed over 65 has needle bearing rod new 80 case larger by-pass exhaust area slide valve carb fits old 65 mounts 0PS 80 produces 455 HP 21000 RPM Order today local hobby shop S6iSPO4 Comkeio#t mftoz4 %ee PO Box 26247 e New Orleans LA 70186 S 504 242-5967 DALLAI RE SPORTSTER SPECI FICATIONS Wing Span 72 Inches Wing Chord 11 Inches Power 21-30 Engine Radio 3 Channels KIT INCLUDES Full size rolled plans Easy-to-follow instructions Machine cut sanded parts Necessary hardware 4g OLD TIMER Rt 1 Box 180 a MS 38754 Telephone 601 247-3578 PRODUCTS earn tuc flICPCflhaMfl mnnra Fm Complete Line Exhaust Systems * Tuned Pipes led Tuned Pipes * Headers uri Mufflers * Expansion Mufflers copter Ball Mufflers Specialized Exhaust Systems Un*urpassd Wfl ~hi b Pedomance RC Electrics/Kopski Continued page 131 directly motor circuit planes Thus motor current flows through assembly causes small propor tionate voltage drop appear between inner voltage-tap wheel collars voltage direct representation actual motor current Now comes fun part calibrating homemade shunt case calibrat ing means adjusting spacing between two innermost wheel collars specific voltage appears specific current flowing through shunt Calibration can done using single multimeter can done easily using two multimeters An accom panying photo illustrates two-meter method text will describe singlemeter method Note second meter connected read tap voltage can either DMM pictured another analog instrument Calibration done configuring test circuit containing shunt several amperes flowing through measuring current normal multimeter cur rent scale measuring again using low-voltage multimeter setting read shunt voltage calibration circuit simple consists two resistors some hookup wire clip leads Power circuit best sup plied car battery similar DC source can supply several amperes sever al minutes steadily used tractor bat tery field boxin warm work shop since December 27 its cold southeastern PA two resistors Radio Shack oneohm 10-watt ones Catalog No 271-13 1 wired series making twoohm 20-watt resistor power-dissipa tion rating resistors increased significantly immersing jar water pictured Fill pint jar cold water plunk resistors leaving wire leads emerging being sure resistor bodies fully covered water resistor pair connected series multimeter 12-volt battery resulting current should fall somewhere between five six amps almost 12 volts being dropped across two-ohm resistor assembly since much voltage loss wiring meter shunt means two-ohm resistors dissipating lots power Specifically P V/R P power watts V nominal battery voltage R resistance ohms So P 2/2 2 atts should now clear 20-watt resistor set immersed water attempt test resistors free air Back calibration procedure Take particular note circuit current reading get relates shunt voltage reading found next step Wait several minutes settle out reading tends drift Mine 53 amps Now remove multimeter/current meter circuitbut reclose circuit two-ohm resistor-set shunt remain series 12-volt battery Set multimeter its lowest voltage rangeusually 025 volts analog multimetersand meter test leads proper jacks ones used current measurement previously made connect meter innermost wheel collar connections shunt should get voltage reading around 50 millivoltsabout full-scale deflection Adjust spacing innermost collars until voltage reading reflects refer back calculated desired resistance shunt circuit current measured previ ously case desired shunt volt age 53 millivolts 0053 volts Snug up inner collar screws Thats shunt calibrated shunt calibration factor 10 per amp 53 amps circuit current produced 53 x 10 53 millivolts voltage shunt taps actual circuit current may different calibration fac tor will same because force way adjusting wheel collars calibration described above reas onably good some error inherent single-meter procedure because circuit current will change slightly up ward current meter removed reconfigured measure shunt voltage procedure can made somewhat betterand easierif two multimeters used series circuit constantly monitor cur rent used voltmeter watch shunt voltage inner wheel collar spacing set However error first approach small onemeter method perfectly adequate use high currents shunt will get hot can such tiny resistance / ohm get hot Recall earlier lessons suppose shunt measuring 25 amps Thus P R P power watts current amperes R resistance ohms So P 25 x 133/100 100 watts typical nite lite medium-size Christmas tree lamp rated about seven watts know hot gets dont just grab onto see second thought dontyoull burn fingers Well shunt metal somewhat larger surface area lamp has thermal mass its slower reach full temperature its hot its hot cause damage Further likely run much current long periods Shunt powerand thus shunt temperaturedrops rapidly lower current case shunt 134 Model Aviation ONLY $4995 GOITIOIIII TIllS PROF/LE0COMBAThRAT WIDE & NARROW WEDGE 15 -- 6 Capacities UNIFLOW & STIIDD Cuutrn hail huh Ingredients Fof detailed brochure50C stamps/check oni CAROLINA-TAFFINDER 8345 Delhi Road charleston Hgts SC 29418 803-563-7169 made common metal like copper aluminum shunt heat would direct ly affect shunt resistance thus voltage readingin some cases grossly Hence use vastly stable nichrome metal actual use power lost shunt power avallable motor Looking another way voltage drop shunt voltage denied motor Thus youre likely notice small drop motors rpm shunt installed motor circuit effect will pronounced systems fewer cells Shunt voltage drop smaller percentage voltage bat teries made up large numbers cells readers having DMM highest scale being two amps calibration circuit current would have set value less two amps no particular problem just substitute single 10-ohm 10-watt resistor Radio Shack 271-132 two-ohm set shown circuit current will around 12 amps shunt voltage will around 12 millivolts low value course pushing practical meter limits resulting shunt calibration may prove less accurate obtained higher calibra tion-circuit current meter ac curacy next month Nevertheless principles mentioned analog meter calibration hold case well resulting shunt DMM combination have measurement capability up 20 amps since DMMs typically have low voltage range 200 millivolts Late news SPARKS all-electric club Houston TX has announced Sec ond Spring Fun-Fly April 12-13 event will held Petrosky Ele mentary School its AMA-sanctioned AMA license required enter will offer competitive opportunity low-key basis information con tact Contest Director Eddie Thomas Houston SPARKS 1427 Ashwood Dr Sugar Land TX 77478 713/491-3375 Just mention name youll get extrafine service Thats month Hope helps whove asking meas ure large currents Any comment question may sent author SASE please Bob Kopski 25 West End Dr Lans dale PA 19446 Oh Silent Spring Flights please hurry RC Old-Timers/Mathews Continued page 53 featured series photos December 1985 column has come home roost Dick Lyons now living Camarillo CA formerly Chicago IL sent some photos took model years ago unbeknown Harry Scatena Dick following explanation photos column set bell ringing after much headscratching remembered seen model years ago contest Gary IN fact seemed remember taking some pictures time After much searching through old albums found enclosed photos young modelers attracted very unusual modelas can see crowd photos contest Gary called Little Nationals annual af fair few years before war WW II local department store sponsor attracted very large turn out attended 1939 1940 dont recall year photos taken also have photos Carl Goldberg flying early Interceptor Jim Cahill Dick Obarski among modeling notables meet have mentioned old Gary IN con test previous columns pointing out degree participation non-modeling business fraternal groups sort makes fellow wonder sort sponsorship no longer exists doesnt Also note Harry Scatena some what well-dressed contemporary flying-attire standardsbut about helper suit yet have situation Harry Scatena will see first time photos taken him pusher almost 50 years ago about matter time Dick Lyons another comment letter enjoy col umneven mostly RC Well now guess Ive out Free Flight its pure form long readers have forgotten Im Free Flighter retrieving problems became agony de-feet moved Wichita Greensburg donated over 100 Free Flight trophies local SAM Society Antique Modelers 56 chapter kept National Grand Champion trophies Among Junior firsts Rubber Scale Gas Scale A-l Nordic A-2 Nordic FAL Power B Gas C Gas plus another 40 nd-place lower trophies bird dogs grew up left rely RC solve retrieving spirit still willingbut flesh weak Im Help Help need pictures Free Flight models designed after 1942that nostalgia era detect very con siderable interest among readers Continued page 139 April1986 135 Well time around may take cake folks fascinating old pusher designed built Harry Scatena
Edition: Model Aviation - 1986/04
Page Numbers: 50, 51, 130, 131, 134, 135
RadioI[VOLT AUTO Contro TRACTOR BATTERY Electrics Bob Kopski NEW Electric club Les Adams president Adams Electronics supplier Electric need wrote tell new all-Electric club has formed northwestern Chicago IL area Elec tric Model Fliers Chicago EMF Chicago presently comprised about 20 modelers has sole interest further advancement Electricpowered flight Les tells number growing steadily AMA member interested should contact either Larry Sperling 312 303-5165 Les Adams 312 364-0660 after 600 pm CST Electric interests welcome Scale Pattern Sailplanesanything Les vice-president group himself very capable Electric modeler club planning Electric fly-in sometime during 1986 info will announced later Watch column particulars Heres wishing best guys EMF Chicago makes second all-Electric club know ofthe other ing SPARKS Houston TX other such Electric groups please let know Ill pass word along column Basic Electricity past several stallments continuing mini-series have discussed multimeters rather exten sively particular familiar moving-needle analog multimeter has examined considerable detail plans month make transition discussion digital multimeters DMMs However reviewing past columns realized 2 1-OHM 10 WATT RESISTORS IN PINT OF COLD WATER MULTIMETER ON 10 AMP RANGE ST LEADS MOOEL AIRPLANE WHEEL COLLAR 4 PLACES MAY BE REMOVED ONCE CIRCUIT CURRENT IS READ LEADS CONNECTED TOGETHER TO CLOSE CIRCUIT 15 PIECES OFMULTIMETER SET WIRE 4 LONGON 250 MILLIVOLT RANGE SHUNT NICHROMgJ WIRE BUNDLE HIGH-CURRENT SHUNT CALIBRATION CIRCUIT Calibrating shunt using two-meter test setup Drawing gives circuit details Analog muitimeter set 10-amp scale digital multlmeter DMM 200 millivolt scale Circuit current case 53 amps dictates shunt adjusted obtain 53 millivolts pint cool water gets pretty warm after few minutes run ning two 1-ohm 10-watt resistors dissipating about 80 watts Constructing high-current shunt L wiring harness can custom-made f needsbut keep connector-wIre length minimum Shunt wires cut five-foot length nichrome foam-cutting wire Wheel collars screws must brass completed shuntor sampling resistorassembly R 15 shunt wires four inches long 50 Model Aviation some things practical nature promised early have grown long overdue So month well take look simple accessory can easily make expand usefulness multimetereither analog digital although analog type will used example easily-constructed device will allow measure very large currents other wise beyond range multime ters future column well see make simple device double useful voltage ranges DMMs accessory shown nothing special external currentmeter SHUNT Youll remember multimeters have several internal select able shunt resistors allow measure current over very wide range Normally lowest current range analog multimeters about 50 microamps millionths ampere 200 microamps DMMs highest ranges usually 10 amps two amps respectively Thus multimeter very useful instrument often cant used measure motor current because latter often exceeds 10 amps special shunt shown will extend capability multimeters upward 25 amperes friends will cover nearly Electric modeling interests world shunt pictured consists small bundle short nichrome wire Continued page 130 Single-meter method calibrating shunt 1 Meter first used ammeter current recorded Meter removed recon nected voltmeter set 250 scale portion circuit used current test closed Note two-meter setup voltmeter reading 53 Voltmeter connected inner pair wheel collars shunt Using shunt R Kopekis Astro cobalt 25 turns 9 x 6 nylon prop Battery dozen 12 Ah cells routed through speed control Note shunt jumper wires inserted motor power wiring motor current can measured Muitimeter shows 155 indicating motor drawing 155 amps Shunt needed because multimeter circuits cant handle large currents Hotativ Horn Ak Acm 7J&W LAIZOs 8 GAS MOSEL Il4odL j 9Ec0O 8REA5ER 1941 BROOKLYN DODGER 56 Cabin EWEST* Retail $52 95**INTRODUCTORY PRICE* $3900 1938 Record Breaker 96 $6956 1939 Zipper 54$5356 1938 Kloud King 63 $4236 1941 Brigiclier 36 $8076 1941 Super Ouaker 76 $7276 1940 So Long 50$3036 1936 Buccaneer 94 $5996 1938 Clipper MKI 7254156 1937 Dallaire 198 $75 16 1935 Miss America 64 $7196 1941 Playboy Sr 60 $5116 1941 Playboy Jr 54 $3116 1938 Powerhouse 84 $5356 1940 Sailplane 78 $6476 1938 Trenton Terror 72 $4070 1940 Ranger 46$3196 1939 Korda Wake 44 $1916 l939Mercury 72 6 kits qualify SAM events FF & K/c feature highest quality machine cut & sanded parts Superior Competition sheet strip wood wire & window material Plans orig PP hut isodela easily convertible Sch K/C KITS Sailplanes Electric power Gas Hobby Horn SENSOAR Glider 78 5s] $1860 Midway Model GNOME K/C Hand Launch Glider$2400 Jolly Models FLINGER K/C HLG 58 Span $2400 Midway Model PAST EDDIE Aerobatic /05 Elec$19 50 Jolly Models ELECTRICUS Electric Glider 05s$3259 Leisure PLAYBOY SR 67 Gear 05 Elect $3000 Astro ASTRO SPORT 37 Direct 05 Elect $2250 Leisure WASP 37 Direct 05 Electrics $2250 Midway ULTRA MK IV 86 Geared 04 EP $3900 Midway PLYING QUAKER 016 00 854 stroke $6476 Oks/Midway DENNY JR 72 Alum Camel $6396 Oks/Midway BUZZARD BOMBSHELL 73$5196 FULL LINE OP ELECTRIC SYSTEMS t Parts AvaIl SHIPPING & HANDLING 04 Page CATALOGUE Up $000 add $159$200 PP/Sat Class $001 $2009 add $225A copy will sent $2001 $4506 add $300 freewhen requested-$4501 ts $7000 add $350 order over $7000 add $006HOBBY HORN CA Addressees add 6$ tax15173 Moran St [A] Send MO Visa/MCI#EapIPO Boa 2212 Check [allow up 30Westistinster Ca 92684 days CK clearance] 7141 8938311 COD Eaact Charges plus $158 Hdl [Cash Only]lAW Hrs [718] DAVE ROBELENS PRONTO AND SUPER PRONTO HIGH QUALITY 48 SPAN KIT FOR 09 TO 25 ENGINES FEATURES 10w Wil desIgn high wing stability excelent inverted perfomiance Gentleforfhenovice orftre expert versatle perfmarEe 46 hour npid-f ire assembly beginner Precision machine-cut 516 balsa plywond spnice Rofed full size plarw showing complete wing Step-by-step irIsucbons easy assembly Finned mate landing gear Exceptonal small field perfonnance May flown 1 3 clunnels Tested recommended aperoved PJC Mndeler Magazine Medel Aviaton -July 1984 r Johnnie Casburns Month Only Super Lucky Fly H Super Lucky Fly II 45 65 List 995Special. $8995 Little Super Lucky Fly II 35 45 LIST. $11995SPECIAL. $8495 Prices Subject Change Without Notice rwi HeW $3995 Pwiw NeW $4995 w *r m yat dsbtur net stuck d5 er order dIrect post pad delivery Virginia residents add 45/a sales tax TIDEWATER HOBBY ENTERPRISES [3 Route 1 Box 241D Lanexa vrgnia 23089 Phone 804 966-5092 2 lage Pre-finished wing ready join Wing covered 1/64 plywood Easy build/Easy fly Excellent Plans Lots Hardware Accessories Johnnie Casburn Manufacturing Co 571 5-5E E Rosedale Fort Worth TX 76112 Day 817/451-7537 t 817/572-1452 April 198651 SAILPLANE LAUNCH EQUIPMENT FOR EVERY S PORT WINCH source QUIET FLIGHT supplies hi-starts accessories electric motors & reducers batteries chutes braided nylon line tow line drums more. VISA MASTERCARD DAVEY 1Pm lE CoRPoRATmN ONE WOOD LANEMALVERNPA19355 215644-6772 SEND SASE FOR INFO Engines/Wilson Continued page 127 tion maintain constant down pressure piston Plastigage mashed out too wide clearance too close thicker shim combination shims shouldbe used Plastigage mashed out wide enough clearance too great thinner shim no shim should used clear ance correct clean off Plastigage piston head reassemble head engine gasket used backplate put place mount backplate engine Tighten screws previously described Rotate crankshaft sure crankpin and/or connecting rod rubbing backplate binding detected tighten propeller crankshaft hold ward doesnt cure problem remove frontplate Using wood block protect crankshaft tap back crankshaft center hammer sure crankshaft rear bearing fully seated forwardmost position Reassemble engine try again crankshaft bearings fully seated should no contact backplate fully-assembled engine turns feels free except case new ABC engine may bind top stroke screw fresh glow plug reassemble carburetor engine 0-ring hold down carburetor against 0-ring tight ening screws nut hold place overhauling procedures have finished engine can broken using same procedures new information article applies generally two-cycle front-intake RC engines conventional constructions Other types engines require somewhat different procedures have better way tasks please write let know Walt Wilson 3000 Persimmon Dr St Charles MO 63301 Addresses companies products mentioned GatorRC Products 3713 Pompano Dr Pensacola FL 32504 K&B Manufacturing 12152 Woodruff Ave Downey CA 90241 Marvel Oil Company Inc Port Ches ter NY 10573 Sealed Power Corp Plastigage 100 Terrace Plaza Muskegon MI 49443 RC Soaring/Pruss Continued page 49 next two years may also thank outgoing officers served two terms four years Warren Plohr LSF/334 Presi dent Larry Jolly LSF/3579 Vice-Presi dent Ken Bates LSF/604 Secretary Cal Sobczynski LSF/2487 Treasurer During 1985 seven gents names added Level V list bringing total up 46 Earle Latimer LSF/31 19 Lansing MI Terry Edmonds LSF/463 Iowa City IA Dale Harber LSF/1880 Yoder IN Charron Smith LSF/4093 Grand MI Richard Ransom LSF/4747 lonia MI Thomas Dickey LSF/3816 Gaithersburg MD Robert Schow LSF/166 Vienna VA Congratulations As column closing out word received Larry Jolly representing USA won first place South Africa flying first International F3H Cross-Country event ever held Larry flying original design Comet Details later article Larry himself Until next month good lift Dan Pruss 131 E Pennington Ln Plainfield IL 60544 RC Electrics/Kopski Continued page 51 lengths nichrome Because nichrome has relatively stable resistance temperature variation copper other conductive wire could used task temperature coefficient copper -many metals around plus % minus 5o per 100 C Thus value shunresistance would vary quite noticeably ambient internal temperature thereby rendering such metals useless purposes later wire used readily available modelers foam-cutting wire RC Modeler PO Box 487 Sierra Madre CA 91024 Cost $225 five-foot length postpaid As received wire measured little over three ohms sug gest confirm yours just sure information given di rectly applicable Ill try give sufficient detail just case can ac commodate somewhat different resist ances few words now before get how-to nittygritty Youll recall discussion last month about ohmmeter function multimeter measure resistance five-foot length nichrome wire set meter selector switch lowest resistance range short test leads together carefully zero ohms adjustment knob until meter pointer rests 0 ohms scale Its often good practice tape meter face gently fingertip sure needle has reached its true resting position connect test leads end nichrome wire Make sure leads make tight contactboth zeroing operation connection What should get 3 33 ohms 130 Model Aviation POW OM RETRIEVER HOBBY HAMMER $Q~ APPROXLENGTH7/Extra Tip INCLUDES$125 ONE STEEL AND ONE BRASS TIP Send check Money Order M &WMODELS PO Box 6627 Huntington Beach CA 92615 Add 150 Post & Hand Rae add 6% tax nave DMM results should same although latter case may have some test lead resistance subtract total reading Just short DMM leads together tightly note reading subtract test-lead resistance wire plus test leads value RCM wire significantly different three-ohm example value would expect itto read apply principles anyway Back shunt What need measure very large motor currents very-low-resistance sampling resistor known stable value sampling resistor connected series motor leads motor current flows through Being small resistance flowing current develops small voltage drop resistor Since multimeters have low voltage scale 200 250 millivolts 02 025 volts very convenient have shunt resistor value such voltage values developed across 20 25 amps flowing respectively earlier les sons can determine resistance needed applying Ohms Law R R resistance ohms V voltage volts current amps So R 20 25 0 ohm 10 milliohms Remember value Well need later calibration shunt get such very tiny resistance three ohms worth nichrome foam-cutting wire three per five feet 50V100 ohm per inch would need piece wire fifth inch long Impractical course Far practical parallel small bundle reasonable-length pieces wire will produce total resistance equal individual piece resistance divided number pieces shunt pictured made just way particular used 15 pieces four inches long Thus resistance bundle 1/15 x 4 x 005 02 ohms divided 15 133 hundredths ohm 133 milliohms clearly close tobut high side ofthe 10 milli ohms want go over size value Read have used multimeter measure resistances few ohms have no doubt discovered important make tight test lead contact shunt resistors such making 1/100 ohm tight electrical contact isnt good enough reason pic tured shunt configured fourterminal device has two current ter minals two voltage terminals outermost connections four-inchlong resistance wire bundle current contacts connecting points current under test enters leaves shunt ie circuit current flows through outermost connec tions two inner contacts tap off some voltage drop along length shunt sampling resistor inner tap points low-voltage scale multimeter will connected effect total 00133-ohm shunt slightly too long inner voltage pickoff points shorten shunt just right value 10 milliohms worth current-sampling resistance Begin assembly shunt first cutting 15 four-inch lengths wire Straighten out kinks bends easily done rolling wires individually between two pieces wood Bundle pieces slip four 5A2-in brass wheel col lars less setscrews over Position wheel collars approximately shown keeping outermost ones just inside very ends wire bundle Select four 6-32 brass machine screws grind ends smooth slightly rounded least deburred screws will hold wheel collars must compress wire bundles tightly important screw ends cut through wire pieces screws tightened very important Assemble flat washer No 6 solder lug another flat washer spring lockwasher 6-32 hex nut order loosely onto two screws thread screws two outer wheel collars Make sure wires neatly bundled collars about / inch inside bundle ends tighten screws Tighten un til wire bundle squeezed tight end holding screwdriver screw slot use small wrench pliers run nut up against washers solder lugs Its easy tempting use wire bundle handle help things alongbut dont screws must loosened collars Hold tighten screw/nut combina tiondont let screw work loose collar doesnt work just right first time start over get right Believe methis far difficult describe Install screws two inner wheel collars tighten gently collars spaced about eigth inch outer collar exact spacing inner collars will determined during calibration shunt shunt assembly can now fitted wire connections choice Mine outfitted short harness hav ing Molex connectors end positive leads connector soldered shunt solder lugs con nector negative leads straight through small Molex connectors same kind used Astro other motor/battery wiring harnesses assembly shown easily inserted Continued page 134 April 1986 131 OPS 80 Fan Enamel Needle Bearing Rod New OPS 80 warmed over 65 has needle bearing rod new 80 case larger by-pass exhaust area slide valve carb fits old 65 mounts 0PS 80 produces 455 HP 21000 RPM Order today local hobby shop S6iSPO4 Comkeio#t mftoz4 %ee PO Box 26247 e New Orleans LA 70186 S 504 242-5967 DALLAI RE SPORTSTER SPECI FICATIONS Wing Span 72 Inches Wing Chord 11 Inches Power 21-30 Engine Radio 3 Channels KIT INCLUDES Full size rolled plans Easy-to-follow instructions Machine cut sanded parts Necessary hardware 4g OLD TIMER Rt 1 Box 180 a MS 38754 Telephone 601 247-3578 PRODUCTS earn tuc flICPCflhaMfl mnnra Fm Complete Line Exhaust Systems * Tuned Pipes led Tuned Pipes * Headers uri Mufflers * Expansion Mufflers copter Ball Mufflers Specialized Exhaust Systems Un*urpassd Wfl ~hi b Pedomance RC Electrics/Kopski Continued page 131 directly motor circuit planes Thus motor current flows through assembly causes small propor tionate voltage drop appear between inner voltage-tap wheel collars voltage direct representation actual motor current Now comes fun part calibrating homemade shunt case calibrat ing means adjusting spacing between two innermost wheel collars specific voltage appears specific current flowing through shunt Calibration can done using single multimeter can done easily using two multimeters An accom panying photo illustrates two-meter method text will describe singlemeter method Note second meter connected read tap voltage can either DMM pictured another analog instrument Calibration done configuring test circuit containing shunt several amperes flowing through measuring current normal multimeter cur rent scale measuring again using low-voltage multimeter setting read shunt voltage calibration circuit simple consists two resistors some hookup wire clip leads Power circuit best sup plied car battery similar DC source can supply several amperes sever al minutes steadily used tractor bat tery field boxin warm work shop since December 27 its cold southeastern PA two resistors Radio Shack oneohm 10-watt ones Catalog No 271-13 1 wired series making twoohm 20-watt resistor power-dissipa tion rating resistors increased significantly immersing jar water pictured Fill pint jar cold water plunk resistors leaving wire leads emerging being sure resistor bodies fully covered water resistor pair connected series multimeter 12-volt battery resulting current should fall somewhere between five six amps almost 12 volts being dropped across two-ohm resistor assembly since much voltage loss wiring meter shunt means two-ohm resistors dissipating lots power Specifically P V/R P power watts V nominal battery voltage R resistance ohms So P 2/2 2 atts should now clear 20-watt resistor set immersed water attempt test resistors free air Back calibration procedure Take particular note circuit current reading get relates shunt voltage reading found next step Wait several minutes settle out reading tends drift Mine 53 amps Now remove multimeter/current meter circuitbut reclose circuit two-ohm resistor-set shunt remain series 12-volt battery Set multimeter its lowest voltage rangeusually 025 volts analog multimetersand meter test leads proper jacks ones used current measurement previously made connect meter innermost wheel collar connections shunt should get voltage reading around 50 millivoltsabout full-scale deflection Adjust spacing innermost collars until voltage reading reflects refer back calculated desired resistance shunt circuit current measured previ ously case desired shunt volt age 53 millivolts 0053 volts Snug up inner collar screws Thats shunt calibrated shunt calibration factor 10 per amp 53 amps circuit current produced 53 x 10 53 millivolts voltage shunt taps actual circuit current may different calibration fac tor will same because force way adjusting wheel collars calibration described above reas onably good some error inherent single-meter procedure because circuit current will change slightly up ward current meter removed reconfigured measure shunt voltage procedure can made somewhat betterand easierif two multimeters used series circuit constantly monitor cur rent used voltmeter watch shunt voltage inner wheel collar spacing set However error first approach small onemeter method perfectly adequate use high currents shunt will get hot can such tiny resistance / ohm get hot Recall earlier lessons suppose shunt measuring 25 amps Thus P R P power watts current amperes R resistance ohms So P 25 x 133/100 100 watts typical nite lite medium-size Christmas tree lamp rated about seven watts know hot gets dont just grab onto see second thought dontyoull burn fingers Well shunt metal somewhat larger surface area lamp has thermal mass its slower reach full temperature its hot its hot cause damage Further likely run much current long periods Shunt powerand thus shunt temperaturedrops rapidly lower current case shunt 134 Model Aviation ONLY $4995 GOITIOIIII TIllS PROF/LE0COMBAThRAT WIDE & NARROW WEDGE 15 -- 6 Capacities UNIFLOW & STIIDD Cuutrn hail huh Ingredients Fof detailed brochure50C stamps/check oni CAROLINA-TAFFINDER 8345 Delhi Road charleston Hgts SC 29418 803-563-7169 made common metal like copper aluminum shunt heat would direct ly affect shunt resistance thus voltage readingin some cases grossly Hence use vastly stable nichrome metal actual use power lost shunt power avallable motor Looking another way voltage drop shunt voltage denied motor Thus youre likely notice small drop motors rpm shunt installed motor circuit effect will pronounced systems fewer cells Shunt voltage drop smaller percentage voltage bat teries made up large numbers cells readers having DMM highest scale being two amps calibration circuit current would have set value less two amps no particular problem just substitute single 10-ohm 10-watt resistor Radio Shack 271-132 two-ohm set shown circuit current will around 12 amps shunt voltage will around 12 millivolts low value course pushing practical meter limits resulting shunt calibration may prove less accurate obtained higher calibra tion-circuit current meter ac curacy next month Nevertheless principles mentioned analog meter calibration hold case well resulting shunt DMM combination have measurement capability up 20 amps since DMMs typically have low voltage range 200 millivolts Late news SPARKS all-electric club Houston TX has announced Sec ond Spring Fun-Fly April 12-13 event will held Petrosky Ele mentary School its AMA-sanctioned AMA license required enter will offer competitive opportunity low-key basis information con tact Contest Director Eddie Thomas Houston SPARKS 1427 Ashwood Dr Sugar Land TX 77478 713/491-3375 Just mention name youll get extrafine service Thats month Hope helps whove asking meas ure large currents Any comment question may sent author SASE please Bob Kopski 25 West End Dr Lans dale PA 19446 Oh Silent Spring Flights please hurry RC Old-Timers/Mathews Continued page 53 featured series photos December 1985 column has come home roost Dick Lyons now living Camarillo CA formerly Chicago IL sent some photos took model years ago unbeknown Harry Scatena Dick following explanation photos column set bell ringing after much headscratching remembered seen model years ago contest Gary IN fact seemed remember taking some pictures time After much searching through old albums found enclosed photos young modelers attracted very unusual modelas can see crowd photos contest Gary called Little Nationals annual af fair few years before war WW II local department store sponsor attracted very large turn out attended 1939 1940 dont recall year photos taken also have photos Carl Goldberg flying early Interceptor Jim Cahill Dick Obarski among modeling notables meet have mentioned old Gary IN con test previous columns pointing out degree participation non-modeling business fraternal groups sort makes fellow wonder sort sponsorship no longer exists doesnt Also note Harry Scatena some what well-dressed contemporary flying-attire standardsbut about helper suit yet have situation Harry Scatena will see first time photos taken him pusher almost 50 years ago about matter time Dick Lyons another comment letter enjoy col umneven mostly RC Well now guess Ive out Free Flight its pure form long readers have forgotten Im Free Flighter retrieving problems became agony de-feet moved Wichita Greensburg donated over 100 Free Flight trophies local SAM Society Antique Modelers 56 chapter kept National Grand Champion trophies Among Junior firsts Rubber Scale Gas Scale A-l Nordic A-2 Nordic FAL Power B Gas C Gas plus another 40 nd-place lower trophies bird dogs grew up left rely RC solve retrieving spirit still willingbut flesh weak Im Help Help need pictures Free Flight models designed after 1942that nostalgia era detect very con siderable interest among readers Continued page 139 April1986 135 Well time around may take cake folks fascinating old pusher designed built Harry Scatena