Radio Control: Electrics

a E lectrics Bob Kopski MORE ELECTRIC ACTIVITY Daniel Boone Silent Fliers meet an nual 2-Meter RC Soaring contest held Saturday Sunday September 28 29 1985 Daniel Boone Homestead near Pottstown PA mention Electric column Because year something 2-Meter Soaring going onthere Electric going too CD Jerry Zeigenfuse explained growing interest Electric among Soaring enthusiasts growing interest getting away some unpleasantness always having haul out winch systems So trial Electric event included 1985s activity Heres worked CD estab lished max eight minutes five flights Any motor run up three minutes duration allowed Flight timing began shutdownwith no motor restart allowed Over three minutes resulted zero score flight Maximum score 60 x 8 480 points per flight flight scores added total Also minute allowed get plane down after max No spot landing task used idea behind format allow lowcost power systems usedsomething would discouraged limited motor runs 30 60 seconds Saturday saw eight participants flying positively vicious wind hurricane gone up East Coast day before Sunday beautiful day another eight participants attended Saturday understand flying Sunday much better first three places respective days Satur day 1 Skip Schow 2139 points 2 Bill Meleske 2114 points 3 Woody Blan chard 1866 points Sunday 1 Bill Meleske 2400 points 2 Ken Stinson 2400 points 3 Skip Schow 2059 points few stories gentlemen participated KRC Electric Fly just week before meet did grand job too LSF Level Five Bill Meleske took Up Last Down Saturday KRC meet same plane KRC Sunday work hard against KRCer Ken Stinsons speck-in-the-sky Spectraboth gentlemen maxed five times went flyoff Kens first contest ever As can see Daniel Boone results time-polished proven skill got Bill first place Hats off Daniel Boone Silent Fliers fine first-ever Electric meet Early indications theyll again 1986 watch column info later year fourth Electric meet know East yearothers covered recent columns Im perfectly delighted see growth Electric interest can add growth trend club has up coming meetadd simple Electric event two operative word simple Dont worry about it seems like small start Concentrate start size doesnt matter sure give details about three months advance Ill tell everyone else about column major chunk model doms future belongs Electric Start make future happen Motor electrical noise Last months col 54 Model Aviation Adams Electronics speed control teatures optical coupling built-In heat sink connectors except RC system Les Adams several versions plus new heavyduty connectors wire Hobby shops Electric should have stock widget Don Siegels Organizer collects Electric wiring plus motor-control servo neat arrangement version holds S-33 servo fuse switch charging jack Mounting tape keeps plane Want Info Write Don SIegel 218 Oyster Creek Dr Sugarland TX 77478 Tell him Bob K sent Bob Ks preferred motor-noisesuppres sian scheme its done three capacitors groundin lug Shown Astro cobalt 40 t9ie end bell drilled tapped after disassembly screw hold ground lug arrow Three capacitors small arrows sol dered place between motor brush connector lug between two brush connectors Ceramic capac itors 001 01 uFd work well Try get em higher 50-volt rating LIttle sphere under middle capacitor diode protect electronic speed control umn made brief mention common sound motor power interruptions caused radio glitches busy skies 1985 KRC Electric Fly easi ly understood its realized on-board Electric power systems can cause radio static quite easily Think built-in on-board glitch maker some things can done about can greatly reduce eliminate problem First plan use electronic speed control sure its opticallycoupled type Optically-coupled means RC receiver associated cir cuitry electrically isolated part speed control circuitry thats connected Electric motor system control signals decoded receiv er connected light-generating -detecting components powercontrol components may obvious look speed control its true Speed controls opticallycoupled have solid electrical connection wiring between airborne receiver system motor/power system absolutely worst possible situation latter case static electrical noise generated motor brushes con ducted right radio system places unnecessary burden receivers ability recognize desired transmitted signal same time rejecting undesired pumped-in noise motor system Some receivers han dle better others will Continued page 144 Scenes Daniel Boone Silent Filers meet 1 BIll Mileske Baldwin NY launches modified Astro Challengeruses Astro 15 cobaltlgearedll3in Geist folding propllo Sanyo 800 mAh cells R Skip Schow Vienna VA launches Kiuge Etudeso named because Etude fuseltali 80-in gilder wing strapped flew very well Sanyo 1200 mAh pack powers Mabuchi 54olKyosho gear drive 13-in Robbe folding prop Crafts allup weight 38 oz NINTH ANNUAL Ii{i]f JANUARY 11 & 12 1986 Saturday 1OAM-6PM Sunday 1OAM-5PM SEE THE LATEST PRUDUGIS ANU VISIT WITH MAJOR MANUFACTURERS AND DISTRIBUTORS OF MODEL AIRCRAFT L ENGINES MODEL BOATS O CONTROL SYSTEMS *GIANT RAFFLE L CARS MODELING ACCESSORIES*SWAP SHOP DES WEST ADMISSION Adults -$500 under 13- $300 under 6- free adult Discount tickets worth 50 cents hobby shops within 500-mile radius Pasadena California STATIC DISPLAY COMPETITION IN MANY CATEGORIES ii iuiuiu f~~I4u 7AU 11 I~ ievI U Kl fI U 1611W February 1986 55 OVERSEAS fXHIBITORS CORD/ALLY IN VI TED INTERNATIONAL MODELER SHOW OFFICE PO Box 10127 Costa Mesa CA 92627 Ph 714 5484700 645-8830 Woody Woodman has appointed succeed Tom Acciavati Rules Coordinator Correspondence concerning RC Rules proposals should sent Woody 233 Longview Drive Bayville NJ 08721 stroker stuff likely readers growing bit weary 01 Doc four-cycle notes expense milking subject death let share some early observations new OS 20 four-cycle little gem well up expectations Im per sonally delighted First foremost much lighter previously-available small four-stroker fits Hayes AL 20 mount rather AL4O Performance slightly stronger 05 15 two-stroke less Fox l9BB Starting starter just easy larger strokers absolutely no need built-in choke havent installed Idle very low reliable though engine uses simple airbleed carb Preliminary flights seem indicate prop selection runs along lines found larger units diameter doesnt seem too critical pitch three-pound 400 sq sporttype model 9 x 5 wide-bladed prop seems slightly superior 10 x 4 Old-Timer-type model suggest 10 x 5 wide-blader starting point feelings about tachometers fuel expressed rather succinctly previ ous column taching 10500 rpm 9 x 5 Super M 10400 10 x 4 broke 10 x 5 before engine broken However suspect would read about 10000 rpm now engine sounds rich peak rpm sounds better lean bit over topso use tach already Dee B Mathews 8420 Nantucket Wichita KS 67212 suffer degree Such hard-wired noise will manifest itself glitches range-reduction motor running often shows up interruptions motor power control itselfin addition flight control glitches Often former reac tion much quicker occur lat terand makes matters worse on-off flow power motor can worsen noise situation caused first place thus increase least sustain noise-induced glitching Personally refuse use anything speed controls optically isolated However installation uses servo-activated switch instead speed control chances no metallic connection between on-board systems thing servo output arms wheels normally non-conductive plastic thats sufficient isolation job second thing can improve situation keep installations neat respect radio motor system wiring Separate two systems wiring other extent possi ble electrical noise motor system present wiringthe latter acting much like miniature transmitting antenna located close sensitive receiving system effective communi cation undesired on-board trans mitter/receiver greatly reduced small separation distances course sure-fire improvement could made eliminating brush noise altogethersomething thats readily possible Reducing noise possible accompanying photo shows very effective approach best knowledge scheme shown best possible noise-reduction method using capacitors As shown three capacitors used right near trouble spotthe motor brushes motor brush capacitively bypassed grounded single electrical contact motor housing again Basic Electricity recent columns weve talked about fundamentals voltmeter ammeter operation basic sensitive meter movementsthe parts move themselves both low-value voltmeters and/or current meters having limited stand-alone utility take useful voltage current ranges combined multiplier shunt resistors respec tively Multimeters nothing meter movement selection precision resistors arranged functions ranges available convenient box Finally emphasis placed using voltmeters measure voltage ACROSS parallel some componentsuch batteryand using ammeters measure current THROUGH componentsuch connected series motor Multimeters normally contain DC voltage current functions covered far example normally separate voltmeter ranges AC circuits such household circuits work using rectifying diodes separate multiplier resistors convert AC voltage equivalent DC voltages needed meter movement AC scales separate because marked slightly non-linearly make up non-linearity caused rectify ing circuit Ordinarily no use scales RC Electric pursuits since scales sure youre reading correct ones what ever Often AC scales color-coded help ohmmeter function multimeters often very useful tool modelers measures resistance scales 144 Model Aviation other have several installations RC Old-Timers/Mathews RC Electrics/Kopskiwere modified after first having Continued page 139Continued page 55flown stock motors results very convincingbig difference before/after in-flight glitching situation So have Ways break up noise path motor-to-receiver way reduce naturally-occurring noise itself Id surprised sug gestions didnt make very noticeable change better Electric fly ing enjoyment responding advertisers mention read about ModelAviation Scale Masters/Oliver Continued page 84 increase dramatically contestants used gaso line-fueled spark-ignition four-cycle en gines popular engine still strangest Normally located uppermost arc meter face grossly non-linear equal movements pointer mark off equal resis tance values using look care fully avoid easy errors different ways construct ohmmeter function pop ular technique connect battery selectable resistors meter move ment series test leads done inside multimeter Often internal battery consists several flashlight cells perhaps ninevolt transistor battery sure keep freshI replace annually Several selectable-range resistors allow measurement very wide range resis tance valuesjust voltmeter current meter ranges Part ohmmeters internal resistor set adjustable resistor potentio meter pot allow zeroing pointer deflection prior use will ap pear knob thumbwheel multimeter housing use desired resistance range chosen test two-cycle glow type usually around 15 cu m civilian/military makeup en try shows strengthening civilian sub jects small degree Some 24% ships flown 1985 civilian types WW II fighters continue dominant group modeler appeal leads shorted togethertouch red lead black lead will cause pointer deflect toward zero ohms usually opposite end scale other functions zero Chances pointer will either quite reach zero will overshoot Thats zero control comes inmove until pointer rests zero un short test leads pointer will return fully other waytoward infinity ohms usually symbolized symbol looks lot like horizontal 8 Thus shorted leads no ohms made meter pointer read zero Open leads represent unbeliev ably large resistance open circuit practical resistance value con nected test leads pointer will wind up somewhere between two limitsprovided course suit able range selected first place Now some incidentals regarding ohmmeter use range zero knob will likely need different setting rangedont get tricked forgetting ernal battery Continued page 147 DIA 63 4 728 3 3* 4 56 83 3&3/4 4 5 6 8 8*4 5 66* 7 94 5 66* 7 7* 104 5 66W 6* 78W 10BEW 114 6 7 7* 7* 7&3/4 8 116EW 11*6 7 124W 5 SW 6 135 6 145 6 155 6 166 78 FOUR-CYCLE TAILORED HELICAL PITCH 126 6* 7 7* 8 13677*8 14677*8 1567 16678 PRICE $149 $179 $189 $1 99 $199 $209 $219 $229 $239 $239 $279 $359 $459 $659 $949 $299 $389 $489 $689 $989 PYLON RACING 7SN SiN 8&3/46* 6&3/4 7 7* 7&3/4 97 7* 7&3/4 W Wide bZade EW Exira wide $279 $289 $289 N Narrow ALL PRICES ARE POSTPAID ON ORDERS OVER $10 ORDERS SHIPPED FIRST CLASS MAIL WITHIN 24 HRS CALIFORNIA RESIDENTS ADD 6% TAX ADO 8100 IF YOU WANT INSURED MAIL ORDER BY MAIL OR PHONE 714 830-5162 SORRY NO COD VISA & MASTERCARD WELCOME DEALER INQUIRIES INVITED SPECIALISTS IN CUSTOM COX TEE DEE & REED ENGINES COMPLETE INVENTORY OF CUSTOM & STOCK PARTS HARD-TO-FIND ITEMS SUCH AS CUSTOM NEEDLE VALVES RACING WHEELS QWCK FILLS SOLID CONTROL LINES ETC SOCIETY OF ANTIQUE MODELERS MA TERIALS CARBON FIBER COILS CONDENSERS SILK TRANSISTOR IGNITION SYSTEMS TIMERS ETC REPLICA OR WICK ENGINES February 1986 145 OUR INVENTORY AVEHA~ OVER 8000 PROPS! SPECIAL PRO SERIES PITCH Dr Ken Lawson brought Plaft-kit Spitfire way Australia Quaiity aii Aussie entries equai spirit can bet theyli back Jeff Foleys beautifullyfinished 109G Plane isa terrific flier powered byan OS 105 multimeters ohmmeter function will cause small voltage applied component under test thus small current will flow through fact ohmmeter worksit applies voltage reads resulting current scale marked indicate ohmic value being measured small test signal normally no consequence power system use very sig nificant used within solid state cir cuitsbut thats beyond scope months column Finally careful connect ohmmeter active circuit such battery running motorthe ohmmeter measuring unpowered circuits components oniy Failure heed ad visory may result instrument damage Now some examples uses Remember optically-coupled speed control discussion can fact verify true separation receiver motor circuits aid ohmmeter Select highest resistance range available zero instrument both receiver motor power system switches OFF mean OFF connect ohmmeter lead elec trical part receiver system battery terminal contact unused servo plug exposed connection charge plug will connect other ohmmeter lead electrical part motor circuit brush connection motor battery terminal will What should see meter isno move ment Infinity ohms complete isola tion receiver motor systems would case nonoptically-isolated controls resis tance very much less infinity would indicate meter depending exact connections made other extreme try measuring motor resistance Select lowest resistance range zero instrument Disconnect motor system connector connect test leads motor terminals What should have very low ohms reading depend ing motor Turn armature slow ly Youre likely find new low ohms reading new armature position demonstrates very low resistance motorand variability low value depending brush contact varia tion armature position prac tical purposes such low readings much value simply because small variable unreliable other hand very poor no brush contactor dead commutator segmentit will show up quite noticeably rather large swing ohmmeter youre set up may well try thing Select low volt age range multimeter spin motor armature fingers pointer should move up down zero volts Reverse meter leads brushes pointer motion will reverse what before spin ning motor generates voltage Yup typical DC permanent-magnet motor also generator just use backward turning instead having turn something windmilling prop does turns out characteristic basic essential way motors work first place thats another long story resistance examples above limit examplesextremes high low resistance fact wide resistance ranges available multimeters little value Electrics often open short continuity information needed in-between ranges quite useful however receivers transmitters other elec tronic assemblies resistances can cover open short limits values between simple household resistance can use get further ac quainted ohmmeter light bulb Unscrew bulb try measuring resistance touching meter leads base contact points Depending lamp rating youll measure values few ohms 100 watt size few hundred ohms nite lite size Finally fun ohmmeter demonstra tion Set ohmmeter highest range hold test leads fingers making contact leads should get large resistance reading Squeeze leadsthe resistance reading should decrease Moisten hands get lower reading See body conductorit has measurable resistance its open circuit Ever wonder about girl friends resistance Thats issue friends Heres wishing happy quiet winter landingsremember Electric just great cold weather otherwise turns glow fuel gooey sticky smelly mess Please forward questions com ments SASE please Bob Kopski 25 West End Dr Lansdale PA 19446 RC Giant Scale/Beckman Continued page 57 tion-type engines witness ing melding advantages both Giant Scale four-cycle engines first look Saito 27 cu four-cycle twin action Its far cry inexpensive converted chainsaw engines few years ago does look nice sound beautiful perform superbly Before weekend over got another introduction four-cycle multicylinder engines told last month about Forest Edwards five-cylinder beau ty After watching two engines per form Im really getting four-cycle bug things go well hope Big Banger articles next few months try concentrate four-cycle engines keep getting vision Sparrowhawk Edwards engine nose should really give scale performance Youve heard babble times about real value flying chance talk people make new friends renew old friendships weekend particularly valuable last category got talk old friend hadnt seen 30 years Back early Fifties privileged work fly learn Continued page 148 February 1986 147

a E lectrics Bob Kopski MORE ELECTRIC ACTIVITY Daniel Boone Silent Fliers meet an nual 2-Meter RC Soaring contest held Saturday Sunday September 28 29 1985 Daniel Boone Homestead near Pottstown PA mention Electric column Because year something 2-Meter Soaring going onthere Electric going too CD Jerry Zeigenfuse explained growing interest Electric among Soaring enthusiasts growing interest getting away some unpleasantness always having haul out winch systems So trial Electric event included 1985s activity Heres worked CD estab lished max eight minutes five flights Any motor run up three minutes duration allowed Flight timing began shutdownwith no motor restart allowed Over three minutes resulted zero score flight Maximum score 60 x 8 480 points per flight flight scores added total Also minute allowed get plane down after max No spot landing task used idea behind format allow lowcost power systems usedsomething would discouraged limited motor runs 30 60 seconds Saturday saw eight participants flying positively vicious wind hurricane gone up East Coast day before Sunday beautiful day another eight participants attended Saturday understand flying Sunday much better first three places respective days Satur day 1 Skip Schow 2139 points 2 Bill Meleske 2114 points 3 Woody Blan chard 1866 points Sunday 1 Bill Meleske 2400 points 2 Ken Stinson 2400 points 3 Skip Schow 2059 points few stories gentlemen participated KRC Electric Fly just week before meet did grand job too LSF Level Five Bill Meleske took Up Last Down Saturday KRC meet same plane KRC Sunday work hard against KRCer Ken Stinsons speck-in-the-sky Spectraboth gentlemen maxed five times went flyoff Kens first contest ever As can see Daniel Boone results time-polished proven skill got Bill first place Hats off Daniel Boone Silent Fliers fine first-ever Electric meet Early indications theyll again 1986 watch column info later year fourth Electric meet know East yearothers covered recent columns Im perfectly delighted see growth Electric interest can add growth trend club has up coming meetadd simple Electric event two operative word simple Dont worry about it seems like small start Concentrate start size doesnt matter sure give details about three months advance Ill tell everyone else about column major chunk model doms future belongs Electric Start make future happen Motor electrical noise Last months col 54 Model Aviation Adams Electronics speed control teatures optical coupling built-In heat sink connectors except RC system Les Adams several versions plus new heavyduty connectors wire Hobby shops Electric should have stock widget Don Siegels Organizer collects Electric wiring plus motor-control servo neat arrangement version holds S-33 servo fuse switch charging jack Mounting tape keeps plane Want Info Write Don SIegel 218 Oyster Creek Dr Sugarland TX 77478 Tell him Bob K sent Bob Ks preferred motor-noisesuppres sian scheme its done three capacitors groundin lug Shown Astro cobalt 40 t9ie end bell drilled tapped after disassembly screw hold ground lug arrow Three capacitors small arrows sol dered place between motor brush connector lug between two brush connectors Ceramic capac itors 001 01 uFd work well Try get em higher 50-volt rating LIttle sphere under middle capacitor diode protect electronic speed control umn made brief mention common sound motor power interruptions caused radio glitches busy skies 1985 KRC Electric Fly easi ly understood its realized on-board Electric power systems can cause radio static quite easily Think built-in on-board glitch maker some things can done about can greatly reduce eliminate problem First plan use electronic speed control sure its opticallycoupled type Optically-coupled means RC receiver associated cir cuitry electrically isolated part speed control circuitry thats connected Electric motor system control signals decoded receiv er connected light-generating -detecting components powercontrol components may obvious look speed control its true Speed controls opticallycoupled have solid electrical connection wiring between airborne receiver system motor/power system absolutely worst possible situation latter case static electrical noise generated motor brushes con ducted right radio system places unnecessary burden receivers ability recognize desired transmitted signal same time rejecting undesired pumped-in noise motor system Some receivers han dle better others will Continued page 144 Scenes Daniel Boone Silent Filers meet 1 BIll Mileske Baldwin NY launches modified Astro Challengeruses Astro 15 cobaltlgearedll3in Geist folding propllo Sanyo 800 mAh cells R Skip Schow Vienna VA launches Kiuge Etudeso named because Etude fuseltali 80-in gilder wing strapped flew very well Sanyo 1200 mAh pack powers Mabuchi 54olKyosho gear drive 13-in Robbe folding prop Crafts allup weight 38 oz NINTH ANNUAL Ii{i]f JANUARY 11 & 12 1986 Saturday 1OAM-6PM Sunday 1OAM-5PM SEE THE LATEST PRUDUGIS ANU VISIT WITH MAJOR MANUFACTURERS AND DISTRIBUTORS OF MODEL AIRCRAFT L ENGINES MODEL BOATS O CONTROL SYSTEMS *GIANT RAFFLE L CARS MODELING ACCESSORIES*SWAP SHOP DES WEST ADMISSION Adults -$500 under 13- $300 under 6- free adult Discount tickets worth 50 cents hobby shops within 500-mile radius Pasadena California STATIC DISPLAY COMPETITION IN MANY CATEGORIES ii iuiuiu f~~I4u 7AU 11 I~ ievI U Kl fI U 1611W February 1986 55 OVERSEAS fXHIBITORS CORD/ALLY IN VI TED INTERNATIONAL MODELER SHOW OFFICE PO Box 10127 Costa Mesa CA 92627 Ph 714 5484700 645-8830 Woody Woodman has appointed succeed Tom Acciavati Rules Coordinator Correspondence concerning RC Rules proposals should sent Woody 233 Longview Drive Bayville NJ 08721 stroker stuff likely readers growing bit weary 01 Doc four-cycle notes expense milking subject death let share some early observations new OS 20 four-cycle little gem well up expectations Im per sonally delighted First foremost much lighter previously-available small four-stroker fits Hayes AL 20 mount rather AL4O Performance slightly stronger 05 15 two-stroke less Fox l9BB Starting starter just easy larger strokers absolutely no need built-in choke havent installed Idle very low reliable though engine uses simple airbleed carb Preliminary flights seem indicate prop selection runs along lines found larger units diameter doesnt seem too critical pitch three-pound 400 sq sporttype model 9 x 5 wide-bladed prop seems slightly superior 10 x 4 Old-Timer-type model suggest 10 x 5 wide-blader starting point feelings about tachometers fuel expressed rather succinctly previ ous column taching 10500 rpm 9 x 5 Super M 10400 10 x 4 broke 10 x 5 before engine broken However suspect would read about 10000 rpm now engine sounds rich peak rpm sounds better lean bit over topso use tach already Dee B Mathews 8420 Nantucket Wichita KS 67212 suffer degree Such hard-wired noise will manifest itself glitches range-reduction motor running often shows up interruptions motor power control itselfin addition flight control glitches Often former reac tion much quicker occur lat terand makes matters worse on-off flow power motor can worsen noise situation caused first place thus increase least sustain noise-induced glitching Personally refuse use anything speed controls optically isolated However installation uses servo-activated switch instead speed control chances no metallic connection between on-board systems thing servo output arms wheels normally non-conductive plastic thats sufficient isolation job second thing can improve situation keep installations neat respect radio motor system wiring Separate two systems wiring other extent possi ble electrical noise motor system present wiringthe latter acting much like miniature transmitting antenna located close sensitive receiving system effective communi cation undesired on-board trans mitter/receiver greatly reduced small separation distances course sure-fire improvement could made eliminating brush noise altogethersomething thats readily possible Reducing noise possible accompanying photo shows very effective approach best knowledge scheme shown best possible noise-reduction method using capacitors As shown three capacitors used right near trouble spotthe motor brushes motor brush capacitively bypassed grounded single electrical contact motor housing again Basic Electricity recent columns weve talked about fundamentals voltmeter ammeter operation basic sensitive meter movementsthe parts move themselves both low-value voltmeters and/or current meters having limited stand-alone utility take useful voltage current ranges combined multiplier shunt resistors respec tively Multimeters nothing meter movement selection precision resistors arranged functions ranges available convenient box Finally emphasis placed using voltmeters measure voltage ACROSS parallel some componentsuch batteryand using ammeters measure current THROUGH componentsuch connected series motor Multimeters normally contain DC voltage current functions covered far example normally separate voltmeter ranges AC circuits such household circuits work using rectifying diodes separate multiplier resistors convert AC voltage equivalent DC voltages needed meter movement AC scales separate because marked slightly non-linearly make up non-linearity caused rectify ing circuit Ordinarily no use scales RC Electric pursuits since scales sure youre reading correct ones what ever Often AC scales color-coded help ohmmeter function multimeters often very useful tool modelers measures resistance scales 144 Model Aviation other have several installations RC Old-Timers/Mathews RC Electrics/Kopskiwere modified after first having Continued page 139Continued page 55flown stock motors results very convincingbig difference before/after in-flight glitching situation So have Ways break up noise path motor-to-receiver way reduce naturally-occurring noise itself Id surprised sug gestions didnt make very noticeable change better Electric fly ing enjoyment responding advertisers mention read about ModelAviation Scale Masters/Oliver Continued page 84 increase dramatically contestants used gaso line-fueled spark-ignition four-cycle en gines popular engine still strangest Normally located uppermost arc meter face grossly non-linear equal movements pointer mark off equal resis tance values using look care fully avoid easy errors different ways construct ohmmeter function pop ular technique connect battery selectable resistors meter move ment series test leads done inside multimeter Often internal battery consists several flashlight cells perhaps ninevolt transistor battery sure keep freshI replace annually Several selectable-range resistors allow measurement very wide range resis tance valuesjust voltmeter current meter ranges Part ohmmeters internal resistor set adjustable resistor potentio meter pot allow zeroing pointer deflection prior use will ap pear knob thumbwheel multimeter housing use desired resistance range chosen test two-cycle glow type usually around 15 cu m civilian/military makeup en try shows strengthening civilian sub jects small degree Some 24% ships flown 1985 civilian types WW II fighters continue dominant group modeler appeal leads shorted togethertouch red lead black lead will cause pointer deflect toward zero ohms usually opposite end scale other functions zero Chances pointer will either quite reach zero will overshoot Thats zero control comes inmove until pointer rests zero un short test leads pointer will return fully other waytoward infinity ohms usually symbolized symbol looks lot like horizontal 8 Thus shorted leads no ohms made meter pointer read zero Open leads represent unbeliev ably large resistance open circuit practical resistance value con nected test leads pointer will wind up somewhere between two limitsprovided course suit able range selected first place Now some incidentals regarding ohmmeter use range zero knob will likely need different setting rangedont get tricked forgetting ernal battery Continued page 147 DIA 63 4 728 3 3* 4 56 83 3&3/4 4 5 6 8 8*4 5 66* 7 94 5 66* 7 7* 104 5 66W 6* 78W 10BEW 114 6 7 7* 7* 7&3/4 8 116EW 11*6 7 124W 5 SW 6 135 6 145 6 155 6 166 78 FOUR-CYCLE TAILORED HELICAL PITCH 126 6* 7 7* 8 13677*8 14677*8 1567 16678 PRICE $149 $179 $189 $1 99 $199 $209 $219 $229 $239 $239 $279 $359 $459 $659 $949 $299 $389 $489 $689 $989 PYLON RACING 7SN SiN 8&3/46* 6&3/4 7 7* 7&3/4 97 7* 7&3/4 W Wide bZade EW Exira wide $279 $289 $289 N Narrow ALL PRICES ARE POSTPAID ON ORDERS OVER $10 ORDERS SHIPPED FIRST CLASS MAIL WITHIN 24 HRS CALIFORNIA RESIDENTS ADD 6% TAX ADO 8100 IF YOU WANT INSURED MAIL ORDER BY MAIL OR PHONE 714 830-5162 SORRY NO COD VISA & MASTERCARD WELCOME DEALER INQUIRIES INVITED SPECIALISTS IN CUSTOM COX TEE DEE & REED ENGINES COMPLETE INVENTORY OF CUSTOM & STOCK PARTS HARD-TO-FIND ITEMS SUCH AS CUSTOM NEEDLE VALVES RACING WHEELS QWCK FILLS SOLID CONTROL LINES ETC SOCIETY OF ANTIQUE MODELERS MA TERIALS CARBON FIBER COILS CONDENSERS SILK TRANSISTOR IGNITION SYSTEMS TIMERS ETC REPLICA OR WICK ENGINES February 1986 145 OUR INVENTORY AVEHA~ OVER 8000 PROPS! SPECIAL PRO SERIES PITCH Dr Ken Lawson brought Plaft-kit Spitfire way Australia Quaiity aii Aussie entries equai spirit can bet theyli back Jeff Foleys beautifullyfinished 109G Plane isa terrific flier powered byan OS 105 multimeters ohmmeter function will cause small voltage applied component under test thus small current will flow through fact ohmmeter worksit applies voltage reads resulting current scale marked indicate ohmic value being measured small test signal normally no consequence power system use very sig nificant used within solid state cir cuitsbut thats beyond scope months column Finally careful connect ohmmeter active circuit such battery running motorthe ohmmeter measuring unpowered circuits components oniy Failure heed ad visory may result instrument damage Now some examples uses Remember optically-coupled speed control discussion can fact verify true separation receiver motor circuits aid ohmmeter Select highest resistance range available zero instrument both receiver motor power system switches OFF mean OFF connect ohmmeter lead elec trical part receiver system battery terminal contact unused servo plug exposed connection charge plug will connect other ohmmeter lead electrical part motor circuit brush connection motor battery terminal will What should see meter isno move ment Infinity ohms complete isola tion receiver motor systems would case nonoptically-isolated controls resis tance very much less infinity would indicate meter depending exact connections made other extreme try measuring motor resistance Select lowest resistance range zero instrument Disconnect motor system connector connect test leads motor terminals What should have very low ohms reading depend ing motor Turn armature slow ly Youre likely find new low ohms reading new armature position demonstrates very low resistance motorand variability low value depending brush contact varia tion armature position prac tical purposes such low readings much value simply because small variable unreliable other hand very poor no brush contactor dead commutator segmentit will show up quite noticeably rather large swing ohmmeter youre set up may well try thing Select low volt age range multimeter spin motor armature fingers pointer should move up down zero volts Reverse meter leads brushes pointer motion will reverse what before spin ning motor generates voltage Yup typical DC permanent-magnet motor also generator just use backward turning instead having turn something windmilling prop does turns out characteristic basic essential way motors work first place thats another long story resistance examples above limit examplesextremes high low resistance fact wide resistance ranges available multimeters little value Electrics often open short continuity information needed in-between ranges quite useful however receivers transmitters other elec tronic assemblies resistances can cover open short limits values between simple household resistance can use get further ac quainted ohmmeter light bulb Unscrew bulb try measuring resistance touching meter leads base contact points Depending lamp rating youll measure values few ohms 100 watt size few hundred ohms nite lite size Finally fun ohmmeter demonstra tion Set ohmmeter highest range hold test leads fingers making contact leads should get large resistance reading Squeeze leadsthe resistance reading should decrease Moisten hands get lower reading See body conductorit has measurable resistance its open circuit Ever wonder about girl friends resistance Thats issue friends Heres wishing happy quiet winter landingsremember Electric just great cold weather otherwise turns glow fuel gooey sticky smelly mess Please forward questions com ments SASE please Bob Kopski 25 West End Dr Lansdale PA 19446 RC Giant Scale/Beckman Continued page 57 tion-type engines witness ing melding advantages both Giant Scale four-cycle engines first look Saito 27 cu four-cycle twin action Its far cry inexpensive converted chainsaw engines few years ago does look nice sound beautiful perform superbly Before weekend over got another introduction four-cycle multicylinder engines told last month about Forest Edwards five-cylinder beau ty After watching two engines per form Im really getting four-cycle bug things go well hope Big Banger articles next few months try concentrate four-cycle engines keep getting vision Sparrowhawk Edwards engine nose should really give scale performance Youve heard babble times about real value flying chance talk people make new friends renew old friendships weekend particularly valuable last category got talk old friend hadnt seen 30 years Back early Fifties privileged work fly learn Continued page 148 February 1986 147