George M Mye Radio Thchnique 70 Froebllch Farm Ed Hlcksville NY 11801 ABSTRACT DVM adapters read peak voltage function ESM Charging voltages Caring Ni-Cd batteriesPart 5 questions answers THIS TIME Im going answer questions about care feeding Ni-Cd batteries sent several readers types ques tions minds RC modelers Question 1 Lou Moriconi Tucson AZ asks does digital voltmeter DVM show lower voltage charger final volt age charged pack OSCILLOSCOPE URE simple answer naked DVM wrong tool job DVM DC mode designed read steady DC voltagesas batteries Correct measurement charger voltages requires different tool depends nature voltage Two factors must considered waveform settling time Waveform I put oscilloscope DVM probes wires doorbell transformer got pictures shown Figure 1 volt age alternates equally olts -24 volts 60 times per second So call voltage alternating current VAC volt age connected ____________________cmoxaeiaxload current will alternate change di rection 60 times per \f\f\second hence door0scoe-F1 VOLTScalled alternating curbellor0 Figure 1 doorbell transformers reduces household 110 VAC like 25 VAC output examined An oscilloscope will show voltage varying sketched DVM correctly shows average voltage zerol OSCILLOSCOPE URE Futaba scoPe5 f N\I ora17891 VOLTS chargerowa Figure 2 Heres what output Futaba charger looks like scope DVM chargers AC output has hall-wave rectifIed now DYM can see something display senses average voltage over time 789 VDC OSCILLOSCOPE URE 25 EKE 564844 40302010DC PutabsOcope o_0 chargerDVII 005 mfd-25 Figure 3 George has small capacitor across output leads Futaba charger peak voltage hasnt changed capac itor increases average voltage seen DVM 2089 VDC OSCILLOSCOPE URE ILL85IUR FutabaOscope oor0 chargerDVII 1 etd Figure 4 very large capacitor substituted small scope shows chargers peak voltage now held con stant DVM reports being 245 VDC ~jo VOLTS o 0 rent AC DVM correctly reports av erage VDC zero Direct current runs direction put oscilloscope DVM probes transmitter charging plug ordinary Futaba RC system charger got picture shown Figure 2 half-wave rectified AC output voltage goes zero its peak value 245 volts 60 times per second Half-wave rectified means voltage goes direction positive case Note waveforms different note also DVM display Lou misap plied DVM deceived Naturally wondered 789-volt charger could charge battery 12 VDC battery may eventually charge peak voltage its charger its chemistry will support voltage will never read peak voltage DC DVM no matter long TYPICAL VOLTAGE DISCHARGE CURVE FOR NICKEL-CADMIUM BATTERY 480 MINIMUM FOR SAFE TAKEOFF 440 NEVER TAKE OFF 7 area bounded time limits flight 8 within 95* area flight 7 though includes knee curve Since area pro portional power predicts safe flight starting 480 VDC area under curve flight 9 shows starting flight 440 VDC unsafe 1234S N 6789l FLIGHTS COMPLETED George using figures left above talking about using digital voltmeter DYM check battery charger output explains column large figure right depicts typical voltage-vs-time history Ni-Cd battery under load fact voltage suddenly drops off sharply over relatively short time shows vital monitor receiver batterys voltage under loadl field 36 Model Aviation ThflLILIU 7 ILSLSSIUP wait unless put right kind charge accumulator end DVM probes Leaving DVM connected Futaba charger put 005-mfd mfd ofarad Ed 600-volt capacitor across probes got pictures shown Figure 3 Note ef fects both oscilloscope picture DVM reading Look waveform shows capacitor charged volt age peaks charger discharged shunt resistance DVM between peaks charging voltage Next replaced 005-mfd capacitor l-mfd 600-volt capacitor got results shown Figure 4 Note DVM produces tiny discharge between charging peaks DVM now indicates peak voltage charger pick value ca pacitor just showed Keep increasing capacitance until DVM indication stops creasing could calculate value need swapping capacitors quicker way get true measurement chargers peak voltage Remember two things 1 voltage rating capacitor should greater voltage being measured 2 Discharge capacitor shorting terminals screwdriver once have finished Otherwise can give nasty surprise Now know 789-VAC charger can charge 12-VDC battery DVM story just voltage Settling time can demonstrate settling time DVM choosing DC mode touching probes isolated battery will observe numbers displayed count up zero takes before stop changing common five seconds elapse before DVM settles fi nal reading Since no reason suppose bat tery terminal voltage actually increasing happening can reasonably certain looking instruments settling time long settling time DVM renders unable follow rapid changes VAC best can report some kind average value Analog dArsenval-type meters settle quickly DVMs respond same way use shunt capacitor Just remember charger voltage actu ally quite bit larger terminal voltage charged battery battery would never reach full charge Lou knew Thats asked question Question 2 Lous next question bit sub tle asks What maximum voltage can apply cell charging simple answer maximum per missible voltage determined maximum permissible charging current total resist ance electrical circuit Lets say want charge four-cell NiCd battery Fully charged will reach about 6 VDC will fall 56 VDC unloaded few minutes after battery disconnected charger use loaded termi nal voltage will fall rapidly something less value will hold nearly constant until charge nearly depleted two basic charger designs put out variable charging current constant terminal voltage put out constant current Whether charging current pulsed steady principles remain same Continued page 170 NOR-RAY PRODUCTS INC 5008 SAND BEACH RD / WICHITA FALLS TX 76310 817-692-4475 Span 104 Length 76 1575 Engine ST 2500-3000 Equiv Cowling ision Cut Foam Fuselage & Wings py tips Scale Landing Gear Video416-17 Lbs Available Dealers Welcome Intro Price $17O Reg 19600 Vistercar Fully Aerobatic Very Stable 1/4 Scale Kit Zlin 526 AS Akrobat Special Designed Modeler Modelers Cuts Both Sides Same Time Easily Cuts Straight & Tapered Wing Panels Available 30 40 50 60 Only $8750 $30O S&H RequiW2 V Power Supply *400 5&H Visa-Mastercard Video Available Send $200 information fine products HANDS OFF CUT TWO August 1990 37 D&J ELECTRONICS 900 Lucy Road ll MI 48843 546-2644 service makes P/C equipment utilizing state art electronics Spectrum Analyzer Precision Frequency Measuring equipment True 1991 Standards endorsed AMA & RCMA Transmitter Sticker Program FCC LicensedSpeed Control RepairsQuality Service Transmitter Checks Only includes GOLD/SILVER sticker$400 Transmitter & Receiver Calibration$2400 Frequency Upgrades & Changes crystals extra$2900 Bench Time Repairs per hour$2500 Transmitters service will receive AMA/RCMA sticker ADD $500 FOR SHIPPING & INSURANCE TURN AROUND TIME TWO WEEKS OR LESSI UPS ISA/MASTERCARD ACCEPTEDCOD market come sizes shapes Most servos use all-plastic gear trains Some have two brass gears very few have full metal gear trains Metal gears stronger break under load easily all-plastic ones Some smaller servos will break plastic gear hard otherwise normal landing two types servo motors normal coreless coreless motors usually faster have power Some servos have ball bearings last output gear Glider guiders have worry about size weight Weight isnt important size Some smaller planes dont have room larger servos Two-Meter trainers can use servos have torque output 35 in-oz less usually smaller servos will fit nicely smaller planes larger planes wingspans range 100-120 stronger servo will required torque output 45 in-oz al ways use powerful will fit within space avallable never hurts have reserve power Some manufacturers have higher speed servos less torque ie less power dont require high-speed servos ap plications Remember cannot always tell pow erful servo its size small servos have high power output large servos have power So dont go size servo Read manufacturers specifications servo powerful servo must have proper servo output arm match its power Most servo output arms come servo good enough Off-brand servo arms also available Some types plastic stiffer others have careful type use con necting clevis servo arm adequate using ball-link-type connector servo end pushrod servo wheel pre ferred height ball-link connector above face servo arm will cause servo arm twist under high load servo wheel can offer support As know Sloping can put some serious loads planes equipment Using right equipment mechanics can make difference between having great Slope ship having pile debris after inadequately equipped plane tears itself apart Dont skimp stuff use planes might paying little start reliable equipment worth New servo market Speaking servos Airtronics finally coming out its new allmetal-geared servo servo has dubbed 94141 should ideal mounting wings aileron flap control Obviously important aspect servo its all-metal gear traln combined hefty 42 in-oz torque will provide outstanding flutter strip resistance Another unique feature servo addi tion four extra mounting tabs tabs located side should make wingmounting snap bad news about servo its cost list price $7995 well probably see available about $50 larger hobby shops diseount houses things con sidered still think servo will worth money Looking back stripped gear sets Ive replace thought having buy makes 141 appeal ing things go planned 141 will avail able time read Future stuff As Im writing months col umn Im also getting things together take up Tn-Cities Scale Fun Fly Wash ington except P-SI Penetrator re cently suffered acute attack radio fail ure plunged its death tidal pool Dav enport least next column will deal happenings fun fly Another thing look forward column de voted pivoting wings Ill taking look some things being done Ken Stuhr VS Sallplanes Harley Michaelis Orca Roto fame well some work have done concept Ill also doing feature Mark Allen work doing Flite Lite Composites opinion Mark presently premier de signer RC Sailplanes designs range strictly fun-to-fly Swift 400 formerly known Nisus very competitive Falcon 880 Swift 800 Ill both looking Marks past see got point future see what hell bringing us next Radio Technique/Myers Continued page 37 real world nothing constant design ers can get close ideal Continued page 174 Amount Stock No Description Price I_____ _ I_I__lii III___ $790HandIng LING CHARGE Sub Total Check order or73/% Tax TN Only redit Card order CODTOTAL Name Street Address _______________________________________ City_______ UMasterCard ElVisa EAmerExp Exp Date ______________ Card No EJShip CODUMy Check enclosed $ MA To order HoBg NOUN El I use order blank call 615 373-1444 I m J 170 Model Aviation ma Name Street Address City State Zi TOWER HOBUES has Mighty UtE worlds first pwtMJTl BOWA time Mighty LItW TOWERS Special Stock Suggested SPECIAL RetailPRICE HEOIOO x12 1560/6 pcs 1Z99/6pcs 01 4950 / 6 pes 49J Bpcs 1/6x1x48 4650/3 pcs 3299/3 pcs Call toll free 1-800-637-6050 Refer ad#01006 Im going refer constant-voltage charger Type 1 get Type 1 charging situation connect very large capacity battery small-capacity battery Fast Chargers act like Type constant-voltage charger has very little inter nal resistance therefore terminal voltage stays constant regardless number cells tached charger difference between instantaneous voltage cells voltage charger determines charging rate example constant-voltage charger has 6O-VDC terminal voltage con nected four-cell battery already charged 40 VDC voltage available push charging current 60 40 DC Given average Ni-Cd pack its wires connections voltage could working against resistance about 05 ohm charging current would 2 amps Obviously shorted battery down 0 VDC connected charger initial current would 6 2 amps current might damage internal connections usual 550-rnAh cell pack fully charged will have terminal voltage 6 VDC charging cur rent will zero So can see constantvoltage charger delivers wide range currents can designed never overcharges battery Constant-voltage chargers usually found connected things seldom completely discharged service must re charged quickly left charger long unattended periodslike battery-powered screwdriver portable telephone Im going call constant-current charger Type 2 type charger will deliver same current whether batteries discharged fully charged can deduce has output voltage greater terminal voltage battery Chargers found RC sets usually set overnight charging rates perform like Type 2 chargers used manufacturer intended Batteries have discharged nearly 0 VDC should recharged first time 24 hours Type 2 charger avoid possibility damage high initial current Type 1 charger some facts about real charger usual RC system charger has two pairs wires pair four-cell airborne battery other eight-cell transmitter battery wires usually equipped different plugs help user avoid mistakes rea son difference voltages driving two leads different 165 245 peak voltages Futaba charger checked connected normally lead Futaba charger delivers 65 mA its respective battery Reversing connections connected flight battery lead transmitter charg ing current 25 mA charged flight battery transmitter lead current 220 mA What tells Futaba RC system charger isnt ideal type 2 should may have noticed transmitter side Futaba charger shows twice voltage fully charged eight-cell Ni-Cd battery flight battery charger shows almost three Continued page 176 174 Model Aviation PC Box 1247 310 N 5th St St Chailes L 50 4 312 584 7815 Radio Technique/Myers Continued page 170 8 - MACH-P R ORDERS ONLY 1 800-633-7556ili/iZZCODs IN ALABAMA 347 3525 COLLECTWELCOME TOP QUALITY FUEL FOR EXPERT OR BEGINNER NO RE-CLAIMED ALCOHOL O METHANE ONLY IS USED Designed tested give top performance both 2-cycle 4-cycle engines ringed Except engines requiring low lubricant content CONTAINS NEW TRULY SPACE AGE ADDITIVE developed outer space vacuum Thia new additive attaches internal metal parts engine will reduce friction much 80/ reduces heat wear absolute minimum WE HAVE 3 LUBRICANT BLENDS ALL SYNTHETIC OR SYNTHETIC BLEND CASTOR castor new high purity much cleaner burning castor ALL OUR FUELS CONTAIN ANTIFOAMERS PREVENTERS WEAR ADDITIVES fuel developed priced individual club direct sales market dealer inquiries invited Oude gallon up MIX OK 4 gallon cases up ALL FUEL EXCEPT 54 GALLON DRUMS SNIPPED FREIGHT PRE-PAID Only continental usA 3 GalTo 23 GalTo 63 GalITo 127 GalAndFreight colIect l l al~64 Gal 128 Ga9 54 Gal Drum 50/1095750700 65057518500 12!149595090085077528000 1995145014001350127547500 500/0269522 5022 00 0207578000 Manufactured MACH-7 PO Box 1201 Enterprise Alabama 36330 RIC FOLLIES PRESENTS Craziest Wackiest -And Funniest ModelAirplane Wrecks Youll Ever See! Over 30 Minutes CRASH after CRASH after CRASH Youll See * Flying off lake smashing ice * What happens hand launch forget turn radio plane * A seaplane turn treeplane * A Rocket engine mounted Eindecker * Four wrecked planes turned Twin land flew * And just lot Bad flying much Dont miss one-of-a-kind exciting funny video offer youll ever See $1995 plus $350 shipping handling TO ORDER Send check money order $1995 plus $350 shipping handling SCRANTON HOBBY DISTRIBUTORS 420 Lackawanna Avenue Scranton PA 18503 phone 1717342-1963 MASTERCARDAMERICAN EXPRESS rders add 6% sates lax Radio Technique/Myers Continued page 174 times voltage fuliy charged four-cell bat tery dont know reasonable suppose Futaba engineer decided provide charger can charge eight- ninecell transmitter batteries either four- fivecell airborne batteries charger delivers 50 mA nine-cell transmitter pack 50 mA five-cell receiver pack checked So can used Overnight charger four packs hope youre confused no simple answers six-volt Type 1 charger would damage four-cell pack overvoltage might melt some internal con nections completely discharged pack during initial surge 165-volt Futaba RC system charger could left connected same pack days small current would damage pack Voltage alone determining fac tor dont know what happening follow manufacturers instructions must exper iment know instrumentation use correctly Remember Test Engineers Motto Get right answers purpose Question 3 Jim Hobelsberger La Crescent MN asks What safe minimum voltage start flight exactly like asking much fuel should tank problem face trying answer question fully charged battery looks just like charge-depleted battery voltage poor indicator charge remaining Battery ter minal voltage goes down current being Continued page 178 176 Model Aviation RC hobby based experience 11 VDC per cell 44 VDC under load four-cell battery little energy left battery never safe start flight Besides never discharge pack below 44 VDC never have worry about cell-reversal failures voltage still up flat part curve ends about 48 VDC av erage four-cell 550-mAh battery under kind load energy remaining battery about plunge over end volt age curve usually enough 10minute flight trouble battery little differ ent average battery really better perform battery tests ground keep track time air know fully charged packs good two hours would wise stop flying after 1 hours Either change batteries use bigger batter ies use field charger like CaRa Automatic Cycler-Charger See June 90 column Polks Multi Charge-A-Matic May 90 column use backup like FailSafe Flight System December 89 column plenty op tions dont have get last possible bit energy out batteries TY FUEL T U B NG Ill RCSoaringlBlakeslee page 47 drawn battery increases though remaining charge doesnt change DVMs cheap readily obtainable people will keep trying use Lets start fundamentals situa tion yields two hours service fully charged 550-mAh pack 15-minute pe nod consumes about 70 mAh havent tested situation know what service get full charge havent timing use batteries can guess charge remaining converting DVM ESM expanded scale meter Buy pair 10-ohm 10-watt wirewound resis tors local Radio Shack Put sideby-side twisting leads end together Obtain charging plug leads fit sys tem solder twisted pair resistor leads wire charging plug Connect DVM wires 11 putting DVM parallel resistorsEd adapter converts DVM no-load volt meter equivalent loaded expandedscale voltmeter ESM Actually scale doesnt change just make use greater resolution DVM relative analog meter plug assembly planes charging jack will see voltage leave plugged full 30 seconds will see voltage falls lower value should fall slowly 05 VDC unless start above 5 VDC Assuming testing four-cell Ni-Cd battery value after 30 seconds 480 volts probably have enough charge left fly another 10-minute flight five-cell bat tery want see 600 volts Re member DVM isnt absolutely correct assuming dont know what real characteristics situation Weve got conservative current drawn test about amp similar what moving two servos same time produces resistors may get warm because test will consume about 10 mAh energy rate five watts ANSI standard end-of-charge voltage Ni-Cd cell 09 VDC measured under load practice will usually translate 1 1 VDC load isnt point end point 11 VDC standard aerodynamic glory thin airfoil hig aspect ratio wing some special construction meth ods materials required wing keep such high aspect ratio wins twisting flapping full-span spar used spar starting bottom consists three tapered layers 7-mu carbon fiber 3A spruce high-density-foam shear web 7-mil layer carbon fiber another strip 3/ spruce whole spar rakes back slight angle %-in stainless wing rod accommodated entirely within spar butt end both spars wrapped three layers 1 7-oz Key lar cloth wing core itself cut extruded 15lb-density foam core cut full size section vacuum bagged between two Mylar carrier sheets glass/epoxy sandwich two layers 2-oz glass laid 450 bias top bottom did experiments various weights combinations Keviar glass before settlin8 layup turns Out two layers 2-oz glass cloth just stiff just light layer 1 7-oz Kevlar can seems weight layup oia amer iS perfectly proportioned modeling Curtiss Robin 049 Engines -Channel RIC 41 Wingapan Electric Power Optional SILI Oh 003 Very few full scale airoraff ideelly nuifed 10 model flighf us s fhe appealing old Curfiss Robin wan burn fhe spruca und linen age beaufifully poporfioned rubber electric glow enginea Easy fun build trainer-like performance Flyfine Models Calalog 50phonn 17031 273-0593 INE MODELS INC PO Box 2136 Fairfax VirginIa 22031 USA 178 Model Aviation Especially formulated use gasoline diesel fuels Wont swell harden use new transparent green fuel line perfect fuel connections fuel pumps smoke systems Sold foot Medium Large local Hobby Shop gb-fuels sure use Du-Bros Neoprene Silicone fuel Tubing.the Modelers Choice DU-BRO PRODUCTS INC 480 BONNER RD WAI iCflNflA II Radio Technique/Myers Continued page 176 HAS MOVED INTO LARGER QUARTERS 21 658 Cloud Way Hayward CA 94545 CAL 415 783-4868 Out CAL 800 482-8663 rre proud announce TATONE PRODUCTS CORPORATION has acquired CB ASSOCIATES 4/9 PRESIDENT TATONE PRODUCTS CORP
Edition: Model Aviation - 1990/08
Page Numbers: 36, 37, 170, 174, 176, 178
George M Mye Radio Thchnique 70 Froebllch Farm Ed Hlcksville NY 11801 ABSTRACT DVM adapters read peak voltage function ESM Charging voltages Caring Ni-Cd batteriesPart 5 questions answers THIS TIME Im going answer questions about care feeding Ni-Cd batteries sent several readers types ques tions minds RC modelers Question 1 Lou Moriconi Tucson AZ asks does digital voltmeter DVM show lower voltage charger final volt age charged pack OSCILLOSCOPE URE simple answer naked DVM wrong tool job DVM DC mode designed read steady DC voltagesas batteries Correct measurement charger voltages requires different tool depends nature voltage Two factors must considered waveform settling time Waveform I put oscilloscope DVM probes wires doorbell transformer got pictures shown Figure 1 volt age alternates equally olts -24 volts 60 times per second So call voltage alternating current VAC volt age connected ____________________cmoxaeiaxload current will alternate change di rection 60 times per \f\f\second hence door0scoe-F1 VOLTScalled alternating curbellor0 Figure 1 doorbell transformers reduces household 110 VAC like 25 VAC output examined An oscilloscope will show voltage varying sketched DVM correctly shows average voltage zerol OSCILLOSCOPE URE Futaba scoPe5 f N\I ora17891 VOLTS chargerowa Figure 2 Heres what output Futaba charger looks like scope DVM chargers AC output has hall-wave rectifIed now DYM can see something display senses average voltage over time 789 VDC OSCILLOSCOPE URE 25 EKE 564844 40302010DC PutabsOcope o_0 chargerDVII 005 mfd-25 Figure 3 George has small capacitor across output leads Futaba charger peak voltage hasnt changed capac itor increases average voltage seen DVM 2089 VDC OSCILLOSCOPE URE ILL85IUR FutabaOscope oor0 chargerDVII 1 etd Figure 4 very large capacitor substituted small scope shows chargers peak voltage now held con stant DVM reports being 245 VDC ~jo VOLTS o 0 rent AC DVM correctly reports av erage VDC zero Direct current runs direction put oscilloscope DVM probes transmitter charging plug ordinary Futaba RC system charger got picture shown Figure 2 half-wave rectified AC output voltage goes zero its peak value 245 volts 60 times per second Half-wave rectified means voltage goes direction positive case Note waveforms different note also DVM display Lou misap plied DVM deceived Naturally wondered 789-volt charger could charge battery 12 VDC battery may eventually charge peak voltage its charger its chemistry will support voltage will never read peak voltage DC DVM no matter long TYPICAL VOLTAGE DISCHARGE CURVE FOR NICKEL-CADMIUM BATTERY 480 MINIMUM FOR SAFE TAKEOFF 440 NEVER TAKE OFF 7 area bounded time limits flight 8 within 95* area flight 7 though includes knee curve Since area pro portional power predicts safe flight starting 480 VDC area under curve flight 9 shows starting flight 440 VDC unsafe 1234S N 6789l FLIGHTS COMPLETED George using figures left above talking about using digital voltmeter DYM check battery charger output explains column large figure right depicts typical voltage-vs-time history Ni-Cd battery under load fact voltage suddenly drops off sharply over relatively short time shows vital monitor receiver batterys voltage under loadl field 36 Model Aviation ThflLILIU 7 ILSLSSIUP wait unless put right kind charge accumulator end DVM probes Leaving DVM connected Futaba charger put 005-mfd mfd ofarad Ed 600-volt capacitor across probes got pictures shown Figure 3 Note ef fects both oscilloscope picture DVM reading Look waveform shows capacitor charged volt age peaks charger discharged shunt resistance DVM between peaks charging voltage Next replaced 005-mfd capacitor l-mfd 600-volt capacitor got results shown Figure 4 Note DVM produces tiny discharge between charging peaks DVM now indicates peak voltage charger pick value ca pacitor just showed Keep increasing capacitance until DVM indication stops creasing could calculate value need swapping capacitors quicker way get true measurement chargers peak voltage Remember two things 1 voltage rating capacitor should greater voltage being measured 2 Discharge capacitor shorting terminals screwdriver once have finished Otherwise can give nasty surprise Now know 789-VAC charger can charge 12-VDC battery DVM story just voltage Settling time can demonstrate settling time DVM choosing DC mode touching probes isolated battery will observe numbers displayed count up zero takes before stop changing common five seconds elapse before DVM settles fi nal reading Since no reason suppose bat tery terminal voltage actually increasing happening can reasonably certain looking instruments settling time long settling time DVM renders unable follow rapid changes VAC best can report some kind average value Analog dArsenval-type meters settle quickly DVMs respond same way use shunt capacitor Just remember charger voltage actu ally quite bit larger terminal voltage charged battery battery would never reach full charge Lou knew Thats asked question Question 2 Lous next question bit sub tle asks What maximum voltage can apply cell charging simple answer maximum per missible voltage determined maximum permissible charging current total resist ance electrical circuit Lets say want charge four-cell NiCd battery Fully charged will reach about 6 VDC will fall 56 VDC unloaded few minutes after battery disconnected charger use loaded termi nal voltage will fall rapidly something less value will hold nearly constant until charge nearly depleted two basic charger designs put out variable charging current constant terminal voltage put out constant current Whether charging current pulsed steady principles remain same Continued page 170 NOR-RAY PRODUCTS INC 5008 SAND BEACH RD / WICHITA FALLS TX 76310 817-692-4475 Span 104 Length 76 1575 Engine ST 2500-3000 Equiv Cowling ision Cut Foam Fuselage & Wings py tips Scale Landing Gear Video416-17 Lbs Available Dealers Welcome Intro Price $17O Reg 19600 Vistercar Fully Aerobatic Very Stable 1/4 Scale Kit Zlin 526 AS Akrobat Special Designed Modeler Modelers Cuts Both Sides Same Time Easily Cuts Straight & Tapered Wing Panels Available 30 40 50 60 Only $8750 $30O S&H RequiW2 V Power Supply *400 5&H Visa-Mastercard Video Available Send $200 information fine products HANDS OFF CUT TWO August 1990 37 D&J ELECTRONICS 900 Lucy Road ll MI 48843 546-2644 service makes P/C equipment utilizing state art electronics Spectrum Analyzer Precision Frequency Measuring equipment True 1991 Standards endorsed AMA & RCMA Transmitter Sticker Program FCC LicensedSpeed Control RepairsQuality Service Transmitter Checks Only includes GOLD/SILVER sticker$400 Transmitter & Receiver Calibration$2400 Frequency Upgrades & Changes crystals extra$2900 Bench Time Repairs per hour$2500 Transmitters service will receive AMA/RCMA sticker ADD $500 FOR SHIPPING & INSURANCE TURN AROUND TIME TWO WEEKS OR LESSI UPS ISA/MASTERCARD ACCEPTEDCOD market come sizes shapes Most servos use all-plastic gear trains Some have two brass gears very few have full metal gear trains Metal gears stronger break under load easily all-plastic ones Some smaller servos will break plastic gear hard otherwise normal landing two types servo motors normal coreless coreless motors usually faster have power Some servos have ball bearings last output gear Glider guiders have worry about size weight Weight isnt important size Some smaller planes dont have room larger servos Two-Meter trainers can use servos have torque output 35 in-oz less usually smaller servos will fit nicely smaller planes larger planes wingspans range 100-120 stronger servo will required torque output 45 in-oz al ways use powerful will fit within space avallable never hurts have reserve power Some manufacturers have higher speed servos less torque ie less power dont require high-speed servos ap plications Remember cannot always tell pow erful servo its size small servos have high power output large servos have power So dont go size servo Read manufacturers specifications servo powerful servo must have proper servo output arm match its power Most servo output arms come servo good enough Off-brand servo arms also available Some types plastic stiffer others have careful type use con necting clevis servo arm adequate using ball-link-type connector servo end pushrod servo wheel pre ferred height ball-link connector above face servo arm will cause servo arm twist under high load servo wheel can offer support As know Sloping can put some serious loads planes equipment Using right equipment mechanics can make difference between having great Slope ship having pile debris after inadequately equipped plane tears itself apart Dont skimp stuff use planes might paying little start reliable equipment worth New servo market Speaking servos Airtronics finally coming out its new allmetal-geared servo servo has dubbed 94141 should ideal mounting wings aileron flap control Obviously important aspect servo its all-metal gear traln combined hefty 42 in-oz torque will provide outstanding flutter strip resistance Another unique feature servo addi tion four extra mounting tabs tabs located side should make wingmounting snap bad news about servo its cost list price $7995 well probably see available about $50 larger hobby shops diseount houses things con sidered still think servo will worth money Looking back stripped gear sets Ive replace thought having buy makes 141 appeal ing things go planned 141 will avail able time read Future stuff As Im writing months col umn Im also getting things together take up Tn-Cities Scale Fun Fly Wash ington except P-SI Penetrator re cently suffered acute attack radio fail ure plunged its death tidal pool Dav enport least next column will deal happenings fun fly Another thing look forward column de voted pivoting wings Ill taking look some things being done Ken Stuhr VS Sallplanes Harley Michaelis Orca Roto fame well some work have done concept Ill also doing feature Mark Allen work doing Flite Lite Composites opinion Mark presently premier de signer RC Sailplanes designs range strictly fun-to-fly Swift 400 formerly known Nisus very competitive Falcon 880 Swift 800 Ill both looking Marks past see got point future see what hell bringing us next Radio Technique/Myers Continued page 37 real world nothing constant design ers can get close ideal Continued page 174 Amount Stock No Description Price I_____ _ I_I__lii III___ $790HandIng LING CHARGE Sub Total Check order or73/% Tax TN Only redit Card order CODTOTAL Name Street Address _______________________________________ City_______ UMasterCard ElVisa EAmerExp Exp Date ______________ Card No EJShip CODUMy Check enclosed $ MA To order HoBg NOUN El I use order blank call 615 373-1444 I m J 170 Model Aviation ma Name Street Address City State Zi TOWER HOBUES has Mighty UtE worlds first pwtMJTl BOWA time Mighty LItW TOWERS Special Stock Suggested SPECIAL RetailPRICE HEOIOO x12 1560/6 pcs 1Z99/6pcs 01 4950 / 6 pes 49J Bpcs 1/6x1x48 4650/3 pcs 3299/3 pcs Call toll free 1-800-637-6050 Refer ad#01006 Im going refer constant-voltage charger Type 1 get Type 1 charging situation connect very large capacity battery small-capacity battery Fast Chargers act like Type constant-voltage charger has very little inter nal resistance therefore terminal voltage stays constant regardless number cells tached charger difference between instantaneous voltage cells voltage charger determines charging rate example constant-voltage charger has 6O-VDC terminal voltage con nected four-cell battery already charged 40 VDC voltage available push charging current 60 40 DC Given average Ni-Cd pack its wires connections voltage could working against resistance about 05 ohm charging current would 2 amps Obviously shorted battery down 0 VDC connected charger initial current would 6 2 amps current might damage internal connections usual 550-rnAh cell pack fully charged will have terminal voltage 6 VDC charging cur rent will zero So can see constantvoltage charger delivers wide range currents can designed never overcharges battery Constant-voltage chargers usually found connected things seldom completely discharged service must re charged quickly left charger long unattended periodslike battery-powered screwdriver portable telephone Im going call constant-current charger Type 2 type charger will deliver same current whether batteries discharged fully charged can deduce has output voltage greater terminal voltage battery Chargers found RC sets usually set overnight charging rates perform like Type 2 chargers used manufacturer intended Batteries have discharged nearly 0 VDC should recharged first time 24 hours Type 2 charger avoid possibility damage high initial current Type 1 charger some facts about real charger usual RC system charger has two pairs wires pair four-cell airborne battery other eight-cell transmitter battery wires usually equipped different plugs help user avoid mistakes rea son difference voltages driving two leads different 165 245 peak voltages Futaba charger checked connected normally lead Futaba charger delivers 65 mA its respective battery Reversing connections connected flight battery lead transmitter charg ing current 25 mA charged flight battery transmitter lead current 220 mA What tells Futaba RC system charger isnt ideal type 2 should may have noticed transmitter side Futaba charger shows twice voltage fully charged eight-cell Ni-Cd battery flight battery charger shows almost three Continued page 176 174 Model Aviation PC Box 1247 310 N 5th St St Chailes L 50 4 312 584 7815 Radio Technique/Myers Continued page 170 8 - MACH-P R ORDERS ONLY 1 800-633-7556ili/iZZCODs IN ALABAMA 347 3525 COLLECTWELCOME TOP QUALITY FUEL FOR EXPERT OR BEGINNER NO RE-CLAIMED ALCOHOL O METHANE ONLY IS USED Designed tested give top performance both 2-cycle 4-cycle engines ringed Except engines requiring low lubricant content CONTAINS NEW TRULY SPACE AGE ADDITIVE developed outer space vacuum Thia new additive attaches internal metal parts engine will reduce friction much 80/ reduces heat wear absolute minimum WE HAVE 3 LUBRICANT BLENDS ALL SYNTHETIC OR SYNTHETIC BLEND CASTOR castor new high purity much cleaner burning castor ALL OUR FUELS CONTAIN ANTIFOAMERS PREVENTERS WEAR ADDITIVES fuel developed priced individual club direct sales market dealer inquiries invited Oude gallon up MIX OK 4 gallon cases up ALL FUEL EXCEPT 54 GALLON DRUMS SNIPPED FREIGHT PRE-PAID Only continental usA 3 GalTo 23 GalTo 63 GalITo 127 GalAndFreight colIect l l al~64 Gal 128 Ga9 54 Gal Drum 50/1095750700 65057518500 12!149595090085077528000 1995145014001350127547500 500/0269522 5022 00 0207578000 Manufactured MACH-7 PO Box 1201 Enterprise Alabama 36330 RIC FOLLIES PRESENTS Craziest Wackiest -And Funniest ModelAirplane Wrecks Youll Ever See! Over 30 Minutes CRASH after CRASH after CRASH Youll See * Flying off lake smashing ice * What happens hand launch forget turn radio plane * A seaplane turn treeplane * A Rocket engine mounted Eindecker * Four wrecked planes turned Twin land flew * And just lot Bad flying much Dont miss one-of-a-kind exciting funny video offer youll ever See $1995 plus $350 shipping handling TO ORDER Send check money order $1995 plus $350 shipping handling SCRANTON HOBBY DISTRIBUTORS 420 Lackawanna Avenue Scranton PA 18503 phone 1717342-1963 MASTERCARDAMERICAN EXPRESS rders add 6% sates lax Radio Technique/Myers Continued page 174 times voltage fuliy charged four-cell bat tery dont know reasonable suppose Futaba engineer decided provide charger can charge eight- ninecell transmitter batteries either four- fivecell airborne batteries charger delivers 50 mA nine-cell transmitter pack 50 mA five-cell receiver pack checked So can used Overnight charger four packs hope youre confused no simple answers six-volt Type 1 charger would damage four-cell pack overvoltage might melt some internal con nections completely discharged pack during initial surge 165-volt Futaba RC system charger could left connected same pack days small current would damage pack Voltage alone determining fac tor dont know what happening follow manufacturers instructions must exper iment know instrumentation use correctly Remember Test Engineers Motto Get right answers purpose Question 3 Jim Hobelsberger La Crescent MN asks What safe minimum voltage start flight exactly like asking much fuel should tank problem face trying answer question fully charged battery looks just like charge-depleted battery voltage poor indicator charge remaining Battery ter minal voltage goes down current being Continued page 178 176 Model Aviation RC hobby based experience 11 VDC per cell 44 VDC under load four-cell battery little energy left battery never safe start flight Besides never discharge pack below 44 VDC never have worry about cell-reversal failures voltage still up flat part curve ends about 48 VDC av erage four-cell 550-mAh battery under kind load energy remaining battery about plunge over end volt age curve usually enough 10minute flight trouble battery little differ ent average battery really better perform battery tests ground keep track time air know fully charged packs good two hours would wise stop flying after 1 hours Either change batteries use bigger batter ies use field charger like CaRa Automatic Cycler-Charger See June 90 column Polks Multi Charge-A-Matic May 90 column use backup like FailSafe Flight System December 89 column plenty op tions dont have get last possible bit energy out batteries TY FUEL T U B NG Ill RCSoaringlBlakeslee page 47 drawn battery increases though remaining charge doesnt change DVMs cheap readily obtainable people will keep trying use Lets start fundamentals situa tion yields two hours service fully charged 550-mAh pack 15-minute pe nod consumes about 70 mAh havent tested situation know what service get full charge havent timing use batteries can guess charge remaining converting DVM ESM expanded scale meter Buy pair 10-ohm 10-watt wirewound resis tors local Radio Shack Put sideby-side twisting leads end together Obtain charging plug leads fit sys tem solder twisted pair resistor leads wire charging plug Connect DVM wires 11 putting DVM parallel resistorsEd adapter converts DVM no-load volt meter equivalent loaded expandedscale voltmeter ESM Actually scale doesnt change just make use greater resolution DVM relative analog meter plug assembly planes charging jack will see voltage leave plugged full 30 seconds will see voltage falls lower value should fall slowly 05 VDC unless start above 5 VDC Assuming testing four-cell Ni-Cd battery value after 30 seconds 480 volts probably have enough charge left fly another 10-minute flight five-cell bat tery want see 600 volts Re member DVM isnt absolutely correct assuming dont know what real characteristics situation Weve got conservative current drawn test about amp similar what moving two servos same time produces resistors may get warm because test will consume about 10 mAh energy rate five watts ANSI standard end-of-charge voltage Ni-Cd cell 09 VDC measured under load practice will usually translate 1 1 VDC load isnt point end point 11 VDC standard aerodynamic glory thin airfoil hig aspect ratio wing some special construction meth ods materials required wing keep such high aspect ratio wins twisting flapping full-span spar used spar starting bottom consists three tapered layers 7-mu carbon fiber 3A spruce high-density-foam shear web 7-mil layer carbon fiber another strip 3/ spruce whole spar rakes back slight angle %-in stainless wing rod accommodated entirely within spar butt end both spars wrapped three layers 1 7-oz Key lar cloth wing core itself cut extruded 15lb-density foam core cut full size section vacuum bagged between two Mylar carrier sheets glass/epoxy sandwich two layers 2-oz glass laid 450 bias top bottom did experiments various weights combinations Keviar glass before settlin8 layup turns Out two layers 2-oz glass cloth just stiff just light layer 1 7-oz Kevlar can seems weight layup oia amer iS perfectly proportioned modeling Curtiss Robin 049 Engines -Channel RIC 41 Wingapan Electric Power Optional SILI Oh 003 Very few full scale airoraff ideelly nuifed 10 model flighf us s fhe appealing old Curfiss Robin wan burn fhe spruca und linen age beaufifully poporfioned rubber electric glow enginea Easy fun build trainer-like performance Flyfine Models Calalog 50phonn 17031 273-0593 INE MODELS INC PO Box 2136 Fairfax VirginIa 22031 USA 178 Model Aviation Especially formulated use gasoline diesel fuels Wont swell harden use new transparent green fuel line perfect fuel connections fuel pumps smoke systems Sold foot Medium Large local Hobby Shop gb-fuels sure use Du-Bros Neoprene Silicone fuel Tubing.the Modelers Choice DU-BRO PRODUCTS INC 480 BONNER RD WAI iCflNflA II Radio Technique/Myers Continued page 176 HAS MOVED INTO LARGER QUARTERS 21 658 Cloud Way Hayward CA 94545 CAL 415 783-4868 Out CAL 800 482-8663 rre proud announce TATONE PRODUCTS CORPORATION has acquired CB ASSOCIATES 4/9 PRESIDENT TATONE PRODUCTS CORP
Edition: Model Aviation - 1990/08
Page Numbers: 36, 37, 170, 174, 176, 178
George M Mye Radio Thchnique 70 Froebllch Farm Ed Hlcksville NY 11801 ABSTRACT DVM adapters read peak voltage function ESM Charging voltages Caring Ni-Cd batteriesPart 5 questions answers THIS TIME Im going answer questions about care feeding Ni-Cd batteries sent several readers types ques tions minds RC modelers Question 1 Lou Moriconi Tucson AZ asks does digital voltmeter DVM show lower voltage charger final volt age charged pack OSCILLOSCOPE URE simple answer naked DVM wrong tool job DVM DC mode designed read steady DC voltagesas batteries Correct measurement charger voltages requires different tool depends nature voltage Two factors must considered waveform settling time Waveform I put oscilloscope DVM probes wires doorbell transformer got pictures shown Figure 1 volt age alternates equally olts -24 volts 60 times per second So call voltage alternating current VAC volt age connected ____________________cmoxaeiaxload current will alternate change di rection 60 times per \f\f\second hence door0scoe-F1 VOLTScalled alternating curbellor0 Figure 1 doorbell transformers reduces household 110 VAC like 25 VAC output examined An oscilloscope will show voltage varying sketched DVM correctly shows average voltage zerol OSCILLOSCOPE URE Futaba scoPe5 f N\I ora17891 VOLTS chargerowa Figure 2 Heres what output Futaba charger looks like scope DVM chargers AC output has hall-wave rectifIed now DYM can see something display senses average voltage over time 789 VDC OSCILLOSCOPE URE 25 EKE 564844 40302010DC PutabsOcope o_0 chargerDVII 005 mfd-25 Figure 3 George has small capacitor across output leads Futaba charger peak voltage hasnt changed capac itor increases average voltage seen DVM 2089 VDC OSCILLOSCOPE URE ILL85IUR FutabaOscope oor0 chargerDVII 1 etd Figure 4 very large capacitor substituted small scope shows chargers peak voltage now held con stant DVM reports being 245 VDC ~jo VOLTS o 0 rent AC DVM correctly reports av erage VDC zero Direct current runs direction put oscilloscope DVM probes transmitter charging plug ordinary Futaba RC system charger got picture shown Figure 2 half-wave rectified AC output voltage goes zero its peak value 245 volts 60 times per second Half-wave rectified means voltage goes direction positive case Note waveforms different note also DVM display Lou misap plied DVM deceived Naturally wondered 789-volt charger could charge battery 12 VDC battery may eventually charge peak voltage its charger its chemistry will support voltage will never read peak voltage DC DVM no matter long TYPICAL VOLTAGE DISCHARGE CURVE FOR NICKEL-CADMIUM BATTERY 480 MINIMUM FOR SAFE TAKEOFF 440 NEVER TAKE OFF 7 area bounded time limits flight 8 within 95* area flight 7 though includes knee curve Since area pro portional power predicts safe flight starting 480 VDC area under curve flight 9 shows starting flight 440 VDC unsafe 1234S N 6789l FLIGHTS COMPLETED George using figures left above talking about using digital voltmeter DYM check battery charger output explains column large figure right depicts typical voltage-vs-time history Ni-Cd battery under load fact voltage suddenly drops off sharply over relatively short time shows vital monitor receiver batterys voltage under loadl field 36 Model Aviation ThflLILIU 7 ILSLSSIUP wait unless put right kind charge accumulator end DVM probes Leaving DVM connected Futaba charger put 005-mfd mfd ofarad Ed 600-volt capacitor across probes got pictures shown Figure 3 Note ef fects both oscilloscope picture DVM reading Look waveform shows capacitor charged volt age peaks charger discharged shunt resistance DVM between peaks charging voltage Next replaced 005-mfd capacitor l-mfd 600-volt capacitor got results shown Figure 4 Note DVM produces tiny discharge between charging peaks DVM now indicates peak voltage charger pick value ca pacitor just showed Keep increasing capacitance until DVM indication stops creasing could calculate value need swapping capacitors quicker way get true measurement chargers peak voltage Remember two things 1 voltage rating capacitor should greater voltage being measured 2 Discharge capacitor shorting terminals screwdriver once have finished Otherwise can give nasty surprise Now know 789-VAC charger can charge 12-VDC battery DVM story just voltage Settling time can demonstrate settling time DVM choosing DC mode touching probes isolated battery will observe numbers displayed count up zero takes before stop changing common five seconds elapse before DVM settles fi nal reading Since no reason suppose bat tery terminal voltage actually increasing happening can reasonably certain looking instruments settling time long settling time DVM renders unable follow rapid changes VAC best can report some kind average value Analog dArsenval-type meters settle quickly DVMs respond same way use shunt capacitor Just remember charger voltage actu ally quite bit larger terminal voltage charged battery battery would never reach full charge Lou knew Thats asked question Question 2 Lous next question bit sub tle asks What maximum voltage can apply cell charging simple answer maximum per missible voltage determined maximum permissible charging current total resist ance electrical circuit Lets say want charge four-cell NiCd battery Fully charged will reach about 6 VDC will fall 56 VDC unloaded few minutes after battery disconnected charger use loaded termi nal voltage will fall rapidly something less value will hold nearly constant until charge nearly depleted two basic charger designs put out variable charging current constant terminal voltage put out constant current Whether charging current pulsed steady principles remain same Continued page 170 NOR-RAY PRODUCTS INC 5008 SAND BEACH RD / WICHITA FALLS TX 76310 817-692-4475 Span 104 Length 76 1575 Engine ST 2500-3000 Equiv Cowling ision Cut Foam Fuselage & Wings py tips Scale Landing Gear Video416-17 Lbs Available Dealers Welcome Intro Price $17O Reg 19600 Vistercar Fully Aerobatic Very Stable 1/4 Scale Kit Zlin 526 AS Akrobat Special Designed Modeler Modelers Cuts Both Sides Same Time Easily Cuts Straight & Tapered Wing Panels Available 30 40 50 60 Only $8750 $30O S&H RequiW2 V Power Supply *400 5&H Visa-Mastercard Video Available Send $200 information fine products HANDS OFF CUT TWO August 1990 37 D&J ELECTRONICS 900 Lucy Road ll MI 48843 546-2644 service makes P/C equipment utilizing state art electronics Spectrum Analyzer Precision Frequency Measuring equipment True 1991 Standards endorsed AMA & RCMA Transmitter Sticker Program FCC LicensedSpeed Control RepairsQuality Service Transmitter Checks Only includes GOLD/SILVER sticker$400 Transmitter & Receiver Calibration$2400 Frequency Upgrades & Changes crystals extra$2900 Bench Time Repairs per hour$2500 Transmitters service will receive AMA/RCMA sticker ADD $500 FOR SHIPPING & INSURANCE TURN AROUND TIME TWO WEEKS OR LESSI UPS ISA/MASTERCARD ACCEPTEDCOD market come sizes shapes Most servos use all-plastic gear trains Some have two brass gears very few have full metal gear trains Metal gears stronger break under load easily all-plastic ones Some smaller servos will break plastic gear hard otherwise normal landing two types servo motors normal coreless coreless motors usually faster have power Some servos have ball bearings last output gear Glider guiders have worry about size weight Weight isnt important size Some smaller planes dont have room larger servos Two-Meter trainers can use servos have torque output 35 in-oz less usually smaller servos will fit nicely smaller planes larger planes wingspans range 100-120 stronger servo will required torque output 45 in-oz al ways use powerful will fit within space avallable never hurts have reserve power Some manufacturers have higher speed servos less torque ie less power dont require high-speed servos ap plications Remember cannot always tell pow erful servo its size small servos have high power output large servos have power So dont go size servo Read manufacturers specifications servo powerful servo must have proper servo output arm match its power Most servo output arms come servo good enough Off-brand servo arms also available Some types plastic stiffer others have careful type use con necting clevis servo arm adequate using ball-link-type connector servo end pushrod servo wheel pre ferred height ball-link connector above face servo arm will cause servo arm twist under high load servo wheel can offer support As know Sloping can put some serious loads planes equipment Using right equipment mechanics can make difference between having great Slope ship having pile debris after inadequately equipped plane tears itself apart Dont skimp stuff use planes might paying little start reliable equipment worth New servo market Speaking servos Airtronics finally coming out its new allmetal-geared servo servo has dubbed 94141 should ideal mounting wings aileron flap control Obviously important aspect servo its all-metal gear traln combined hefty 42 in-oz torque will provide outstanding flutter strip resistance Another unique feature servo addi tion four extra mounting tabs tabs located side should make wingmounting snap bad news about servo its cost list price $7995 well probably see available about $50 larger hobby shops diseount houses things con sidered still think servo will worth money Looking back stripped gear sets Ive replace thought having buy makes 141 appeal ing things go planned 141 will avail able time read Future stuff As Im writing months col umn Im also getting things together take up Tn-Cities Scale Fun Fly Wash ington except P-SI Penetrator re cently suffered acute attack radio fail ure plunged its death tidal pool Dav enport least next column will deal happenings fun fly Another thing look forward column de voted pivoting wings Ill taking look some things being done Ken Stuhr VS Sallplanes Harley Michaelis Orca Roto fame well some work have done concept Ill also doing feature Mark Allen work doing Flite Lite Composites opinion Mark presently premier de signer RC Sailplanes designs range strictly fun-to-fly Swift 400 formerly known Nisus very competitive Falcon 880 Swift 800 Ill both looking Marks past see got point future see what hell bringing us next Radio Technique/Myers Continued page 37 real world nothing constant design ers can get close ideal Continued page 174 Amount Stock No Description Price I_____ _ I_I__lii III___ $790HandIng LING CHARGE Sub Total Check order or73/% Tax TN Only redit Card order CODTOTAL Name Street Address _______________________________________ City_______ UMasterCard ElVisa EAmerExp Exp Date ______________ Card No EJShip CODUMy Check enclosed $ MA To order HoBg NOUN El I use order blank call 615 373-1444 I m J 170 Model Aviation ma Name Street Address City State Zi TOWER HOBUES has Mighty UtE worlds first pwtMJTl BOWA time Mighty LItW TOWERS Special Stock Suggested SPECIAL RetailPRICE HEOIOO x12 1560/6 pcs 1Z99/6pcs 01 4950 / 6 pes 49J Bpcs 1/6x1x48 4650/3 pcs 3299/3 pcs Call toll free 1-800-637-6050 Refer ad#01006 Im going refer constant-voltage charger Type 1 get Type 1 charging situation connect very large capacity battery small-capacity battery Fast Chargers act like Type constant-voltage charger has very little inter nal resistance therefore terminal voltage stays constant regardless number cells tached charger difference between instantaneous voltage cells voltage charger determines charging rate example constant-voltage charger has 6O-VDC terminal voltage con nected four-cell battery already charged 40 VDC voltage available push charging current 60 40 DC Given average Ni-Cd pack its wires connections voltage could working against resistance about 05 ohm charging current would 2 amps Obviously shorted battery down 0 VDC connected charger initial current would 6 2 amps current might damage internal connections usual 550-rnAh cell pack fully charged will have terminal voltage 6 VDC charging cur rent will zero So can see constantvoltage charger delivers wide range currents can designed never overcharges battery Constant-voltage chargers usually found connected things seldom completely discharged service must re charged quickly left charger long unattended periodslike battery-powered screwdriver portable telephone Im going call constant-current charger Type 2 type charger will deliver same current whether batteries discharged fully charged can deduce has output voltage greater terminal voltage battery Chargers found RC sets usually set overnight charging rates perform like Type 2 chargers used manufacturer intended Batteries have discharged nearly 0 VDC should recharged first time 24 hours Type 2 charger avoid possibility damage high initial current Type 1 charger some facts about real charger usual RC system charger has two pairs wires pair four-cell airborne battery other eight-cell transmitter battery wires usually equipped different plugs help user avoid mistakes rea son difference voltages driving two leads different 165 245 peak voltages Futaba charger checked connected normally lead Futaba charger delivers 65 mA its respective battery Reversing connections connected flight battery lead transmitter charg ing current 25 mA charged flight battery transmitter lead current 220 mA What tells Futaba RC system charger isnt ideal type 2 should may have noticed transmitter side Futaba charger shows twice voltage fully charged eight-cell Ni-Cd battery flight battery charger shows almost three Continued page 176 174 Model Aviation PC Box 1247 310 N 5th St St Chailes L 50 4 312 584 7815 Radio Technique/Myers Continued page 170 8 - MACH-P R ORDERS ONLY 1 800-633-7556ili/iZZCODs IN ALABAMA 347 3525 COLLECTWELCOME TOP QUALITY FUEL FOR EXPERT OR BEGINNER NO RE-CLAIMED ALCOHOL O METHANE ONLY IS USED Designed tested give top performance both 2-cycle 4-cycle engines ringed Except engines requiring low lubricant content CONTAINS NEW TRULY SPACE AGE ADDITIVE developed outer space vacuum Thia new additive attaches internal metal parts engine will reduce friction much 80/ reduces heat wear absolute minimum WE HAVE 3 LUBRICANT BLENDS ALL SYNTHETIC OR SYNTHETIC BLEND CASTOR castor new high purity much cleaner burning castor ALL OUR FUELS CONTAIN ANTIFOAMERS PREVENTERS WEAR ADDITIVES fuel developed priced individual club direct sales market dealer inquiries invited Oude gallon up MIX OK 4 gallon cases up ALL FUEL EXCEPT 54 GALLON DRUMS SNIPPED FREIGHT PRE-PAID Only continental usA 3 GalTo 23 GalTo 63 GalITo 127 GalAndFreight colIect l l al~64 Gal 128 Ga9 54 Gal Drum 50/1095750700 65057518500 12!149595090085077528000 1995145014001350127547500 500/0269522 5022 00 0207578000 Manufactured MACH-7 PO Box 1201 Enterprise Alabama 36330 RIC FOLLIES PRESENTS Craziest Wackiest -And Funniest ModelAirplane Wrecks Youll Ever See! Over 30 Minutes CRASH after CRASH after CRASH Youll See * Flying off lake smashing ice * What happens hand launch forget turn radio plane * A seaplane turn treeplane * A Rocket engine mounted Eindecker * Four wrecked planes turned Twin land flew * And just lot Bad flying much Dont miss one-of-a-kind exciting funny video offer youll ever See $1995 plus $350 shipping handling TO ORDER Send check money order $1995 plus $350 shipping handling SCRANTON HOBBY DISTRIBUTORS 420 Lackawanna Avenue Scranton PA 18503 phone 1717342-1963 MASTERCARDAMERICAN EXPRESS rders add 6% sates lax Radio Technique/Myers Continued page 174 times voltage fuliy charged four-cell bat tery dont know reasonable suppose Futaba engineer decided provide charger can charge eight- ninecell transmitter batteries either four- fivecell airborne batteries charger delivers 50 mA nine-cell transmitter pack 50 mA five-cell receiver pack checked So can used Overnight charger four packs hope youre confused no simple answers six-volt Type 1 charger would damage four-cell pack overvoltage might melt some internal con nections completely discharged pack during initial surge 165-volt Futaba RC system charger could left connected same pack days small current would damage pack Voltage alone determining fac tor dont know what happening follow manufacturers instructions must exper iment know instrumentation use correctly Remember Test Engineers Motto Get right answers purpose Question 3 Jim Hobelsberger La Crescent MN asks What safe minimum voltage start flight exactly like asking much fuel should tank problem face trying answer question fully charged battery looks just like charge-depleted battery voltage poor indicator charge remaining Battery ter minal voltage goes down current being Continued page 178 176 Model Aviation RC hobby based experience 11 VDC per cell 44 VDC under load four-cell battery little energy left battery never safe start flight Besides never discharge pack below 44 VDC never have worry about cell-reversal failures voltage still up flat part curve ends about 48 VDC av erage four-cell 550-mAh battery under kind load energy remaining battery about plunge over end volt age curve usually enough 10minute flight trouble battery little differ ent average battery really better perform battery tests ground keep track time air know fully charged packs good two hours would wise stop flying after 1 hours Either change batteries use bigger batter ies use field charger like CaRa Automatic Cycler-Charger See June 90 column Polks Multi Charge-A-Matic May 90 column use backup like FailSafe Flight System December 89 column plenty op tions dont have get last possible bit energy out batteries TY FUEL T U B NG Ill RCSoaringlBlakeslee page 47 drawn battery increases though remaining charge doesnt change DVMs cheap readily obtainable people will keep trying use Lets start fundamentals situa tion yields two hours service fully charged 550-mAh pack 15-minute pe nod consumes about 70 mAh havent tested situation know what service get full charge havent timing use batteries can guess charge remaining converting DVM ESM expanded scale meter Buy pair 10-ohm 10-watt wirewound resis tors local Radio Shack Put sideby-side twisting leads end together Obtain charging plug leads fit sys tem solder twisted pair resistor leads wire charging plug Connect DVM wires 11 putting DVM parallel resistorsEd adapter converts DVM no-load volt meter equivalent loaded expandedscale voltmeter ESM Actually scale doesnt change just make use greater resolution DVM relative analog meter plug assembly planes charging jack will see voltage leave plugged full 30 seconds will see voltage falls lower value should fall slowly 05 VDC unless start above 5 VDC Assuming testing four-cell Ni-Cd battery value after 30 seconds 480 volts probably have enough charge left fly another 10-minute flight five-cell bat tery want see 600 volts Re member DVM isnt absolutely correct assuming dont know what real characteristics situation Weve got conservative current drawn test about amp similar what moving two servos same time produces resistors may get warm because test will consume about 10 mAh energy rate five watts ANSI standard end-of-charge voltage Ni-Cd cell 09 VDC measured under load practice will usually translate 1 1 VDC load isnt point end point 11 VDC standard aerodynamic glory thin airfoil hig aspect ratio wing some special construction meth ods materials required wing keep such high aspect ratio wins twisting flapping full-span spar used spar starting bottom consists three tapered layers 7-mu carbon fiber 3A spruce high-density-foam shear web 7-mil layer carbon fiber another strip 3/ spruce whole spar rakes back slight angle %-in stainless wing rod accommodated entirely within spar butt end both spars wrapped three layers 1 7-oz Key lar cloth wing core itself cut extruded 15lb-density foam core cut full size section vacuum bagged between two Mylar carrier sheets glass/epoxy sandwich two layers 2-oz glass laid 450 bias top bottom did experiments various weights combinations Keviar glass before settlin8 layup turns Out two layers 2-oz glass cloth just stiff just light layer 1 7-oz Kevlar can seems weight layup oia amer iS perfectly proportioned modeling Curtiss Robin 049 Engines -Channel RIC 41 Wingapan Electric Power Optional SILI Oh 003 Very few full scale airoraff ideelly nuifed 10 model flighf us s fhe appealing old Curfiss Robin wan burn fhe spruca und linen age beaufifully poporfioned rubber electric glow enginea Easy fun build trainer-like performance Flyfine Models Calalog 50phonn 17031 273-0593 INE MODELS INC PO Box 2136 Fairfax VirginIa 22031 USA 178 Model Aviation Especially formulated use gasoline diesel fuels Wont swell harden use new transparent green fuel line perfect fuel connections fuel pumps smoke systems Sold foot Medium Large local Hobby Shop gb-fuels sure use Du-Bros Neoprene Silicone fuel Tubing.the Modelers Choice DU-BRO PRODUCTS INC 480 BONNER RD WAI iCflNflA II Radio Technique/Myers Continued page 176 HAS MOVED INTO LARGER QUARTERS 21 658 Cloud Way Hayward CA 94545 CAL 415 783-4868 Out CAL 800 482-8663 rre proud announce TATONE PRODUCTS CORPORATION has acquired CB ASSOCIATES 4/9 PRESIDENT TATONE PRODUCTS CORP
Edition: Model Aviation - 1990/08
Page Numbers: 36, 37, 170, 174, 176, 178
George M Mye Radio Thchnique 70 Froebllch Farm Ed Hlcksville NY 11801 ABSTRACT DVM adapters read peak voltage function ESM Charging voltages Caring Ni-Cd batteriesPart 5 questions answers THIS TIME Im going answer questions about care feeding Ni-Cd batteries sent several readers types ques tions minds RC modelers Question 1 Lou Moriconi Tucson AZ asks does digital voltmeter DVM show lower voltage charger final volt age charged pack OSCILLOSCOPE URE simple answer naked DVM wrong tool job DVM DC mode designed read steady DC voltagesas batteries Correct measurement charger voltages requires different tool depends nature voltage Two factors must considered waveform settling time Waveform I put oscilloscope DVM probes wires doorbell transformer got pictures shown Figure 1 volt age alternates equally olts -24 volts 60 times per second So call voltage alternating current VAC volt age connected ____________________cmoxaeiaxload current will alternate change di rection 60 times per \f\f\second hence door0scoe-F1 VOLTScalled alternating curbellor0 Figure 1 doorbell transformers reduces household 110 VAC like 25 VAC output examined An oscilloscope will show voltage varying sketched DVM correctly shows average voltage zerol OSCILLOSCOPE URE Futaba scoPe5 f N\I ora17891 VOLTS chargerowa Figure 2 Heres what output Futaba charger looks like scope DVM chargers AC output has hall-wave rectifIed now DYM can see something display senses average voltage over time 789 VDC OSCILLOSCOPE URE 25 EKE 564844 40302010DC PutabsOcope o_0 chargerDVII 005 mfd-25 Figure 3 George has small capacitor across output leads Futaba charger peak voltage hasnt changed capac itor increases average voltage seen DVM 2089 VDC OSCILLOSCOPE URE ILL85IUR FutabaOscope oor0 chargerDVII 1 etd Figure 4 very large capacitor substituted small scope shows chargers peak voltage now held con stant DVM reports being 245 VDC ~jo VOLTS o 0 rent AC DVM correctly reports av erage VDC zero Direct current runs direction put oscilloscope DVM probes transmitter charging plug ordinary Futaba RC system charger got picture shown Figure 2 half-wave rectified AC output voltage goes zero its peak value 245 volts 60 times per second Half-wave rectified means voltage goes direction positive case Note waveforms different note also DVM display Lou misap plied DVM deceived Naturally wondered 789-volt charger could charge battery 12 VDC battery may eventually charge peak voltage its charger its chemistry will support voltage will never read peak voltage DC DVM no matter long TYPICAL VOLTAGE DISCHARGE CURVE FOR NICKEL-CADMIUM BATTERY 480 MINIMUM FOR SAFE TAKEOFF 440 NEVER TAKE OFF 7 area bounded time limits flight 8 within 95* area flight 7 though includes knee curve Since area pro portional power predicts safe flight starting 480 VDC area under curve flight 9 shows starting flight 440 VDC unsafe 1234S N 6789l FLIGHTS COMPLETED George using figures left above talking about using digital voltmeter DYM check battery charger output explains column large figure right depicts typical voltage-vs-time history Ni-Cd battery under load fact voltage suddenly drops off sharply over relatively short time shows vital monitor receiver batterys voltage under loadl field 36 Model Aviation ThflLILIU 7 ILSLSSIUP wait unless put right kind charge accumulator end DVM probes Leaving DVM connected Futaba charger put 005-mfd mfd ofarad Ed 600-volt capacitor across probes got pictures shown Figure 3 Note ef fects both oscilloscope picture DVM reading Look waveform shows capacitor charged volt age peaks charger discharged shunt resistance DVM between peaks charging voltage Next replaced 005-mfd capacitor l-mfd 600-volt capacitor got results shown Figure 4 Note DVM produces tiny discharge between charging peaks DVM now indicates peak voltage charger pick value ca pacitor just showed Keep increasing capacitance until DVM indication stops creasing could calculate value need swapping capacitors quicker way get true measurement chargers peak voltage Remember two things 1 voltage rating capacitor should greater voltage being measured 2 Discharge capacitor shorting terminals screwdriver once have finished Otherwise can give nasty surprise Now know 789-VAC charger can charge 12-VDC battery DVM story just voltage Settling time can demonstrate settling time DVM choosing DC mode touching probes isolated battery will observe numbers displayed count up zero takes before stop changing common five seconds elapse before DVM settles fi nal reading Since no reason suppose bat tery terminal voltage actually increasing happening can reasonably certain looking instruments settling time long settling time DVM renders unable follow rapid changes VAC best can report some kind average value Analog dArsenval-type meters settle quickly DVMs respond same way use shunt capacitor Just remember charger voltage actu ally quite bit larger terminal voltage charged battery battery would never reach full charge Lou knew Thats asked question Question 2 Lous next question bit sub tle asks What maximum voltage can apply cell charging simple answer maximum per missible voltage determined maximum permissible charging current total resist ance electrical circuit Lets say want charge four-cell NiCd battery Fully charged will reach about 6 VDC will fall 56 VDC unloaded few minutes after battery disconnected charger use loaded termi nal voltage will fall rapidly something less value will hold nearly constant until charge nearly depleted two basic charger designs put out variable charging current constant terminal voltage put out constant current Whether charging current pulsed steady principles remain same Continued page 170 NOR-RAY PRODUCTS INC 5008 SAND BEACH RD / WICHITA FALLS TX 76310 817-692-4475 Span 104 Length 76 1575 Engine ST 2500-3000 Equiv Cowling ision Cut Foam Fuselage & Wings py tips Scale Landing Gear Video416-17 Lbs Available Dealers Welcome Intro Price $17O Reg 19600 Vistercar Fully Aerobatic Very Stable 1/4 Scale Kit Zlin 526 AS Akrobat Special Designed Modeler Modelers Cuts Both Sides Same Time Easily Cuts Straight & Tapered Wing Panels Available 30 40 50 60 Only $8750 $30O S&H RequiW2 V Power Supply *400 5&H Visa-Mastercard Video Available Send $200 information fine products HANDS OFF CUT TWO August 1990 37 D&J ELECTRONICS 900 Lucy Road ll MI 48843 546-2644 service makes P/C equipment utilizing state art electronics Spectrum Analyzer Precision Frequency Measuring equipment True 1991 Standards endorsed AMA & RCMA Transmitter Sticker Program FCC LicensedSpeed Control RepairsQuality Service Transmitter Checks Only includes GOLD/SILVER sticker$400 Transmitter & Receiver Calibration$2400 Frequency Upgrades & Changes crystals extra$2900 Bench Time Repairs per hour$2500 Transmitters service will receive AMA/RCMA sticker ADD $500 FOR SHIPPING & INSURANCE TURN AROUND TIME TWO WEEKS OR LESSI UPS ISA/MASTERCARD ACCEPTEDCOD market come sizes shapes Most servos use all-plastic gear trains Some have two brass gears very few have full metal gear trains Metal gears stronger break under load easily all-plastic ones Some smaller servos will break plastic gear hard otherwise normal landing two types servo motors normal coreless coreless motors usually faster have power Some servos have ball bearings last output gear Glider guiders have worry about size weight Weight isnt important size Some smaller planes dont have room larger servos Two-Meter trainers can use servos have torque output 35 in-oz less usually smaller servos will fit nicely smaller planes larger planes wingspans range 100-120 stronger servo will required torque output 45 in-oz al ways use powerful will fit within space avallable never hurts have reserve power Some manufacturers have higher speed servos less torque ie less power dont require high-speed servos ap plications Remember cannot always tell pow erful servo its size small servos have high power output large servos have power So dont go size servo Read manufacturers specifications servo powerful servo must have proper servo output arm match its power Most servo output arms come servo good enough Off-brand servo arms also available Some types plastic stiffer others have careful type use con necting clevis servo arm adequate using ball-link-type connector servo end pushrod servo wheel pre ferred height ball-link connector above face servo arm will cause servo arm twist under high load servo wheel can offer support As know Sloping can put some serious loads planes equipment Using right equipment mechanics can make difference between having great Slope ship having pile debris after inadequately equipped plane tears itself apart Dont skimp stuff use planes might paying little start reliable equipment worth New servo market Speaking servos Airtronics finally coming out its new allmetal-geared servo servo has dubbed 94141 should ideal mounting wings aileron flap control Obviously important aspect servo its all-metal gear traln combined hefty 42 in-oz torque will provide outstanding flutter strip resistance Another unique feature servo addi tion four extra mounting tabs tabs located side should make wingmounting snap bad news about servo its cost list price $7995 well probably see available about $50 larger hobby shops diseount houses things con sidered still think servo will worth money Looking back stripped gear sets Ive replace thought having buy makes 141 appeal ing things go planned 141 will avail able time read Future stuff As Im writing months col umn Im also getting things together take up Tn-Cities Scale Fun Fly Wash ington except P-SI Penetrator re cently suffered acute attack radio fail ure plunged its death tidal pool Dav enport least next column will deal happenings fun fly Another thing look forward column de voted pivoting wings Ill taking look some things being done Ken Stuhr VS Sallplanes Harley Michaelis Orca Roto fame well some work have done concept Ill also doing feature Mark Allen work doing Flite Lite Composites opinion Mark presently premier de signer RC Sailplanes designs range strictly fun-to-fly Swift 400 formerly known Nisus very competitive Falcon 880 Swift 800 Ill both looking Marks past see got point future see what hell bringing us next Radio Technique/Myers Continued page 37 real world nothing constant design ers can get close ideal Continued page 174 Amount Stock No Description Price I_____ _ I_I__lii III___ $790HandIng LING CHARGE Sub Total Check order or73/% Tax TN Only redit Card order CODTOTAL Name Street Address _______________________________________ City_______ UMasterCard ElVisa EAmerExp Exp Date ______________ Card No EJShip CODUMy Check enclosed $ MA To order HoBg NOUN El I use order blank call 615 373-1444 I m J 170 Model Aviation ma Name Street Address City State Zi TOWER HOBUES has Mighty UtE worlds first pwtMJTl BOWA time Mighty LItW TOWERS Special Stock Suggested SPECIAL RetailPRICE HEOIOO x12 1560/6 pcs 1Z99/6pcs 01 4950 / 6 pes 49J Bpcs 1/6x1x48 4650/3 pcs 3299/3 pcs Call toll free 1-800-637-6050 Refer ad#01006 Im going refer constant-voltage charger Type 1 get Type 1 charging situation connect very large capacity battery small-capacity battery Fast Chargers act like Type constant-voltage charger has very little inter nal resistance therefore terminal voltage stays constant regardless number cells tached charger difference between instantaneous voltage cells voltage charger determines charging rate example constant-voltage charger has 6O-VDC terminal voltage con nected four-cell battery already charged 40 VDC voltage available push charging current 60 40 DC Given average Ni-Cd pack its wires connections voltage could working against resistance about 05 ohm charging current would 2 amps Obviously shorted battery down 0 VDC connected charger initial current would 6 2 amps current might damage internal connections usual 550-rnAh cell pack fully charged will have terminal voltage 6 VDC charging cur rent will zero So can see constantvoltage charger delivers wide range currents can designed never overcharges battery Constant-voltage chargers usually found connected things seldom completely discharged service must re charged quickly left charger long unattended periodslike battery-powered screwdriver portable telephone Im going call constant-current charger Type 2 type charger will deliver same current whether batteries discharged fully charged can deduce has output voltage greater terminal voltage battery Chargers found RC sets usually set overnight charging rates perform like Type 2 chargers used manufacturer intended Batteries have discharged nearly 0 VDC should recharged first time 24 hours Type 2 charger avoid possibility damage high initial current Type 1 charger some facts about real charger usual RC system charger has two pairs wires pair four-cell airborne battery other eight-cell transmitter battery wires usually equipped different plugs help user avoid mistakes rea son difference voltages driving two leads different 165 245 peak voltages Futaba charger checked connected normally lead Futaba charger delivers 65 mA its respective battery Reversing connections connected flight battery lead transmitter charg ing current 25 mA charged flight battery transmitter lead current 220 mA What tells Futaba RC system charger isnt ideal type 2 should may have noticed transmitter side Futaba charger shows twice voltage fully charged eight-cell Ni-Cd battery flight battery charger shows almost three Continued page 176 174 Model Aviation PC Box 1247 310 N 5th St St Chailes L 50 4 312 584 7815 Radio Technique/Myers Continued page 170 8 - MACH-P R ORDERS ONLY 1 800-633-7556ili/iZZCODs IN ALABAMA 347 3525 COLLECTWELCOME TOP QUALITY FUEL FOR EXPERT OR BEGINNER NO RE-CLAIMED ALCOHOL O METHANE ONLY IS USED Designed tested give top performance both 2-cycle 4-cycle engines ringed Except engines requiring low lubricant content CONTAINS NEW TRULY SPACE AGE ADDITIVE developed outer space vacuum Thia new additive attaches internal metal parts engine will reduce friction much 80/ reduces heat wear absolute minimum WE HAVE 3 LUBRICANT BLENDS ALL SYNTHETIC OR SYNTHETIC BLEND CASTOR castor new high purity much cleaner burning castor ALL OUR FUELS CONTAIN ANTIFOAMERS PREVENTERS WEAR ADDITIVES fuel developed priced individual club direct sales market dealer inquiries invited Oude gallon up MIX OK 4 gallon cases up ALL FUEL EXCEPT 54 GALLON DRUMS SNIPPED FREIGHT PRE-PAID Only continental usA 3 GalTo 23 GalTo 63 GalITo 127 GalAndFreight colIect l l al~64 Gal 128 Ga9 54 Gal Drum 50/1095750700 65057518500 12!149595090085077528000 1995145014001350127547500 500/0269522 5022 00 0207578000 Manufactured MACH-7 PO Box 1201 Enterprise Alabama 36330 RIC FOLLIES PRESENTS Craziest Wackiest -And Funniest ModelAirplane Wrecks Youll Ever See! Over 30 Minutes CRASH after CRASH after CRASH Youll See * Flying off lake smashing ice * What happens hand launch forget turn radio plane * A seaplane turn treeplane * A Rocket engine mounted Eindecker * Four wrecked planes turned Twin land flew * And just lot Bad flying much Dont miss one-of-a-kind exciting funny video offer youll ever See $1995 plus $350 shipping handling TO ORDER Send check money order $1995 plus $350 shipping handling SCRANTON HOBBY DISTRIBUTORS 420 Lackawanna Avenue Scranton PA 18503 phone 1717342-1963 MASTERCARDAMERICAN EXPRESS rders add 6% sates lax Radio Technique/Myers Continued page 174 times voltage fuliy charged four-cell bat tery dont know reasonable suppose Futaba engineer decided provide charger can charge eight- ninecell transmitter batteries either four- fivecell airborne batteries charger delivers 50 mA nine-cell transmitter pack 50 mA five-cell receiver pack checked So can used Overnight charger four packs hope youre confused no simple answers six-volt Type 1 charger would damage four-cell pack overvoltage might melt some internal con nections completely discharged pack during initial surge 165-volt Futaba RC system charger could left connected same pack days small current would damage pack Voltage alone determining fac tor dont know what happening follow manufacturers instructions must exper iment know instrumentation use correctly Remember Test Engineers Motto Get right answers purpose Question 3 Jim Hobelsberger La Crescent MN asks What safe minimum voltage start flight exactly like asking much fuel should tank problem face trying answer question fully charged battery looks just like charge-depleted battery voltage poor indicator charge remaining Battery ter minal voltage goes down current being Continued page 178 176 Model Aviation RC hobby based experience 11 VDC per cell 44 VDC under load four-cell battery little energy left battery never safe start flight Besides never discharge pack below 44 VDC never have worry about cell-reversal failures voltage still up flat part curve ends about 48 VDC av erage four-cell 550-mAh battery under kind load energy remaining battery about plunge over end volt age curve usually enough 10minute flight trouble battery little differ ent average battery really better perform battery tests ground keep track time air know fully charged packs good two hours would wise stop flying after 1 hours Either change batteries use bigger batter ies use field charger like CaRa Automatic Cycler-Charger See June 90 column Polks Multi Charge-A-Matic May 90 column use backup like FailSafe Flight System December 89 column plenty op tions dont have get last possible bit energy out batteries TY FUEL T U B NG Ill RCSoaringlBlakeslee page 47 drawn battery increases though remaining charge doesnt change DVMs cheap readily obtainable people will keep trying use Lets start fundamentals situa tion yields two hours service fully charged 550-mAh pack 15-minute pe nod consumes about 70 mAh havent tested situation know what service get full charge havent timing use batteries can guess charge remaining converting DVM ESM expanded scale meter Buy pair 10-ohm 10-watt wirewound resis tors local Radio Shack Put sideby-side twisting leads end together Obtain charging plug leads fit sys tem solder twisted pair resistor leads wire charging plug Connect DVM wires 11 putting DVM parallel resistorsEd adapter converts DVM no-load volt meter equivalent loaded expandedscale voltmeter ESM Actually scale doesnt change just make use greater resolution DVM relative analog meter plug assembly planes charging jack will see voltage leave plugged full 30 seconds will see voltage falls lower value should fall slowly 05 VDC unless start above 5 VDC Assuming testing four-cell Ni-Cd battery value after 30 seconds 480 volts probably have enough charge left fly another 10-minute flight five-cell bat tery want see 600 volts Re member DVM isnt absolutely correct assuming dont know what real characteristics situation Weve got conservative current drawn test about amp similar what moving two servos same time produces resistors may get warm because test will consume about 10 mAh energy rate five watts ANSI standard end-of-charge voltage Ni-Cd cell 09 VDC measured under load practice will usually translate 1 1 VDC load isnt point end point 11 VDC standard aerodynamic glory thin airfoil hig aspect ratio wing some special construction meth ods materials required wing keep such high aspect ratio wins twisting flapping full-span spar used spar starting bottom consists three tapered layers 7-mu carbon fiber 3A spruce high-density-foam shear web 7-mil layer carbon fiber another strip 3/ spruce whole spar rakes back slight angle %-in stainless wing rod accommodated entirely within spar butt end both spars wrapped three layers 1 7-oz Key lar cloth wing core itself cut extruded 15lb-density foam core cut full size section vacuum bagged between two Mylar carrier sheets glass/epoxy sandwich two layers 2-oz glass laid 450 bias top bottom did experiments various weights combinations Keviar glass before settlin8 layup turns Out two layers 2-oz glass cloth just stiff just light layer 1 7-oz Kevlar can seems weight layup oia amer iS perfectly proportioned modeling Curtiss Robin 049 Engines -Channel RIC 41 Wingapan Electric Power Optional SILI Oh 003 Very few full scale airoraff ideelly nuifed 10 model flighf us s fhe appealing old Curfiss Robin wan burn fhe spruca und linen age beaufifully poporfioned rubber electric glow enginea Easy fun build trainer-like performance Flyfine Models Calalog 50phonn 17031 273-0593 INE MODELS INC PO Box 2136 Fairfax VirginIa 22031 USA 178 Model Aviation Especially formulated use gasoline diesel fuels Wont swell harden use new transparent green fuel line perfect fuel connections fuel pumps smoke systems Sold foot Medium Large local Hobby Shop gb-fuels sure use Du-Bros Neoprene Silicone fuel Tubing.the Modelers Choice DU-BRO PRODUCTS INC 480 BONNER RD WAI iCflNflA II Radio Technique/Myers Continued page 176 HAS MOVED INTO LARGER QUARTERS 21 658 Cloud Way Hayward CA 94545 CAL 415 783-4868 Out CAL 800 482-8663 rre proud announce TATONE PRODUCTS CORPORATION has acquired CB ASSOCIATES 4/9 PRESIDENT TATONE PRODUCTS CORP
Edition: Model Aviation - 1990/08
Page Numbers: 36, 37, 170, 174, 176, 178
George M Mye Radio Thchnique 70 Froebllch Farm Ed Hlcksville NY 11801 ABSTRACT DVM adapters read peak voltage function ESM Charging voltages Caring Ni-Cd batteriesPart 5 questions answers THIS TIME Im going answer questions about care feeding Ni-Cd batteries sent several readers types ques tions minds RC modelers Question 1 Lou Moriconi Tucson AZ asks does digital voltmeter DVM show lower voltage charger final volt age charged pack OSCILLOSCOPE URE simple answer naked DVM wrong tool job DVM DC mode designed read steady DC voltagesas batteries Correct measurement charger voltages requires different tool depends nature voltage Two factors must considered waveform settling time Waveform I put oscilloscope DVM probes wires doorbell transformer got pictures shown Figure 1 volt age alternates equally olts -24 volts 60 times per second So call voltage alternating current VAC volt age connected ____________________cmoxaeiaxload current will alternate change di rection 60 times per \f\f\second hence door0scoe-F1 VOLTScalled alternating curbellor0 Figure 1 doorbell transformers reduces household 110 VAC like 25 VAC output examined An oscilloscope will show voltage varying sketched DVM correctly shows average voltage zerol OSCILLOSCOPE URE Futaba scoPe5 f N\I ora17891 VOLTS chargerowa Figure 2 Heres what output Futaba charger looks like scope DVM chargers AC output has hall-wave rectifIed now DYM can see something display senses average voltage over time 789 VDC OSCILLOSCOPE URE 25 EKE 564844 40302010DC PutabsOcope o_0 chargerDVII 005 mfd-25 Figure 3 George has small capacitor across output leads Futaba charger peak voltage hasnt changed capac itor increases average voltage seen DVM 2089 VDC OSCILLOSCOPE URE ILL85IUR FutabaOscope oor0 chargerDVII 1 etd Figure 4 very large capacitor substituted small scope shows chargers peak voltage now held con stant DVM reports being 245 VDC ~jo VOLTS o 0 rent AC DVM correctly reports av erage VDC zero Direct current runs direction put oscilloscope DVM probes transmitter charging plug ordinary Futaba RC system charger got picture shown Figure 2 half-wave rectified AC output voltage goes zero its peak value 245 volts 60 times per second Half-wave rectified means voltage goes direction positive case Note waveforms different note also DVM display Lou misap plied DVM deceived Naturally wondered 789-volt charger could charge battery 12 VDC battery may eventually charge peak voltage its charger its chemistry will support voltage will never read peak voltage DC DVM no matter long TYPICAL VOLTAGE DISCHARGE CURVE FOR NICKEL-CADMIUM BATTERY 480 MINIMUM FOR SAFE TAKEOFF 440 NEVER TAKE OFF 7 area bounded time limits flight 8 within 95* area flight 7 though includes knee curve Since area pro portional power predicts safe flight starting 480 VDC area under curve flight 9 shows starting flight 440 VDC unsafe 1234S N 6789l FLIGHTS COMPLETED George using figures left above talking about using digital voltmeter DYM check battery charger output explains column large figure right depicts typical voltage-vs-time history Ni-Cd battery under load fact voltage suddenly drops off sharply over relatively short time shows vital monitor receiver batterys voltage under loadl field 36 Model Aviation ThflLILIU 7 ILSLSSIUP wait unless put right kind charge accumulator end DVM probes Leaving DVM connected Futaba charger put 005-mfd mfd ofarad Ed 600-volt capacitor across probes got pictures shown Figure 3 Note ef fects both oscilloscope picture DVM reading Look waveform shows capacitor charged volt age peaks charger discharged shunt resistance DVM between peaks charging voltage Next replaced 005-mfd capacitor l-mfd 600-volt capacitor got results shown Figure 4 Note DVM produces tiny discharge between charging peaks DVM now indicates peak voltage charger pick value ca pacitor just showed Keep increasing capacitance until DVM indication stops creasing could calculate value need swapping capacitors quicker way get true measurement chargers peak voltage Remember two things 1 voltage rating capacitor should greater voltage being measured 2 Discharge capacitor shorting terminals screwdriver once have finished Otherwise can give nasty surprise Now know 789-VAC charger can charge 12-VDC battery DVM story just voltage Settling time can demonstrate settling time DVM choosing DC mode touching probes isolated battery will observe numbers displayed count up zero takes before stop changing common five seconds elapse before DVM settles fi nal reading Since no reason suppose bat tery terminal voltage actually increasing happening can reasonably certain looking instruments settling time long settling time DVM renders unable follow rapid changes VAC best can report some kind average value Analog dArsenval-type meters settle quickly DVMs respond same way use shunt capacitor Just remember charger voltage actu ally quite bit larger terminal voltage charged battery battery would never reach full charge Lou knew Thats asked question Question 2 Lous next question bit sub tle asks What maximum voltage can apply cell charging simple answer maximum per missible voltage determined maximum permissible charging current total resist ance electrical circuit Lets say want charge four-cell NiCd battery Fully charged will reach about 6 VDC will fall 56 VDC unloaded few minutes after battery disconnected charger use loaded termi nal voltage will fall rapidly something less value will hold nearly constant until charge nearly depleted two basic charger designs put out variable charging current constant terminal voltage put out constant current Whether charging current pulsed steady principles remain same Continued page 170 NOR-RAY PRODUCTS INC 5008 SAND BEACH RD / WICHITA FALLS TX 76310 817-692-4475 Span 104 Length 76 1575 Engine ST 2500-3000 Equiv Cowling ision Cut Foam Fuselage & Wings py tips Scale Landing Gear Video416-17 Lbs Available Dealers Welcome Intro Price $17O Reg 19600 Vistercar Fully Aerobatic Very Stable 1/4 Scale Kit Zlin 526 AS Akrobat Special Designed Modeler Modelers Cuts Both Sides Same Time Easily Cuts Straight & Tapered Wing Panels Available 30 40 50 60 Only $8750 $30O S&H RequiW2 V Power Supply *400 5&H Visa-Mastercard Video Available Send $200 information fine products HANDS OFF CUT TWO August 1990 37 D&J ELECTRONICS 900 Lucy Road ll MI 48843 546-2644 service makes P/C equipment utilizing state art electronics Spectrum Analyzer Precision Frequency Measuring equipment True 1991 Standards endorsed AMA & RCMA Transmitter Sticker Program FCC LicensedSpeed Control RepairsQuality Service Transmitter Checks Only includes GOLD/SILVER sticker$400 Transmitter & Receiver Calibration$2400 Frequency Upgrades & Changes crystals extra$2900 Bench Time Repairs per hour$2500 Transmitters service will receive AMA/RCMA sticker ADD $500 FOR SHIPPING & INSURANCE TURN AROUND TIME TWO WEEKS OR LESSI UPS ISA/MASTERCARD ACCEPTEDCOD market come sizes shapes Most servos use all-plastic gear trains Some have two brass gears very few have full metal gear trains Metal gears stronger break under load easily all-plastic ones Some smaller servos will break plastic gear hard otherwise normal landing two types servo motors normal coreless coreless motors usually faster have power Some servos have ball bearings last output gear Glider guiders have worry about size weight Weight isnt important size Some smaller planes dont have room larger servos Two-Meter trainers can use servos have torque output 35 in-oz less usually smaller servos will fit nicely smaller planes larger planes wingspans range 100-120 stronger servo will required torque output 45 in-oz al ways use powerful will fit within space avallable never hurts have reserve power Some manufacturers have higher speed servos less torque ie less power dont require high-speed servos ap plications Remember cannot always tell pow erful servo its size small servos have high power output large servos have power So dont go size servo Read manufacturers specifications servo powerful servo must have proper servo output arm match its power Most servo output arms come servo good enough Off-brand servo arms also available Some types plastic stiffer others have careful type use con necting clevis servo arm adequate using ball-link-type connector servo end pushrod servo wheel pre ferred height ball-link connector above face servo arm will cause servo arm twist under high load servo wheel can offer support As know Sloping can put some serious loads planes equipment Using right equipment mechanics can make difference between having great Slope ship having pile debris after inadequately equipped plane tears itself apart Dont skimp stuff use planes might paying little start reliable equipment worth New servo market Speaking servos Airtronics finally coming out its new allmetal-geared servo servo has dubbed 94141 should ideal mounting wings aileron flap control Obviously important aspect servo its all-metal gear traln combined hefty 42 in-oz torque will provide outstanding flutter strip resistance Another unique feature servo addi tion four extra mounting tabs tabs located side should make wingmounting snap bad news about servo its cost list price $7995 well probably see available about $50 larger hobby shops diseount houses things con sidered still think servo will worth money Looking back stripped gear sets Ive replace thought having buy makes 141 appeal ing things go planned 141 will avail able time read Future stuff As Im writing months col umn Im also getting things together take up Tn-Cities Scale Fun Fly Wash ington except P-SI Penetrator re cently suffered acute attack radio fail ure plunged its death tidal pool Dav enport least next column will deal happenings fun fly Another thing look forward column de voted pivoting wings Ill taking look some things being done Ken Stuhr VS Sallplanes Harley Michaelis Orca Roto fame well some work have done concept Ill also doing feature Mark Allen work doing Flite Lite Composites opinion Mark presently premier de signer RC Sailplanes designs range strictly fun-to-fly Swift 400 formerly known Nisus very competitive Falcon 880 Swift 800 Ill both looking Marks past see got point future see what hell bringing us next Radio Technique/Myers Continued page 37 real world nothing constant design ers can get close ideal Continued page 174 Amount Stock No Description Price I_____ _ I_I__lii III___ $790HandIng LING CHARGE Sub Total Check order or73/% Tax TN Only redit Card order CODTOTAL Name Street Address _______________________________________ City_______ UMasterCard ElVisa EAmerExp Exp Date ______________ Card No EJShip CODUMy Check enclosed $ MA To order HoBg NOUN El I use order blank call 615 373-1444 I m J 170 Model Aviation ma Name Street Address City State Zi TOWER HOBUES has Mighty UtE worlds first pwtMJTl BOWA time Mighty LItW TOWERS Special Stock Suggested SPECIAL RetailPRICE HEOIOO x12 1560/6 pcs 1Z99/6pcs 01 4950 / 6 pes 49J Bpcs 1/6x1x48 4650/3 pcs 3299/3 pcs Call toll free 1-800-637-6050 Refer ad#01006 Im going refer constant-voltage charger Type 1 get Type 1 charging situation connect very large capacity battery small-capacity battery Fast Chargers act like Type constant-voltage charger has very little inter nal resistance therefore terminal voltage stays constant regardless number cells tached charger difference between instantaneous voltage cells voltage charger determines charging rate example constant-voltage charger has 6O-VDC terminal voltage con nected four-cell battery already charged 40 VDC voltage available push charging current 60 40 DC Given average Ni-Cd pack its wires connections voltage could working against resistance about 05 ohm charging current would 2 amps Obviously shorted battery down 0 VDC connected charger initial current would 6 2 amps current might damage internal connections usual 550-rnAh cell pack fully charged will have terminal voltage 6 VDC charging cur rent will zero So can see constantvoltage charger delivers wide range currents can designed never overcharges battery Constant-voltage chargers usually found connected things seldom completely discharged service must re charged quickly left charger long unattended periodslike battery-powered screwdriver portable telephone Im going call constant-current charger Type 2 type charger will deliver same current whether batteries discharged fully charged can deduce has output voltage greater terminal voltage battery Chargers found RC sets usually set overnight charging rates perform like Type 2 chargers used manufacturer intended Batteries have discharged nearly 0 VDC should recharged first time 24 hours Type 2 charger avoid possibility damage high initial current Type 1 charger some facts about real charger usual RC system charger has two pairs wires pair four-cell airborne battery other eight-cell transmitter battery wires usually equipped different plugs help user avoid mistakes rea son difference voltages driving two leads different 165 245 peak voltages Futaba charger checked connected normally lead Futaba charger delivers 65 mA its respective battery Reversing connections connected flight battery lead transmitter charg ing current 25 mA charged flight battery transmitter lead current 220 mA What tells Futaba RC system charger isnt ideal type 2 should may have noticed transmitter side Futaba charger shows twice voltage fully charged eight-cell Ni-Cd battery flight battery charger shows almost three Continued page 176 174 Model Aviation PC Box 1247 310 N 5th St St Chailes L 50 4 312 584 7815 Radio Technique/Myers Continued page 170 8 - MACH-P R ORDERS ONLY 1 800-633-7556ili/iZZCODs IN ALABAMA 347 3525 COLLECTWELCOME TOP QUALITY FUEL FOR EXPERT OR BEGINNER NO RE-CLAIMED ALCOHOL O METHANE ONLY IS USED Designed tested give top performance both 2-cycle 4-cycle engines ringed Except engines requiring low lubricant content CONTAINS NEW TRULY SPACE AGE ADDITIVE developed outer space vacuum Thia new additive attaches internal metal parts engine will reduce friction much 80/ reduces heat wear absolute minimum WE HAVE 3 LUBRICANT BLENDS ALL SYNTHETIC OR SYNTHETIC BLEND CASTOR castor new high purity much cleaner burning castor ALL OUR FUELS CONTAIN ANTIFOAMERS PREVENTERS WEAR ADDITIVES fuel developed priced individual club direct sales market dealer inquiries invited Oude gallon up MIX OK 4 gallon cases up ALL FUEL EXCEPT 54 GALLON DRUMS SNIPPED FREIGHT PRE-PAID Only continental usA 3 GalTo 23 GalTo 63 GalITo 127 GalAndFreight colIect l l al~64 Gal 128 Ga9 54 Gal Drum 50/1095750700 65057518500 12!149595090085077528000 1995145014001350127547500 500/0269522 5022 00 0207578000 Manufactured MACH-7 PO Box 1201 Enterprise Alabama 36330 RIC FOLLIES PRESENTS Craziest Wackiest -And Funniest ModelAirplane Wrecks Youll Ever See! Over 30 Minutes CRASH after CRASH after CRASH Youll See * Flying off lake smashing ice * What happens hand launch forget turn radio plane * A seaplane turn treeplane * A Rocket engine mounted Eindecker * Four wrecked planes turned Twin land flew * And just lot Bad flying much Dont miss one-of-a-kind exciting funny video offer youll ever See $1995 plus $350 shipping handling TO ORDER Send check money order $1995 plus $350 shipping handling SCRANTON HOBBY DISTRIBUTORS 420 Lackawanna Avenue Scranton PA 18503 phone 1717342-1963 MASTERCARDAMERICAN EXPRESS rders add 6% sates lax Radio Technique/Myers Continued page 174 times voltage fuliy charged four-cell bat tery dont know reasonable suppose Futaba engineer decided provide charger can charge eight- ninecell transmitter batteries either four- fivecell airborne batteries charger delivers 50 mA nine-cell transmitter pack 50 mA five-cell receiver pack checked So can used Overnight charger four packs hope youre confused no simple answers six-volt Type 1 charger would damage four-cell pack overvoltage might melt some internal con nections completely discharged pack during initial surge 165-volt Futaba RC system charger could left connected same pack days small current would damage pack Voltage alone determining fac tor dont know what happening follow manufacturers instructions must exper iment know instrumentation use correctly Remember Test Engineers Motto Get right answers purpose Question 3 Jim Hobelsberger La Crescent MN asks What safe minimum voltage start flight exactly like asking much fuel should tank problem face trying answer question fully charged battery looks just like charge-depleted battery voltage poor indicator charge remaining Battery ter minal voltage goes down current being Continued page 178 176 Model Aviation RC hobby based experience 11 VDC per cell 44 VDC under load four-cell battery little energy left battery never safe start flight Besides never discharge pack below 44 VDC never have worry about cell-reversal failures voltage still up flat part curve ends about 48 VDC av erage four-cell 550-mAh battery under kind load energy remaining battery about plunge over end volt age curve usually enough 10minute flight trouble battery little differ ent average battery really better perform battery tests ground keep track time air know fully charged packs good two hours would wise stop flying after 1 hours Either change batteries use bigger batter ies use field charger like CaRa Automatic Cycler-Charger See June 90 column Polks Multi Charge-A-Matic May 90 column use backup like FailSafe Flight System December 89 column plenty op tions dont have get last possible bit energy out batteries TY FUEL T U B NG Ill RCSoaringlBlakeslee page 47 drawn battery increases though remaining charge doesnt change DVMs cheap readily obtainable people will keep trying use Lets start fundamentals situa tion yields two hours service fully charged 550-mAh pack 15-minute pe nod consumes about 70 mAh havent tested situation know what service get full charge havent timing use batteries can guess charge remaining converting DVM ESM expanded scale meter Buy pair 10-ohm 10-watt wirewound resis tors local Radio Shack Put sideby-side twisting leads end together Obtain charging plug leads fit sys tem solder twisted pair resistor leads wire charging plug Connect DVM wires 11 putting DVM parallel resistorsEd adapter converts DVM no-load volt meter equivalent loaded expandedscale voltmeter ESM Actually scale doesnt change just make use greater resolution DVM relative analog meter plug assembly planes charging jack will see voltage leave plugged full 30 seconds will see voltage falls lower value should fall slowly 05 VDC unless start above 5 VDC Assuming testing four-cell Ni-Cd battery value after 30 seconds 480 volts probably have enough charge left fly another 10-minute flight five-cell bat tery want see 600 volts Re member DVM isnt absolutely correct assuming dont know what real characteristics situation Weve got conservative current drawn test about amp similar what moving two servos same time produces resistors may get warm because test will consume about 10 mAh energy rate five watts ANSI standard end-of-charge voltage Ni-Cd cell 09 VDC measured under load practice will usually translate 1 1 VDC load isnt point end point 11 VDC standard aerodynamic glory thin airfoil hig aspect ratio wing some special construction meth ods materials required wing keep such high aspect ratio wins twisting flapping full-span spar used spar starting bottom consists three tapered layers 7-mu carbon fiber 3A spruce high-density-foam shear web 7-mil layer carbon fiber another strip 3/ spruce whole spar rakes back slight angle %-in stainless wing rod accommodated entirely within spar butt end both spars wrapped three layers 1 7-oz Key lar cloth wing core itself cut extruded 15lb-density foam core cut full size section vacuum bagged between two Mylar carrier sheets glass/epoxy sandwich two layers 2-oz glass laid 450 bias top bottom did experiments various weights combinations Keviar glass before settlin8 layup turns Out two layers 2-oz glass cloth just stiff just light layer 1 7-oz Kevlar can seems weight layup oia amer iS perfectly proportioned modeling Curtiss Robin 049 Engines -Channel RIC 41 Wingapan Electric Power Optional SILI Oh 003 Very few full scale airoraff ideelly nuifed 10 model flighf us s fhe appealing old Curfiss Robin wan burn fhe spruca und linen age beaufifully poporfioned rubber electric glow enginea Easy fun build trainer-like performance Flyfine Models Calalog 50phonn 17031 273-0593 INE MODELS INC PO Box 2136 Fairfax VirginIa 22031 USA 178 Model Aviation Especially formulated use gasoline diesel fuels Wont swell harden use new transparent green fuel line perfect fuel connections fuel pumps smoke systems Sold foot Medium Large local Hobby Shop gb-fuels sure use Du-Bros Neoprene Silicone fuel Tubing.the Modelers Choice DU-BRO PRODUCTS INC 480 BONNER RD WAI iCflNflA II Radio Technique/Myers Continued page 176 HAS MOVED INTO LARGER QUARTERS 21 658 Cloud Way Hayward CA 94545 CAL 415 783-4868 Out CAL 800 482-8663 rre proud announce TATONE PRODUCTS CORPORATION has acquired CB ASSOCIATES 4/9 PRESIDENT TATONE PRODUCTS CORP
Edition: Model Aviation - 1990/08
Page Numbers: 36, 37, 170, 174, 176, 178
George M Mye Radio Thchnique 70 Froebllch Farm Ed Hlcksville NY 11801 ABSTRACT DVM adapters read peak voltage function ESM Charging voltages Caring Ni-Cd batteriesPart 5 questions answers THIS TIME Im going answer questions about care feeding Ni-Cd batteries sent several readers types ques tions minds RC modelers Question 1 Lou Moriconi Tucson AZ asks does digital voltmeter DVM show lower voltage charger final volt age charged pack OSCILLOSCOPE URE simple answer naked DVM wrong tool job DVM DC mode designed read steady DC voltagesas batteries Correct measurement charger voltages requires different tool depends nature voltage Two factors must considered waveform settling time Waveform I put oscilloscope DVM probes wires doorbell transformer got pictures shown Figure 1 volt age alternates equally olts -24 volts 60 times per second So call voltage alternating current VAC volt age connected ____________________cmoxaeiaxload current will alternate change di rection 60 times per \f\f\second hence door0scoe-F1 VOLTScalled alternating curbellor0 Figure 1 doorbell transformers reduces household 110 VAC like 25 VAC output examined An oscilloscope will show voltage varying sketched DVM correctly shows average voltage zerol OSCILLOSCOPE URE Futaba scoPe5 f N\I ora17891 VOLTS chargerowa Figure 2 Heres what output Futaba charger looks like scope DVM chargers AC output has hall-wave rectifIed now DYM can see something display senses average voltage over time 789 VDC OSCILLOSCOPE URE 25 EKE 564844 40302010DC PutabsOcope o_0 chargerDVII 005 mfd-25 Figure 3 George has small capacitor across output leads Futaba charger peak voltage hasnt changed capac itor increases average voltage seen DVM 2089 VDC OSCILLOSCOPE URE ILL85IUR FutabaOscope oor0 chargerDVII 1 etd Figure 4 very large capacitor substituted small scope shows chargers peak voltage now held con stant DVM reports being 245 VDC ~jo VOLTS o 0 rent AC DVM correctly reports av erage VDC zero Direct current runs direction put oscilloscope DVM probes transmitter charging plug ordinary Futaba RC system charger got picture shown Figure 2 half-wave rectified AC output voltage goes zero its peak value 245 volts 60 times per second Half-wave rectified means voltage goes direction positive case Note waveforms different note also DVM display Lou misap plied DVM deceived Naturally wondered 789-volt charger could charge battery 12 VDC battery may eventually charge peak voltage its charger its chemistry will support voltage will never read peak voltage DC DVM no matter long TYPICAL VOLTAGE DISCHARGE CURVE FOR NICKEL-CADMIUM BATTERY 480 MINIMUM FOR SAFE TAKEOFF 440 NEVER TAKE OFF 7 area bounded time limits flight 8 within 95* area flight 7 though includes knee curve Since area pro portional power predicts safe flight starting 480 VDC area under curve flight 9 shows starting flight 440 VDC unsafe 1234S N 6789l FLIGHTS COMPLETED George using figures left above talking about using digital voltmeter DYM check battery charger output explains column large figure right depicts typical voltage-vs-time history Ni-Cd battery under load fact voltage suddenly drops off sharply over relatively short time shows vital monitor receiver batterys voltage under loadl field 36 Model Aviation ThflLILIU 7 ILSLSSIUP wait unless put right kind charge accumulator end DVM probes Leaving DVM connected Futaba charger put 005-mfd mfd ofarad Ed 600-volt capacitor across probes got pictures shown Figure 3 Note ef fects both oscilloscope picture DVM reading Look waveform shows capacitor charged volt age peaks charger discharged shunt resistance DVM between peaks charging voltage Next replaced 005-mfd capacitor l-mfd 600-volt capacitor got results shown Figure 4 Note DVM produces tiny discharge between charging peaks DVM now indicates peak voltage charger pick value ca pacitor just showed Keep increasing capacitance until DVM indication stops creasing could calculate value need swapping capacitors quicker way get true measurement chargers peak voltage Remember two things 1 voltage rating capacitor should greater voltage being measured 2 Discharge capacitor shorting terminals screwdriver once have finished Otherwise can give nasty surprise Now know 789-VAC charger can charge 12-VDC battery DVM story just voltage Settling time can demonstrate settling time DVM choosing DC mode touching probes isolated battery will observe numbers displayed count up zero takes before stop changing common five seconds elapse before DVM settles fi nal reading Since no reason suppose bat tery terminal voltage actually increasing happening can reasonably certain looking instruments settling time long settling time DVM renders unable follow rapid changes VAC best can report some kind average value Analog dArsenval-type meters settle quickly DVMs respond same way use shunt capacitor Just remember charger voltage actu ally quite bit larger terminal voltage charged battery battery would never reach full charge Lou knew Thats asked question Question 2 Lous next question bit sub tle asks What maximum voltage can apply cell charging simple answer maximum per missible voltage determined maximum permissible charging current total resist ance electrical circuit Lets say want charge four-cell NiCd battery Fully charged will reach about 6 VDC will fall 56 VDC unloaded few minutes after battery disconnected charger use loaded termi nal voltage will fall rapidly something less value will hold nearly constant until charge nearly depleted two basic charger designs put out variable charging current constant terminal voltage put out constant current Whether charging current pulsed steady principles remain same Continued page 170 NOR-RAY PRODUCTS INC 5008 SAND BEACH RD / WICHITA FALLS TX 76310 817-692-4475 Span 104 Length 76 1575 Engine ST 2500-3000 Equiv Cowling ision Cut Foam Fuselage & Wings py tips Scale Landing Gear Video416-17 Lbs Available Dealers Welcome Intro Price $17O Reg 19600 Vistercar Fully Aerobatic Very Stable 1/4 Scale Kit Zlin 526 AS Akrobat Special Designed Modeler Modelers Cuts Both Sides Same Time Easily Cuts Straight & Tapered Wing Panels Available 30 40 50 60 Only $8750 $30O S&H RequiW2 V Power Supply *400 5&H Visa-Mastercard Video Available Send $200 information fine products HANDS OFF CUT TWO August 1990 37 D&J ELECTRONICS 900 Lucy Road ll MI 48843 546-2644 service makes P/C equipment utilizing state art electronics Spectrum Analyzer Precision Frequency Measuring equipment True 1991 Standards endorsed AMA & RCMA Transmitter Sticker Program FCC LicensedSpeed Control RepairsQuality Service Transmitter Checks Only includes GOLD/SILVER sticker$400 Transmitter & Receiver Calibration$2400 Frequency Upgrades & Changes crystals extra$2900 Bench Time Repairs per hour$2500 Transmitters service will receive AMA/RCMA sticker ADD $500 FOR SHIPPING & INSURANCE TURN AROUND TIME TWO WEEKS OR LESSI UPS ISA/MASTERCARD ACCEPTEDCOD market come sizes shapes Most servos use all-plastic gear trains Some have two brass gears very few have full metal gear trains Metal gears stronger break under load easily all-plastic ones Some smaller servos will break plastic gear hard otherwise normal landing two types servo motors normal coreless coreless motors usually faster have power Some servos have ball bearings last output gear Glider guiders have worry about size weight Weight isnt important size Some smaller planes dont have room larger servos Two-Meter trainers can use servos have torque output 35 in-oz less usually smaller servos will fit nicely smaller planes larger planes wingspans range 100-120 stronger servo will required torque output 45 in-oz al ways use powerful will fit within space avallable never hurts have reserve power Some manufacturers have higher speed servos less torque ie less power dont require high-speed servos ap plications Remember cannot always tell pow erful servo its size small servos have high power output large servos have power So dont go size servo Read manufacturers specifications servo powerful servo must have proper servo output arm match its power Most servo output arms come servo good enough Off-brand servo arms also available Some types plastic stiffer others have careful type use con necting clevis servo arm adequate using ball-link-type connector servo end pushrod servo wheel pre ferred height ball-link connector above face servo arm will cause servo arm twist under high load servo wheel can offer support As know Sloping can put some serious loads planes equipment Using right equipment mechanics can make difference between having great Slope ship having pile debris after inadequately equipped plane tears itself apart Dont skimp stuff use planes might paying little start reliable equipment worth New servo market Speaking servos Airtronics finally coming out its new allmetal-geared servo servo has dubbed 94141 should ideal mounting wings aileron flap control Obviously important aspect servo its all-metal gear traln combined hefty 42 in-oz torque will provide outstanding flutter strip resistance Another unique feature servo addi tion four extra mounting tabs tabs located side should make wingmounting snap bad news about servo its cost list price $7995 well probably see available about $50 larger hobby shops diseount houses things con sidered still think servo will worth money Looking back stripped gear sets Ive replace thought having buy makes 141 appeal ing things go planned 141 will avail able time read Future stuff As Im writing months col umn Im also getting things together take up Tn-Cities Scale Fun Fly Wash ington except P-SI Penetrator re cently suffered acute attack radio fail ure plunged its death tidal pool Dav enport least next column will deal happenings fun fly Another thing look forward column de voted pivoting wings Ill taking look some things being done Ken Stuhr VS Sallplanes Harley Michaelis Orca Roto fame well some work have done concept Ill also doing feature Mark Allen work doing Flite Lite Composites opinion Mark presently premier de signer RC Sailplanes designs range strictly fun-to-fly Swift 400 formerly known Nisus very competitive Falcon 880 Swift 800 Ill both looking Marks past see got point future see what hell bringing us next Radio Technique/Myers Continued page 37 real world nothing constant design ers can get close ideal Continued page 174 Amount Stock No Description Price I_____ _ I_I__lii III___ $790HandIng LING CHARGE Sub Total Check order or73/% Tax TN Only redit Card order CODTOTAL Name Street Address _______________________________________ City_______ UMasterCard ElVisa EAmerExp Exp Date ______________ Card No EJShip CODUMy Check enclosed $ MA To order HoBg NOUN El I use order blank call 615 373-1444 I m J 170 Model Aviation ma Name Street Address City State Zi TOWER HOBUES has Mighty UtE worlds first pwtMJTl BOWA time Mighty LItW TOWERS Special Stock Suggested SPECIAL RetailPRICE HEOIOO x12 1560/6 pcs 1Z99/6pcs 01 4950 / 6 pes 49J Bpcs 1/6x1x48 4650/3 pcs 3299/3 pcs Call toll free 1-800-637-6050 Refer ad#01006 Im going refer constant-voltage charger Type 1 get Type 1 charging situation connect very large capacity battery small-capacity battery Fast Chargers act like Type constant-voltage charger has very little inter nal resistance therefore terminal voltage stays constant regardless number cells tached charger difference between instantaneous voltage cells voltage charger determines charging rate example constant-voltage charger has 6O-VDC terminal voltage con nected four-cell battery already charged 40 VDC voltage available push charging current 60 40 DC Given average Ni-Cd pack its wires connections voltage could working against resistance about 05 ohm charging current would 2 amps Obviously shorted battery down 0 VDC connected charger initial current would 6 2 amps current might damage internal connections usual 550-rnAh cell pack fully charged will have terminal voltage 6 VDC charging cur rent will zero So can see constantvoltage charger delivers wide range currents can designed never overcharges battery Constant-voltage chargers usually found connected things seldom completely discharged service must re charged quickly left charger long unattended periodslike battery-powered screwdriver portable telephone Im going call constant-current charger Type 2 type charger will deliver same current whether batteries discharged fully charged can deduce has output voltage greater terminal voltage battery Chargers found RC sets usually set overnight charging rates perform like Type 2 chargers used manufacturer intended Batteries have discharged nearly 0 VDC should recharged first time 24 hours Type 2 charger avoid possibility damage high initial current Type 1 charger some facts about real charger usual RC system charger has two pairs wires pair four-cell airborne battery other eight-cell transmitter battery wires usually equipped different plugs help user avoid mistakes rea son difference voltages driving two leads different 165 245 peak voltages Futaba charger checked connected normally lead Futaba charger delivers 65 mA its respective battery Reversing connections connected flight battery lead transmitter charg ing current 25 mA charged flight battery transmitter lead current 220 mA What tells Futaba RC system charger isnt ideal type 2 should may have noticed transmitter side Futaba charger shows twice voltage fully charged eight-cell Ni-Cd battery flight battery charger shows almost three Continued page 176 174 Model Aviation PC Box 1247 310 N 5th St St Chailes L 50 4 312 584 7815 Radio Technique/Myers Continued page 170 8 - MACH-P R ORDERS ONLY 1 800-633-7556ili/iZZCODs IN ALABAMA 347 3525 COLLECTWELCOME TOP QUALITY FUEL FOR EXPERT OR BEGINNER NO RE-CLAIMED ALCOHOL O METHANE ONLY IS USED Designed tested give top performance both 2-cycle 4-cycle engines ringed Except engines requiring low lubricant content CONTAINS NEW TRULY SPACE AGE ADDITIVE developed outer space vacuum Thia new additive attaches internal metal parts engine will reduce friction much 80/ reduces heat wear absolute minimum WE HAVE 3 LUBRICANT BLENDS ALL SYNTHETIC OR SYNTHETIC BLEND CASTOR castor new high purity much cleaner burning castor ALL OUR FUELS CONTAIN ANTIFOAMERS PREVENTERS WEAR ADDITIVES fuel developed priced individual club direct sales market dealer inquiries invited Oude gallon up MIX OK 4 gallon cases up ALL FUEL EXCEPT 54 GALLON DRUMS SNIPPED FREIGHT PRE-PAID Only continental usA 3 GalTo 23 GalTo 63 GalITo 127 GalAndFreight colIect l l al~64 Gal 128 Ga9 54 Gal Drum 50/1095750700 65057518500 12!149595090085077528000 1995145014001350127547500 500/0269522 5022 00 0207578000 Manufactured MACH-7 PO Box 1201 Enterprise Alabama 36330 RIC FOLLIES PRESENTS Craziest Wackiest -And Funniest ModelAirplane Wrecks Youll Ever See! Over 30 Minutes CRASH after CRASH after CRASH Youll See * Flying off lake smashing ice * What happens hand launch forget turn radio plane * A seaplane turn treeplane * A Rocket engine mounted Eindecker * Four wrecked planes turned Twin land flew * And just lot Bad flying much Dont miss one-of-a-kind exciting funny video offer youll ever See $1995 plus $350 shipping handling TO ORDER Send check money order $1995 plus $350 shipping handling SCRANTON HOBBY DISTRIBUTORS 420 Lackawanna Avenue Scranton PA 18503 phone 1717342-1963 MASTERCARDAMERICAN EXPRESS rders add 6% sates lax Radio Technique/Myers Continued page 174 times voltage fuliy charged four-cell bat tery dont know reasonable suppose Futaba engineer decided provide charger can charge eight- ninecell transmitter batteries either four- fivecell airborne batteries charger delivers 50 mA nine-cell transmitter pack 50 mA five-cell receiver pack checked So can used Overnight charger four packs hope youre confused no simple answers six-volt Type 1 charger would damage four-cell pack overvoltage might melt some internal con nections completely discharged pack during initial surge 165-volt Futaba RC system charger could left connected same pack days small current would damage pack Voltage alone determining fac tor dont know what happening follow manufacturers instructions must exper iment know instrumentation use correctly Remember Test Engineers Motto Get right answers purpose Question 3 Jim Hobelsberger La Crescent MN asks What safe minimum voltage start flight exactly like asking much fuel should tank problem face trying answer question fully charged battery looks just like charge-depleted battery voltage poor indicator charge remaining Battery ter minal voltage goes down current being Continued page 178 176 Model Aviation RC hobby based experience 11 VDC per cell 44 VDC under load four-cell battery little energy left battery never safe start flight Besides never discharge pack below 44 VDC never have worry about cell-reversal failures voltage still up flat part curve ends about 48 VDC av erage four-cell 550-mAh battery under kind load energy remaining battery about plunge over end volt age curve usually enough 10minute flight trouble battery little differ ent average battery really better perform battery tests ground keep track time air know fully charged packs good two hours would wise stop flying after 1 hours Either change batteries use bigger batter ies use field charger like CaRa Automatic Cycler-Charger See June 90 column Polks Multi Charge-A-Matic May 90 column use backup like FailSafe Flight System December 89 column plenty op tions dont have get last possible bit energy out batteries TY FUEL T U B NG Ill RCSoaringlBlakeslee page 47 drawn battery increases though remaining charge doesnt change DVMs cheap readily obtainable people will keep trying use Lets start fundamentals situa tion yields two hours service fully charged 550-mAh pack 15-minute pe nod consumes about 70 mAh havent tested situation know what service get full charge havent timing use batteries can guess charge remaining converting DVM ESM expanded scale meter Buy pair 10-ohm 10-watt wirewound resis tors local Radio Shack Put sideby-side twisting leads end together Obtain charging plug leads fit sys tem solder twisted pair resistor leads wire charging plug Connect DVM wires 11 putting DVM parallel resistorsEd adapter converts DVM no-load volt meter equivalent loaded expandedscale voltmeter ESM Actually scale doesnt change just make use greater resolution DVM relative analog meter plug assembly planes charging jack will see voltage leave plugged full 30 seconds will see voltage falls lower value should fall slowly 05 VDC unless start above 5 VDC Assuming testing four-cell Ni-Cd battery value after 30 seconds 480 volts probably have enough charge left fly another 10-minute flight five-cell bat tery want see 600 volts Re member DVM isnt absolutely correct assuming dont know what real characteristics situation Weve got conservative current drawn test about amp similar what moving two servos same time produces resistors may get warm because test will consume about 10 mAh energy rate five watts ANSI standard end-of-charge voltage Ni-Cd cell 09 VDC measured under load practice will usually translate 1 1 VDC load isnt point end point 11 VDC standard aerodynamic glory thin airfoil hig aspect ratio wing some special construction meth ods materials required wing keep such high aspect ratio wins twisting flapping full-span spar used spar starting bottom consists three tapered layers 7-mu carbon fiber 3A spruce high-density-foam shear web 7-mil layer carbon fiber another strip 3/ spruce whole spar rakes back slight angle %-in stainless wing rod accommodated entirely within spar butt end both spars wrapped three layers 1 7-oz Key lar cloth wing core itself cut extruded 15lb-density foam core cut full size section vacuum bagged between two Mylar carrier sheets glass/epoxy sandwich two layers 2-oz glass laid 450 bias top bottom did experiments various weights combinations Keviar glass before settlin8 layup turns Out two layers 2-oz glass cloth just stiff just light layer 1 7-oz Kevlar can seems weight layup oia amer iS perfectly proportioned modeling Curtiss Robin 049 Engines -Channel RIC 41 Wingapan Electric Power Optional SILI Oh 003 Very few full scale airoraff ideelly nuifed 10 model flighf us s fhe appealing old Curfiss Robin wan burn fhe spruca und linen age beaufifully poporfioned rubber electric glow enginea Easy fun build trainer-like performance Flyfine Models Calalog 50phonn 17031 273-0593 INE MODELS INC PO Box 2136 Fairfax VirginIa 22031 USA 178 Model Aviation Especially formulated use gasoline diesel fuels Wont swell harden use new transparent green fuel line perfect fuel connections fuel pumps smoke systems Sold foot Medium Large local Hobby Shop gb-fuels sure use Du-Bros Neoprene Silicone fuel Tubing.the Modelers Choice DU-BRO PRODUCTS INC 480 BONNER RD WAI iCflNflA II Radio Technique/Myers Continued page 176 HAS MOVED INTO LARGER QUARTERS 21 658 Cloud Way Hayward CA 94545 CAL 415 783-4868 Out CAL 800 482-8663 rre proud announce TATONE PRODUCTS CORPORATION has acquired CB ASSOCIATES 4/9 PRESIDENT TATONE PRODUCTS CORP