Model Engines: And Their Essentials

The Coma 40 engine top tested four different exhaust systems shown tuned muffler middle stock Supertigre muffler two optional outlet cans bottom left MACS Quickie-X flow-through muffler bottom right Table No 2 shows test results ~ Essentials FIRST THINGS FIRST article engines motors ther modynamics professor years ago quite insistent students should understand engines motors Since have always tried learn lessons well foremost pet peeve has remained engines called motors An engine prime mover engine primary converter energy mechanical motion Motors normally secondary energy converters Actually some model airplanes use motors power source electric motor rubber strands CO-2 motor article about engines Introduction Since inception model engines have two-cycle type means simply combus tion process takes place revolution opposed four-cycle engine such found automotive uses combustion process cylinder takes place other revolution crankshaft physical difference two-cycle engines have no valves associated cams pushrods rocker arms etc pres ent four-cycle engines Rather twocycle engines ported through crankcase cylinder have less moving parts reducing friction allow ing much higher speed operation Early model engines sparkignition type using mixture gasoline oil fuel spark system similar older automobilesincluding break er points coil condenser spark plug glow plug invented late 1940s Ed Actually much earlier hear soon became norm because its simplicity increased power available glow fuel growing interest four-cycle model engines primarily due more-pleasing authentic sound economical operation say nothing about mechanical intrigue far represent fraction total interest also resurging interest spark-ignition engines adaptation chainsaw engines Giant 54 Model Aviation Various piston designs picture L-R Tension ring Schnuerle port Dykes ring Schnuerle port tension ring baffled piston ABC lapped piston forSchnuerle port TENSiON RING DYKES RING Buzzwords Some times seems like invented experts just confound others Actually theyre shortened ver sions longer terms would too cumber some use repeatedly dis cussing subject installment defines terms associ ated model engines indepth discussions follow Part 1 John Kilsdonk Scale models conversion glow engines ignition either novelty economic reasons modern ignition systems feature significant improvements such breakerless ignition low battery drain Additionally diesel model engines have around varying degrees pop ularity almost 40 years diesel conversion kits modern glow engines available Davis Diesel Development along few dieseldesigned engines produced primarily Europe Diesels popular fuel volume weight prime considerations topics article applicable four-cycle ignition diesel engines entire article centered around backbone hobby two-cycle glow engine information presented tended describe critical components outline various consideration select ing operating model engine first step define certain terminology words' will encounter Fundamentally two-cycle model engine works like incoming fuel air mixed enter venturi carburetor front intake engines mixture inducted through port crankshaft travels through crankshaft crankcase As piston comes down positive pressure generated crankcase airfuel mixture forced up bypass port cylinder time pis ton has gone through BDC bottom dead center now traveling up towards TDC top dead center As piston its upstroke traverses bypass cylinder intake port picks up pressurized mixture compresses it gets top center mixture ignited slightly before TDC pressure builds until piston goes through TDC after TDC piston pushed down combus tion process until exhaust port un covered exhaust gases evacuated time another incoming charge going through same channels next stroke actuality very fast process Consider engine running 15000 rpm complete intake compression combustion exhaust process takes place 250 times second Before go further should define discuss some technical terms necessary understand mechanics model engines Rings Engines have lapped pistons say very precision-handfitted piston/cylinders will use piston ring rings purpose ring seal piston-cylinder fit have advan tage engine wears-in ring will maintain clearance between piston cylinder lapped ring less piston other hand will con tinually increase clearance cylinder assembly thereby losing com pression engine wears ring mounted just below top piston disadvantage ring spring tension its rubbing effect increases friction drag minutely March 1985 55 bunch different cylinderdesigns L-R K&B ABC Schnuerle Supertigre steel fora ringed baffled piston Supertigre steel Schnuerle fora ringed piston Supertigre steel airfoil port fora lapped piston OS chromed steel Schnuerlefora ringed piston Photos bysuthor etimi rees ope, decreases performance Rings usually made cast iron normally mehanite two types rings used model engines first type tension ring common ring used today has built-in tension similar spring maintains piston-cylinder seal irrespective rorsc Chu cylinder size compression pressure 1 0 some degree also will compensate small cylinder out-of-round conditions rings can either free-floating pinned prevent rotation Engines us ing system ideal general sport flying feature extremely long life very consistent operation es RPM 18000 other type Dykes ring low-tension ring accurately no tension L-shaped rings fitted extreme top piston must made very carefully tolerant varying cylinder toler ances Dykes ring seal principally obtained compression pressure actually pushed ring out against cylinder near TDC advan tage design lower friction maximum performance Generally though life span somewhat shorter Baffled pistons oldest designs pistons used two-cycle engines named protrusion baffle top piston Engines baffled pistons sometimes re ferred cross-flow loop scav enged function baffle direct incoming air/fuel mixture combustion chamber Older engines less-defined baffle known dome top piston very practical design first engine design highly recom mended sport flying Generally engines using configuration con servatively timed will operate com fortably wide range peak rpms recent years some baffled piston engines have included Perry Ports PDP noticeably improve performance Engines using baffled piston usually priced about 20% less Schnuerle ported engines because cylin ders crankcases less costly produce Popular modern engines using pis ton design 05 non-Schnuerle engines 15 20303540 HB engines Supertigre 60 Como 40 51 ever-popular K&B 40 #4011 Perry ports developed John Perry carburetor fame auxiliary ports carefully located both sides main bypass port baffled piston engines next boost ports Schnuerle engines ports use base crankcase com pression help purge scavenge residual exhaust gases claimed proper use system can add about 500 rpm Usually engines using system labeled PP Perry Port PDP Perry Directional Port Airfoil ports airfoil-ported laminar-ported engines characterized two angeled bypass ports flat-top baffled piston airfoiled bypass ports serve direct incoming air/fuel mix ture combustion chamber need baffle piston makes cleaner combustion chamber hence performance system patented Supertigre design first used 1960 knowl edge still used some ST Como engines considered fore runner Schnuerle-port application 56 Model Aviation model engines Engines using design port have conventional crankcaseusually same baffled piston engine Thus slightly expensive baffled-piston engines engines timed somewhat higher Therefore run higher rpms have narrower operating range Perry Ports sometimes also used design Between 1960 1975 vast major ity Supertigre engines used system However few modern engines still retain airfoil port including ST-35 STG-6OABC Como 40 ABC Schnuerle ports type porting has continued increase popularity since early 1970s originally adopted model engines early 1960s Bill Wisniewski Bill designer modern K&B engines Originally Bill used Schnuerle porting homemade CL Speed engines WART TWA eventually seen several production engines Some first K&B 40-S K&B 1 5R Rossi 15 HP 40 05405R ST X-40 system normally characterized three bypass ports strategically de signed located Normally bypass port directly opposite exhaust port two boost ports located side port roughly 90 0angles center port bypass port resembles small version ST laminar port boost ports being angled towards bypass port prin cipal advantage system aside obvious increased porting area combination high-velocity mixture induction scavening effect purg ing residual exhaust gases Schnuerle porting incorporates flat-top baffleless piston literally identical laminar port piston Actually newer K&B engines use two bypass ports two boost ports Because complicated casting requirements crankcase moreinvolved machining process cylin der engines porting system usually carry premium price tag Most Schnuerle engines timed high performance will operate much better higher rpms means realize full advantage porting system small prop higher nitro fuel may required Schnuerle engines pro duce significantly power baf fled piston designs somewhat power laminar-port designs An ever-growing list modern engines use Schnuerle ports Some morepopular ones OS engines marked SR FSR VF 10 21 25 40 45 46 50 60 90 108 Supertigre engines marked either X 5 11 21 25 29 40 45 60 75 2000 2500 K&B engines metric nomenclature 35 58 65 75 other manufactur ers may say simply Schnuerle ABC Most older some newer lapped-piston engines use combination steel cast iron materials piston cylinder Ringed engines usual ly use steel cylinder sleeve aluminum piston cast iron ring ABC-labeled engines means alumi num piston brass sleeve B chrome plated C Another version AAC has same aluminum piston utilizes chrome-plated aluminum cylinder systems developed Supertigre late 1960s ABC acronym attributable old friend Harry Roe writing virtually engine manufacturer provides some form system ABC pistons machined highsilicone aluminum selected both hard ness compatible thermal expansion characteristics base cylinder material chrome plating provides reduced-friction wear surface aluminum piston happy ABC system has used piston ring although ring increases friction drag has lost popularity engines character ized squeaky bump feel TDC turned over cold glow plug quite normal because operating temperature increases during running clearance will increase slight ly fit becomes ideal assemblies usually found high-performance engines utilizing Continued page 58 March 1985 57 * 9 PLANS * TARBaby Especially Turn-around thio 850 sq 120 4 cycle powered Ron Chidgey design smooth solid performer Rib templates computer plotted Plans construction hints $1 195 TIGER TAIL Li Ron Chidgeys atest series littie arger lighter siomer retains honest flight characteristics its predecess ors Plans construction hints WELLER 3 BLADE FIBERGLASS PROP Proven ih Nats Interna tional competition /4 $2000 IVANS MAGIC GADGET protractor device used Ivan Kriatensen accurately measue aileron elevator arfd rudder throw Takes guess work Out trimming out airplane quality tool complete Instructions log book carrying case SEE YOUR DEALER OR ORDER DIRECT WING TUBE ETS Aluminum alloy tubing plug-In wings Included peir specIal slipfit phenolk sockets build wing structure Now size models 7/0 dia x 2 $795 1* dia x 3 5 1* dia x 3 5 ENGINE SLEEVE BEARING PULLER Pull tight sleeves bearings easily damage new 00s 17MM rea bearing Both $1395 PULLER $795 BEAR INC PULLER $095 TRANSMITTER CASE An inexpensive rugged molded case protect expensive transmitter both two stick single stick transmitters Brown leather grain aluminum trim locking clasp $1095 Gator NIC Products jifl 3713 Pompano Drive sacola FL 325111 Phone 9011 11768639 INCLUbE $100 PER ITEM FOR UPS TIDEWATER ENGR & MACH CO L79P 0 BOX 1135BASTROP LA 71220 MICROMOTORSPHONE 318- 281-2460US DISTRIBUTOR P-21 Car SE$6500P65 Marine$9000P-60 Acre SE$8500 P-21 Car RE$6500P-SO Marine$11000P60 Aero RE$9000 P21 Buggy SE $6500P90 Marine$14000P80 Aero SE$9000 P-21 Buggy RE $6500P-21 Aero SE$5000P-SO Aero RE$9500 P-21 Delta$7500P-21 Aero RE$5500P-45 Duct Fan$7500 P21 Marine SE $6500P-40 Pylon RE$6500P-65 Duct Fan$9500 P-21 Marine RE $6500P40 Aero SE$5800P-SO Duct Fan$10000 P-45 Mar-Disc RV $8500P-45 Aero SE$6000Picco Caps$300 INITROMETHANE PACKING & HANDLING $400 PICCO GLOW PLUGS $3150 Gal Plus Fr Pay Shipping ChargeI$1500KLOTZ KL-200 COD $165 CASH ONLYD 0 Z E N51375 Gal Plus Fr COMPETITION BOAT KITS ANDPICCO ENGINE PARTS HARDWARE IN STOCKFOR ALL CURRENT MODELS i 0 ~5 0 001Sg $G Box 1902 GreenvilleTX 75401 2144545441 flat-top piston Schnuerle airfoil porting always carry premium price tag due materials manufacturing processes involved engines always labeled ABC TDC BDC As said earlier TDC stands top dead center occurring piston extreme top its travel Similarly BDC refers bottom dead center occurs 1800 away piston extreme bottom its travel Dimensions intake exhaust tim ing sometimes measured respect BDC TDC Usually speci fied degrees before top center BTC BTDC after top center ATC ATDC similarly can refer BDC such ABDC etc Timing Dimensions various ports two-cycle engines usually specified degrees crankshaft rotation critical dimensions control performance engine word tim ing refers opening closing posi tions ports typical modern Schnuerle-ported engine might have following timing specification exhaust 1500 bypass 1250 boost ports 1300 crankshaft 1900 Most modern model engines have cyl inder centerline crankshaft therefore cylinder timing points sym metrical about BDC typical engines timing exam ple exhaust open 75 0 BBDC 1050 ATC close 750 ABDC 1050 BTC total opening 1500 duration bypass boost ports simply divide total dura tion two its degrees both before after BDC should pointed out always true Some older engines particular original Fox 35s what known desaxe configuration cylinder offset side decrease connecting rod angle thereby increasing mechanical advan tage down power stroke Crankshaft timing different story because crank port inch away cylinder ports order fuel-air mixture available cylinder ports right time maintain proper pressure-vacuum relationships crankcase crank port must anticipate mixture require ments controlling proper crank case pressures Therefore crank tim ing say 1900 would translate typical Opening 450 ATC typical closing 550 ABC Engine timing best left engine designers hop-up artists another buzzword frequently flaunted misunderstood typical engine timing chart shown used OS courtesy World Engines Continued Page 142 58 Model Aviation 995 Add $500 shippingi z Rolled Plens $2000 Add $300 Shipping1 Texas residents add 5125% Designed Turnaround Pattern LI5 A5L ENc__ MODEL AIRCRAFT aerosol can has done away much pinning taping praying parts permanently joined youll find less time gluing time flying SUPER JET 1/4 oz No 383 $199 1/2 oz No 384 $299 1 oz No 382 $499 2 oz No 388 $999 X-CEL 3 oz No 389 $399 REGULAR JET 1/4 oz No 385 $199 1/2 oz No 386 $299 1 oz No 381 $499 2 oz No 387 $999 4735 West Chicago Avenue 0 Chicago Illinois 60651 area Spinner rules require scalelike round-nose spinner used models pointless very carefully balance propeller use con junction unbalanced spinner Equal care must taken balancing propeller spinner alike Both may balanced accurately using special device such Hi-Point Products USA Balancer Bearing life may greatly reduced due adverse gyroscopic forces generated spinner therefore advisable remove spinner fit round-nose nut during engine testing practice sessions Fox spun-aluminum spinners have proved relia ble Unfortunately readily available country England RMcM CD cast aluminum spinners alternative require modifi cation increasing retaining bolt size 2BA Maintenance carefully-maintained engine essential consistent reli able performance great knowledge required sensible techniques must employed competitive life new engine will depend skill operator Certain parts will need replace ment time time excessive wear normally result incorrect operation regular stripping clean ing will preserve life engine Always use correct tools possible employ use small torque wrench reduces assembly time eliminates distortion due unequally-tensioned bolts have found torque 10 oz-inches round sufficient Flying Having produced reliable competitive model success dependent flying ability No matter proficient pilot may other fields Pylon Racing will present new challenge should stressed useful practice may gained under race conditions therefore necessary novice expert alike race opportunity have month Thanks Paul Bowman timely advice See next month Bill Hager 706 Glen Haven Dr Conroe TX 77385 Engines/Kilsdonk Continued page 58 Compression Technically reduction volume given amount gas such air increases pressure resulting reaction force opposite direction Compression generally referred model engines usually subjective feel force required turn propeller over dry engine Compression direct function piston-to-cylinder fit attendant wear Generally speaking engines compression will perform better some exceptions particularly ringed engines new ringed engine usually needs some running wear ring maximum compression Similar ly well-fitted ABC engine will give false feeling compression due cylinder taper characteristic bump near TDC Compression should confused compression ratio compression ratio should concern average modeler rather best left engine designers manufacturers Just record though compression ratio total cylinder volume piston BDC including volume com bustion chamber displaced pis ton divided volume displaced piston remaining volume piston TDC Compression ratio factor four-cycle engines theoretical value two-cycle engines since intake exhaust ports wide open BDC in-depth article engine authored Glenn Lee published Model Aviation 1979 Pressurization fuel system par ticular need often misunder stood should consider some form pressurization engine 142 Model Aviation iAiILiLIi J j 41 iii 14 3 Clii Using Super Jet Regular Jet X-CEL new Great unexpected field repairs Whether add fillet fill gap always keep combination best service see dealer items want available write direct add $100 per item $200 outside US Minissum order $2 tap CARL GOLDBERG MODELS INC G-285 ft draw suck its fuel tank y means anjnfantesimall small mount suction negative pressure ie engines venturi Obviously size f venturi carburetor opening con ols much suction available ith tiniest venturi few inches f vertical suction possible Worse ducing venturi/carb diameter iso restrict engines ability breathe comng air resulting diminished power effort maximize engines ower largest practical venturi size referred necessitates some form iel system pressurization Pressure im roves delivery fuel engine uulting consistent needle valve ating beginning end ie tank would like interject referred fuel tank location always ic centerline fuel tank directly ie centerline needle valve rovides consistent fuel head pressure y horizontal attitude Sometimes t easily done Slight variations tank wer will work satisfactorily some rm pressure used Personally ways try side-mount engines dur g model construction generally akes easier keep centerlines gether fuel tank will fuel ad change full tank empty enerally represents about two inchof pressure head variation mi*mI INALS assume engine can draw two inches fuel vertically actual head variation two-inch-high tank pres sure changes 2 ches full 2 1 ptya 66% variation Add good muffler pressure system five inches pressure go through numbers again 2 ches full 2 1 inches emptyonly 25% variation Thats quite improvement will translate much consistent engine run novice just flying around level Vertical maneuvers high G-load turns also enhanced pressure Con sider RC model prolonged vertical maneuver less half tank fuel Without some form pressure engine must draw eight inches fuel its own Without pressure cant done mixture goes lean resultant power loss Therefore some form fuel pressurization always recommended Crankcase pressure uses average pressure available engines crank case Actually engines piston goes up down crankcase pressure varies plus minus However due timing induction port positive pressure cycle negative pressure vacuum resulting average positive pressure average pressure approximately 05 PSIabout 14 inches water Crankcase pressure does work well carbureted engines does modulate well part-throttle settings ideal though full-throttle-only applications such some CL FF events RC Pylon Racing requiring maximum engine performance Muffler tuned pipe pressure utilizes back pressure present exhaust system pressurize fuel tank system modulates well part-throttle operation works very well car bureted engines Typical muffler pressures range eight inches water dependent exhaust muffler configu ration Refer Table No 1 also some external pumps manufactured Perry Robart provide greater pressure boost pumps have internal regulator provide consistent pressure driven either crankcase pressure engine vibration Any fuel system pressurization system course additive pre-existing venturi suction Some form pressure certainly recommended almost model engine use free use authored in-depth article devot ed entirely muffler pressure June 1979 ModelAviation article worth reading would like detail Mufflers required RC flying March 1985 143 wuc v e ronu ho bb ya prod uc tsin PO Box 2480 0 Sandusky Ohio 44870 419 627-1877 fields Personally feel can plus hobby flying fields have lost result noise prob lems Most modern engines now shipped muffler very least muf fler available manufacturer separate item Additionally some excellent after-market mufflers avail able various configurations both conventional special applications such Helicopters Scale Racing should realize muffler design has its own characteristics noise reduction exhaust back pressure resultant performance Most model engine mufflers consist adapter bolts directly strapped engines crankcase fits tightly over exhaust stack adapt er transfers exhaust gases expan sion chamber large tube end expansion chamber outlet tube restricts flow thereby generating back pressure can use pressurize fuel tank Most generally back muffler pressure noise reduction given engine inversely proportional performance other words smaller outlet restriction less noise less performance Some mufflers particularly after-mar ket models available flow through version Unlike conventional configurations mufflers have opening front straightthrough tube covered another con centric tube forms outside expansion chamber Flow-through mufflers generally pro vide maximum performance muchlessened noise control Primarily used maximum performance events some muffler required such Club 500 Pylon Racing Next month will cover tuned pipes engine break-in idle settings other topics Please stay tuned FF Duration/Murphy Continued page 61 flashes its predecessors performance did garner number significant wins before being damaged retired As Ive never built same design twice other different sizes never tried constructing exact replica 1949 model Perhaps should have made exception case No pictures 49 job taken am enclosing three-view construction sketch photos similar 1951 version hope short story accom panying three-view might motivate other modelers recalling some memories Nostalgia Gas era aiding cause Nostalgia movement reference Bobs three-view drawing note differences between 49 51 models basically wing stab spans plus basic construc tion fuselages Should anyone inclined take up pencil scale draw up full size plans following additional info would helpful As wingthe top spars x / main bottom spar x rear spar x / LE blank A-in square tapered TE x 1 wing ribs Y,-in sheet double rib tip dihedral measured trailing edge 2 inner panel/tip joint poly hedral being 4 wing tip meas ured flat plane inner panel Note dihedral break moves out rib station 51 model stab material list specifies /16 x LE /16 x 7/ TE /16 x % bottom spar x top spar Stab ribs /16 sheet Neither fuselage construction what would call conventional dif ferences fairly well defined drawing 49 version incorporates X-shaped core center bottom horizontal components /6-in sheet vertical backbones %-in sheet / x hardwood motor bearers used 49 model K&B steel mounts latter design /16 sheet horizontal plan view outline moved downward become flat bot tom fuselage 51 model top backbone /16 x pylon core both versions both instances pylon entire fuselages planked /16-in sheet Bob states 49 model incorporated single-wheel LG 51 used both single- two-wheel arrangement various times foregoing should suffice proper duplication effort have fellas Supercharged Brown Jr oddball engines occasionally brought light dogged persistence some model engine collectors seem always accompanied some tall tale discov ery oft times just interesting engine itself Such case recently discovered Supercharged Brown Jr depicted photo accompanies months column took picture Bob Larshs find recent CIA Club meeting Bob subsequently narrated following story seems Bob heard rumors various sources over years two brothers name Scott quite active Control Line Indianapolis area during early Forties Following lead last sum mer hoped might bring him con tact Bob ultimately knocked door answered young man uniform US Navy Bob soon learn indeed located two brothers sought however gentleman recently passed away young 144 Model Aviation 54 now have plans available forthe famoun A-J Fireball Plans show six production vaaiants plus FOUR modified designs including Fireball Bipe Ihe heaulil, Sportster set also includes Fireball Floats instructions few other nice surprises Orderyour Fireball Plan PakTOOAY andstartbuildingyourownA-JAIRFORCE COLLECTIONPrice includes Mailing Tube First Class UPS delivery charges price complete $2500 Ad P0 Box 548

The Coma 40 engine top tested four different exhaust systems shown tuned muffler middle stock Supertigre muffler two optional outlet cans bottom left MACS Quickie-X flow-through muffler bottom right Table No 2 shows test results ~ Essentials FIRST THINGS FIRST article engines motors ther modynamics professor years ago quite insistent students should understand engines motors Since have always tried learn lessons well foremost pet peeve has remained engines called motors An engine prime mover engine primary converter energy mechanical motion Motors normally secondary energy converters Actually some model airplanes use motors power source electric motor rubber strands CO-2 motor article about engines Introduction Since inception model engines have two-cycle type means simply combus tion process takes place revolution opposed four-cycle engine such found automotive uses combustion process cylinder takes place other revolution crankshaft physical difference two-cycle engines have no valves associated cams pushrods rocker arms etc pres ent four-cycle engines Rather twocycle engines ported through crankcase cylinder have less moving parts reducing friction allow ing much higher speed operation Early model engines sparkignition type using mixture gasoline oil fuel spark system similar older automobilesincluding break er points coil condenser spark plug glow plug invented late 1940s Ed Actually much earlier hear soon became norm because its simplicity increased power available glow fuel growing interest four-cycle model engines primarily due more-pleasing authentic sound economical operation say nothing about mechanical intrigue far represent fraction total interest also resurging interest spark-ignition engines adaptation chainsaw engines Giant 54 Model Aviation Various piston designs picture L-R Tension ring Schnuerle port Dykes ring Schnuerle port tension ring baffled piston ABC lapped piston forSchnuerle port TENSiON RING DYKES RING Buzzwords Some times seems like invented experts just confound others Actually theyre shortened ver sions longer terms would too cumber some use repeatedly dis cussing subject installment defines terms associ ated model engines indepth discussions follow Part 1 John Kilsdonk Scale models conversion glow engines ignition either novelty economic reasons modern ignition systems feature significant improvements such breakerless ignition low battery drain Additionally diesel model engines have around varying degrees pop ularity almost 40 years diesel conversion kits modern glow engines available Davis Diesel Development along few dieseldesigned engines produced primarily Europe Diesels popular fuel volume weight prime considerations topics article applicable four-cycle ignition diesel engines entire article centered around backbone hobby two-cycle glow engine information presented tended describe critical components outline various consideration select ing operating model engine first step define certain terminology words' will encounter Fundamentally two-cycle model engine works like incoming fuel air mixed enter venturi carburetor front intake engines mixture inducted through port crankshaft travels through crankshaft crankcase As piston comes down positive pressure generated crankcase airfuel mixture forced up bypass port cylinder time pis ton has gone through BDC bottom dead center now traveling up towards TDC top dead center As piston its upstroke traverses bypass cylinder intake port picks up pressurized mixture compresses it gets top center mixture ignited slightly before TDC pressure builds until piston goes through TDC after TDC piston pushed down combus tion process until exhaust port un covered exhaust gases evacuated time another incoming charge going through same channels next stroke actuality very fast process Consider engine running 15000 rpm complete intake compression combustion exhaust process takes place 250 times second Before go further should define discuss some technical terms necessary understand mechanics model engines Rings Engines have lapped pistons say very precision-handfitted piston/cylinders will use piston ring rings purpose ring seal piston-cylinder fit have advan tage engine wears-in ring will maintain clearance between piston cylinder lapped ring less piston other hand will con tinually increase clearance cylinder assembly thereby losing com pression engine wears ring mounted just below top piston disadvantage ring spring tension its rubbing effect increases friction drag minutely March 1985 55 bunch different cylinderdesigns L-R K&B ABC Schnuerle Supertigre steel fora ringed baffled piston Supertigre steel Schnuerle fora ringed piston Supertigre steel airfoil port fora lapped piston OS chromed steel Schnuerlefora ringed piston Photos bysuthor etimi rees ope, decreases performance Rings usually made cast iron normally mehanite two types rings used model engines first type tension ring common ring used today has built-in tension similar spring maintains piston-cylinder seal irrespective rorsc Chu cylinder size compression pressure 1 0 some degree also will compensate small cylinder out-of-round conditions rings can either free-floating pinned prevent rotation Engines us ing system ideal general sport flying feature extremely long life very consistent operation es RPM 18000 other type Dykes ring low-tension ring accurately no tension L-shaped rings fitted extreme top piston must made very carefully tolerant varying cylinder toler ances Dykes ring seal principally obtained compression pressure actually pushed ring out against cylinder near TDC advan tage design lower friction maximum performance Generally though life span somewhat shorter Baffled pistons oldest designs pistons used two-cycle engines named protrusion baffle top piston Engines baffled pistons sometimes re ferred cross-flow loop scav enged function baffle direct incoming air/fuel mixture combustion chamber Older engines less-defined baffle known dome top piston very practical design first engine design highly recom mended sport flying Generally engines using configuration con servatively timed will operate com fortably wide range peak rpms recent years some baffled piston engines have included Perry Ports PDP noticeably improve performance Engines using baffled piston usually priced about 20% less Schnuerle ported engines because cylin ders crankcases less costly produce Popular modern engines using pis ton design 05 non-Schnuerle engines 15 20303540 HB engines Supertigre 60 Como 40 51 ever-popular K&B 40 #4011 Perry ports developed John Perry carburetor fame auxiliary ports carefully located both sides main bypass port baffled piston engines next boost ports Schnuerle engines ports use base crankcase com pression help purge scavenge residual exhaust gases claimed proper use system can add about 500 rpm Usually engines using system labeled PP Perry Port PDP Perry Directional Port Airfoil ports airfoil-ported laminar-ported engines characterized two angeled bypass ports flat-top baffled piston airfoiled bypass ports serve direct incoming air/fuel mix ture combustion chamber need baffle piston makes cleaner combustion chamber hence performance system patented Supertigre design first used 1960 knowl edge still used some ST Como engines considered fore runner Schnuerle-port application 56 Model Aviation model engines Engines using design port have conventional crankcaseusually same baffled piston engine Thus slightly expensive baffled-piston engines engines timed somewhat higher Therefore run higher rpms have narrower operating range Perry Ports sometimes also used design Between 1960 1975 vast major ity Supertigre engines used system However few modern engines still retain airfoil port including ST-35 STG-6OABC Como 40 ABC Schnuerle ports type porting has continued increase popularity since early 1970s originally adopted model engines early 1960s Bill Wisniewski Bill designer modern K&B engines Originally Bill used Schnuerle porting homemade CL Speed engines WART TWA eventually seen several production engines Some first K&B 40-S K&B 1 5R Rossi 15 HP 40 05405R ST X-40 system normally characterized three bypass ports strategically de signed located Normally bypass port directly opposite exhaust port two boost ports located side port roughly 90 0angles center port bypass port resembles small version ST laminar port boost ports being angled towards bypass port prin cipal advantage system aside obvious increased porting area combination high-velocity mixture induction scavening effect purg ing residual exhaust gases Schnuerle porting incorporates flat-top baffleless piston literally identical laminar port piston Actually newer K&B engines use two bypass ports two boost ports Because complicated casting requirements crankcase moreinvolved machining process cylin der engines porting system usually carry premium price tag Most Schnuerle engines timed high performance will operate much better higher rpms means realize full advantage porting system small prop higher nitro fuel may required Schnuerle engines pro duce significantly power baf fled piston designs somewhat power laminar-port designs An ever-growing list modern engines use Schnuerle ports Some morepopular ones OS engines marked SR FSR VF 10 21 25 40 45 46 50 60 90 108 Supertigre engines marked either X 5 11 21 25 29 40 45 60 75 2000 2500 K&B engines metric nomenclature 35 58 65 75 other manufactur ers may say simply Schnuerle ABC Most older some newer lapped-piston engines use combination steel cast iron materials piston cylinder Ringed engines usual ly use steel cylinder sleeve aluminum piston cast iron ring ABC-labeled engines means alumi num piston brass sleeve B chrome plated C Another version AAC has same aluminum piston utilizes chrome-plated aluminum cylinder systems developed Supertigre late 1960s ABC acronym attributable old friend Harry Roe writing virtually engine manufacturer provides some form system ABC pistons machined highsilicone aluminum selected both hard ness compatible thermal expansion characteristics base cylinder material chrome plating provides reduced-friction wear surface aluminum piston happy ABC system has used piston ring although ring increases friction drag has lost popularity engines character ized squeaky bump feel TDC turned over cold glow plug quite normal because operating temperature increases during running clearance will increase slight ly fit becomes ideal assemblies usually found high-performance engines utilizing Continued page 58 March 1985 57 * 9 PLANS * TARBaby Especially Turn-around thio 850 sq 120 4 cycle powered Ron Chidgey design smooth solid performer Rib templates computer plotted Plans construction hints $1 195 TIGER TAIL Li Ron Chidgeys atest series littie arger lighter siomer retains honest flight characteristics its predecess ors Plans construction hints WELLER 3 BLADE FIBERGLASS PROP Proven ih Nats Interna tional competition /4 $2000 IVANS MAGIC GADGET protractor device used Ivan Kriatensen accurately measue aileron elevator arfd rudder throw Takes guess work Out trimming out airplane quality tool complete Instructions log book carrying case SEE YOUR DEALER OR ORDER DIRECT WING TUBE ETS Aluminum alloy tubing plug-In wings Included peir specIal slipfit phenolk sockets build wing structure Now size models 7/0 dia x 2 $795 1* dia x 3 5 1* dia x 3 5 ENGINE SLEEVE BEARING PULLER Pull tight sleeves bearings easily damage new 00s 17MM rea bearing Both $1395 PULLER $795 BEAR INC PULLER $095 TRANSMITTER CASE An inexpensive rugged molded case protect expensive transmitter both two stick single stick transmitters Brown leather grain aluminum trim locking clasp $1095 Gator NIC Products jifl 3713 Pompano Drive sacola FL 325111 Phone 9011 11768639 INCLUbE $100 PER ITEM FOR UPS TIDEWATER ENGR & MACH CO L79P 0 BOX 1135BASTROP LA 71220 MICROMOTORSPHONE 318- 281-2460US DISTRIBUTOR P-21 Car SE$6500P65 Marine$9000P-60 Acre SE$8500 P-21 Car RE$6500P-SO Marine$11000P60 Aero RE$9000 P21 Buggy SE $6500P90 Marine$14000P80 Aero SE$9000 P-21 Buggy RE $6500P-21 Aero SE$5000P-SO Aero RE$9500 P-21 Delta$7500P-21 Aero RE$5500P-45 Duct Fan$7500 P21 Marine SE $6500P-40 Pylon RE$6500P-65 Duct Fan$9500 P-21 Marine RE $6500P40 Aero SE$5800P-SO Duct Fan$10000 P-45 Mar-Disc RV $8500P-45 Aero SE$6000Picco Caps$300 INITROMETHANE PACKING & HANDLING $400 PICCO GLOW PLUGS $3150 Gal Plus Fr Pay Shipping ChargeI$1500KLOTZ KL-200 COD $165 CASH ONLYD 0 Z E N51375 Gal Plus Fr COMPETITION BOAT KITS ANDPICCO ENGINE PARTS HARDWARE IN STOCKFOR ALL CURRENT MODELS i 0 ~5 0 001Sg $G Box 1902 GreenvilleTX 75401 2144545441 flat-top piston Schnuerle airfoil porting always carry premium price tag due materials manufacturing processes involved engines always labeled ABC TDC BDC As said earlier TDC stands top dead center occurring piston extreme top its travel Similarly BDC refers bottom dead center occurs 1800 away piston extreme bottom its travel Dimensions intake exhaust tim ing sometimes measured respect BDC TDC Usually speci fied degrees before top center BTC BTDC after top center ATC ATDC similarly can refer BDC such ABDC etc Timing Dimensions various ports two-cycle engines usually specified degrees crankshaft rotation critical dimensions control performance engine word tim ing refers opening closing posi tions ports typical modern Schnuerle-ported engine might have following timing specification exhaust 1500 bypass 1250 boost ports 1300 crankshaft 1900 Most modern model engines have cyl inder centerline crankshaft therefore cylinder timing points sym metrical about BDC typical engines timing exam ple exhaust open 75 0 BBDC 1050 ATC close 750 ABDC 1050 BTC total opening 1500 duration bypass boost ports simply divide total dura tion two its degrees both before after BDC should pointed out always true Some older engines particular original Fox 35s what known desaxe configuration cylinder offset side decrease connecting rod angle thereby increasing mechanical advan tage down power stroke Crankshaft timing different story because crank port inch away cylinder ports order fuel-air mixture available cylinder ports right time maintain proper pressure-vacuum relationships crankcase crank port must anticipate mixture require ments controlling proper crank case pressures Therefore crank tim ing say 1900 would translate typical Opening 450 ATC typical closing 550 ABC Engine timing best left engine designers hop-up artists another buzzword frequently flaunted misunderstood typical engine timing chart shown used OS courtesy World Engines Continued Page 142 58 Model Aviation 995 Add $500 shippingi z Rolled Plens $2000 Add $300 Shipping1 Texas residents add 5125% Designed Turnaround Pattern LI5 A5L ENc__ MODEL AIRCRAFT aerosol can has done away much pinning taping praying parts permanently joined youll find less time gluing time flying SUPER JET 1/4 oz No 383 $199 1/2 oz No 384 $299 1 oz No 382 $499 2 oz No 388 $999 X-CEL 3 oz No 389 $399 REGULAR JET 1/4 oz No 385 $199 1/2 oz No 386 $299 1 oz No 381 $499 2 oz No 387 $999 4735 West Chicago Avenue 0 Chicago Illinois 60651 area Spinner rules require scalelike round-nose spinner used models pointless very carefully balance propeller use con junction unbalanced spinner Equal care must taken balancing propeller spinner alike Both may balanced accurately using special device such Hi-Point Products USA Balancer Bearing life may greatly reduced due adverse gyroscopic forces generated spinner therefore advisable remove spinner fit round-nose nut during engine testing practice sessions Fox spun-aluminum spinners have proved relia ble Unfortunately readily available country England RMcM CD cast aluminum spinners alternative require modifi cation increasing retaining bolt size 2BA Maintenance carefully-maintained engine essential consistent reli able performance great knowledge required sensible techniques must employed competitive life new engine will depend skill operator Certain parts will need replace ment time time excessive wear normally result incorrect operation regular stripping clean ing will preserve life engine Always use correct tools possible employ use small torque wrench reduces assembly time eliminates distortion due unequally-tensioned bolts have found torque 10 oz-inches round sufficient Flying Having produced reliable competitive model success dependent flying ability No matter proficient pilot may other fields Pylon Racing will present new challenge should stressed useful practice may gained under race conditions therefore necessary novice expert alike race opportunity have month Thanks Paul Bowman timely advice See next month Bill Hager 706 Glen Haven Dr Conroe TX 77385 Engines/Kilsdonk Continued page 58 Compression Technically reduction volume given amount gas such air increases pressure resulting reaction force opposite direction Compression generally referred model engines usually subjective feel force required turn propeller over dry engine Compression direct function piston-to-cylinder fit attendant wear Generally speaking engines compression will perform better some exceptions particularly ringed engines new ringed engine usually needs some running wear ring maximum compression Similar ly well-fitted ABC engine will give false feeling compression due cylinder taper characteristic bump near TDC Compression should confused compression ratio compression ratio should concern average modeler rather best left engine designers manufacturers Just record though compression ratio total cylinder volume piston BDC including volume com bustion chamber displaced pis ton divided volume displaced piston remaining volume piston TDC Compression ratio factor four-cycle engines theoretical value two-cycle engines since intake exhaust ports wide open BDC in-depth article engine authored Glenn Lee published Model Aviation 1979 Pressurization fuel system par ticular need often misunder stood should consider some form pressurization engine 142 Model Aviation iAiILiLIi J j 41 iii 14 3 Clii Using Super Jet Regular Jet X-CEL new Great unexpected field repairs Whether add fillet fill gap always keep combination best service see dealer items want available write direct add $100 per item $200 outside US Minissum order $2 tap CARL GOLDBERG MODELS INC G-285 ft draw suck its fuel tank y means anjnfantesimall small mount suction negative pressure ie engines venturi Obviously size f venturi carburetor opening con ols much suction available ith tiniest venturi few inches f vertical suction possible Worse ducing venturi/carb diameter iso restrict engines ability breathe comng air resulting diminished power effort maximize engines ower largest practical venturi size referred necessitates some form iel system pressurization Pressure im roves delivery fuel engine uulting consistent needle valve ating beginning end ie tank would like interject referred fuel tank location always ic centerline fuel tank directly ie centerline needle valve rovides consistent fuel head pressure y horizontal attitude Sometimes t easily done Slight variations tank wer will work satisfactorily some rm pressure used Personally ways try side-mount engines dur g model construction generally akes easier keep centerlines gether fuel tank will fuel ad change full tank empty enerally represents about two inchof pressure head variation mi*mI INALS assume engine can draw two inches fuel vertically actual head variation two-inch-high tank pres sure changes 2 ches full 2 1 ptya 66% variation Add good muffler pressure system five inches pressure go through numbers again 2 ches full 2 1 inches emptyonly 25% variation Thats quite improvement will translate much consistent engine run novice just flying around level Vertical maneuvers high G-load turns also enhanced pressure Con sider RC model prolonged vertical maneuver less half tank fuel Without some form pressure engine must draw eight inches fuel its own Without pressure cant done mixture goes lean resultant power loss Therefore some form fuel pressurization always recommended Crankcase pressure uses average pressure available engines crank case Actually engines piston goes up down crankcase pressure varies plus minus However due timing induction port positive pressure cycle negative pressure vacuum resulting average positive pressure average pressure approximately 05 PSIabout 14 inches water Crankcase pressure does work well carbureted engines does modulate well part-throttle settings ideal though full-throttle-only applications such some CL FF events RC Pylon Racing requiring maximum engine performance Muffler tuned pipe pressure utilizes back pressure present exhaust system pressurize fuel tank system modulates well part-throttle operation works very well car bureted engines Typical muffler pressures range eight inches water dependent exhaust muffler configu ration Refer Table No 1 also some external pumps manufactured Perry Robart provide greater pressure boost pumps have internal regulator provide consistent pressure driven either crankcase pressure engine vibration Any fuel system pressurization system course additive pre-existing venturi suction Some form pressure certainly recommended almost model engine use free use authored in-depth article devot ed entirely muffler pressure June 1979 ModelAviation article worth reading would like detail Mufflers required RC flying March 1985 143 wuc v e ronu ho bb ya prod uc tsin PO Box 2480 0 Sandusky Ohio 44870 419 627-1877 fields Personally feel can plus hobby flying fields have lost result noise prob lems Most modern engines now shipped muffler very least muf fler available manufacturer separate item Additionally some excellent after-market mufflers avail able various configurations both conventional special applications such Helicopters Scale Racing should realize muffler design has its own characteristics noise reduction exhaust back pressure resultant performance Most model engine mufflers consist adapter bolts directly strapped engines crankcase fits tightly over exhaust stack adapt er transfers exhaust gases expan sion chamber large tube end expansion chamber outlet tube restricts flow thereby generating back pressure can use pressurize fuel tank Most generally back muffler pressure noise reduction given engine inversely proportional performance other words smaller outlet restriction less noise less performance Some mufflers particularly after-mar ket models available flow through version Unlike conventional configurations mufflers have opening front straightthrough tube covered another con centric tube forms outside expansion chamber Flow-through mufflers generally pro vide maximum performance muchlessened noise control Primarily used maximum performance events some muffler required such Club 500 Pylon Racing Next month will cover tuned pipes engine break-in idle settings other topics Please stay tuned FF Duration/Murphy Continued page 61 flashes its predecessors performance did garner number significant wins before being damaged retired As Ive never built same design twice other different sizes never tried constructing exact replica 1949 model Perhaps should have made exception case No pictures 49 job taken am enclosing three-view construction sketch photos similar 1951 version hope short story accom panying three-view might motivate other modelers recalling some memories Nostalgia Gas era aiding cause Nostalgia movement reference Bobs three-view drawing note differences between 49 51 models basically wing stab spans plus basic construc tion fuselages Should anyone inclined take up pencil scale draw up full size plans following additional info would helpful As wingthe top spars x / main bottom spar x rear spar x / LE blank A-in square tapered TE x 1 wing ribs Y,-in sheet double rib tip dihedral measured trailing edge 2 inner panel/tip joint poly hedral being 4 wing tip meas ured flat plane inner panel Note dihedral break moves out rib station 51 model stab material list specifies /16 x LE /16 x 7/ TE /16 x % bottom spar x top spar Stab ribs /16 sheet Neither fuselage construction what would call conventional dif ferences fairly well defined drawing 49 version incorporates X-shaped core center bottom horizontal components /6-in sheet vertical backbones %-in sheet / x hardwood motor bearers used 49 model K&B steel mounts latter design /16 sheet horizontal plan view outline moved downward become flat bot tom fuselage 51 model top backbone /16 x pylon core both versions both instances pylon entire fuselages planked /16-in sheet Bob states 49 model incorporated single-wheel LG 51 used both single- two-wheel arrangement various times foregoing should suffice proper duplication effort have fellas Supercharged Brown Jr oddball engines occasionally brought light dogged persistence some model engine collectors seem always accompanied some tall tale discov ery oft times just interesting engine itself Such case recently discovered Supercharged Brown Jr depicted photo accompanies months column took picture Bob Larshs find recent CIA Club meeting Bob subsequently narrated following story seems Bob heard rumors various sources over years two brothers name Scott quite active Control Line Indianapolis area during early Forties Following lead last sum mer hoped might bring him con tact Bob ultimately knocked door answered young man uniform US Navy Bob soon learn indeed located two brothers sought however gentleman recently passed away young 144 Model Aviation 54 now have plans available forthe famoun A-J Fireball Plans show six production vaaiants plus FOUR modified designs including Fireball Bipe Ihe heaulil, Sportster set also includes Fireball Floats instructions few other nice surprises Orderyour Fireball Plan PakTOOAY andstartbuildingyourownA-JAIRFORCE COLLECTIONPrice includes Mailing Tube First Class UPS delivery charges price complete $2500 Ad P0 Box 548

The Coma 40 engine top tested four different exhaust systems shown tuned muffler middle stock Supertigre muffler two optional outlet cans bottom left MACS Quickie-X flow-through muffler bottom right Table No 2 shows test results ~ Essentials FIRST THINGS FIRST article engines motors ther modynamics professor years ago quite insistent students should understand engines motors Since have always tried learn lessons well foremost pet peeve has remained engines called motors An engine prime mover engine primary converter energy mechanical motion Motors normally secondary energy converters Actually some model airplanes use motors power source electric motor rubber strands CO-2 motor article about engines Introduction Since inception model engines have two-cycle type means simply combus tion process takes place revolution opposed four-cycle engine such found automotive uses combustion process cylinder takes place other revolution crankshaft physical difference two-cycle engines have no valves associated cams pushrods rocker arms etc pres ent four-cycle engines Rather twocycle engines ported through crankcase cylinder have less moving parts reducing friction allow ing much higher speed operation Early model engines sparkignition type using mixture gasoline oil fuel spark system similar older automobilesincluding break er points coil condenser spark plug glow plug invented late 1940s Ed Actually much earlier hear soon became norm because its simplicity increased power available glow fuel growing interest four-cycle model engines primarily due more-pleasing authentic sound economical operation say nothing about mechanical intrigue far represent fraction total interest also resurging interest spark-ignition engines adaptation chainsaw engines Giant 54 Model Aviation Various piston designs picture L-R Tension ring Schnuerle port Dykes ring Schnuerle port tension ring baffled piston ABC lapped piston forSchnuerle port TENSiON RING DYKES RING Buzzwords Some times seems like invented experts just confound others Actually theyre shortened ver sions longer terms would too cumber some use repeatedly dis cussing subject installment defines terms associ ated model engines indepth discussions follow Part 1 John Kilsdonk Scale models conversion glow engines ignition either novelty economic reasons modern ignition systems feature significant improvements such breakerless ignition low battery drain Additionally diesel model engines have around varying degrees pop ularity almost 40 years diesel conversion kits modern glow engines available Davis Diesel Development along few dieseldesigned engines produced primarily Europe Diesels popular fuel volume weight prime considerations topics article applicable four-cycle ignition diesel engines entire article centered around backbone hobby two-cycle glow engine information presented tended describe critical components outline various consideration select ing operating model engine first step define certain terminology words' will encounter Fundamentally two-cycle model engine works like incoming fuel air mixed enter venturi carburetor front intake engines mixture inducted through port crankshaft travels through crankshaft crankcase As piston comes down positive pressure generated crankcase airfuel mixture forced up bypass port cylinder time pis ton has gone through BDC bottom dead center now traveling up towards TDC top dead center As piston its upstroke traverses bypass cylinder intake port picks up pressurized mixture compresses it gets top center mixture ignited slightly before TDC pressure builds until piston goes through TDC after TDC piston pushed down combus tion process until exhaust port un covered exhaust gases evacuated time another incoming charge going through same channels next stroke actuality very fast process Consider engine running 15000 rpm complete intake compression combustion exhaust process takes place 250 times second Before go further should define discuss some technical terms necessary understand mechanics model engines Rings Engines have lapped pistons say very precision-handfitted piston/cylinders will use piston ring rings purpose ring seal piston-cylinder fit have advan tage engine wears-in ring will maintain clearance between piston cylinder lapped ring less piston other hand will con tinually increase clearance cylinder assembly thereby losing com pression engine wears ring mounted just below top piston disadvantage ring spring tension its rubbing effect increases friction drag minutely March 1985 55 bunch different cylinderdesigns L-R K&B ABC Schnuerle Supertigre steel fora ringed baffled piston Supertigre steel Schnuerle fora ringed piston Supertigre steel airfoil port fora lapped piston OS chromed steel Schnuerlefora ringed piston Photos bysuthor etimi rees ope, decreases performance Rings usually made cast iron normally mehanite two types rings used model engines first type tension ring common ring used today has built-in tension similar spring maintains piston-cylinder seal irrespective rorsc Chu cylinder size compression pressure 1 0 some degree also will compensate small cylinder out-of-round conditions rings can either free-floating pinned prevent rotation Engines us ing system ideal general sport flying feature extremely long life very consistent operation es RPM 18000 other type Dykes ring low-tension ring accurately no tension L-shaped rings fitted extreme top piston must made very carefully tolerant varying cylinder toler ances Dykes ring seal principally obtained compression pressure actually pushed ring out against cylinder near TDC advan tage design lower friction maximum performance Generally though life span somewhat shorter Baffled pistons oldest designs pistons used two-cycle engines named protrusion baffle top piston Engines baffled pistons sometimes re ferred cross-flow loop scav enged function baffle direct incoming air/fuel mixture combustion chamber Older engines less-defined baffle known dome top piston very practical design first engine design highly recom mended sport flying Generally engines using configuration con servatively timed will operate com fortably wide range peak rpms recent years some baffled piston engines have included Perry Ports PDP noticeably improve performance Engines using baffled piston usually priced about 20% less Schnuerle ported engines because cylin ders crankcases less costly produce Popular modern engines using pis ton design 05 non-Schnuerle engines 15 20303540 HB engines Supertigre 60 Como 40 51 ever-popular K&B 40 #4011 Perry ports developed John Perry carburetor fame auxiliary ports carefully located both sides main bypass port baffled piston engines next boost ports Schnuerle engines ports use base crankcase com pression help purge scavenge residual exhaust gases claimed proper use system can add about 500 rpm Usually engines using system labeled PP Perry Port PDP Perry Directional Port Airfoil ports airfoil-ported laminar-ported engines characterized two angeled bypass ports flat-top baffled piston airfoiled bypass ports serve direct incoming air/fuel mix ture combustion chamber need baffle piston makes cleaner combustion chamber hence performance system patented Supertigre design first used 1960 knowl edge still used some ST Como engines considered fore runner Schnuerle-port application 56 Model Aviation model engines Engines using design port have conventional crankcaseusually same baffled piston engine Thus slightly expensive baffled-piston engines engines timed somewhat higher Therefore run higher rpms have narrower operating range Perry Ports sometimes also used design Between 1960 1975 vast major ity Supertigre engines used system However few modern engines still retain airfoil port including ST-35 STG-6OABC Como 40 ABC Schnuerle ports type porting has continued increase popularity since early 1970s originally adopted model engines early 1960s Bill Wisniewski Bill designer modern K&B engines Originally Bill used Schnuerle porting homemade CL Speed engines WART TWA eventually seen several production engines Some first K&B 40-S K&B 1 5R Rossi 15 HP 40 05405R ST X-40 system normally characterized three bypass ports strategically de signed located Normally bypass port directly opposite exhaust port two boost ports located side port roughly 90 0angles center port bypass port resembles small version ST laminar port boost ports being angled towards bypass port prin cipal advantage system aside obvious increased porting area combination high-velocity mixture induction scavening effect purg ing residual exhaust gases Schnuerle porting incorporates flat-top baffleless piston literally identical laminar port piston Actually newer K&B engines use two bypass ports two boost ports Because complicated casting requirements crankcase moreinvolved machining process cylin der engines porting system usually carry premium price tag Most Schnuerle engines timed high performance will operate much better higher rpms means realize full advantage porting system small prop higher nitro fuel may required Schnuerle engines pro duce significantly power baf fled piston designs somewhat power laminar-port designs An ever-growing list modern engines use Schnuerle ports Some morepopular ones OS engines marked SR FSR VF 10 21 25 40 45 46 50 60 90 108 Supertigre engines marked either X 5 11 21 25 29 40 45 60 75 2000 2500 K&B engines metric nomenclature 35 58 65 75 other manufactur ers may say simply Schnuerle ABC Most older some newer lapped-piston engines use combination steel cast iron materials piston cylinder Ringed engines usual ly use steel cylinder sleeve aluminum piston cast iron ring ABC-labeled engines means alumi num piston brass sleeve B chrome plated C Another version AAC has same aluminum piston utilizes chrome-plated aluminum cylinder systems developed Supertigre late 1960s ABC acronym attributable old friend Harry Roe writing virtually engine manufacturer provides some form system ABC pistons machined highsilicone aluminum selected both hard ness compatible thermal expansion characteristics base cylinder material chrome plating provides reduced-friction wear surface aluminum piston happy ABC system has used piston ring although ring increases friction drag has lost popularity engines character ized squeaky bump feel TDC turned over cold glow plug quite normal because operating temperature increases during running clearance will increase slight ly fit becomes ideal assemblies usually found high-performance engines utilizing Continued page 58 March 1985 57 * 9 PLANS * TARBaby Especially Turn-around thio 850 sq 120 4 cycle powered Ron Chidgey design smooth solid performer Rib templates computer plotted Plans construction hints $1 195 TIGER TAIL Li Ron Chidgeys atest series littie arger lighter siomer retains honest flight characteristics its predecess ors Plans construction hints WELLER 3 BLADE FIBERGLASS PROP Proven ih Nats Interna tional competition /4 $2000 IVANS MAGIC GADGET protractor device used Ivan Kriatensen accurately measue aileron elevator arfd rudder throw Takes guess work Out trimming out airplane quality tool complete Instructions log book carrying case SEE YOUR DEALER OR ORDER DIRECT WING TUBE ETS Aluminum alloy tubing plug-In wings Included peir specIal slipfit phenolk sockets build wing structure Now size models 7/0 dia x 2 $795 1* dia x 3 5 1* dia x 3 5 ENGINE SLEEVE BEARING PULLER Pull tight sleeves bearings easily damage new 00s 17MM rea bearing Both $1395 PULLER $795 BEAR INC PULLER $095 TRANSMITTER CASE An inexpensive rugged molded case protect expensive transmitter both two stick single stick transmitters Brown leather grain aluminum trim locking clasp $1095 Gator NIC Products jifl 3713 Pompano Drive sacola FL 325111 Phone 9011 11768639 INCLUbE $100 PER ITEM FOR UPS TIDEWATER ENGR & MACH CO L79P 0 BOX 1135BASTROP LA 71220 MICROMOTORSPHONE 318- 281-2460US DISTRIBUTOR P-21 Car SE$6500P65 Marine$9000P-60 Acre SE$8500 P-21 Car RE$6500P-SO Marine$11000P60 Aero RE$9000 P21 Buggy SE $6500P90 Marine$14000P80 Aero SE$9000 P-21 Buggy RE $6500P-21 Aero SE$5000P-SO Aero RE$9500 P-21 Delta$7500P-21 Aero RE$5500P-45 Duct Fan$7500 P21 Marine SE $6500P-40 Pylon RE$6500P-65 Duct Fan$9500 P-21 Marine RE $6500P40 Aero SE$5800P-SO Duct Fan$10000 P-45 Mar-Disc RV $8500P-45 Aero SE$6000Picco Caps$300 INITROMETHANE PACKING & HANDLING $400 PICCO GLOW PLUGS $3150 Gal Plus Fr Pay Shipping ChargeI$1500KLOTZ KL-200 COD $165 CASH ONLYD 0 Z E N51375 Gal Plus Fr COMPETITION BOAT KITS ANDPICCO ENGINE PARTS HARDWARE IN STOCKFOR ALL CURRENT MODELS i 0 ~5 0 001Sg $G Box 1902 GreenvilleTX 75401 2144545441 flat-top piston Schnuerle airfoil porting always carry premium price tag due materials manufacturing processes involved engines always labeled ABC TDC BDC As said earlier TDC stands top dead center occurring piston extreme top its travel Similarly BDC refers bottom dead center occurs 1800 away piston extreme bottom its travel Dimensions intake exhaust tim ing sometimes measured respect BDC TDC Usually speci fied degrees before top center BTC BTDC after top center ATC ATDC similarly can refer BDC such ABDC etc Timing Dimensions various ports two-cycle engines usually specified degrees crankshaft rotation critical dimensions control performance engine word tim ing refers opening closing posi tions ports typical modern Schnuerle-ported engine might have following timing specification exhaust 1500 bypass 1250 boost ports 1300 crankshaft 1900 Most modern model engines have cyl inder centerline crankshaft therefore cylinder timing points sym metrical about BDC typical engines timing exam ple exhaust open 75 0 BBDC 1050 ATC close 750 ABDC 1050 BTC total opening 1500 duration bypass boost ports simply divide total dura tion two its degrees both before after BDC should pointed out always true Some older engines particular original Fox 35s what known desaxe configuration cylinder offset side decrease connecting rod angle thereby increasing mechanical advan tage down power stroke Crankshaft timing different story because crank port inch away cylinder ports order fuel-air mixture available cylinder ports right time maintain proper pressure-vacuum relationships crankcase crank port must anticipate mixture require ments controlling proper crank case pressures Therefore crank tim ing say 1900 would translate typical Opening 450 ATC typical closing 550 ABC Engine timing best left engine designers hop-up artists another buzzword frequently flaunted misunderstood typical engine timing chart shown used OS courtesy World Engines Continued Page 142 58 Model Aviation 995 Add $500 shippingi z Rolled Plens $2000 Add $300 Shipping1 Texas residents add 5125% Designed Turnaround Pattern LI5 A5L ENc__ MODEL AIRCRAFT aerosol can has done away much pinning taping praying parts permanently joined youll find less time gluing time flying SUPER JET 1/4 oz No 383 $199 1/2 oz No 384 $299 1 oz No 382 $499 2 oz No 388 $999 X-CEL 3 oz No 389 $399 REGULAR JET 1/4 oz No 385 $199 1/2 oz No 386 $299 1 oz No 381 $499 2 oz No 387 $999 4735 West Chicago Avenue 0 Chicago Illinois 60651 area Spinner rules require scalelike round-nose spinner used models pointless very carefully balance propeller use con junction unbalanced spinner Equal care must taken balancing propeller spinner alike Both may balanced accurately using special device such Hi-Point Products USA Balancer Bearing life may greatly reduced due adverse gyroscopic forces generated spinner therefore advisable remove spinner fit round-nose nut during engine testing practice sessions Fox spun-aluminum spinners have proved relia ble Unfortunately readily available country England RMcM CD cast aluminum spinners alternative require modifi cation increasing retaining bolt size 2BA Maintenance carefully-maintained engine essential consistent reli able performance great knowledge required sensible techniques must employed competitive life new engine will depend skill operator Certain parts will need replace ment time time excessive wear normally result incorrect operation regular stripping clean ing will preserve life engine Always use correct tools possible employ use small torque wrench reduces assembly time eliminates distortion due unequally-tensioned bolts have found torque 10 oz-inches round sufficient Flying Having produced reliable competitive model success dependent flying ability No matter proficient pilot may other fields Pylon Racing will present new challenge should stressed useful practice may gained under race conditions therefore necessary novice expert alike race opportunity have month Thanks Paul Bowman timely advice See next month Bill Hager 706 Glen Haven Dr Conroe TX 77385 Engines/Kilsdonk Continued page 58 Compression Technically reduction volume given amount gas such air increases pressure resulting reaction force opposite direction Compression generally referred model engines usually subjective feel force required turn propeller over dry engine Compression direct function piston-to-cylinder fit attendant wear Generally speaking engines compression will perform better some exceptions particularly ringed engines new ringed engine usually needs some running wear ring maximum compression Similar ly well-fitted ABC engine will give false feeling compression due cylinder taper characteristic bump near TDC Compression should confused compression ratio compression ratio should concern average modeler rather best left engine designers manufacturers Just record though compression ratio total cylinder volume piston BDC including volume com bustion chamber displaced pis ton divided volume displaced piston remaining volume piston TDC Compression ratio factor four-cycle engines theoretical value two-cycle engines since intake exhaust ports wide open BDC in-depth article engine authored Glenn Lee published Model Aviation 1979 Pressurization fuel system par ticular need often misunder stood should consider some form pressurization engine 142 Model Aviation iAiILiLIi J j 41 iii 14 3 Clii Using Super Jet Regular Jet X-CEL new Great unexpected field repairs Whether add fillet fill gap always keep combination best service see dealer items want available write direct add $100 per item $200 outside US Minissum order $2 tap CARL GOLDBERG MODELS INC G-285 ft draw suck its fuel tank y means anjnfantesimall small mount suction negative pressure ie engines venturi Obviously size f venturi carburetor opening con ols much suction available ith tiniest venturi few inches f vertical suction possible Worse ducing venturi/carb diameter iso restrict engines ability breathe comng air resulting diminished power effort maximize engines ower largest practical venturi size referred necessitates some form iel system pressurization Pressure im roves delivery fuel engine uulting consistent needle valve ating beginning end ie tank would like interject referred fuel tank location always ic centerline fuel tank directly ie centerline needle valve rovides consistent fuel head pressure y horizontal attitude Sometimes t easily done Slight variations tank wer will work satisfactorily some rm pressure used Personally ways try side-mount engines dur g model construction generally akes easier keep centerlines gether fuel tank will fuel ad change full tank empty enerally represents about two inchof pressure head variation mi*mI INALS assume engine can draw two inches fuel vertically actual head variation two-inch-high tank pres sure changes 2 ches full 2 1 ptya 66% variation Add good muffler pressure system five inches pressure go through numbers again 2 ches full 2 1 inches emptyonly 25% variation Thats quite improvement will translate much consistent engine run novice just flying around level Vertical maneuvers high G-load turns also enhanced pressure Con sider RC model prolonged vertical maneuver less half tank fuel Without some form pressure engine must draw eight inches fuel its own Without pressure cant done mixture goes lean resultant power loss Therefore some form fuel pressurization always recommended Crankcase pressure uses average pressure available engines crank case Actually engines piston goes up down crankcase pressure varies plus minus However due timing induction port positive pressure cycle negative pressure vacuum resulting average positive pressure average pressure approximately 05 PSIabout 14 inches water Crankcase pressure does work well carbureted engines does modulate well part-throttle settings ideal though full-throttle-only applications such some CL FF events RC Pylon Racing requiring maximum engine performance Muffler tuned pipe pressure utilizes back pressure present exhaust system pressurize fuel tank system modulates well part-throttle operation works very well car bureted engines Typical muffler pressures range eight inches water dependent exhaust muffler configu ration Refer Table No 1 also some external pumps manufactured Perry Robart provide greater pressure boost pumps have internal regulator provide consistent pressure driven either crankcase pressure engine vibration Any fuel system pressurization system course additive pre-existing venturi suction Some form pressure certainly recommended almost model engine use free use authored in-depth article devot ed entirely muffler pressure June 1979 ModelAviation article worth reading would like detail Mufflers required RC flying March 1985 143 wuc v e ronu ho bb ya prod uc tsin PO Box 2480 0 Sandusky Ohio 44870 419 627-1877 fields Personally feel can plus hobby flying fields have lost result noise prob lems Most modern engines now shipped muffler very least muf fler available manufacturer separate item Additionally some excellent after-market mufflers avail able various configurations both conventional special applications such Helicopters Scale Racing should realize muffler design has its own characteristics noise reduction exhaust back pressure resultant performance Most model engine mufflers consist adapter bolts directly strapped engines crankcase fits tightly over exhaust stack adapt er transfers exhaust gases expan sion chamber large tube end expansion chamber outlet tube restricts flow thereby generating back pressure can use pressurize fuel tank Most generally back muffler pressure noise reduction given engine inversely proportional performance other words smaller outlet restriction less noise less performance Some mufflers particularly after-mar ket models available flow through version Unlike conventional configurations mufflers have opening front straightthrough tube covered another con centric tube forms outside expansion chamber Flow-through mufflers generally pro vide maximum performance muchlessened noise control Primarily used maximum performance events some muffler required such Club 500 Pylon Racing Next month will cover tuned pipes engine break-in idle settings other topics Please stay tuned FF Duration/Murphy Continued page 61 flashes its predecessors performance did garner number significant wins before being damaged retired As Ive never built same design twice other different sizes never tried constructing exact replica 1949 model Perhaps should have made exception case No pictures 49 job taken am enclosing three-view construction sketch photos similar 1951 version hope short story accom panying three-view might motivate other modelers recalling some memories Nostalgia Gas era aiding cause Nostalgia movement reference Bobs three-view drawing note differences between 49 51 models basically wing stab spans plus basic construc tion fuselages Should anyone inclined take up pencil scale draw up full size plans following additional info would helpful As wingthe top spars x / main bottom spar x rear spar x / LE blank A-in square tapered TE x 1 wing ribs Y,-in sheet double rib tip dihedral measured trailing edge 2 inner panel/tip joint poly hedral being 4 wing tip meas ured flat plane inner panel Note dihedral break moves out rib station 51 model stab material list specifies /16 x LE /16 x 7/ TE /16 x % bottom spar x top spar Stab ribs /16 sheet Neither fuselage construction what would call conventional dif ferences fairly well defined drawing 49 version incorporates X-shaped core center bottom horizontal components /6-in sheet vertical backbones %-in sheet / x hardwood motor bearers used 49 model K&B steel mounts latter design /16 sheet horizontal plan view outline moved downward become flat bot tom fuselage 51 model top backbone /16 x pylon core both versions both instances pylon entire fuselages planked /16-in sheet Bob states 49 model incorporated single-wheel LG 51 used both single- two-wheel arrangement various times foregoing should suffice proper duplication effort have fellas Supercharged Brown Jr oddball engines occasionally brought light dogged persistence some model engine collectors seem always accompanied some tall tale discov ery oft times just interesting engine itself Such case recently discovered Supercharged Brown Jr depicted photo accompanies months column took picture Bob Larshs find recent CIA Club meeting Bob subsequently narrated following story seems Bob heard rumors various sources over years two brothers name Scott quite active Control Line Indianapolis area during early Forties Following lead last sum mer hoped might bring him con tact Bob ultimately knocked door answered young man uniform US Navy Bob soon learn indeed located two brothers sought however gentleman recently passed away young 144 Model Aviation 54 now have plans available forthe famoun A-J Fireball Plans show six production vaaiants plus FOUR modified designs including Fireball Bipe Ihe heaulil, Sportster set also includes Fireball Floats instructions few other nice surprises Orderyour Fireball Plan PakTOOAY andstartbuildingyourownA-JAIRFORCE COLLECTIONPrice includes Mailing Tube First Class UPS delivery charges price complete $2500 Ad P0 Box 548