Engine TechniqueDon Jehuik FUEL SYSTEMS ideal fuel system isnt yet lot work has put making engines run optimum fashion Lets begin taking look some forces affect fuel de livered engine gravity centrifugal CONVENTIONAL Al R PRESSURE A$A*A AA -p PLUS WEIGHT OF FUEL IN TANJ~ FUEL LEVEL ~ LOW 1/2 VARIABLE PRESSURE VARIABLE FLOW principle chicken hopper tank Height fuel larger reservoir tank main tains pressure smaller tank feed note fuel lineremains constant throughout engine run Details text force partial vacuum turbulent lami nar flow Starting fuel tank different types tanks serve basic purpose hold en gines fuel supply Tanks can further broken two basic categories pressure demand Pressure tanks ex panded bladder type hard tanks external pressure sourcesuch crank case muffler pipe pressure supplied CHICKEN HOPPER A 0 0 CONSTANT PRESSURE CONSTANT FLOW tank supply fuel engine forcing fuel carburetor Demand tanks unpressurized bladder hard tanks supply fuel engine result partial vacuum fuel draw created flow air through car buretor venturi Its hard understand type tank pressure demand doesnt change fact nearly applications fuel supplied engine varies quan tity throughout run means needle valve setting will compro mise must allow larger amount fuel flow provided beginning run smaller amount flow end Its easier use picture drawing explain some concepts first drawing shows conventional demand pressure tank works compared Stockton Chicken Hopper tank Air pres sure whether supplied air vent tank pressure source con stant both designs difference tween pressure exists fuel line pickup weight fuel varies height fuel conventional tank fuel produces pressure typical condition exists flier adjusts engine before releasing model Too often engine adjusted peak setting before release results engine going over-lean during run due decreased fuel pressure tank empties way compensate condition out special changes fuel system adjust needle valve engine reaches peak setting end run means releasing rich enough compen sate total variation fuel pressure beginning end flight 48 Model Aviation Over 25 years fuel-control concept Left Jim Walker pressure regulator 1950fuel bladder pressurized sandwiching between two thin ply boards squeezed together rubberbands Center Servo-adjustable needle valve Paul Bugi circa 1950 Right Modern fuel pump Chicken Hopper tank differs designed deliver constant fuel pres sure fuel line pickup As can see fuel pickup located separate constant pressure tank supplied reservoir relationship between air pressure fuel head height fuel small hopper tank remains constant throughout entire run photo hopper tank team race installation illustrates several things First note extremely small size hopper tank circle compared reservoir tank Second note size shape reservoir tank has no effect flow fuel engine Third location tank relative engine carburetor critical because constant pressure fuel source provided hopper tank enables dial optimum needle valve setting will remain constant throughout flight drawing Goodyear tank hopper tank adapted example adaptation principle specialized event Similar hoppers can adapted CL stunt tanks speed tanks photo etc RC boats have adapted locating small hopper tank 1 oz carburetor connecting main reservoir tank located aft boat Model race cars RC thethered can also benefit similar installations Jim Walker CL pioneer recognized problem variable fuel flow mar keted earliest device am aware solve problem fuel regulator see photo wired intake en gine inlet regulator sup plied rubber fuel bladder pressurized placing between two sheets plywood wrapped rubberbands outlet connected needle valve fitting regulator con tained diaphragm controlled spring loaded ball valve supplied fuel carburetor Whenever pressure fuel line fell below atmospheric pressure diaphram would push ball off its seat allow fuel flow carbure tor used system first came out worked advertised recent developments affecting fuel control include servo adjustable needle valve valve picture made Paul BugI around 1966 help top Austrian RC boat competitor solve problem controlling needle valve during race As can see needle valve mounted large threaded body servo arm thread coarse servo travel can adjust needle full rich full lean 900 arm ro tation last item picture fuel pump Pumps currently popular combined servo-controlled needle valve provide maximum power precise engine adjustment Continued page 92 FUEL June 1978 49 P..I Dd f.I tnIo unnhiA fuel tn engine under Dressure oiea irom engliw uraIrnI~ rierruw turi , u, have used CL models long time reduce effect centrifugal forces needle settings may difficult relate picture TO chicken hopper demonstration picture chicken hopper tank typical speed modeladditionally utilizes case pressure 25cc smaller Suit 40s Also Pilatus PC7 Turbo Trainer 60s Strictly European big lowwings offer lots fuselage room ruggedness suit grass fields None rugged Topps ARTF Class 2 scale line has expanded sleek Mirage 2000 stunning F-18 Cobra has droop snoot leading edges latest camou ouflage looks part model 80s sells around $160 Germany Sport RC also has its share innova tions Another flush trainer kits include several 20 engines trend upheld RC gear itself Last show saw rash super-sophisticated equipment controls would take ace handle year same trend perpetuated yet toned down shade modular concept becomes common place Almost manufacturer now add-a-box state frequency purpose can changed plugging-in another module Multiplex put control mixer Ix way like several other prominent German firms have sunk national pride badge-engineered Japanese imports meet sports market other wise neglecting Thus Futaba Sanwa product review product review product review Whats Angle Measuring rigging angles wings tails thrust lines offset thrust etc. has always irksome task unrealized error could effect flight perfor mance Robarts new incidence meter ends use adjustable notched tops positioned steel bar according type measurement made box containing steel counterweight pre cision pointer dial scale also slides bar required Operation simple using carpenters level Price $1595 Ro bart PO Box 122 Wheaton 1160187 product review product review product review JM 10 etc. have strong grip dont always appear under own name Did someone say What about en gines---helicopters Only Dieter Schlut ers Heli-Boy acrobatic version Bell 222 could claimed new among rotary wings thats sign consolidation Helicopter trainer pads coming solu tion training risk clever never-leave-the-ground device Hel mut Fett Cologne said selling generation garden fliers want no simulate flight risk As engines car boom has fluence has boosted 19 size opposite end big Sueva 25 05 20 Damo 18 cc sizes plus new OS 90 OPS 65 show way trade thinking Only Webra has thought lunior size produced 15 cc 09 theres hardly unit show throttle way stimulate young CL flier free-flight sportster Engine Technique/Jehlik continued page 49 ideal RC applications million words said about fuel systems Im going try summarize few RC aircraft Since fuel system subjected relatively long distances fuel draw vertical climb large varia tions fuel pressure point pickup maneuvers use fuel pumps rec ommended may supplemented servo-controlled needle valve special applications Control Line Although understood Stockton Chicken Hooper concept adaptable CL events result being perfectly constant runs throughout flight am unaware other fuel tank design provides level performance Ill glad answer questions about adaptation hop pers tanks different events Carburetors carburetor acts partial regulator velocity air venturi throat results lowered air pres NEW/ MUFF-L-IT SERIES Available e C engines Sis eight Ob reduction noise engines Proportional nolumne expan sion chamber Large exhaust nozzle low back pressure 4 Little no loss power REGULAR & NO 30109-191749 No 0022940t839 no 30340801949 *nI o B d C y00fl No 304N4 wln 51095 NO305R4294011195 No30km488411395 1/2A MUFFLER Fits COX 049 engInes NO 30080491149 No ODIN0511149 sure provides suction draw fuel carburetor degree needle valve opening will allow much fuel pass given setting get idea variation attach fuel line about 12 long tank adjust en gine tank located carburetor level raise lower tank will observe engine change very rich very lean depending vertical location tank regula tion provided carburetor slight Engines Can tolerate wide range fuel settings Simply put power curve engines relatively flat peak power settings means can generally adjust engine run up 1000 rpm rich peak setting still use nearly maximum power Forces Gravity basic force usu ally smallest force affecting model fuel system G forces maneuvers can approach 40 centrifugal forces CL speed models over 20 times gravity Vibration air stream forces tend cause fuel foam tanks recent approach Dave Gierke places fuel bladder hard tank will eliminate foaming air enters tank outside bladder fuel inside system used Huntsville speed fliers Dick Hall Bob Lauderdale FAI CL speed models early 60s system eliminates Inland Sport eye-catcning classic orom Golden Era VNJith 37% span Herb Clu key-designed parasol scale RC model takes 02 electric 049 power excellent schoolyard flying Decals printed balsa rolled plans proof-of-scale data etc Price $1395 Flyline Models Inc. 2820 Dorr Ave B-2 Fairfax VA 22030 product review product review product review 92 Model Aviation Droduct review product review product review foaming fuel does provide constant pressure fuel source Turbulent Laminar Flow Fuel tanks lines often blamed engine running problems caused carbure tor RC carburetors adjusted rotating sliding barrels change laminar flow full open position inter nal turbulent flow patterns restricted turbulent flow can unpredictably af fect fuel draw depending relative air pressure fuel jet Suction pres sure carburetors similarly affected fuel droplet size variations caused consistent flow forces past fuel jets turn affects engine combustion effici ency Among efficient RC car buretors have tested have Fox engines engineered flow bench Duke have excellent full-range characteristics Now just word about fixed venturi carburetors efficient multi-jet design Cox engines fuel enters venturi through several small jets instead fuel droplets entering engine average smaller size results better needle valve ad justment b improved fuel economy Now Ive started fuel systems can see lot needs said about design application theory system product review product review product review Kavalier well-thought-out concept aileron trainer strong emphasis fly ing qualities designer Claude McCullough Like other popular name-brand-trainers has 56-in wing kind magic number takes 29- 40-size engines distinctive clean shoulder-wing slim bit rakish moderately tapered wing swept fin elevator aft fuselage Semi-sym metrical airfoil strength high-lift stability Differential aileron control horns give up less down movement eliminate aileron yaw Assembled flat surface wing incorporates precise amount incidence changeless tips enhances control tip stall way touchdown low airspeeds result ing non-expert piloting Performance handling characteristics qualifies Kavalier both sport stunt flying Kit includes illustrated instruction book die-cut balsa plywood molded cowling formed aluminum main gear nylon horns molded canopy framing hardware printed fuse lage sides build directly wood 5/32 steel nose gear full-size plan Price $3995 Sig Manufacturing Co Montezuma IA 50171 product review product review product review integrity plain old good practices like soldering no leaks etc will have wait future articles Dave Palmer Bowie Md asks always under impression mi crosopic grooves should never have relationship changed regarding piston sleeve Once piston sleeve have seated ground would second third disassembly reduce com pression worried about mi croscopic grooves engine breaks lapped broken metal surfaces interfere other worn away contact No mi croscopic grooves exist surfaces either piston sleeve run full length stroke borne out fact both piston sleeve rotate relative another engine runs Look exhaust port dark night good light youll see rotation random What can account power losses engine dismantled re assembled Referring previous col umn engine set-up engine dismantled checked set up can have unevenly torqued screws misaligned parts causing warps relieved running wear etc Such engine can indeed loose power reassembled identical duplication bolt torque sleeve June 1978 93 Peak Peormance U S E Greater RPM FIRST AROUND IB[ WORLD DOUGLAS WORLD CRUIS[R 1 72 SCALE PLASTIC MODEL KIT During 1924 history-making Douglas World Cruisers made first around world flight Covering some 27553 miles epic voyage lasted 175 days Now can construct highly-detailed model famous aircraft KIT FEATURES WHEELS AND PONTOONS DECALS TO ALLOW FINISHING MODEL AS ANY ONE OF FIVE DIFFERENT AIRCRAFT TLE AGO ON NEW ORLEANS ON II $495 Pro, dealer direct adding 15% postage ond handlieg Send SOt complete illustrated catalogDEPT MAjJLLA1$ 181 PAWNEE ST SAN MARCOS CA 92069 CL Scale/Gretz continued page 44 CA 92345 another source economical b&w photos Ive tried selection isnt extensive Collect Air Photos different type photo service have 14-page catalog lists individual photos specifics such aircrafts registration number attitude airplane photo 5 int costs $1 8 X 10 $150 catalog $1 An inadvertent transposition what did April column Some probably noticed drawing Dick Ruckels engine shutoff directions shown high low throttle opposite commonly used use standard G-S i-Roberts handle matching bellcrank engines throttle arm like below throttle barrel normally high throttle will forward low throttle will back towards Regardless direction prefer high low throttle control handle just position 94 Model Aviation Uhicken hopper thK snstalea ieam racer 11W Isisy Isuppo os. attached large reservoir tanknote circled area Bladder tanks may Suction operated illustrated 1/2A Gold berg balloon tank pressure force provided speed model type surgical tubing tank Combat baby pacifier ement etc due mi- imperfections best set croscopic grooves caused macro up unrun nearly new tight engine problems relating stress geometric rather tired engine never quite right Don Jehlik 438A Schweer Dr Star Route Hat home NV894 15 Two classic CL tanks wedge aerobatics rat race tank fills fuselage Both cause engine lean out during engine run
Edition: Model Aviation - 1978/06
Page Numbers: 48, 49, 92, 93, 94
Engine TechniqueDon Jehuik FUEL SYSTEMS ideal fuel system isnt yet lot work has put making engines run optimum fashion Lets begin taking look some forces affect fuel de livered engine gravity centrifugal CONVENTIONAL Al R PRESSURE A$A*A AA -p PLUS WEIGHT OF FUEL IN TANJ~ FUEL LEVEL ~ LOW 1/2 VARIABLE PRESSURE VARIABLE FLOW principle chicken hopper tank Height fuel larger reservoir tank main tains pressure smaller tank feed note fuel lineremains constant throughout engine run Details text force partial vacuum turbulent lami nar flow Starting fuel tank different types tanks serve basic purpose hold en gines fuel supply Tanks can further broken two basic categories pressure demand Pressure tanks ex panded bladder type hard tanks external pressure sourcesuch crank case muffler pipe pressure supplied CHICKEN HOPPER A 0 0 CONSTANT PRESSURE CONSTANT FLOW tank supply fuel engine forcing fuel carburetor Demand tanks unpressurized bladder hard tanks supply fuel engine result partial vacuum fuel draw created flow air through car buretor venturi Its hard understand type tank pressure demand doesnt change fact nearly applications fuel supplied engine varies quan tity throughout run means needle valve setting will compro mise must allow larger amount fuel flow provided beginning run smaller amount flow end Its easier use picture drawing explain some concepts first drawing shows conventional demand pressure tank works compared Stockton Chicken Hopper tank Air pres sure whether supplied air vent tank pressure source con stant both designs difference tween pressure exists fuel line pickup weight fuel varies height fuel conventional tank fuel produces pressure typical condition exists flier adjusts engine before releasing model Too often engine adjusted peak setting before release results engine going over-lean during run due decreased fuel pressure tank empties way compensate condition out special changes fuel system adjust needle valve engine reaches peak setting end run means releasing rich enough compen sate total variation fuel pressure beginning end flight 48 Model Aviation Over 25 years fuel-control concept Left Jim Walker pressure regulator 1950fuel bladder pressurized sandwiching between two thin ply boards squeezed together rubberbands Center Servo-adjustable needle valve Paul Bugi circa 1950 Right Modern fuel pump Chicken Hopper tank differs designed deliver constant fuel pres sure fuel line pickup As can see fuel pickup located separate constant pressure tank supplied reservoir relationship between air pressure fuel head height fuel small hopper tank remains constant throughout entire run photo hopper tank team race installation illustrates several things First note extremely small size hopper tank circle compared reservoir tank Second note size shape reservoir tank has no effect flow fuel engine Third location tank relative engine carburetor critical because constant pressure fuel source provided hopper tank enables dial optimum needle valve setting will remain constant throughout flight drawing Goodyear tank hopper tank adapted example adaptation principle specialized event Similar hoppers can adapted CL stunt tanks speed tanks photo etc RC boats have adapted locating small hopper tank 1 oz carburetor connecting main reservoir tank located aft boat Model race cars RC thethered can also benefit similar installations Jim Walker CL pioneer recognized problem variable fuel flow mar keted earliest device am aware solve problem fuel regulator see photo wired intake en gine inlet regulator sup plied rubber fuel bladder pressurized placing between two sheets plywood wrapped rubberbands outlet connected needle valve fitting regulator con tained diaphragm controlled spring loaded ball valve supplied fuel carburetor Whenever pressure fuel line fell below atmospheric pressure diaphram would push ball off its seat allow fuel flow carbure tor used system first came out worked advertised recent developments affecting fuel control include servo adjustable needle valve valve picture made Paul BugI around 1966 help top Austrian RC boat competitor solve problem controlling needle valve during race As can see needle valve mounted large threaded body servo arm thread coarse servo travel can adjust needle full rich full lean 900 arm ro tation last item picture fuel pump Pumps currently popular combined servo-controlled needle valve provide maximum power precise engine adjustment Continued page 92 FUEL June 1978 49 P..I Dd f.I tnIo unnhiA fuel tn engine under Dressure oiea irom engliw uraIrnI~ rierruw turi , u, have used CL models long time reduce effect centrifugal forces needle settings may difficult relate picture TO chicken hopper demonstration picture chicken hopper tank typical speed modeladditionally utilizes case pressure 25cc smaller Suit 40s Also Pilatus PC7 Turbo Trainer 60s Strictly European big lowwings offer lots fuselage room ruggedness suit grass fields None rugged Topps ARTF Class 2 scale line has expanded sleek Mirage 2000 stunning F-18 Cobra has droop snoot leading edges latest camou ouflage looks part model 80s sells around $160 Germany Sport RC also has its share innova tions Another flush trainer kits include several 20 engines trend upheld RC gear itself Last show saw rash super-sophisticated equipment controls would take ace handle year same trend perpetuated yet toned down shade modular concept becomes common place Almost manufacturer now add-a-box state frequency purpose can changed plugging-in another module Multiplex put control mixer Ix way like several other prominent German firms have sunk national pride badge-engineered Japanese imports meet sports market other wise neglecting Thus Futaba Sanwa product review product review product review Whats Angle Measuring rigging angles wings tails thrust lines offset thrust etc. has always irksome task unrealized error could effect flight perfor mance Robarts new incidence meter ends use adjustable notched tops positioned steel bar according type measurement made box containing steel counterweight pre cision pointer dial scale also slides bar required Operation simple using carpenters level Price $1595 Ro bart PO Box 122 Wheaton 1160187 product review product review product review JM 10 etc. have strong grip dont always appear under own name Did someone say What about en gines---helicopters Only Dieter Schlut ers Heli-Boy acrobatic version Bell 222 could claimed new among rotary wings thats sign consolidation Helicopter trainer pads coming solu tion training risk clever never-leave-the-ground device Hel mut Fett Cologne said selling generation garden fliers want no simulate flight risk As engines car boom has fluence has boosted 19 size opposite end big Sueva 25 05 20 Damo 18 cc sizes plus new OS 90 OPS 65 show way trade thinking Only Webra has thought lunior size produced 15 cc 09 theres hardly unit show throttle way stimulate young CL flier free-flight sportster Engine Technique/Jehlik continued page 49 ideal RC applications million words said about fuel systems Im going try summarize few RC aircraft Since fuel system subjected relatively long distances fuel draw vertical climb large varia tions fuel pressure point pickup maneuvers use fuel pumps rec ommended may supplemented servo-controlled needle valve special applications Control Line Although understood Stockton Chicken Hooper concept adaptable CL events result being perfectly constant runs throughout flight am unaware other fuel tank design provides level performance Ill glad answer questions about adaptation hop pers tanks different events Carburetors carburetor acts partial regulator velocity air venturi throat results lowered air pres NEW/ MUFF-L-IT SERIES Available e C engines Sis eight Ob reduction noise engines Proportional nolumne expan sion chamber Large exhaust nozzle low back pressure 4 Little no loss power REGULAR & NO 30109-191749 No 0022940t839 no 30340801949 *nI o B d C y00fl No 304N4 wln 51095 NO305R4294011195 No30km488411395 1/2A MUFFLER Fits COX 049 engInes NO 30080491149 No ODIN0511149 sure provides suction draw fuel carburetor degree needle valve opening will allow much fuel pass given setting get idea variation attach fuel line about 12 long tank adjust en gine tank located carburetor level raise lower tank will observe engine change very rich very lean depending vertical location tank regula tion provided carburetor slight Engines Can tolerate wide range fuel settings Simply put power curve engines relatively flat peak power settings means can generally adjust engine run up 1000 rpm rich peak setting still use nearly maximum power Forces Gravity basic force usu ally smallest force affecting model fuel system G forces maneuvers can approach 40 centrifugal forces CL speed models over 20 times gravity Vibration air stream forces tend cause fuel foam tanks recent approach Dave Gierke places fuel bladder hard tank will eliminate foaming air enters tank outside bladder fuel inside system used Huntsville speed fliers Dick Hall Bob Lauderdale FAI CL speed models early 60s system eliminates Inland Sport eye-catcning classic orom Golden Era VNJith 37% span Herb Clu key-designed parasol scale RC model takes 02 electric 049 power excellent schoolyard flying Decals printed balsa rolled plans proof-of-scale data etc Price $1395 Flyline Models Inc. 2820 Dorr Ave B-2 Fairfax VA 22030 product review product review product review 92 Model Aviation Droduct review product review product review foaming fuel does provide constant pressure fuel source Turbulent Laminar Flow Fuel tanks lines often blamed engine running problems caused carbure tor RC carburetors adjusted rotating sliding barrels change laminar flow full open position inter nal turbulent flow patterns restricted turbulent flow can unpredictably af fect fuel draw depending relative air pressure fuel jet Suction pres sure carburetors similarly affected fuel droplet size variations caused consistent flow forces past fuel jets turn affects engine combustion effici ency Among efficient RC car buretors have tested have Fox engines engineered flow bench Duke have excellent full-range characteristics Now just word about fixed venturi carburetors efficient multi-jet design Cox engines fuel enters venturi through several small jets instead fuel droplets entering engine average smaller size results better needle valve ad justment b improved fuel economy Now Ive started fuel systems can see lot needs said about design application theory system product review product review product review Kavalier well-thought-out concept aileron trainer strong emphasis fly ing qualities designer Claude McCullough Like other popular name-brand-trainers has 56-in wing kind magic number takes 29- 40-size engines distinctive clean shoulder-wing slim bit rakish moderately tapered wing swept fin elevator aft fuselage Semi-sym metrical airfoil strength high-lift stability Differential aileron control horns give up less down movement eliminate aileron yaw Assembled flat surface wing incorporates precise amount incidence changeless tips enhances control tip stall way touchdown low airspeeds result ing non-expert piloting Performance handling characteristics qualifies Kavalier both sport stunt flying Kit includes illustrated instruction book die-cut balsa plywood molded cowling formed aluminum main gear nylon horns molded canopy framing hardware printed fuse lage sides build directly wood 5/32 steel nose gear full-size plan Price $3995 Sig Manufacturing Co Montezuma IA 50171 product review product review product review integrity plain old good practices like soldering no leaks etc will have wait future articles Dave Palmer Bowie Md asks always under impression mi crosopic grooves should never have relationship changed regarding piston sleeve Once piston sleeve have seated ground would second third disassembly reduce com pression worried about mi croscopic grooves engine breaks lapped broken metal surfaces interfere other worn away contact No mi croscopic grooves exist surfaces either piston sleeve run full length stroke borne out fact both piston sleeve rotate relative another engine runs Look exhaust port dark night good light youll see rotation random What can account power losses engine dismantled re assembled Referring previous col umn engine set-up engine dismantled checked set up can have unevenly torqued screws misaligned parts causing warps relieved running wear etc Such engine can indeed loose power reassembled identical duplication bolt torque sleeve June 1978 93 Peak Peormance U S E Greater RPM FIRST AROUND IB[ WORLD DOUGLAS WORLD CRUIS[R 1 72 SCALE PLASTIC MODEL KIT During 1924 history-making Douglas World Cruisers made first around world flight Covering some 27553 miles epic voyage lasted 175 days Now can construct highly-detailed model famous aircraft KIT FEATURES WHEELS AND PONTOONS DECALS TO ALLOW FINISHING MODEL AS ANY ONE OF FIVE DIFFERENT AIRCRAFT TLE AGO ON NEW ORLEANS ON II $495 Pro, dealer direct adding 15% postage ond handlieg Send SOt complete illustrated catalogDEPT MAjJLLA1$ 181 PAWNEE ST SAN MARCOS CA 92069 CL Scale/Gretz continued page 44 CA 92345 another source economical b&w photos Ive tried selection isnt extensive Collect Air Photos different type photo service have 14-page catalog lists individual photos specifics such aircrafts registration number attitude airplane photo 5 int costs $1 8 X 10 $150 catalog $1 An inadvertent transposition what did April column Some probably noticed drawing Dick Ruckels engine shutoff directions shown high low throttle opposite commonly used use standard G-S i-Roberts handle matching bellcrank engines throttle arm like below throttle barrel normally high throttle will forward low throttle will back towards Regardless direction prefer high low throttle control handle just position 94 Model Aviation Uhicken hopper thK snstalea ieam racer 11W Isisy Isuppo os. attached large reservoir tanknote circled area Bladder tanks may Suction operated illustrated 1/2A Gold berg balloon tank pressure force provided speed model type surgical tubing tank Combat baby pacifier ement etc due mi- imperfections best set croscopic grooves caused macro up unrun nearly new tight engine problems relating stress geometric rather tired engine never quite right Don Jehlik 438A Schweer Dr Star Route Hat home NV894 15 Two classic CL tanks wedge aerobatics rat race tank fills fuselage Both cause engine lean out during engine run
Edition: Model Aviation - 1978/06
Page Numbers: 48, 49, 92, 93, 94
Engine TechniqueDon Jehuik FUEL SYSTEMS ideal fuel system isnt yet lot work has put making engines run optimum fashion Lets begin taking look some forces affect fuel de livered engine gravity centrifugal CONVENTIONAL Al R PRESSURE A$A*A AA -p PLUS WEIGHT OF FUEL IN TANJ~ FUEL LEVEL ~ LOW 1/2 VARIABLE PRESSURE VARIABLE FLOW principle chicken hopper tank Height fuel larger reservoir tank main tains pressure smaller tank feed note fuel lineremains constant throughout engine run Details text force partial vacuum turbulent lami nar flow Starting fuel tank different types tanks serve basic purpose hold en gines fuel supply Tanks can further broken two basic categories pressure demand Pressure tanks ex panded bladder type hard tanks external pressure sourcesuch crank case muffler pipe pressure supplied CHICKEN HOPPER A 0 0 CONSTANT PRESSURE CONSTANT FLOW tank supply fuel engine forcing fuel carburetor Demand tanks unpressurized bladder hard tanks supply fuel engine result partial vacuum fuel draw created flow air through car buretor venturi Its hard understand type tank pressure demand doesnt change fact nearly applications fuel supplied engine varies quan tity throughout run means needle valve setting will compro mise must allow larger amount fuel flow provided beginning run smaller amount flow end Its easier use picture drawing explain some concepts first drawing shows conventional demand pressure tank works compared Stockton Chicken Hopper tank Air pres sure whether supplied air vent tank pressure source con stant both designs difference tween pressure exists fuel line pickup weight fuel varies height fuel conventional tank fuel produces pressure typical condition exists flier adjusts engine before releasing model Too often engine adjusted peak setting before release results engine going over-lean during run due decreased fuel pressure tank empties way compensate condition out special changes fuel system adjust needle valve engine reaches peak setting end run means releasing rich enough compen sate total variation fuel pressure beginning end flight 48 Model Aviation Over 25 years fuel-control concept Left Jim Walker pressure regulator 1950fuel bladder pressurized sandwiching between two thin ply boards squeezed together rubberbands Center Servo-adjustable needle valve Paul Bugi circa 1950 Right Modern fuel pump Chicken Hopper tank differs designed deliver constant fuel pres sure fuel line pickup As can see fuel pickup located separate constant pressure tank supplied reservoir relationship between air pressure fuel head height fuel small hopper tank remains constant throughout entire run photo hopper tank team race installation illustrates several things First note extremely small size hopper tank circle compared reservoir tank Second note size shape reservoir tank has no effect flow fuel engine Third location tank relative engine carburetor critical because constant pressure fuel source provided hopper tank enables dial optimum needle valve setting will remain constant throughout flight drawing Goodyear tank hopper tank adapted example adaptation principle specialized event Similar hoppers can adapted CL stunt tanks speed tanks photo etc RC boats have adapted locating small hopper tank 1 oz carburetor connecting main reservoir tank located aft boat Model race cars RC thethered can also benefit similar installations Jim Walker CL pioneer recognized problem variable fuel flow mar keted earliest device am aware solve problem fuel regulator see photo wired intake en gine inlet regulator sup plied rubber fuel bladder pressurized placing between two sheets plywood wrapped rubberbands outlet connected needle valve fitting regulator con tained diaphragm controlled spring loaded ball valve supplied fuel carburetor Whenever pressure fuel line fell below atmospheric pressure diaphram would push ball off its seat allow fuel flow carbure tor used system first came out worked advertised recent developments affecting fuel control include servo adjustable needle valve valve picture made Paul BugI around 1966 help top Austrian RC boat competitor solve problem controlling needle valve during race As can see needle valve mounted large threaded body servo arm thread coarse servo travel can adjust needle full rich full lean 900 arm ro tation last item picture fuel pump Pumps currently popular combined servo-controlled needle valve provide maximum power precise engine adjustment Continued page 92 FUEL June 1978 49 P..I Dd f.I tnIo unnhiA fuel tn engine under Dressure oiea irom engliw uraIrnI~ rierruw turi , u, have used CL models long time reduce effect centrifugal forces needle settings may difficult relate picture TO chicken hopper demonstration picture chicken hopper tank typical speed modeladditionally utilizes case pressure 25cc smaller Suit 40s Also Pilatus PC7 Turbo Trainer 60s Strictly European big lowwings offer lots fuselage room ruggedness suit grass fields None rugged Topps ARTF Class 2 scale line has expanded sleek Mirage 2000 stunning F-18 Cobra has droop snoot leading edges latest camou ouflage looks part model 80s sells around $160 Germany Sport RC also has its share innova tions Another flush trainer kits include several 20 engines trend upheld RC gear itself Last show saw rash super-sophisticated equipment controls would take ace handle year same trend perpetuated yet toned down shade modular concept becomes common place Almost manufacturer now add-a-box state frequency purpose can changed plugging-in another module Multiplex put control mixer Ix way like several other prominent German firms have sunk national pride badge-engineered Japanese imports meet sports market other wise neglecting Thus Futaba Sanwa product review product review product review Whats Angle Measuring rigging angles wings tails thrust lines offset thrust etc. has always irksome task unrealized error could effect flight perfor mance Robarts new incidence meter ends use adjustable notched tops positioned steel bar according type measurement made box containing steel counterweight pre cision pointer dial scale also slides bar required Operation simple using carpenters level Price $1595 Ro bart PO Box 122 Wheaton 1160187 product review product review product review JM 10 etc. have strong grip dont always appear under own name Did someone say What about en gines---helicopters Only Dieter Schlut ers Heli-Boy acrobatic version Bell 222 could claimed new among rotary wings thats sign consolidation Helicopter trainer pads coming solu tion training risk clever never-leave-the-ground device Hel mut Fett Cologne said selling generation garden fliers want no simulate flight risk As engines car boom has fluence has boosted 19 size opposite end big Sueva 25 05 20 Damo 18 cc sizes plus new OS 90 OPS 65 show way trade thinking Only Webra has thought lunior size produced 15 cc 09 theres hardly unit show throttle way stimulate young CL flier free-flight sportster Engine Technique/Jehlik continued page 49 ideal RC applications million words said about fuel systems Im going try summarize few RC aircraft Since fuel system subjected relatively long distances fuel draw vertical climb large varia tions fuel pressure point pickup maneuvers use fuel pumps rec ommended may supplemented servo-controlled needle valve special applications Control Line Although understood Stockton Chicken Hooper concept adaptable CL events result being perfectly constant runs throughout flight am unaware other fuel tank design provides level performance Ill glad answer questions about adaptation hop pers tanks different events Carburetors carburetor acts partial regulator velocity air venturi throat results lowered air pres NEW/ MUFF-L-IT SERIES Available e C engines Sis eight Ob reduction noise engines Proportional nolumne expan sion chamber Large exhaust nozzle low back pressure 4 Little no loss power REGULAR & NO 30109-191749 No 0022940t839 no 30340801949 *nI o B d C y00fl No 304N4 wln 51095 NO305R4294011195 No30km488411395 1/2A MUFFLER Fits COX 049 engInes NO 30080491149 No ODIN0511149 sure provides suction draw fuel carburetor degree needle valve opening will allow much fuel pass given setting get idea variation attach fuel line about 12 long tank adjust en gine tank located carburetor level raise lower tank will observe engine change very rich very lean depending vertical location tank regula tion provided carburetor slight Engines Can tolerate wide range fuel settings Simply put power curve engines relatively flat peak power settings means can generally adjust engine run up 1000 rpm rich peak setting still use nearly maximum power Forces Gravity basic force usu ally smallest force affecting model fuel system G forces maneuvers can approach 40 centrifugal forces CL speed models over 20 times gravity Vibration air stream forces tend cause fuel foam tanks recent approach Dave Gierke places fuel bladder hard tank will eliminate foaming air enters tank outside bladder fuel inside system used Huntsville speed fliers Dick Hall Bob Lauderdale FAI CL speed models early 60s system eliminates Inland Sport eye-catcning classic orom Golden Era VNJith 37% span Herb Clu key-designed parasol scale RC model takes 02 electric 049 power excellent schoolyard flying Decals printed balsa rolled plans proof-of-scale data etc Price $1395 Flyline Models Inc. 2820 Dorr Ave B-2 Fairfax VA 22030 product review product review product review 92 Model Aviation Droduct review product review product review foaming fuel does provide constant pressure fuel source Turbulent Laminar Flow Fuel tanks lines often blamed engine running problems caused carbure tor RC carburetors adjusted rotating sliding barrels change laminar flow full open position inter nal turbulent flow patterns restricted turbulent flow can unpredictably af fect fuel draw depending relative air pressure fuel jet Suction pres sure carburetors similarly affected fuel droplet size variations caused consistent flow forces past fuel jets turn affects engine combustion effici ency Among efficient RC car buretors have tested have Fox engines engineered flow bench Duke have excellent full-range characteristics Now just word about fixed venturi carburetors efficient multi-jet design Cox engines fuel enters venturi through several small jets instead fuel droplets entering engine average smaller size results better needle valve ad justment b improved fuel economy Now Ive started fuel systems can see lot needs said about design application theory system product review product review product review Kavalier well-thought-out concept aileron trainer strong emphasis fly ing qualities designer Claude McCullough Like other popular name-brand-trainers has 56-in wing kind magic number takes 29- 40-size engines distinctive clean shoulder-wing slim bit rakish moderately tapered wing swept fin elevator aft fuselage Semi-sym metrical airfoil strength high-lift stability Differential aileron control horns give up less down movement eliminate aileron yaw Assembled flat surface wing incorporates precise amount incidence changeless tips enhances control tip stall way touchdown low airspeeds result ing non-expert piloting Performance handling characteristics qualifies Kavalier both sport stunt flying Kit includes illustrated instruction book die-cut balsa plywood molded cowling formed aluminum main gear nylon horns molded canopy framing hardware printed fuse lage sides build directly wood 5/32 steel nose gear full-size plan Price $3995 Sig Manufacturing Co Montezuma IA 50171 product review product review product review integrity plain old good practices like soldering no leaks etc will have wait future articles Dave Palmer Bowie Md asks always under impression mi crosopic grooves should never have relationship changed regarding piston sleeve Once piston sleeve have seated ground would second third disassembly reduce com pression worried about mi croscopic grooves engine breaks lapped broken metal surfaces interfere other worn away contact No mi croscopic grooves exist surfaces either piston sleeve run full length stroke borne out fact both piston sleeve rotate relative another engine runs Look exhaust port dark night good light youll see rotation random What can account power losses engine dismantled re assembled Referring previous col umn engine set-up engine dismantled checked set up can have unevenly torqued screws misaligned parts causing warps relieved running wear etc Such engine can indeed loose power reassembled identical duplication bolt torque sleeve June 1978 93 Peak Peormance U S E Greater RPM FIRST AROUND IB[ WORLD DOUGLAS WORLD CRUIS[R 1 72 SCALE PLASTIC MODEL KIT During 1924 history-making Douglas World Cruisers made first around world flight Covering some 27553 miles epic voyage lasted 175 days Now can construct highly-detailed model famous aircraft KIT FEATURES WHEELS AND PONTOONS DECALS TO ALLOW FINISHING MODEL AS ANY ONE OF FIVE DIFFERENT AIRCRAFT TLE AGO ON NEW ORLEANS ON II $495 Pro, dealer direct adding 15% postage ond handlieg Send SOt complete illustrated catalogDEPT MAjJLLA1$ 181 PAWNEE ST SAN MARCOS CA 92069 CL Scale/Gretz continued page 44 CA 92345 another source economical b&w photos Ive tried selection isnt extensive Collect Air Photos different type photo service have 14-page catalog lists individual photos specifics such aircrafts registration number attitude airplane photo 5 int costs $1 8 X 10 $150 catalog $1 An inadvertent transposition what did April column Some probably noticed drawing Dick Ruckels engine shutoff directions shown high low throttle opposite commonly used use standard G-S i-Roberts handle matching bellcrank engines throttle arm like below throttle barrel normally high throttle will forward low throttle will back towards Regardless direction prefer high low throttle control handle just position 94 Model Aviation Uhicken hopper thK snstalea ieam racer 11W Isisy Isuppo os. attached large reservoir tanknote circled area Bladder tanks may Suction operated illustrated 1/2A Gold berg balloon tank pressure force provided speed model type surgical tubing tank Combat baby pacifier ement etc due mi- imperfections best set croscopic grooves caused macro up unrun nearly new tight engine problems relating stress geometric rather tired engine never quite right Don Jehlik 438A Schweer Dr Star Route Hat home NV894 15 Two classic CL tanks wedge aerobatics rat race tank fills fuselage Both cause engine lean out during engine run
Edition: Model Aviation - 1978/06
Page Numbers: 48, 49, 92, 93, 94
Engine TechniqueDon Jehuik FUEL SYSTEMS ideal fuel system isnt yet lot work has put making engines run optimum fashion Lets begin taking look some forces affect fuel de livered engine gravity centrifugal CONVENTIONAL Al R PRESSURE A$A*A AA -p PLUS WEIGHT OF FUEL IN TANJ~ FUEL LEVEL ~ LOW 1/2 VARIABLE PRESSURE VARIABLE FLOW principle chicken hopper tank Height fuel larger reservoir tank main tains pressure smaller tank feed note fuel lineremains constant throughout engine run Details text force partial vacuum turbulent lami nar flow Starting fuel tank different types tanks serve basic purpose hold en gines fuel supply Tanks can further broken two basic categories pressure demand Pressure tanks ex panded bladder type hard tanks external pressure sourcesuch crank case muffler pipe pressure supplied CHICKEN HOPPER A 0 0 CONSTANT PRESSURE CONSTANT FLOW tank supply fuel engine forcing fuel carburetor Demand tanks unpressurized bladder hard tanks supply fuel engine result partial vacuum fuel draw created flow air through car buretor venturi Its hard understand type tank pressure demand doesnt change fact nearly applications fuel supplied engine varies quan tity throughout run means needle valve setting will compro mise must allow larger amount fuel flow provided beginning run smaller amount flow end Its easier use picture drawing explain some concepts first drawing shows conventional demand pressure tank works compared Stockton Chicken Hopper tank Air pres sure whether supplied air vent tank pressure source con stant both designs difference tween pressure exists fuel line pickup weight fuel varies height fuel conventional tank fuel produces pressure typical condition exists flier adjusts engine before releasing model Too often engine adjusted peak setting before release results engine going over-lean during run due decreased fuel pressure tank empties way compensate condition out special changes fuel system adjust needle valve engine reaches peak setting end run means releasing rich enough compen sate total variation fuel pressure beginning end flight 48 Model Aviation Over 25 years fuel-control concept Left Jim Walker pressure regulator 1950fuel bladder pressurized sandwiching between two thin ply boards squeezed together rubberbands Center Servo-adjustable needle valve Paul Bugi circa 1950 Right Modern fuel pump Chicken Hopper tank differs designed deliver constant fuel pres sure fuel line pickup As can see fuel pickup located separate constant pressure tank supplied reservoir relationship between air pressure fuel head height fuel small hopper tank remains constant throughout entire run photo hopper tank team race installation illustrates several things First note extremely small size hopper tank circle compared reservoir tank Second note size shape reservoir tank has no effect flow fuel engine Third location tank relative engine carburetor critical because constant pressure fuel source provided hopper tank enables dial optimum needle valve setting will remain constant throughout flight drawing Goodyear tank hopper tank adapted example adaptation principle specialized event Similar hoppers can adapted CL stunt tanks speed tanks photo etc RC boats have adapted locating small hopper tank 1 oz carburetor connecting main reservoir tank located aft boat Model race cars RC thethered can also benefit similar installations Jim Walker CL pioneer recognized problem variable fuel flow mar keted earliest device am aware solve problem fuel regulator see photo wired intake en gine inlet regulator sup plied rubber fuel bladder pressurized placing between two sheets plywood wrapped rubberbands outlet connected needle valve fitting regulator con tained diaphragm controlled spring loaded ball valve supplied fuel carburetor Whenever pressure fuel line fell below atmospheric pressure diaphram would push ball off its seat allow fuel flow carbure tor used system first came out worked advertised recent developments affecting fuel control include servo adjustable needle valve valve picture made Paul BugI around 1966 help top Austrian RC boat competitor solve problem controlling needle valve during race As can see needle valve mounted large threaded body servo arm thread coarse servo travel can adjust needle full rich full lean 900 arm ro tation last item picture fuel pump Pumps currently popular combined servo-controlled needle valve provide maximum power precise engine adjustment Continued page 92 FUEL June 1978 49 P..I Dd f.I tnIo unnhiA fuel tn engine under Dressure oiea irom engliw uraIrnI~ rierruw turi , u, have used CL models long time reduce effect centrifugal forces needle settings may difficult relate picture TO chicken hopper demonstration picture chicken hopper tank typical speed modeladditionally utilizes case pressure 25cc smaller Suit 40s Also Pilatus PC7 Turbo Trainer 60s Strictly European big lowwings offer lots fuselage room ruggedness suit grass fields None rugged Topps ARTF Class 2 scale line has expanded sleek Mirage 2000 stunning F-18 Cobra has droop snoot leading edges latest camou ouflage looks part model 80s sells around $160 Germany Sport RC also has its share innova tions Another flush trainer kits include several 20 engines trend upheld RC gear itself Last show saw rash super-sophisticated equipment controls would take ace handle year same trend perpetuated yet toned down shade modular concept becomes common place Almost manufacturer now add-a-box state frequency purpose can changed plugging-in another module Multiplex put control mixer Ix way like several other prominent German firms have sunk national pride badge-engineered Japanese imports meet sports market other wise neglecting Thus Futaba Sanwa product review product review product review Whats Angle Measuring rigging angles wings tails thrust lines offset thrust etc. has always irksome task unrealized error could effect flight perfor mance Robarts new incidence meter ends use adjustable notched tops positioned steel bar according type measurement made box containing steel counterweight pre cision pointer dial scale also slides bar required Operation simple using carpenters level Price $1595 Ro bart PO Box 122 Wheaton 1160187 product review product review product review JM 10 etc. have strong grip dont always appear under own name Did someone say What about en gines---helicopters Only Dieter Schlut ers Heli-Boy acrobatic version Bell 222 could claimed new among rotary wings thats sign consolidation Helicopter trainer pads coming solu tion training risk clever never-leave-the-ground device Hel mut Fett Cologne said selling generation garden fliers want no simulate flight risk As engines car boom has fluence has boosted 19 size opposite end big Sueva 25 05 20 Damo 18 cc sizes plus new OS 90 OPS 65 show way trade thinking Only Webra has thought lunior size produced 15 cc 09 theres hardly unit show throttle way stimulate young CL flier free-flight sportster Engine Technique/Jehlik continued page 49 ideal RC applications million words said about fuel systems Im going try summarize few RC aircraft Since fuel system subjected relatively long distances fuel draw vertical climb large varia tions fuel pressure point pickup maneuvers use fuel pumps rec ommended may supplemented servo-controlled needle valve special applications Control Line Although understood Stockton Chicken Hooper concept adaptable CL events result being perfectly constant runs throughout flight am unaware other fuel tank design provides level performance Ill glad answer questions about adaptation hop pers tanks different events Carburetors carburetor acts partial regulator velocity air venturi throat results lowered air pres NEW/ MUFF-L-IT SERIES Available e C engines Sis eight Ob reduction noise engines Proportional nolumne expan sion chamber Large exhaust nozzle low back pressure 4 Little no loss power REGULAR & NO 30109-191749 No 0022940t839 no 30340801949 *nI o B d C y00fl No 304N4 wln 51095 NO305R4294011195 No30km488411395 1/2A MUFFLER Fits COX 049 engInes NO 30080491149 No ODIN0511149 sure provides suction draw fuel carburetor degree needle valve opening will allow much fuel pass given setting get idea variation attach fuel line about 12 long tank adjust en gine tank located carburetor level raise lower tank will observe engine change very rich very lean depending vertical location tank regula tion provided carburetor slight Engines Can tolerate wide range fuel settings Simply put power curve engines relatively flat peak power settings means can generally adjust engine run up 1000 rpm rich peak setting still use nearly maximum power Forces Gravity basic force usu ally smallest force affecting model fuel system G forces maneuvers can approach 40 centrifugal forces CL speed models over 20 times gravity Vibration air stream forces tend cause fuel foam tanks recent approach Dave Gierke places fuel bladder hard tank will eliminate foaming air enters tank outside bladder fuel inside system used Huntsville speed fliers Dick Hall Bob Lauderdale FAI CL speed models early 60s system eliminates Inland Sport eye-catcning classic orom Golden Era VNJith 37% span Herb Clu key-designed parasol scale RC model takes 02 electric 049 power excellent schoolyard flying Decals printed balsa rolled plans proof-of-scale data etc Price $1395 Flyline Models Inc. 2820 Dorr Ave B-2 Fairfax VA 22030 product review product review product review 92 Model Aviation Droduct review product review product review foaming fuel does provide constant pressure fuel source Turbulent Laminar Flow Fuel tanks lines often blamed engine running problems caused carbure tor RC carburetors adjusted rotating sliding barrels change laminar flow full open position inter nal turbulent flow patterns restricted turbulent flow can unpredictably af fect fuel draw depending relative air pressure fuel jet Suction pres sure carburetors similarly affected fuel droplet size variations caused consistent flow forces past fuel jets turn affects engine combustion effici ency Among efficient RC car buretors have tested have Fox engines engineered flow bench Duke have excellent full-range characteristics Now just word about fixed venturi carburetors efficient multi-jet design Cox engines fuel enters venturi through several small jets instead fuel droplets entering engine average smaller size results better needle valve ad justment b improved fuel economy Now Ive started fuel systems can see lot needs said about design application theory system product review product review product review Kavalier well-thought-out concept aileron trainer strong emphasis fly ing qualities designer Claude McCullough Like other popular name-brand-trainers has 56-in wing kind magic number takes 29- 40-size engines distinctive clean shoulder-wing slim bit rakish moderately tapered wing swept fin elevator aft fuselage Semi-sym metrical airfoil strength high-lift stability Differential aileron control horns give up less down movement eliminate aileron yaw Assembled flat surface wing incorporates precise amount incidence changeless tips enhances control tip stall way touchdown low airspeeds result ing non-expert piloting Performance handling characteristics qualifies Kavalier both sport stunt flying Kit includes illustrated instruction book die-cut balsa plywood molded cowling formed aluminum main gear nylon horns molded canopy framing hardware printed fuse lage sides build directly wood 5/32 steel nose gear full-size plan Price $3995 Sig Manufacturing Co Montezuma IA 50171 product review product review product review integrity plain old good practices like soldering no leaks etc will have wait future articles Dave Palmer Bowie Md asks always under impression mi crosopic grooves should never have relationship changed regarding piston sleeve Once piston sleeve have seated ground would second third disassembly reduce com pression worried about mi croscopic grooves engine breaks lapped broken metal surfaces interfere other worn away contact No mi croscopic grooves exist surfaces either piston sleeve run full length stroke borne out fact both piston sleeve rotate relative another engine runs Look exhaust port dark night good light youll see rotation random What can account power losses engine dismantled re assembled Referring previous col umn engine set-up engine dismantled checked set up can have unevenly torqued screws misaligned parts causing warps relieved running wear etc Such engine can indeed loose power reassembled identical duplication bolt torque sleeve June 1978 93 Peak Peormance U S E Greater RPM FIRST AROUND IB[ WORLD DOUGLAS WORLD CRUIS[R 1 72 SCALE PLASTIC MODEL KIT During 1924 history-making Douglas World Cruisers made first around world flight Covering some 27553 miles epic voyage lasted 175 days Now can construct highly-detailed model famous aircraft KIT FEATURES WHEELS AND PONTOONS DECALS TO ALLOW FINISHING MODEL AS ANY ONE OF FIVE DIFFERENT AIRCRAFT TLE AGO ON NEW ORLEANS ON II $495 Pro, dealer direct adding 15% postage ond handlieg Send SOt complete illustrated catalogDEPT MAjJLLA1$ 181 PAWNEE ST SAN MARCOS CA 92069 CL Scale/Gretz continued page 44 CA 92345 another source economical b&w photos Ive tried selection isnt extensive Collect Air Photos different type photo service have 14-page catalog lists individual photos specifics such aircrafts registration number attitude airplane photo 5 int costs $1 8 X 10 $150 catalog $1 An inadvertent transposition what did April column Some probably noticed drawing Dick Ruckels engine shutoff directions shown high low throttle opposite commonly used use standard G-S i-Roberts handle matching bellcrank engines throttle arm like below throttle barrel normally high throttle will forward low throttle will back towards Regardless direction prefer high low throttle control handle just position 94 Model Aviation Uhicken hopper thK snstalea ieam racer 11W Isisy Isuppo os. attached large reservoir tanknote circled area Bladder tanks may Suction operated illustrated 1/2A Gold berg balloon tank pressure force provided speed model type surgical tubing tank Combat baby pacifier ement etc due mi- imperfections best set croscopic grooves caused macro up unrun nearly new tight engine problems relating stress geometric rather tired engine never quite right Don Jehlik 438A Schweer Dr Star Route Hat home NV894 15 Two classic CL tanks wedge aerobatics rat race tank fills fuselage Both cause engine lean out during engine run
Edition: Model Aviation - 1978/06
Page Numbers: 48, 49, 92, 93, 94
Engine TechniqueDon Jehuik FUEL SYSTEMS ideal fuel system isnt yet lot work has put making engines run optimum fashion Lets begin taking look some forces affect fuel de livered engine gravity centrifugal CONVENTIONAL Al R PRESSURE A$A*A AA -p PLUS WEIGHT OF FUEL IN TANJ~ FUEL LEVEL ~ LOW 1/2 VARIABLE PRESSURE VARIABLE FLOW principle chicken hopper tank Height fuel larger reservoir tank main tains pressure smaller tank feed note fuel lineremains constant throughout engine run Details text force partial vacuum turbulent lami nar flow Starting fuel tank different types tanks serve basic purpose hold en gines fuel supply Tanks can further broken two basic categories pressure demand Pressure tanks ex panded bladder type hard tanks external pressure sourcesuch crank case muffler pipe pressure supplied CHICKEN HOPPER A 0 0 CONSTANT PRESSURE CONSTANT FLOW tank supply fuel engine forcing fuel carburetor Demand tanks unpressurized bladder hard tanks supply fuel engine result partial vacuum fuel draw created flow air through car buretor venturi Its hard understand type tank pressure demand doesnt change fact nearly applications fuel supplied engine varies quan tity throughout run means needle valve setting will compro mise must allow larger amount fuel flow provided beginning run smaller amount flow end Its easier use picture drawing explain some concepts first drawing shows conventional demand pressure tank works compared Stockton Chicken Hopper tank Air pres sure whether supplied air vent tank pressure source con stant both designs difference tween pressure exists fuel line pickup weight fuel varies height fuel conventional tank fuel produces pressure typical condition exists flier adjusts engine before releasing model Too often engine adjusted peak setting before release results engine going over-lean during run due decreased fuel pressure tank empties way compensate condition out special changes fuel system adjust needle valve engine reaches peak setting end run means releasing rich enough compen sate total variation fuel pressure beginning end flight 48 Model Aviation Over 25 years fuel-control concept Left Jim Walker pressure regulator 1950fuel bladder pressurized sandwiching between two thin ply boards squeezed together rubberbands Center Servo-adjustable needle valve Paul Bugi circa 1950 Right Modern fuel pump Chicken Hopper tank differs designed deliver constant fuel pres sure fuel line pickup As can see fuel pickup located separate constant pressure tank supplied reservoir relationship between air pressure fuel head height fuel small hopper tank remains constant throughout entire run photo hopper tank team race installation illustrates several things First note extremely small size hopper tank circle compared reservoir tank Second note size shape reservoir tank has no effect flow fuel engine Third location tank relative engine carburetor critical because constant pressure fuel source provided hopper tank enables dial optimum needle valve setting will remain constant throughout flight drawing Goodyear tank hopper tank adapted example adaptation principle specialized event Similar hoppers can adapted CL stunt tanks speed tanks photo etc RC boats have adapted locating small hopper tank 1 oz carburetor connecting main reservoir tank located aft boat Model race cars RC thethered can also benefit similar installations Jim Walker CL pioneer recognized problem variable fuel flow mar keted earliest device am aware solve problem fuel regulator see photo wired intake en gine inlet regulator sup plied rubber fuel bladder pressurized placing between two sheets plywood wrapped rubberbands outlet connected needle valve fitting regulator con tained diaphragm controlled spring loaded ball valve supplied fuel carburetor Whenever pressure fuel line fell below atmospheric pressure diaphram would push ball off its seat allow fuel flow carbure tor used system first came out worked advertised recent developments affecting fuel control include servo adjustable needle valve valve picture made Paul BugI around 1966 help top Austrian RC boat competitor solve problem controlling needle valve during race As can see needle valve mounted large threaded body servo arm thread coarse servo travel can adjust needle full rich full lean 900 arm ro tation last item picture fuel pump Pumps currently popular combined servo-controlled needle valve provide maximum power precise engine adjustment Continued page 92 FUEL June 1978 49 P..I Dd f.I tnIo unnhiA fuel tn engine under Dressure oiea irom engliw uraIrnI~ rierruw turi , u, have used CL models long time reduce effect centrifugal forces needle settings may difficult relate picture TO chicken hopper demonstration picture chicken hopper tank typical speed modeladditionally utilizes case pressure 25cc smaller Suit 40s Also Pilatus PC7 Turbo Trainer 60s Strictly European big lowwings offer lots fuselage room ruggedness suit grass fields None rugged Topps ARTF Class 2 scale line has expanded sleek Mirage 2000 stunning F-18 Cobra has droop snoot leading edges latest camou ouflage looks part model 80s sells around $160 Germany Sport RC also has its share innova tions Another flush trainer kits include several 20 engines trend upheld RC gear itself Last show saw rash super-sophisticated equipment controls would take ace handle year same trend perpetuated yet toned down shade modular concept becomes common place Almost manufacturer now add-a-box state frequency purpose can changed plugging-in another module Multiplex put control mixer Ix way like several other prominent German firms have sunk national pride badge-engineered Japanese imports meet sports market other wise neglecting Thus Futaba Sanwa product review product review product review Whats Angle Measuring rigging angles wings tails thrust lines offset thrust etc. has always irksome task unrealized error could effect flight perfor mance Robarts new incidence meter ends use adjustable notched tops positioned steel bar according type measurement made box containing steel counterweight pre cision pointer dial scale also slides bar required Operation simple using carpenters level Price $1595 Ro bart PO Box 122 Wheaton 1160187 product review product review product review JM 10 etc. have strong grip dont always appear under own name Did someone say What about en gines---helicopters Only Dieter Schlut ers Heli-Boy acrobatic version Bell 222 could claimed new among rotary wings thats sign consolidation Helicopter trainer pads coming solu tion training risk clever never-leave-the-ground device Hel mut Fett Cologne said selling generation garden fliers want no simulate flight risk As engines car boom has fluence has boosted 19 size opposite end big Sueva 25 05 20 Damo 18 cc sizes plus new OS 90 OPS 65 show way trade thinking Only Webra has thought lunior size produced 15 cc 09 theres hardly unit show throttle way stimulate young CL flier free-flight sportster Engine Technique/Jehlik continued page 49 ideal RC applications million words said about fuel systems Im going try summarize few RC aircraft Since fuel system subjected relatively long distances fuel draw vertical climb large varia tions fuel pressure point pickup maneuvers use fuel pumps rec ommended may supplemented servo-controlled needle valve special applications Control Line Although understood Stockton Chicken Hooper concept adaptable CL events result being perfectly constant runs throughout flight am unaware other fuel tank design provides level performance Ill glad answer questions about adaptation hop pers tanks different events Carburetors carburetor acts partial regulator velocity air venturi throat results lowered air pres NEW/ MUFF-L-IT SERIES Available e C engines Sis eight Ob reduction noise engines Proportional nolumne expan sion chamber Large exhaust nozzle low back pressure 4 Little no loss power REGULAR & NO 30109-191749 No 0022940t839 no 30340801949 *nI o B d C y00fl No 304N4 wln 51095 NO305R4294011195 No30km488411395 1/2A MUFFLER Fits COX 049 engInes NO 30080491149 No ODIN0511149 sure provides suction draw fuel carburetor degree needle valve opening will allow much fuel pass given setting get idea variation attach fuel line about 12 long tank adjust en gine tank located carburetor level raise lower tank will observe engine change very rich very lean depending vertical location tank regula tion provided carburetor slight Engines Can tolerate wide range fuel settings Simply put power curve engines relatively flat peak power settings means can generally adjust engine run up 1000 rpm rich peak setting still use nearly maximum power Forces Gravity basic force usu ally smallest force affecting model fuel system G forces maneuvers can approach 40 centrifugal forces CL speed models over 20 times gravity Vibration air stream forces tend cause fuel foam tanks recent approach Dave Gierke places fuel bladder hard tank will eliminate foaming air enters tank outside bladder fuel inside system used Huntsville speed fliers Dick Hall Bob Lauderdale FAI CL speed models early 60s system eliminates Inland Sport eye-catcning classic orom Golden Era VNJith 37% span Herb Clu key-designed parasol scale RC model takes 02 electric 049 power excellent schoolyard flying Decals printed balsa rolled plans proof-of-scale data etc Price $1395 Flyline Models Inc. 2820 Dorr Ave B-2 Fairfax VA 22030 product review product review product review 92 Model Aviation Droduct review product review product review foaming fuel does provide constant pressure fuel source Turbulent Laminar Flow Fuel tanks lines often blamed engine running problems caused carbure tor RC carburetors adjusted rotating sliding barrels change laminar flow full open position inter nal turbulent flow patterns restricted turbulent flow can unpredictably af fect fuel draw depending relative air pressure fuel jet Suction pres sure carburetors similarly affected fuel droplet size variations caused consistent flow forces past fuel jets turn affects engine combustion effici ency Among efficient RC car buretors have tested have Fox engines engineered flow bench Duke have excellent full-range characteristics Now just word about fixed venturi carburetors efficient multi-jet design Cox engines fuel enters venturi through several small jets instead fuel droplets entering engine average smaller size results better needle valve ad justment b improved fuel economy Now Ive started fuel systems can see lot needs said about design application theory system product review product review product review Kavalier well-thought-out concept aileron trainer strong emphasis fly ing qualities designer Claude McCullough Like other popular name-brand-trainers has 56-in wing kind magic number takes 29- 40-size engines distinctive clean shoulder-wing slim bit rakish moderately tapered wing swept fin elevator aft fuselage Semi-sym metrical airfoil strength high-lift stability Differential aileron control horns give up less down movement eliminate aileron yaw Assembled flat surface wing incorporates precise amount incidence changeless tips enhances control tip stall way touchdown low airspeeds result ing non-expert piloting Performance handling characteristics qualifies Kavalier both sport stunt flying Kit includes illustrated instruction book die-cut balsa plywood molded cowling formed aluminum main gear nylon horns molded canopy framing hardware printed fuse lage sides build directly wood 5/32 steel nose gear full-size plan Price $3995 Sig Manufacturing Co Montezuma IA 50171 product review product review product review integrity plain old good practices like soldering no leaks etc will have wait future articles Dave Palmer Bowie Md asks always under impression mi crosopic grooves should never have relationship changed regarding piston sleeve Once piston sleeve have seated ground would second third disassembly reduce com pression worried about mi croscopic grooves engine breaks lapped broken metal surfaces interfere other worn away contact No mi croscopic grooves exist surfaces either piston sleeve run full length stroke borne out fact both piston sleeve rotate relative another engine runs Look exhaust port dark night good light youll see rotation random What can account power losses engine dismantled re assembled Referring previous col umn engine set-up engine dismantled checked set up can have unevenly torqued screws misaligned parts causing warps relieved running wear etc Such engine can indeed loose power reassembled identical duplication bolt torque sleeve June 1978 93 Peak Peormance U S E Greater RPM FIRST AROUND IB[ WORLD DOUGLAS WORLD CRUIS[R 1 72 SCALE PLASTIC MODEL KIT During 1924 history-making Douglas World Cruisers made first around world flight Covering some 27553 miles epic voyage lasted 175 days Now can construct highly-detailed model famous aircraft KIT FEATURES WHEELS AND PONTOONS DECALS TO ALLOW FINISHING MODEL AS ANY ONE OF FIVE DIFFERENT AIRCRAFT TLE AGO ON NEW ORLEANS ON II $495 Pro, dealer direct adding 15% postage ond handlieg Send SOt complete illustrated catalogDEPT MAjJLLA1$ 181 PAWNEE ST SAN MARCOS CA 92069 CL Scale/Gretz continued page 44 CA 92345 another source economical b&w photos Ive tried selection isnt extensive Collect Air Photos different type photo service have 14-page catalog lists individual photos specifics such aircrafts registration number attitude airplane photo 5 int costs $1 8 X 10 $150 catalog $1 An inadvertent transposition what did April column Some probably noticed drawing Dick Ruckels engine shutoff directions shown high low throttle opposite commonly used use standard G-S i-Roberts handle matching bellcrank engines throttle arm like below throttle barrel normally high throttle will forward low throttle will back towards Regardless direction prefer high low throttle control handle just position 94 Model Aviation Uhicken hopper thK snstalea ieam racer 11W Isisy Isuppo os. attached large reservoir tanknote circled area Bladder tanks may Suction operated illustrated 1/2A Gold berg balloon tank pressure force provided speed model type surgical tubing tank Combat baby pacifier ement etc due mi- imperfections best set croscopic grooves caused macro up unrun nearly new tight engine problems relating stress geometric rather tired engine never quite right Don Jehlik 438A Schweer Dr Star Route Hat home NV894 15 Two classic CL tanks wedge aerobatics rat race tank fills fuselage Both cause engine lean out during engine run