Technique Picking Propeller SAY DAD what size propeller use engine 12 und field kit seems pull lot better 9 X 7 gave coming 13-year-old son Timothy AMA 61366 led consider fact really isnt very much information around help select best propeller among dozens offered mer chants Therefore will demonstrate simplified procedure making choice Bear mind propeller must connect engine airplane aerodynamically speaking both variable quantities engine sub ject wear changes fuel air prop erties effects various add-on devices like mufflers air cleaners spinners etc propeller used airplane affected shape factors weight atmospheric changes pi lots skill easy understand propeller taken right out box will approximately correct situation order match propeller particular engine setup may find first problem solved shaft diameter Prop manufacturers drill hub diameter indicates use mind made prop general keeps using propeller intended use 049 something completely ridiculous like 40 engine manufacturers complicate life using stepped shaft diameters foreign metric sizes forth best answer prob lem have found stepped ream er made Fox Manufacturing Co 5305 Towson Fort Smith AR 72901 part no 70201 Using can fit propellers size engine larger 15 Tim poked around workshop found 24 propellers might fit shaft engine selected 10 would test Tims engine K&B 40 FR fitted Semco 29-40 closed-end muffler Perry air cleaner engine mounted horizontally Kraft KM-40 mount drilled tapped #6-32 machine screws avoid mount breakage sometimes occurs sheet-metal screws supplied mount used mount screwed front RCM 15-500 muffler pressure used Dukes fuel de scription necessary set conditions propeller must satisfy live fly sea level New York took propellers model field kit Heath Thumb-Tac out yard some tests propeller fitted engine turn run until temperatures stabilized needlevalve adjusted maximum rpm recorded Propeller flying speed George M Myers 85% efficiency nothing 100% efficient calculated using equation Iv- PR 1250 VSpeed mph propeller will advance through air 85% efficiency P Propeller pitch inches second number propeller usually given 9 X 7 9/7 9 diameter 7 pitch R measured tachometer Now have know much horse power engine putting through propeller can measure torque twisting force applied fuselage engine use formula PROPELLER DATADIAPITCHRPMH TE Power Prop TE Power Prop TF Power Prop Toroado Top Elite Top Elite Top Elite Toroado TE Power Prop Top Elite TF Power Prop wood wood wood Nyloo wood wood wood Nyloo wood wood wood 710514000 8616000 8813000 9415000 9713200 9812000 10513000 10612300 11512300 11610500 12510500 2H- 3000 T ue measured foot-pounds RRPM requires some kind pivoted cradle airplane scale measuring force generated some point along left wing point about 10 inches fuselage centerline postagetype scale will Friction setup gusts wind unbalance model spiral motion air leaving prop complicate life pur poses easier way Obtain Peter G F Chinns fine engine reviews published Model Airplane News cover ing engine Read horsepower versus rpm curve summary listing reviews given August 1975 issue beginning page 6 info com VSCSERVICEREMARKS 771183 78773 74837 79483 75750 72773 74523 73589 73492 65507 65423 726161 729105 716117 73366 720104 710108 71673 71383 71369 68683 68662 cr0 joe cr0 toe climb climb BEST BEST Ia Fig 2A practical range values 7 8 3 H - La U 0 S U U U N U U I 3H 8 Model Aviation Fig 1Evaluation propellers RCM 15-500/K & B 40 FR 3j~7-8 pliments Bob Aberle W2QPP Now will estimate what devel oped horsepower will airplane using approximate formula 33 H 5120 SAirplane speed horsepower mph H epower developed rpm area Square feet calculation performed horsepower developed propeller final activity compute per formance coefficient propeller tested can evaluate cor rectness particular engine model equation 4 using definitions above C greater 11 propeller should used C between 95 105 propeller will provide widest possible speed range may consid ered cruise propeller situation C between 75 95 propel ler can considered climb propeller may useful providing quick takeoffs rough surfaces tall grass C less 75 propeller should used Fig gives data Tims model worked out preparing col umn Fig 2 provides cube roots calculator wont solve problem Ive tried show simple way estimate propeller performance Scientists will grumble about factors arent considered think pro cedure adequate presented con stant 120 equation 3 can reduced 100 Old-Timer type designs creased 150 very clean retractable gear pattern designs generally cor rect RC designs feature three ex posed wheels engine muffler hang ing breeze exposed engine mounts firewall spin ner advantages measurements taken directly own plane account wear trim needle-valve technique field conditions other realities ever having measure quantify illustrator goofed up Fig page 10 December 1976 issue Model vialion battery positive terminal should indicated long line left side figure Its very important though because cant hurt diodes reversing connections will happen nothinguntil connect things should Sorry about George M Myers 70 Froehlich Farm Rd Hicksville NY 11801 February 1977 9 After experimentation other sizes Brad Franciscos Midwest Sweet Stik currently pulled around Top Flite 10-6 Power Prop Steuart Estep fuels dads RCM 40 Trainer pow ered OS Max 40 swinging Top Flight 10-6 nylon prop Though engine manufacturer specifies props thats approximation
Edition: Model Aviation - 1977/02
Page Numbers: 8, 9
Technique Picking Propeller SAY DAD what size propeller use engine 12 und field kit seems pull lot better 9 X 7 gave coming 13-year-old son Timothy AMA 61366 led consider fact really isnt very much information around help select best propeller among dozens offered mer chants Therefore will demonstrate simplified procedure making choice Bear mind propeller must connect engine airplane aerodynamically speaking both variable quantities engine sub ject wear changes fuel air prop erties effects various add-on devices like mufflers air cleaners spinners etc propeller used airplane affected shape factors weight atmospheric changes pi lots skill easy understand propeller taken right out box will approximately correct situation order match propeller particular engine setup may find first problem solved shaft diameter Prop manufacturers drill hub diameter indicates use mind made prop general keeps using propeller intended use 049 something completely ridiculous like 40 engine manufacturers complicate life using stepped shaft diameters foreign metric sizes forth best answer prob lem have found stepped ream er made Fox Manufacturing Co 5305 Towson Fort Smith AR 72901 part no 70201 Using can fit propellers size engine larger 15 Tim poked around workshop found 24 propellers might fit shaft engine selected 10 would test Tims engine K&B 40 FR fitted Semco 29-40 closed-end muffler Perry air cleaner engine mounted horizontally Kraft KM-40 mount drilled tapped #6-32 machine screws avoid mount breakage sometimes occurs sheet-metal screws supplied mount used mount screwed front RCM 15-500 muffler pressure used Dukes fuel de scription necessary set conditions propeller must satisfy live fly sea level New York took propellers model field kit Heath Thumb-Tac out yard some tests propeller fitted engine turn run until temperatures stabilized needlevalve adjusted maximum rpm recorded Propeller flying speed George M Myers 85% efficiency nothing 100% efficient calculated using equation Iv- PR 1250 VSpeed mph propeller will advance through air 85% efficiency P Propeller pitch inches second number propeller usually given 9 X 7 9/7 9 diameter 7 pitch R measured tachometer Now have know much horse power engine putting through propeller can measure torque twisting force applied fuselage engine use formula PROPELLER DATADIAPITCHRPMH TE Power Prop TE Power Prop TF Power Prop Toroado Top Elite Top Elite Top Elite Toroado TE Power Prop Top Elite TF Power Prop wood wood wood Nyloo wood wood wood Nyloo wood wood wood 710514000 8616000 8813000 9415000 9713200 9812000 10513000 10612300 11512300 11610500 12510500 2H- 3000 T ue measured foot-pounds RRPM requires some kind pivoted cradle airplane scale measuring force generated some point along left wing point about 10 inches fuselage centerline postagetype scale will Friction setup gusts wind unbalance model spiral motion air leaving prop complicate life pur poses easier way Obtain Peter G F Chinns fine engine reviews published Model Airplane News cover ing engine Read horsepower versus rpm curve summary listing reviews given August 1975 issue beginning page 6 info com VSCSERVICEREMARKS 771183 78773 74837 79483 75750 72773 74523 73589 73492 65507 65423 726161 729105 716117 73366 720104 710108 71673 71383 71369 68683 68662 cr0 joe cr0 toe climb climb BEST BEST Ia Fig 2A practical range values 7 8 3 H - La U 0 S U U U N U U I 3H 8 Model Aviation Fig 1Evaluation propellers RCM 15-500/K & B 40 FR 3j~7-8 pliments Bob Aberle W2QPP Now will estimate what devel oped horsepower will airplane using approximate formula 33 H 5120 SAirplane speed horsepower mph H epower developed rpm area Square feet calculation performed horsepower developed propeller final activity compute per formance coefficient propeller tested can evaluate cor rectness particular engine model equation 4 using definitions above C greater 11 propeller should used C between 95 105 propeller will provide widest possible speed range may consid ered cruise propeller situation C between 75 95 propel ler can considered climb propeller may useful providing quick takeoffs rough surfaces tall grass C less 75 propeller should used Fig gives data Tims model worked out preparing col umn Fig 2 provides cube roots calculator wont solve problem Ive tried show simple way estimate propeller performance Scientists will grumble about factors arent considered think pro cedure adequate presented con stant 120 equation 3 can reduced 100 Old-Timer type designs creased 150 very clean retractable gear pattern designs generally cor rect RC designs feature three ex posed wheels engine muffler hang ing breeze exposed engine mounts firewall spin ner advantages measurements taken directly own plane account wear trim needle-valve technique field conditions other realities ever having measure quantify illustrator goofed up Fig page 10 December 1976 issue Model vialion battery positive terminal should indicated long line left side figure Its very important though because cant hurt diodes reversing connections will happen nothinguntil connect things should Sorry about George M Myers 70 Froehlich Farm Rd Hicksville NY 11801 February 1977 9 After experimentation other sizes Brad Franciscos Midwest Sweet Stik currently pulled around Top Flite 10-6 Power Prop Steuart Estep fuels dads RCM 40 Trainer pow ered OS Max 40 swinging Top Flight 10-6 nylon prop Though engine manufacturer specifies props thats approximation