Low Cost: Torque Meter

and select motors fine-tune pertormance TORQUE meter can used compare rubber motors determine optimum motor model help learn about character istics rubber motors Commercial torque meters available quite expensive can easily made scrap material just few minutes however will serve purpose quite well both teaching device practical tool meter shown suitable rubber motors used models up about 20-in wing span larger motors some experimenting wire size length will necessary principle remains same operation twisting force torque rubber motor acts piece wire anchored end measure much torque developed pointer attached wire near motor hook scale used comparison purposes Within some reasonable limits twisting force does deform wire permanently pointer will return 0 motor unwound simple meter scale calibrated measured units ie in/oz ft/lbs nor necessary What well looking comparison torque data between motor another torque few tums compared turns measured units arent required difference torque number scale next can referred simply torque unit Building torque meter should pose few problems Begin photocopying meter scale rubber cementing copy some card stock Make up meter frame 3/16 sq balsa glue scale long upright Drill 1/16 hole through center scale upright working parts meter both made 032 music wire Bend hook rubber motor end 7 length make torque rod pointer bend 1/4 1-1/2 length wire right angle wrapping joint some fine copper wire solder 1/4 part torque rod just behind hook Pass torque rod through hole scale back through another hole I anchor block torque rod must drag passes through scale theres doubt about clearance enlarge hole slightly Now making sure pointer 0 bend over end torque wire glue securely anchor block use meter clamp anchor block small vise have helper hold Hook motor 12 long loop 1/8 rubber good sample torque rod begin winding After 50 75 turns motor gets plateau level torque will much slower increase over next few hundred turns turns capacity motor approached torque readings begin increase faster rate Eventually course motor will break wound far enough worthwhile break few find out turns can wound what kind torque readings obtained up burst point use meter compare characteristics other brands strand sizes motor known capable flying particular model example motor makes model climb has torque reading 4 its winds can used base point Another motor can reach 3 may fly model reads 5 6 might really job probably some extra down-thrust meter can used experiments longer motors longer flights trying match torque readings known motor Torque can plotted graph against time turns motor unwinds either using prop just unwinding winder Some energy put winding lost due friction/heat within rubber will see lower readings unwinding think youll agree small amount time spent make learn use torque meter wise investmentone will repaid times apply knowledge gained models 3/16 sq /-032 wire joints half-la solder pointer H 1/16 dia hole 6 ADRAWING IS FULL SIZE 60 Model Aviation dJ -r le wayto know about rubber its capacity torque meter attached end 0 rubber motor motor recorded reading 2 4 units throughout its range Near peakturns torque value rose rapidly up 8 few turns motor broke 008