astrocyl

There is this motor which says it is good with 4.5:1 or 5:1 gears. Lets say the big gear connected to the main rotor shaft on my heli is 100T, so what pinion should I get? A 20T pinion? that would make a 5:1 ratio isn't it? So far the pinions I saw at helihobby is at 14T max. Is there a trick here? Anyway the motor is Acro Speed 280BB. Any help is appreciated.

stirlingnut

There is probably a better person to answer this,but this is my two cents: you need to know the motor rpm,then subtract about 25% for load,gear the heli for 1000-1200 rpm ROTOR speed. Say 20,000 rpm max loaded,8 tooth pinion,100 spur= 1600 max ROTOR speed,which is still a little high.(an article I read in "rotory modeler" said rotor speed 900=1000 rpm at hover.)But a lot of the threads on this subject have reported good results with this motor,an 8 tooth pinion on the stock main shaft gear. I hope this helps,blade type,pitch,yadda yadda, can /will change the rotor speed,and things break faster too(ouch). I guess we will all go brushless someday.
Has anyone connected an ampmeter inline to their motors to test current draw?It was hard to do with r/c cars,but is much easier in a heli,where load is more constant,and of course stationary.And last but not least,I have yet to read a post about motor lube,tiny amounts will add hours to the life of your motor.Both of my stock motors have over 40 battery packs thru them,and they still run fine.I just replaced them,and will tear down and post what I find.