What does 6mm of can diameter buy me?
 

Hey all! Happy holidays!

I have an rc18t set up for on-road running. I used to run a 20mm 6800kv mamba with 12/60 gearing, and it ran perfectly.

During the recent Castle sale I snatched up a couple of nice 26mm motors, one of which is a 6800kv. I'm going to use this in my rc18 but figure I can go up a couple of teeth on the pinion. Does anyone have any idea what a sensible number of teeth to go up is?

My extremely naive maths says 6 extra mm of can might equal 30% extra torque (6/20=0.3), so I can get 3 or possibly even 4 extra teeth for that. (12*0.3 =3.6)

Of course I have no idea if it even works that way (Does power scale linearly with can size?). I was thinking either hopping up 2 or 3 teeth.

Anyone have any wise words?

Thanks

I wouldnt like to guess how power scales with the motor size- can be affected by length, diameter, magnet strength, pole count, copper losses etc etc, but I like your theory so lets roll with it :mdr:

I'd say jump a couple teeth up on the pinion and see how temps do- thats the main decider/ factor that tells you if the motor/esc/batts are happy or being overworked. if temps stay in check then go up a few more teeth and compare temps to see if they've stayed stable or really increased too in line with gearing.

Since we are talking a 3D cylinder rather than a line, I would say you are increasing the rotor mass by (pi*13^2)-(pi*10^2), or +69%. It shouldn't be linear but more exponential.

The torque should also increase as the force vector would move outward. IE, I would take a guess that the power would be more than 30% if everything else was equal.

In real terms, how many more teeth? Hell if I know :D

Thanks for the great replies guys! I think I'll try 3 teeth first :)

E=MC^2
Take a guess, multiply by 3, divide by the date your mother-in-law was born, minus 1 then try something within arms reach and let us know how it goes. LOL
I have had a few beers and just having some fun with numbers.

Good luck though.

Just saw you joined way before me and have even less posts than me - another lurker - I like you!!