Working out the gear ratio

[Cossett]

Hi all does anyone know how to work out the gear ratio for rc trucks ?
Im running a 13.5 turn brushless motor connected direct to a 16-1 planetry box and connected a stock rear diff thats been locked,
Also how would that change if I replaced it wth a 5 turn motor ?

Cheers Tracy

[JamesBC]

The one part I can help you with is the motor, higher turns mean slower KV.
I think, big think there, but the highest turns on a brushless is 21.5 which gives you around 1600KV. A 13.5 should turn around 2300KV.

I use a 21.5 Brushless in my Tamiya Brusier but it is really to slow for just speeding through the park so it is going in a new Semi build that is being started soon.

The one thing about brushless is every maker rates their motor different so take the RPM I listed above only as a guideline.

Jim

[JamesBC]

So all you have to do is take the RPM and divide 16 into it, that gives you RPM out of the box, then do the same on the axle. You might have to find the ratio on the rear end first by counting gears or looking up the axle you are using.

[frizzen]

Whats your axle gear ratio?