Mechanum Gear Ratio Recommendations

[bakejame]

I have looked through the other posts about Mechanum wheels and the discussion about direct drive or chain drive to try to find my answer. I haven't had any luck.

What I would like to know is: what the best gear ratio supplied to the wheel should be for 8" Mechanum wheels? For last year's competition we had a GR of ~20:1 between the toughbox and the sprockets. We were very maneuverable, but we weren't very fast. That was mostly so we would have enough torque to get over the bumps. We don't have bumps this year, so torque won't be quite as necessary. We do think speed will be important though.

If someone knows of a formula we could use to calculate the GR we should use with our Mechanums, we would really, really, really appreciate it.

Thanks in advance.