Fisher Price Gearbox Torque

[Andy A.]

Originally Posted by kramarczyk

Awesome! I just came up with a slightly different number, 122:1. Attached is my counting work from this evening for comparison.

An exact ratio isn't very important for most FIRST applications. There are a lot of factors in play that make those pristine speed/torque calculations only a rough suggestion. You won't get either the speed or torque that you expect due to frictional losses, voltage drop during a match, manufacturing inconsistencies, directional bias etc. By all means, do the math and use it to design with, but always include a healthy skepticism about your numbers.

I've just used 128:1 in the past to make the math a little easier. I think we arrived at that number many years ago by hooking the motor and gearbox combo up to a charged battery and counting the number of Revs of the output shaft observed in 30 seconds. Then compared that to the specified no-load RPM and rounded off.