[Jnadke]

If you wanted to do it with calculations, you can figure it out theorhetically. You need the diameter of your wheels. With this, you can find out the circumference of your wheels with:

Circumference = (Diameter) * (pi)

Then, you need to figure out what speed your output shaft revolves at. You can figure this out with:

Shaft speed = (Motor free speed) / (Gearbox & sprocket reduction)

Then, just multiply the shaft speed (rev/sec) by the wheel circumference (ft/rev) to get the speed (ft/sec). For all practical purposes, I would multiply the speed # by 0.90 or 0.95 to take in account a 90-95% drivetrain efficiency. You're not going to get 100% of the motor speed to your robot wheels.



For example, last year we used the Chiaphua motors geared overall 30:1, with ~7" diameter wheels (including traction material). The Chiaphua rotates at approximately 5400 revolutions per minute, or 90 rev/second.
Circumference = 1.83 FT
Shaft Speed = 3 rev/second
Speed = 5.5 ft/second


Of course, the most accurate way is tape measure + stopwatch + calculator, as said above. Get your robot up to speed, and let it go for 50FT (the longer, the better, the less error). Time how long it takes to travel this distance, and divide the length by the time.