Help in choosing a proper motor

Using Arduino Motors, Mechanics, Power and CNC
1

So I'm asking a question that I'm sure is common knowledge to engineers out there. I'm in the planning phase of a new robot, and I don't know how powerful of a motor to get.

My question is this: is there a formula or equation for figuring out the oz/in or kg/cm of a needed motor? Like if I know the wheels will be 12 inches in diameter, and the robot will weigh 20 pounds, what would be the necessary oz/in of each of the two motors? And if anyone knows a resource where I can learn these mechanical calculations, that would be greatly appreciated. Thanks!

-T

2

Oriental Motor has a nice motor sizing calculation page, though you have to register:

The answer will not be as easy as you think, and will depend upon how fast you need it to accelerate/decelerate, wheel rolling resistance, and perhaps others.

If you Google for "motor sizing" you may find several more links.

--
The Ruggeduino: compatible with Arduino UNO, 24V operation, all I/O's fused and protected