A group of us were trying to build a small tank for a competition that could climb over 4 x 4s. The vehicle has to fit in a box that is 370 mm x 165 mm x 165 mm and that lighter it is the better, as we lose points for every gram it is, so we were hoping to keep it under 5 lbs., just for a weight estimate. Any suggestions on what size of electric motor that we should use as far as torque ratings and rpm go? We were planning on using two motors, one for each tread. Also, the cheaper, the better. Any help would be greatly appreciated.

when it comes to building custom r/c cheap doesn't always work lol

If you want to use something with lots of torque look at crawler motors from http://www.rcrockcrawling.com/ they have 540 size lathe motors that are 60turn and up, produce lots of torque.

Assuming no time limit, and minimal steering requirements, I'd get the smallest motors that will work, and use massive gear reduction. Motor power is pretty meaningless unless you are restricted by gearing, parts, or a time limit.

Using