Building a better caster.

[IVIaxor]

It sounds to me like you are trying to build a sort of crab drive system. I tried to push one of those systems on my team last year, they shot it down. Such a system is very diffuclt to construct and code (though I know I could have done the code part).

Anyway, you are looking for a thrust bearing to support the load on the caster. (a thrust load on an axle means the load goes down the axis of the axle) You will also need to use standard bearings to prevent the axle from twisting, even more so if the axle is not directly over the wheel.

Hope that helps.