I for one am not convinced that going with a RC model car and converting it for RW style combat is the cheaper option.

First of all, you need a good car as the base for youre robot. They run up in the costs. It is safe to say all chassis onder the 100 pound mark are not suitable. 200 to 500 pounds are very normal prices for a robust RC car that can handle the punnishment. Especially since you state yourself its going to be a rambot.

For me, the most expensive part in my feather (still under construction) are the speed controllers, in total the costs is nearing the 160 pound mark. that includes RC tx/rx, speedos, motors and wheels. Chassis and armour i make from whatever i have left over from the heavyweights.

my two cents worth.

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Leo