I'd like to try a scratch build myself. I think a dozer is a better choice for starters due to the less complex system. Drives and blade that's it, compared to boom, bucket, steer, drive systems. All the geometry and linkage in a loader compared to , a blade.
My plan is to figure out how heavy it's going to be, how strong a drive motor will I need and what to use for tracks, pads and rollers. I figure, buy the motors and undercarriage first and build a structure according to them rather than build something and then search for motors and undercarriage to fit what you built?
I've played with converting toys to rc and hate all the searching for things strong enough and small enough to fit in limited space. I want to avoid that for once!
