I'm looking forward to this build. You wont need too many speed controls you may get away with just 12 or 24v gearmotors from a power supply or one 110v motor through gear reductions or chain and sprockets or cog belts. Look over ebay. I spend hours scrounging for parts that may work for projects. Here's a video I came across on youtube of a mobile plant that crushes plaster. This guy even has a hammer for his excavator. I think LilGiants has a crusher he uses in his basement PIT.
http://www.youtube.com/watch?v=jWSbW...er_profilepage