I have always wanted to build a mid-evil type of drive crusher for one of those (nothing else to do on a weekend) projects. I'm thinking two sledge hammer heads welded together face to face to make a nice heavy cylinder with a little eye welded to one end with witch to attach a very strong, thin nylon cord. Some guide rails of about 10FT tall and a small pulley and hand crank to hoist the hammer up to the top, then some means of releasing it. Great fun, only problem is I never have one of those (weekends with nothing to do)