I have had a large part in building 8 tire hammers. The blueprint is for 1 hp., which is fine, a 1 1/2 hp is available new with the same 7/8 shaft. It is the same physical size and frame. I would lean towards that. My two hammers have 1 hp motors, which I bought used at the flea market $15 - $30 each. Make sure the're 1725 rpm.