Allied's Hammerhead II Model HB 550 is not a drop hammer. It's a 1,130-pound hydraulic concrete-slab buster sized to mount on a 5,000- to 9,000-pound skid-steer or 7,000- to 16,500-pound mini-excavator or backhoe-loader. An internal hydraulic cylinder compresses a heavy spring set that loads the system with 3,350 psi of hydraulic pressure. The return stroke of the cylinder triggers the 388-pound impact bar at the concrete with the impact force of a 4,000-foot-pound hammer. Estimated list price range: $10,000 to $13,000.