drop hammer
noun1
Engineering, Mechanical, Mechanical engineering, Natural sciences, Physical sciences A heavy weight that is raised and then allowed to drop, as used for piledriving and drop-forging.
- On embankments these troughs are supported by piles driven into the ground and recent practice has been to drive them in by a drop hammer, manually operated from a railway wagon, [...].1961 November, “Talking of Trains: The North Eastern's new rail-mounted piling unit”, in Trains Illustrated, page 646: