Model (scale 1:12) of double standard, double acting steam hammer, c.1906, with some replica parts replacing broken components that have been retained (see 1906-20/2).

This working model represents a double-acting steam hammer with self-acting gear, made by Messrs Davy Brothers.

The cylinder is mounted on a double frame of the ordinary Nasmyth pattern and the hammer head slides between guides formed on it. Steam is admitted through a sliding regulator valve, and distributed by a piston valve having a third central piston which divides the steam chest into two parts, each with a separate steam inlet controlled by the regulator so that steam may be admitted to the under-side of the piston only.

The self-acting mechanism consists of a bell-crank lever, one arm of which is fitted with a swivel block working in an inclined slot formed in the face of the tup, while the other arm is connected with the piston valve spindle. The bell-crank lever is pivoted on a movable fulcrum, the raising or lowering of which varies the stroke.

The hammer frame is bolted to a base plate resting on concrete piers and having a central opening through which the top of the anvil projects. The anvil block rests on a separate foundation of timber balks, bolted together, with a bed of concrete beneath it.