Engine (such as pneumatic motors), springs (clockwork motors) and elastic bands. Historic military siege engines included large catapults, trebuchets, and (to some extent) battering rams were powered by potential energy. A pneumatic motor is a machine that converts potential energy in the form of compressed air into mechanical work. Pneumatic motors generally convert the compressed air to mechanical work though either linear or rotary motion. Linear motion can come from either a diaphragm or piston actuator, while rotary motion is supplied by either a vane type air motor or piston air motor. Pneumatic motors have found widespread success in the hand-held
Dunlop Pneumatic Tyre Co Ltd v New Garage & Motor Co Ltd damages and not as a penalty’. The judge held the £5 sum was liquidated damages and enforceable. The Court of Appeal held the clause was a penalty and Dunlop could only get nominal damages. Dunlop appealed. The House of Lords held the clause was not a penalty, and merely a genuine preestimate of Dunlop’s potential loss, and so Dunlop could enforce the agreement. Lord Dunedin set out the following principles. Dunlop Pneumatic Tyre Co Ltd v New Garage & Motor Co Ltd It should not be confused with "Dunlop Pneumatic Tyre Co Ltd v Selfridge & Co Ltd", which held