Labels:text | screenshot | font OCR: DOUBLE ACTING A piston is Double Acting when it is driven in both directions, usually in a steam engine, but some large stationary diesels are also double acting. A double acting engine requires a cylinder piston rod seal and cross head to absorb the side load normally carried by the piston in single acting engines, such as the one depicted in the animated stacks. EFFICIENCY The ratio of work produced to the equivalent work of the fuel burned. Needless to say, this cannot exceed 100%, and in practice seldom exceeds 50%. ENGINE BRAKING The energy absorbed by an engine when it is driven from an external source with the throttle closed. Normally used on heavy vehicles going downgrade to save wear on the brakes.
