ECCENTRICS.
The Eccentric on an engine is for the purpose of moving the valve back and forth upon the valve seat and has a throw equal to the travel of the valve. The throw of eccentric is caused by the wheel or plate being bored to one side of its true center, and generally equals one-half the travel of the valve. If more or less, the difference is caused by the use of rocker arm or similar devices for increasing or diminishing the throw of eccentric as the case may be. The eccentric is accurately fitted and fastened to the main shaft of the engine with set screws or key.