Flywheel:
The flywheel is situated on one end of the crankshaft and serves three reasons. First one, by its inertia, it decreases vibration through smoothing out the power stroke as each cylinder fires. Second one, it is the mounting surface used to bolt the engine up to its load. Third one, on a few diesels, the flywheel has gear teeth around its perimeter which permit the beginning motors to crank and engage the diesel.