Page:The Russell Engine-Four Valve Automatic Cut Off.djvu/12

 that a slight increase or decrease in speed must make a change in the cut-off and bring the engine again to, standard speed. The governor is the most sensitive, and more instantly feels any variation in speed when the centrifugal or outward force of the weights is just balanced by the centripetal or inward force of the springs, but as this condition of the governor produces racing or unsteadiness, it is our practice to reduce the tension of the springs a trifle, and thereby give the weights or centrifugal force enough preponderance to insure stability. When a governor is thus adjusted, if a change in speed is wanted it must be obtained by adding weights for slower speed and reducing for faster speed. The mechanism of the governor permits of a very delicate adjustment. It will be seen by referring to the cut that the point of attachment of the springs to the weight arms may be shifted, so as to get more or less leverage and the extension of the springs, and therefore more or less centripetal force. The weights and spring tension are calculated as closely as possible, but the final adjustment is made by attaching the springs at a greater or less distance from the weight arm fulcrum, and thus the balance between the opposing forces may be exactly determined and the adjustment so accurately made that these forces increase and decrease in the same ratio. The effectiveness and force of the weights varies in the ratio of the squares of the velocities, and as the velocity depends upon the radius of gyration, it is easily seen why the weights should approach and recede from the center by only a small amount, and this is permitted by the small movement required to operate the eccentric.

Dimensions and Powers

The Russell Four Valve Simple Engines

Cut off at about .25 stroke.