This pump is provided with a hand-controlled speed-changing device mounted on the body of the pump. It consists of a link C which is threaded at one end to receive a wing-nut D and which is slotted at the other end to engage a pin E on the pump plunger. If it is desired to lower the speed, the wing-nut is screwed up, shortening the link and lessening the outward movement of the plunger. The link is provided with a lock-nut F that serves to hold the link in the desired position. By using this adjust ment the plunger travel can be reduced until practically no oil is injected into the engine so that an excellent speed control is obtained. It has another important advantage that is of more benefit than is its speed-regulating ability. This is its use in changing the point of injection, which principle will be discussed later in the chapter.
The pump is simple in design and requires but little attention, but probably some degree of fuel control has been sacrificed in obtaining this simplicity. The valves are steel balls; to .reseat these, a sharp blow with a hardwood stick and a mallet will usu ally be all.that is needed. The lift of the ball valves should be limited to IA2 inch by dressing off the plug seat until this value is attained. The packing around the plunger, as in all pumps, in time wears out. In replacing the worn rings, they should be well soaped before being inserted into .the stuffing-box. It is never advisable to screw down very hard on the gland as the side pres sure of the rings will cause the pump plunger to stick, or at least to score.
On the larger Muncie engines the company has brought out a combined fuel and water injection pump, Fig. 292. This unit consists of a heavy bracket pump casting with two cavities for the fuel and water plungers. The pump plunger b is actuated directly by the eccentric push-rod a. The push-rod has an ad justable end which allows the clearance between rod and plunger to be adjusted. Due to the pounding of the rod end, the clear ance increases and should be checked at least every two months. To make the adjustment the engineer should proceed as follows: Set the fuel pump plunger out to its extreme forward or suction position by unloosening the adjusting or regulator rod. Loosen the governor springs and block the governor weights to their maximum outward position so that, as the crankshaft is turned, no motion is given to the push-rod—the eccentric is now concen tric with the shaft. The adjusting stud should now be set to allow the clearance between stud and pump plunger to be 342 inch. The lock-nut should be screwed up and the governor
springs tightened into place. The engine should be started and brought up to maximum speed by manipulating the pump handle. At this speed, with the governor weights at their greatest throw, the plunger clearance should be 342 inch. If the governor weights do not throw out enough to cut down the throw of the eccentric, the springs are too tight and should be loosened a slight amount.
Fairbanks-Morse Horizontal Engine Governor.—Figure 293 is a sketch of the shaft governor used on the Fairbanks-Morse horizontal oil engines of 25 h.p. and under. It is of the well-known Rites inertia type which has been adopted by many builders of high-speed steam engines. This governor, at first glance, appears to be the simplest and most reliable of all; how ever, there are certain features to be borne in mind. Since the governor arm is supported at one point and all the weight is con centrated on a line falling outside of this pivot point, the governor is out of balance. All the thrust of the weights is against one side of the pivot or fulcrum pin, and the natural result is wear of this pin on that one side, causing the governor to bind. The engine, in conse quence of this binding, shows marked racing or "hunting," especially on low or varying loads. In the Fairbanks-Morse governor, to eliminate this defect, the pin is hardened and ground, and the governor carries a hardened bushing into which this pin fits. This serves to reduce the wear, but the friction between pin and bush ing, produced by the side thrust of the weights, is considerable.
If the compression grease cup is not watched, the friction will make the governor very sluggish in action. In those engines where the design does not embody a hardened bushing, the pin should be given a quarter turn each thirty days. This will distribute the wear evenly about the entire periphery of the pin. If a soft bushing is used, this, rather than the pin, should be turned.
The weights are held in equilibrium by a tension spring, and the speed of the engine is increased by tightening the spring. The engine will regulate more closely if. the end of the spring, held in the slot in the weight arm, is moved outward. Moving it inward decreases the sensitiveness of the governor, allowing the engine to have quite a range in speed variation; but this is the proper way to have the engine govern if it is pulling an in dustrial load, such as a cereal Mill.