In operation, this governor is practically trouble-proof. A point to be remembered is the necessity of keeping the pivots and the guides well oiled. The guides will quite likely collect dirt and grit. This will hinder the movement of the eccentric, and the engine will tend to race. The governor should be wiped with a rag or wiping cloth each time the engine is stopped. Every few months the governor should be dismantled and every part thoroughly cleaned and oiled. If the guides seem rough, they should be smoothed with a scraper. An engine must be in service a number of years before much play develops in the guides. When this does occur, the guides should be removed and the base filed down. If there is side play, a copper strip can be placed between the guide and the disk and flanged up so that it fills the space between the guide and the eccentric. It is also a good plan to keep on hand a spare set of governor springs. Some operators have the idea that any spring will meet the re quirements. In governor construction, the spring must be of a length and the wire of a cross-section such as will allow the gover nor weights to be in equilibrium in any position. If the spring has too many coils, even though of the correct size wire, the governor may "hunt," and the engine may even have a higher speed at full load than at no load. This is true where there is any inertia effect from the arms. There are few shaft governors that do not display some inertia effect in operation.
While it is possible to move the disk on the shaft, it is not advisable for the inexperienced engineer to attempt to alter the setting. The builders always set the eccentric at the point where the oil injection should best begin when the average gravity fuel oil is used. Even though a different oil be used, the operator can seldom better the conditions; none but an expert should make this adjustment. However, when an engineer• is meeting with preignition trouble due to light oils, there is no reason why he should not experiment with the setting, using an off-set key to secure any alteration in the position of the disk.
This governor belongs to that class wherein the point of be ginning of oil injection, as well as the amount of oil injected, which depends on the length of pump stroke, is altered as the load changes. In other words, speaking in steam engine nomen clature, both the angular advance and the eccentricity change.
' The action of this governor may be understood from Figs. 289 and 290. In Fig. 289 the full lines show the eccentric position at low load. The crankshaft center is at 0 and the center of the eccentric at A. The crank is at an angle a from the center line XY. In this position fuel injection is just commencing, as in dicated by the contact of the eccentrics with the push-rod B of the fuel pump. Under full load the eccentric is moved to the position shown in Fig. 290, the eccentric center being then at
A' and contact with the push-rod being made at These same positions are shown dotted in Fig. 289.
In the first position of the eccentric the injection of oil begins when the crank is a degrees from rear dead-center, and the total movement of the plunger is C. In the new position of the eccentric, the crank is a + 6' degrees from dead-center when the injection begins, while the total plunger movement is C'. It a is apparent that the eccentricity or throw of the eccentric in Fig. 289 is greater than C, but the difference represents the movement of the eccentric before it strikes the push-rod or the pump plunger and might well be called the of the pump.
In operation, on low loads, the angle of advance of the eccen tric is such that the fuel is injected somewhat later in the com pression stroke than on full load, the crank being about 15 degrees ahead of the rear dead-center and the change in crank position being about 15 degrees. This results in poor combustion and a smoky exhaust since the oil charge has insufficient time to vapor ize and burn. With the use of kerosene or light distillates this objection cannot be raised since the rate of vaporization is very rapid even at a low temperature. On full load the point of injection advances to practically 30 degrees ahead of rear dead center. With heavy fuel oil or "tops" this point of admission is not objectionable; in fact, it is an advantage since there is a greater time interval before dead-center is reached for the heavy oil to completely vaporize and ignite. But with light oils, such as distillates or a crude containing a considerable percentage of light hydrocarbons, this early injection causes preignition. Such preignition often becomes so heavy that it is impossible to eliminate the knock by using water injection; for, if enough water is used to prevent preignition, the cylinder will be flooded and the hot bulb cooled to an extent that combustion is entirely suppressed. This early injection of the fuel charge is not re quired, and in actual operation the skilled engineer makes the admission occur later by manipulation of the fuel pump regulator which will be mentioned on succeeding pages.
Muncie Fuel Injection fuel pump used on all the Muncie engines, with the exception of a few of the larger sizes, is shown in Fig. 291. The stroke of the pump plunger is controlled by the eccentric push-rod, as outlined in Fig. 289. The spring A is seated against a collar B on the pump plunger and serves to move the plunger on the outward, or suction, stroke. The eccentric push-rod, of course, actuates the plunger on the dis charge stroke; any change of the shaft governor, by altering the throw of the eccentric, causes an alteration in the plunger movement.