The fuel is pumped into the pump tank by a plunger pump driven off the eccentric rocker shaft. The tank is fitted with a sight glass and a small gauze filter. This filter must be cleaned at least twice each day since the mesh is very fine and the collec tion of dirt soon stops the flow of oil.
Fairbanks-Morse Vertical Engine Governor.—The governor shown in Figs. 297 and 298 is the one used by the Fairbanks-Morse Co. on their vertical type "Y," both single- and multi-cylinder engines. It consists of a small wheel, which is mounted on the engine shaft opposite the flywheel, and two weight arms whose centrifugal effort is resisted by the tension springs shown. Through the agency of two links the arms are connected to the cam sleeve. This sleeve is mounted on the engine shaft, about which it is free to move under control of the weights. The cam, which is a part of the. sleeve, controls the opening and closure of the injection pump suction valve. The governor, as shown, is for an engine running anti-clockwise, as seen when facing the governor side of the engine.
To obtain a clear understanding of the action of the governor, it must be considered in conjunction with the action of the fuel pump. Figures 298 and 299 show views of the pump for a three cylinder engine.
The fuel pump plunger C is driven by the cam A. This cam is clamped to the engine shaft as outlined in Fig. 297A. This cam, which has its nose or lifting surface extending over about 15 degrees, strikes the roller B, which is mounted on the end of the pump plunger. This movement, extending over 15 degrees, injects the fuel charge into the cylinder. The exact point of injection is shown in Fig. 300. Just before the pump plunger begins its outward or discharge stroke, the governor cam, which has been holding the pump suction valve open, presents a low surface Y and the suction valve closes. After the engine shaft has revolved sufficiently to allow the pump to complete its in jection stroke, the governor cam, which is rotating with the shaft, presents its high surface to the suction valve plunger. This again opens the valve, enabling the pump to take in another fuel charge. The positions of both governor and pump cams are shown in Fig. 298. This view shows the relative position of the cams at the beginning of injection.
The governor action is as follows: If the engine speeds up, the weight arms, due to the increased centrifugal force, move outward to a new position. This movement of the governor arms causes the governor cam to shift clockwise, or opposite to the direction of rotation. The consequence of this shifting of the governor cam is to cause the low surface on the cam to move under the suction valve push-rod E at a later position of the engine crank, that is, the suction valve is held open during the first part of plunger's discharge stroke. The pump plunger then
actually forces a part of the fuel charge back through the open suction valve before it is closed. When the low surface on the governor cam comes under the suction valve plunger, the valve closes, and the remainder of the fuel charge is forced through the discharge valve into the cylinder.
It follows that the injection point of the engine varies with the load. The change from no load to full load is not great, and no objectionable results occur when oils below 38° Brame are used. It is always advisable to have the pump injection cam timing, and the governor cam timing as well, adjusted to suit the particular fuel used. Where heavy crude under 24° is used, the injection angle of 45 degrees is not sufficiently early to insure complete combustion. It then becomes good engineering for the operator to set the injection at an earlier point. This is by no means beyond the powers of the intelligent engineer, and this adjustment should be made when the combustion is not good. This is especially true where the engine is operated con stantly, for a 10 to 15 per cent. fuel saving, which may result, is attractive.
When the engine is tested out at the factory, the cam and shaft are marked. This marking represents the proper timing for usual conditions. If it is desired to have the injection occur earlier, the pump cam should be undamped and shifted, in the direction of the engine's rotation, the desired number of degrees. The governor should now be shifted a corresponding amount. Since the governor, when the engine is at rest, holds the governor cam in a position slightly more advanced than when under operat ing conditions, to reset the governor to conform to the new pump cam timing, it should be shifted until the leading high cam point is 35 degrees ahead of the high cam point of the pump cam. To shift the governor, it is necessary to unclamp the bolts and use a wedge to open the split in the hub. If the adjustment of the pump cam is to be but slight, the engineer is not justified in altering the governor setting. Loosening up the governor spring tension will cause the governor to shift its cam enough to bring the two cams into proper relationship. These springs can be ad justed until the correct speed is obtained. If kerosene or very light distillate is to be used, the timing should be made later. In fact, with kerosene 20 degrees ahead of dead-center is ample for the injection point. This allows all the fuel to enter the cylinder before dead-center is reached.