The principal points requiring attention are the condition of the slide block C and the weight pivot pin D. This pin is fitted into the weight arm bushing, and the side pressure will eventually wear the hole oblong. The only remedy is a new bushing. The operator should in no event neglect the pivot oiler. If this clogs up, the pin wear will be excessive and the governor will be sluggish in action. As in all governors, the pins will in time wear out and should be renewed when there is any excessive side play in the parts.
Mietz and Weiss Fuel fuel pump used with the governor just outlined is shown in Fig. 302. This particular pump, is for a two-cylinder engine; the single-cylinder engine's pump consists, in all respects, of one-half of the pump shown.
The governor eccentric strap, through its connection with the rocker arm E, controls the pump actuator lever F. This lever in turn gives the two fuel pump plungers G a travel sufficient to inject the required amount of fuel into the cylinder.
The actuator used on the horizontal twin engine is pivoted in its center. The pump plungers are then in opposition. The engine cranks are 180 degrees apart, and the actuator causes the pump to inject the oil charges into the two cylinders the corre sponding degrees apart. The pump is provided with a stroke regulator which allows the stroke of the pump to be altered and the speed to be controlled by this means, however, only to a minor extent.
Mietz and Weiss Vertical Engine Governor.—Figure 303 is a cross-section of the governor and pump used on the single-cylinder vertical Mietz and Weiss engine. The governor is of the flywheel type, closely following the lines of the horizontal engine governor, while the pump is quite similar to the horizontal engine fuel pump.
Figure 304 is a cross-section of the governor and pump used on the Mietz and Weiss vertical multi-cylinder engines. The governor is mounted on a shaft which is driven by a chain belt from a sprocket wheel on the crankshaft, the gear ratio depending on the number of cylinders—as example, a four-cylinder unit has a ratio of 1 to 4, and a three-cylinder engine has a ratio of 1 to 3. The governor consists of an eccentric C fitted with two weight arms A that are in a plane at a slight angle with the plane of the horizontal governor shaft D. These arms are fitted with tension springs.
The governor shaft passes through the eccentric which bears on la milled sur face on the shaft to which the eccentric is pinned as shown. The eccentric strap fits the spherical surface of the eccentric and drives the pump plunger through the linkage outlined. In operation, when the load decreases the engine speeds up slightly. The increased cen trifugal force of the revolving weight arms overcomes the resistance of the springs, and the weights move outward to a position where the additional tension of the springs counteracts the effect of the increased centrifugal force. The movement of the arms causes the eccen tric, which is pinned to the shaft at a point outside of the plane passing through the center of the spherical eccentric and perpendicular to the shaft, to shift. This produces a decreased eccentricity, resulting in a lessened pump plunger movement, as well as altering the injection angle.
To change the engine speed, it is only necessary to adjust the spring tension. The timing of the oil injection can be changed by removing the drive chain and advancing or retarding the governor sprocket wheel the desired amount.
Fuel Pump for the Mietz and Weiss Vertical Engines.—The 'uel pump for the multi-cylinder engines is incorporated in the 4overnor assembly. It consists of a single pump block with ,he necessary suction and discharge valves and is equipped with Hie plunger. The pump is further provided with a regulator lever. This lever, through a wedge, regulates the stroke of the pump, in addition to the regulation effected by the governor.
On starting the engine, the regulator should be adjusted to limit the plunger travel to a low value. The stroke can be gradually increased as the engine comes up to speed. The hand regulation is especially desirable when the engine is in marine service. The regulator is also of use in advancing or retarding the injection angle in case of preignition or delayed combustion.
The suction and discharge valves are of the 'spring-loaded poppet type. For regrinding, pumice flour and vaseline make an ideal mixture. The valve spring should be removed and the valve lightly held against its seat, and the amount of grinding material applied should be very meager. If a thick coat of the compound is placed on the valve, the seat will be cut to a rounded form.