Fig. 76.—Wrist Pin Lubrication
In the force feed system a pump driven by the engine forces oil through pipes and channels to all of the bearing surfaces. Oil collects in a pocket in the crank case, called the sump, and is drawn from it by the pump. The sump is usually provided with a wire mesh strainer that separates out any dirt.
Fig. 77.—Force Feed Oiling System of “Gray” Engine
From the oil pump the oil is forced to the bearings by pipes and by holes drilled in the crank shaft and other parts, as shown in [Figure 77].
Fig. 78.—Oil Pump
An oil pump is illustrated in [Figure 78]. It consists of a plunger driven by the engine, working in a cylinder provided with two ball check valves, one for inlet and the other for outlet. On an upward stroke of the plunger the cylinder fills with oil, which is forced to the engine bearings by the following inward stroke.
Fig. 79.—“E.B.” Oil Pump