Improved System of Splash Lubrication.—This is a combination of the splash system and the forced system, and is shown in Figs. [55] and [56]. In these figures A2 and A3 represent two of the main engine bearings which support the crankshaft; C1, C2, C3 are three of the crankpins; F1, F2, F3 are oil troughs placed under the crankpins; D2, D3 are oil feed pipes to the main bearings. Generally speaking, the oil is drawn from the bottom of the crankcase by means of a pump, and this pump delivers the oil to some form of indicator mounted on the dashboard of the car. After passing through the indicator the oil flows by two main pipes, one of which feeds the main bearings by means of branches D2, D3, etc., and the other feeds oil troughs by means of branches such as G2. When the troughs are full the oil overflows into the bottom of the crankchamber, and so there is always a constant depth of oil for the scoops attached to the connecting rod ends to dip into, and one great drawback to the splash system is overcome; also the main bearings are always sure of being amply supplied. The oil pump may be an ordinary plunger type pump or a rotary pump.
Fig. 56.—Sectional View of End
of Connecting Rod, showing
Arrangement of Scoop and
Oil Trough.
Forced Lubrication.—One system of forced lubrication is shown in Fig. [57]. The general arrangement of the system is very similar to the preceding one, except that there are no troughs in the crankchamber and all the bearings receive an ample supply of oil under pressure so that the journals are supported in their bearings on a film of oil and the metals never come in direct contact with each other. After entering the main bearings the oil passes through holes drilled in the crankshaft and thus positively lubricates the crankpin bearing, passing up the connecting rod either internally as shown or by an external pipe it lubricates the gudgeon pin and then falls down into the crankchamber. On its way down it gets splashed about and thus lubricates the cylinder walls and piston; sometimes these are positively lubricated by leading the oil through the centre of the gudgeon pin direct to the surface of the cylinder walls—but this often gives an excess of oil and causes a smoky exhaust. In Figs. [58] and [59] we show two views of a very popular form of oil pump for forced lubrication systems. It consists of two gear wheels, one of which is driven by a spindle from the engine crankshaft, and it drives the second wheel by means of the projecting teeth. The oil is picked up by the teeth and passed round from the suction to the delivery side of the pump on the outer edge of the wheels; no liquid can pass direct across between the teeth which are in mesh, and hence the direction of rotation is as shown by the arrows.
Fig. 57.—Forced Lubrication System.
