The document describes the lubrication system of a unit construction engine. It has a forced lubrication system with an oil pump that supplies oil to main components through three passages. The oil lubricates the crankshaft, pistons and gears before draining into the sump. The gearbox is splash lubricated by oil thrown from the rotating crankshaft and collected from the flywheel chamber. The primary drive case is also lubricated by oil entering from the crankcase through openings.

1. LUBRICATION PROCESSES IN UNIT CONSTRUCTION ENGINE

2. LUBRICATION PROCESSES IN UNIT CONSTRUCTION ENGINE Unit Construction Engine has a forced lubrication system as shown in Fig.1 in which a trochoidal oil pump which supplies oil under a controlled pressure at a flow rate of up to10 litres/min. The oil pump contains a pressure relief valve which maintains a system pressure of around 1 bar. When the engine is started, the oil from the sump is drawn by the oil pump through a primary suction filter and then delivered to the main oil filter. After filtration, the clean oil is routed through three passages. OIL PASSAGES (See Fig.1) Passage 1 feeds pressurised oil directly to the big end bearing via a drilling in the right-hand flywheel shaft. Oil leaving the big end bearing lubricates the piston, connecting rod small end bearing and crankshaft main bearings after which it is collected in the flywheel chamber. Passage 2 lubricates and cools the rocker bearings and valve gear, and then drains to the timing chest through the pushrod tunnels. The oil in the timing chest lubricates the cams and their drive gears. Oil is also fed to the timing chest from the oil pump pressure relief valve, ensuring an immediate supply on start-up. During normal running, the oil level in the timing chest is maintained by the generator rotor, which throws excess oil back to the sump over a baffle in the chest. Passage 3 supplies a pressurised feed to the hydraulic tappets for maintaining valve train clearances.

3. Fig 1 Forced Lubrication System

4. Fig 1 Forced Lubrication System GEARBOX LUBRICATION The oil which lubricates the flywheel assembly, piston and connecting rod through passage 1 gets collected in the flywheel chamber. This collected oil is used for splash lubrication of the gearbox components. As the crankshaft rotates, the oil in the flywheel chamber is thrown up by the flywheels, collected by a knife-edge in the crankcase and directed on to the gearbox components as shown in Fig.2. This lubricates the gears, their bearings and the gear selector mechanism. Fig 2 Splash Lubrication of Gearbox

5. Fig 3 Side View of the Engine, showing Sump and Splash Lubrication of Gearbox GEARBOX LUBRICATION The oil then drains back to the sump, which is in a chamber beneath the gearbox, as shown in Fig. 3.

7. OIL FLOW PATHS FOR FREE-RUNNING GEARS Mainshaft 4 th Gear (see Fig. 4) Oil falling on the Mainshaft 2 nd gear spline lubricates the 4 th gear from the right side. There is an oil groove provided on the Mainshaft 4 th gear to lubricate the gear from the left side. Additional oil enters through the gap between the Circlip and the left side washer. Fig. 4 Oil Flow Paths to Mainshaft 4 th Gear Shaft Oil groove 4 th gear Washer Circlip Washer

8. OIL FLOW PATHS FOR FREE-RUNNING GEARS Mainshaft 3 rd Gear (see Fig. 5) Oil falling on the Mainshaft lubricates the 3 rd gear and the shaft directly from the left side. Oil passes through the recess between the Circlip and the 3 rd gear, to lubricate from the right side. Fig. 5 Oil Flow Paths to Mainshaft 3 rd Gear Washer 3 rd gear Circlip Main shaft Main shaft

9. OIL FLOW PATHS FOR FREE-RUNNING GEARS Layshaft 2 nd Gear (see Fig. 6) Oil falling on the layshaft enters through the grooves provided on the side of the high gear to lubricate the layshaft 2 nd gear from the right side. Oil from the layshaft double gear spline lubricates the layshaft 2 nd gear from the left side. Fig.6 Oil Flow Paths to Layshaft 2 nd Gear 2 nd Gear High Gear Lay shaft Lay shaft Oil groove

10. OIL FLOW PATHS FOR FREE-RUNNING GEARS Layshaft 1 st Gear (see Fig. 7) Oil falling on the layshaft lubricates the layshaft 1 st gear through the gap between the washer and layshaft face from the right side. On the left side it is lubricated by oil grooves provided on the face of the gear and also by the clearance between the gear and the face of the layshaft thrust washer. The needle roller bearing which supports the layshaft is also lubricated by this oil. Fig.7 Oil Flow Paths to Layshaft 1 st Gear Oil groove 1 st gear Washer Washer

11. PRIMARY DRIVE LUBRICATION (See Fig.8 andFig.9) The primary drive system and electric start mechanism are lubricated by oil passing into the primary drive case from the crank chamber via the left hand main bearings (Fig.8) and through breather holes cast (Fig.9) into the wall between the crank chamber and primary case. This oil collects in the base of the primary drive case and is picked up by the primary chain during normal running. Thus the chain itself, the sprockets, and the electric start gears and sprag clutch are lubricated by the oil picked up and distributed around the primary case by the chain. Fig.8 Oil entry into the primary drive side through bearings

12. Fig.9 Crankcase opening for oil transfer Excess oil is skimmed from the moving chain by a knife-edge located above the clutch and is returned to the sump after passing over the gear selector mechanism and gearbox. The primary drive case is charged with an initial measured quantity of oil in order to provide lubrication when first starting the engine after assembly PRIMARY DRIVE LUBRICATION (See Fig.8 andFig.9)