Page 136 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

2
120 Automobile mechanical and electrical systems

Linear motion

Rotary motion

Figure 2.73 Conversion of linear to rotary motion: 1, engine block; 2, silicon carbonate;
3, nickel phosphate

Crankshaft pulley Timing belt drive gear

Figure 2.74 Crankshaft pulleys

The crankshaft receives the linear force of the pistons, via the connecting
rods, and converts this force into a rotating torque ( Fig. 2.73 ). The crankshaft
is generally manufactured from cast iron or steel alloy via a forging or casting
process.
Key fact
2.1.3.3 Crankshaft
The crankshaft of a four-cylinder
engine generally has fi ve main The crankshaft of a four-cylinder engine usually has fi ve main bearings. At the
bearings. front of the crankshaft provision is made to locate and drive the crankshaft pulley
and timing gear via keyways and securing bolts ( Fig. 2.74 ). Behind this, the oil
pump drive is located, and then the fi rst or front main bearing.
The big-end bearing for the fi rst cylinder is fi tted in between the crankshaft webs
radiating from the main bearing journals ( Figs 2.75 and 2.76 ). These webs form
counter-balance weights to the big-end journal. One of the main bearings is
usually fi tted with an thrust washer to control axial movement of the crankshaft.
At the rear of the main bearing journal, at the back of the engine, a machined
face is formed on the crankshaft as a mating surface for a sealing ring. This
is the main oil seal at the back of the engine ( Fig. 2.77 ). In addition, there is a