Crankshafts are generally made from steel and sit below the cylinders and pistons in the engine block.
Their job is to convert the vertical movement of the pistons into a rotation.
The crankshaft has crank pins along its length that line up horizontally with the pistons above.
The connection between the pistons and the crankpins is through connecting rods, whose ‘big ends’ connect onto the crank pins.
The rotation of the crankshaft is then transferred through to the flywheel. It sits at the end of the shaft to balance it in case of irregular engine pulses.
Despite the effective design of the crankshaft most of an engine’s power losses occur in the crankshaft area. Balancing a crankshaft can also be extremely difficult which is why engineers try to minimise a crankshaft’s length as much as possible. This is the big reason why the V8 engine took over from an engine configuration like an in-line eight, due to its relatively small and controllable crankshaft setup that stops any unwanted flexing occurring.
The relationship between the camshaft and crankshaft is extremely vital for the integration of a car’s drivetrain. They essentially start and end the engine cycle – from inlet stroke to exhaust stroke – keeping the different mechanical processes of each cycle in perfect harmony.
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As the first part of the drive shaft, the crankshaft fulfils other functions than simply passing on the drive. The front end of the crankshaft protrudes through a main bearing and oil-seal and carries the sprocket which drives the camshaft. Also at this end is the pulley that drives the generator, fan and water pump.
At the rear end of the shaft is another main bearing and oil-seal and the shaft again protrudes to end in a flange, to which is bolted the flywheel. While with better engine balancing, the size of the flywheel in modern engines has been reduced.
An equally important function of the flywheel is its part in the starting of the engine. Around its perimeter is a toothed edge. This toothed ring is engaged by the pinion on the starter motor to turn the crankshaft and start the engine.