184000251 - 1024A FLYWHEEL SELF-LEARNING
CONSTRUCTION FEATURES
Made from spheroidal graphite cast iron, induction hardened. It rests on five main bearings with bearing shells graded into different sizes.The crankshaft endfloat is adjusted by two thrust washers located in relation to the centre main bearing.Eight counterweights arranged at 180° ensure that the crankshaft rotating masses are perfectly balanced. A channel runs along the inside of the shaft to lubricate the main bearings and big end bearings.COMPOSITION
The crankshaft consists of:
- main journals (1), through which it rolls on the supports with (friction type) bearings;
- crank pins (2), over which the connecting rod big ends fit;
- crank arms (3), the same height as half the travel, which connect the main journals to the crank pins.
The shaft is also prepared for:the fitting of the flywheel; - the fitting of the sprocket which, via a toothed belt, transmits motion to the timing system components.
OPERATION
The crankshaft is the component which, via the connecting rod, transforms the reciprocating rectilinear motion of the piston into a rotary motion.It is subjected to forces which change dramatically in terms of intensity and direction and must therefore be sufficiently resistant.Its shape is designed according to the:
- number of cylinders
- type of engine (in line, a v, a w, etc.)
- number of main bearings
- number of strokes (2 stroke or 4 stroke)
In order to prevent damaging engine vibrations, the crankshaft should be both statically and dynamically balanced. These vibrations are due to:
- centrifugal forces, generated by the masses with rotary motion (crank pins, big ends, 1/3 of the weight of the connecting rod, crank arms);
- inertia forces, generated by the masses with reciprocating rectilinear motion (piston, gudgeon pin, 2/3 of the weight of the connecting rod).
where:
- t = engine strokes
- i = number of cylinders
There may be two firing orders: 1, 2, 4, 3 or 1, 3, 4, 2; the most common firing order is 1, 3, 4, 1 as the centrifugal forces and inertia forces are more balanced.