About crankshafts

crankshafts are made from forged steel or cast iron. crankshafts for high-volume, low-load production vehicles are generally constructed from nodular cast iron, which has high strength (see Appendix D). Fuel-efficient engines require a high power-to-displacement ratio, which has increased the use of forged crankshafts. The proportions of the materials used for crankshafts in car engines in 2003 were estimated to be, cast iron 25%, toughened (quenched and high-temperature tempered) or normalized steel 20%, and micro-alloyed steel 55%. Table 8.2 shows the chemical compositions of steel crankshafts. 2.2.2 Torsional damping of driven plate
Crankshaft torsional vibration(Fig. 2.6) Engine crankshafts are subjected to torsional wind-up and vibration at certain speeds due to the power impulses. Superimposed onto some steady mean rotational speed of the crankshaft will be additional fluctuating torques which will accelerate and decelerate the crankshaft, particularly at the front pulley end and to a lesser extent the rear flywheel end (Fig. 2.6). If the flywheel end of the crankshaft were allowed to twist in one direction and then the other while rotating at certain critical speeds, the oscillating angular movements would take up the backlash between meshing gear teeth in the transmission system. Consequently, the teeth of the driving gears would be moving between the drive (pressure side) and non-drive tooth profiles of the driven gears. This would result in repeated shockloads imposed on the gear teeth, wear, and noise in the form of gear clatter. To overcome the effects of crankshaft torsional vibrations a torsion damping device is normally incorporated within the driven plate hub assembly which will now be described and explained.
Multistage driven plate torsional spring dampers may be incorporated by using a range of different springs having various stiffnesses and spring location slots of different lengths to produce a variety of parabolic torsional load-deflection characteristics (Fig. 2.7) to suit specific vehicle applications.
The amount of torsional deflection necessary varies for each particular application. For example, with a front mounted engine and rear wheel drive vehicle, a moderate driven plate angular movement is necessary, say six degrees, since the normal transmission elastic wind-up is almost adequate, but with an integral engine, gearbox and final drive arrangement, the short transmission drive length necessitates considerably more relative angular deflection, say twelve degrees, within the driven plate hub assembly to produce the same quality of take-up.
Construction and operation of torsional damper washers (Figs 2.2, 2.3 and 2.8) The torsional energy created by the oscillating crankshaft is partially absorbed and damped by the friction washer clutch situated on either side of the hub flange (Figs 2.2 and 2.3). Axial damping load is achieved by a Belleville dished washer spring mounted between one of the side plates and a four lug thrust washer.
The outer diameter of this dished spring presses against the side plate and the inner diameter pushes onto the lugged thrust washer. In its free state the Belleville spring is conical in shape but when assembled it is compressed almost flat. As the friction washers wear, the dished spring cone angle increases. This exerts a greater axial thrust, but since the distance between the side plate and lugged thrust washer has increased, the resultant clamping thrust remains almost constant (Fig. 2.8).
Vibration analysis of a shafting system for a marine diesel generator set including dynamic characteristics between shell and housing of generator bearing W.H. Kim, ... W.H. Joo, in 10th International Conference on Vibrations in Rotating Machinery, 2012 3.1 Crankshaft The 9H21/32 crankshaft was modelled using idealized Timoshenko beam elements, in which the crank pin was idealized by taking an equivalent mass and inertia moment. To take account of the mean kinematic energy that would be induced by the reciprocating masses and moments of inertia under running condition, the total reciprocating mass and moments were attached at the two ends of crank pin. Table 2 presents the calculated masses and inertia moments of crank shaft.
Table 2. Mass and inertia moment of crankshaft Mass [kgf] Moment of inertia [Kg-m2]
Crank pin 49.41 1.26
Reciprocating element 34.38 1.54
For the solid structure of crankshaft in which the crank-throws are not arranged in the same plane, bending stiffnesses are different as rotating angle changes. Therefore, the beam model for the crank pin is necessary to check the percentage error with crank structural natural frequencies obtained by impact tests. Figure 3 shows mode shapes of idealized crankshaft system with error percentages to impact results. The impact tests were performed at 45 points with an accelerometer and impact hammer. Error percentages within second bending mode shape do not exceed by 3 %. Considering the operating speed of diesel engine, 15 Hz (900 rpm), higher natural frequencies of crankshaft would not affect vibration characteristics.

here we have a form about engine ,you can find the OE number with this form

if you have any question please contact us