The crankshaft exists as long as the four-stroke engine. The atmospheric gas engine as the
precursor did not have a crankshaft, however, the steam engine had, even if most often just for one cylinder or with integrated flywheel. The first crankshaft in the car four-stroke engine managed a rev of less than 200 1/min, its
bearings were lubricated by small oil tanks from which one can be recognised at the big-end bearing in the side outline. The counterbalances are quite noteworthy.
How it works
If the costs are a big issue, counterbalances can be partially absent also for modern engines. In history there are also crankshafts completely without counterbalances, not only opposed cylinder engines. Also there
are not always main bearings between all cylinders. This applies even today for opposed cylinder engines and V engines. In earlier times
also in-line engines featured less main bearing. There were crankshafts for four and even six cylinders which had bearings only at its ends.
Crankshafts are highly demanded. Hammer-forged blanks from quenched and tempered steel were used at the beginning of the last century. The substantially less expensive, cast crankshaft asserted itself only in
the second half of the century. Highly demanded crankshafts were first hammer forged, and afterwards pressed with very high pressures with which already the final form was approached. (More expensive) alloying
was partially substituted by changing the crystalline structure while hardening.
The appearance and the manufacturing of crankshafts has changed. A bigger number of main bearings and more counterbalances reflect the crankshaft production of in-line engines. New cylinder designs developed
like the W-12 which cause considerable demands for the production. Producing millions of pieces, only fully automated manufacturing processes, which imply pouring and pressing, can do the trick. A good example
is the twisting. This process implies that, e.g., the crankshafts of in-line six-cylinder engines are first manufactured with all their headers in
one level, and subsequently
some crank pins are twisted by machine to receive the right ignition interval. The firmness of such shafts is rather higher due to the uninterrupted fibre course. 05/08