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Crankshaft - sense of rotation

Clockwise rotation of the V-belt pulley

According to the German Institute for Standardization and its DIN norm the crankshaft of an engine turns to the right (clockwise) if you stand at the side of the V-belt, opposite the power delivery side of the engine, and the crankshaft turns clockwise. Accordingly there is the definition of a counter clockwise rotary engine. There have been enough of them in the history of the automobile.

Formerly British, today Japanese counter clockwise rotation

Today it is relatively easy to recognize a counter clockwise rotary transverse engine if it is positioned, e.g., in front of the car towards the left instead of towards the right. Indeed, the engine may not feature an additional redirector in the gearbox or final drive, corresponding to the figure above back to front. Talking about old-timers the Austin Mini comes to mind as having a counter-clockwise engine. Nowadays, Honda's compact cars work after this principle. Historically remarkably is that English vehicles frequently feature anti-clockwise turning engines. In case of a longitudinal engine this can be compensated relatively simply by turning the crown wheel 180°, and mounting it on the other side of the engine. There have been vehicles (as for example the VW Beetle) for which it was possible, due to wrongfully assembling the final drive, to have afterwards one forward gear and four reverse gears.

Counter clockwise in view of cranking comfort or generator

Another reason for a counter clockwise turning engine: When Renault passes over from the Renault 4CV (rear engine) to the R4 (front-middle engine) the complete power train assembly moves from rear to front. Presumably because the pulleys must now be mounted to the gearbox side of the engine, the same engine turns the other way around now. Maybe the old D.C. generator is the decisive factor. With a modern alternator this would probably not have been a problem, because it would have been sufficient to exchange the fan.

We may go back even further in time, namely to the first vehicle of Karl Benz. He has doubts regarding the design. A vertically mounted engine could affect the driving stability negatively. So he lies the engine flat down and with it also the flywheel. Without starter the engine must be started by a solid crank. Thus, the rotation direction is fixed for right- handed persons.

A lot of engines are/were able to run backwards

The subject can be expanded towards engines which are, indeed, designed, clockwise rotary, however, do not always follow suit during operation. The early Lanz Buldog has a single cylinder diesel engine which can be cranked, just as many two-stroke petrol engines, also in counter-direction. If the engine is started, the driver should keep in mind a small rotation direction indicator. If it turns into the wrong direction, the piston has changed direction shortly before TDC in view of the immense compression of the diesel engine. The engine sucks in through the exhaust gas pipe and blows out into the air filter. If you would attempt to initial drive the vehicle with verve in the first gear, the vehicle would fully go off towards the back. Nowadays, electronics suppresses such treatment efficiently; in the seventies it was common to use unsymmetrical cams in the fuel injection pump of diesel engines to make reverse running impossible. Of course, it is still possible to bump-start a car in reverse gear. Do not do it, if you want to preserve your old-timer engine from destruction, because together with the engine the oil pump also runs backwards... 06/07