Hi, Mick Maguire wrote: > > Bruce said: "I know of no crankshaft using aluminum. Pistons, heads, blocks, > yes: no crankshafts." > > You don't? you'd better take a look at: > > http://www.autoswalk.com/bmwm1.html (6th paragraph).
Interesting but almost certainly a mistake of some kind, for the following reasons: 1. Aluminium has a much lower tensile strength than steel, so the crank would have to be that proportion larger to be as strong as a steel one. 2. Unlike steel, aluminium has a (can't remember the correct term for this) finite number of times it can be flexed before it fractures. Steel can be flexed (effectively) infinitely if the flexure is kept (again, can't remember the correct term) below the point of exceeding its elasticity (elastic limit?). Therefore an aluminium crankshaft would have to be (once more, if I remember correctly) about six times larger than an equvalent steel one and would need to be replaced after a certain number of revolutions due to the fatigue limit being reached. There are all sorts of other complications too, such as dealing with bearing surfaces, etc. This is not to say that _no-one_ has _ever_ made a crank out of aluminium but I do not see any advantage in doing so. mike - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
