>I dont think that there is a big difference between the modulous of
>elasticity of Cast Iron compared to Steel, but since the steel 3 main
>is spun on three points instead of 5, identical forces will flex the
>shaft at least double the displacement.
>
>Jarrid Gross
>
Interestingly, perhaps, is the fact that the distortions are much greater
than this.
If with three bearings the distance b/n bearings is 2 units then with 5
bearings the distance will be 1 unit.
The rotating crank can be assumed a distributed load and the deflection is
proportional to length to the power 4 (2^4 = 16) so the 3 main crank
deflects 16 times as much.
The big ends could be considered a point load and deflection is
proportional to length cubed (2^3 = 8), 8 times as much.
Actually a three main bearing crank with all materials and cross sections
equal to a five main crank would deflect b/n 8 and 16 times as much. Other
considerations could make it even larger.
AJR
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