Odd noise

[Tony Press]

I don't understand why originally they took the thrust up on the front bearings,especially with the 1 1/8" crank,A design flaw?

Trying to understand the reasons behind design of the Austin Seven engine is not easy.

If rolling bearings were to be used in the engine I think the accepted practice at the time would be to use roller bearings for the crankshaft.

If the rear roller was selected for design life and the thrust taken here by a similar sized ball bearing it may have been thought this would give too much overhang between the crank and flywheel .
 
Taking the thrust at the front would also ensure the cam gears were correctly aligned.

The end thrust is from the clutch which is only for a brief part of the running time.

The bearing shaft size is often dictated by the crankshaft size and calculating the bearing design life based on a very fluctuating load is not easy.

For each shaft size there is a light and a medium bearing available and in this case the medium bearing was selected.

Cheers, Tony.