"cavelamb" wrote in message
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---------------preceding posts snipped------------------

I am really not dissagreeing with you--as the pressure system that I am
thinking of would use a VW type cooling fan to augment the ram air
pressure. That would be a rather obvious source of added weight and an
easily visible use of power--and would never be popular.

Interestingly, the guys I knew who broke cranks (amoung other interesting
problems) were also flying KR2s--although they were based in Florida.

Personally, that is not a level of reliability that I could accept; and I
have never considered an application that I believed would draw much more
than 40 HP continuously from a VW--even though I have been willing to
consider ideas that asserted a theoretical peak power of 60 HP.


I've always thought that the broken cranks were the cast versions not
forged cranks.


I've never heard of anyone breaking a forged crank.

FWIW

Richard

I had thought that as well, but it appears that my information was
incomplete and Veeduber included some probable reasons in an adjacent post.

In any case, the broken cranks that locally came to my attention occurred in
the range of 150 to 160 hours of operation and I was told at that time that
failures of that type were well known at a similar time in service.
Although I no longer recall what I was told about the exact nature of the
breaks, the engines involved were driving props on the accessory end and the
failure was probably the gradual crack progression that Veeduber describes
from a point between the threads and the woodruff key slot.

Peter