I'd like to clarify what I wrote yesterday about crankshafts. That page
is devoted to crankshaft failures, but doesn't emphasize enough that
another key ingredient is the "fifth bearing".....a much larger and
longer bearing (twice the diameter and more than 2" longer than the
factory's "fourth" main bearing journal), which provides significant
support for the nose of the crankshaft and prop hub. I've talked about
this many times on this list and on my website, but that is absolutely
imperative at well. We in the Corvair world should have taken that
lesson from Revmaster and Great Plains, who'd already learned that
lesson and created much larger front bearings on their engines to
prevent crankshaft flexing due to prop forces. I'm sure you've all
heard enough about that stuff from me, but a very large front bearing at
the prop hub and near-perfect crankshaft are a must for airplane use,
and nobody should have tried to fly behind one until the prop forces
were dealt with in that manner. 20/20 hindsight.....
Also, I built N56ML's fuel tanks out of vinylester resin to handle
ethanol-laced fuel, and burned 91 or 92 octane gasoline with ethanol
almost exclusively for 1030 hours. I only used 100LL when I was forced
to refuel while cross-country. I think I calculated that I'd run 6000
gallons through it at one point.
A warning regarding airport "mogas".....it's often 80 octane, and
probably quite stale, so be careful out there. I currently have to burn
"ethanol free" fuel from the local Raceway in N891JF, because the tank
is built of some kind of epoxy which ethanol will dissolve. N357CJ is
similar, having RR tanks in it. On my list is replacing the main tank
in it with a home-built ethanol- tolerant tank using vinylester epoxy.
See enclosed photo of Sport Performance Aircraft's "Gen2" fifth bearing
on my soon-to-be-flying 3100cc Corvair engine.....
Mark Langford
[email protected]
http://www.n56ml.com
Huntsville, AL
Mark Langford
[email protected]
http://www.n56ml.com
Huntsville, AL
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