Hey Shad,
It was a pleasure to meet you up at Brodhead this year. Sorry to hear about
your cracked ring gear. Thankfully you caught it when you did before it
caused any issues. There have been a few cracked ring gears reported in the
flying Corvair population. This issue came up on the Corvaircraft list back
in June. There was the usual drama slinging back and forth between various
parties, but eventually William Wynne made a post regarding the issue. In
the interest of brevity, here is the portion of that post that deals with
the ring gears (the rest dealt with unrelated issues or the ongoing drama):
------------------------------------------------
On the subject of ring gears; We have used the FRA-235 gear for 6 or 7
years. I have made hundreds of these, and they are chosen because they are
light.
Like the ignition system, they are on a lot of planes and racking up a lot
of
hours. We have had at least 6 out of the fleet crack across a web. These
have four webs, and it will still run and start the motor with two adjacent
webs
cracked. It is an easy check on preflight.
About 3 years ago we started polishing the stamped edges of the webs to
reduce the stress risers. I have not had a polished one crack. Every one who
had
one crack got a free polished replacement from us. This information applies
to Black hub systems with a puck to hold the ring gear. Although we don't
have
nearly as many Gold hubs flying, none of them have shown any issue, and it
supports the gear with more contact area.
18 months ago I tacked several welds on Bill Clapp's ring gear to his front
alternator pulley. This stopped the issue on his aircraft. At the time his
aircraft built time faster than any other one with a front starter, so we
tested
ideas on his aircraft, while keeping track of reports from the field. This
was tried concurrently with other aircraft using polished webs.
What makes it crack? One sky dog is right, and his thought on lowering
stress risers is what we are doing. Here is another factor: bad starter
alignment
where the setting is poor enough that you can see it work the ring gear.
This
was a factor on at least two of the planes. Second is cracked cranks. Two of
the cracked ring gears showed up on engines which were later found to have
broken cranks. Jeff Garret, AKA AeroliteLLC who is claiming to offer the
solution in the form of a solid ring gear is had one of our ring gears crack
on
the engine he built for Ben Bradners 601. This is the plane which was flown
and
detonated until the crank was broken at Ocala airport last year. Yes, his
ring gear was cracked, but he also broke the crank, the case, a cylinder
assembly etc. Not really a fair test.
------------------------------------------------
That's what I have been able to find on the ring gear situation. If you
verify that your starter alignment is satisfactory, and your replacement
ring gear is polished along the webs, then hopefully you won't have any more
problems. Good luck, and let us know how it turns out. Have a good night,
Ryan
On Sun, Aug 24, 2008 at 4:21 PM, shad bell <aviatorbell@yahoo.com> wrote:
> Hello guys, anyone on here ever have the flywheel on a front mounted
> starter corvair crack? I was taking the cowling off the piet yesterday to
> do an oil change and a line on the ring gear caught my eye. Low and behold
> it was a crack. And I found 2 more cracks, one of them broke one of the
> "webbs" in half, cracked out completley. Glad I found it, it was only a
> matter of 5-10 hrs from self destructing. We have ordered a replacement
> flywheel from Wynne, but wodering what to do th prevent this from repeating
> itself. So just as precaution anyone with a Wynne style front mount starter
> flywheel look closely for cracks. Look at the webbing that makes the cross
> at the center, and look behind the crank pully for the alternator belt, that
> is where the worst crack was on ours. Just thought I would warn, and
> possibly keep some one out of trouble. Please let me know if anyone finds
> any cracks, or has in the past.
>
> Shad
>
