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Corvair conversion engines



 
 
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  #1  
Old January 18th 06, 08:19 PM posted to rec.aviation.homebuilt
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Default Corvair conversion engines


As my research continues, I have been investigating possible engines for
a 601XL. The Corvair engines looked like a good candidate. The reports
seemed very good and the engine was surprisingly inexpensive for initial
purchase and long-term maintenance.

The stated expected TBO is 1500 hours and the Corvair Authority website
documents the use of a Corvair engine in a 601XL.

Everything seemed OK until yesterday when I read the most recent updates
on their website. Seems that the "untreated" automotive cranks have
been cracking in a very short time. Nitriding seems like the only
solution. But with standard cranks cracking at under 100 hours, what
would be the expected life of a nitrided crank. Twice as long, four
times as long, eight times as long? This would still fall short of the
1500 hour TBO stated by the Corvair Authority.

Does anyone have any first hand experience with Corvair conversion
engines? Any info on their realistic life and reliability?

TIA,

CV


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  #2  
Old January 18th 06, 09:16 PM posted to rec.aviation.homebuilt
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Default Corvair conversion engines

Cal Vanize wrote:

As my research continues, I have been investigating possible engines for
a 601XL. The Corvair engines looked like a good candidate. The reports
seemed very good and the engine was surprisingly inexpensive for initial
purchase and long-term maintenance.

The stated expected TBO is 1500 hours and the Corvair Authority website
documents the use of a Corvair engine in a 601XL.

Everything seemed OK until yesterday when I read the most recent updates
on their website. Seems that the "untreated" automotive cranks have
been cracking in a very short time. Nitriding seems like the only
solution. But with standard cranks cracking at under 100 hours, what
would be the expected life of a nitrided crank. Twice as long, four
times as long, eight times as long? This would still fall short of the
1500 hour TBO stated by the Corvair Authority.

Does anyone have any first hand experience with Corvair conversion
engines? Any info on their realistic life and reliability?

TIA,

CV


Welcome to the real world of auto engine conversions, Cal.

I have never flown a Corvair, and of them only by reputation, so I'm
not much help with your crank problem.

I've flown several VW conversions, a couple of Subarus, and one Chevy
V6 in an RV-6, so I don't claim to be an expert, just another
experienced fool.

The Great Plains crank for my 2180cc VW is a massive chunk of steel.

It bears no resemblance the the auto market cranks I've ever seen.
But then auto motors _usually_ don't have to deal with propeller
loads... (if that helps?)


My ex-next-door-neighbor built a 601-HDS with a Rotax 912 and a 74"?
electric Ivo prop for power. Now that is a sweet setup.
He has over a hundred hours on it now and only has to feed it gas and
change the oil (and electric prop bushings).

His airplane is heavy - with every conceivable gadget to play with.
But the little Rotax just ignores it and slings the airplane into the
sky anyway.

Other than a minor problem with the oil tank plumbing (I saw the
"instructions" and yes they are ambiguous at best...) that caused the
oil temp to track the airspeed indicator on the first taxi runs, the
engine has performed smoothly and flawlessly.
Every time.

That's something I really like in an airplane motor...

Richard
  #3  
Old January 18th 06, 10:03 PM posted to rec.aviation.homebuilt
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Default Corvair conversion engines

Do you have a link for the broken cranks? I cannot find anything about
broken cranks on the "Corvair authority" site.

http://www.flycorvair.com/

I did find the following statement:

"I have never seen a cracked head, cylinder, case, crank or rod in the
hundreds of Corvair engines I have inspected. It is a very strong engine."

The Corvair engine has been flying since the early 1960's. Seems odd that
ANY flaw would only now be being discovered.






Everything seemed OK until yesterday when I read the most recent updates
on their website. Seems that the "untreated" automotive cranks have been
cracking in a very short time. Nitriding seems like the only solution.
But with standard cranks cracking at under 100 hours, what would be the
expected life of a nitrided crank. Twice as long, four times as long,
eight times as long? This would still fall short of the 1500 hour TBO
stated by the Corvair Authority.

Does anyone have any first hand experience with Corvair conversion
engines? Any info on their realistic life and reliability?

TIA,

CV




  #4  
Old January 18th 06, 10:04 PM posted to rec.aviation.homebuilt
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Default Corvair conversion engines

Let's say you have to replace the engine 4 times to get 2000 hours. You are
still saving money over the cost of a Lyc or Cont and there is no guarantee
they will make it to TBO either.



"Cal Vanize" wrote in message
...

As my research continues, I have been investigating possible engines for a
601XL. The Corvair engines looked like a good candidate. The reports
seemed very good and the engine was surprisingly inexpensive for initial
purchase and long-term maintenance.

The stated expected TBO is 1500 hours and the Corvair Authority website
documents the use of a Corvair engine in a 601XL.

Everything seemed OK until yesterday when I read the most recent updates
on their website. Seems that the "untreated" automotive cranks have been
cracking in a very short time. Nitriding seems like the only solution.
But with standard cranks cracking at under 100 hours, what would be the
expected life of a nitrided crank. Twice as long, four times as long,
eight times as long? This would still fall short of the 1500 hour TBO
stated by the Corvair Authority.

Does anyone have any first hand experience with Corvair conversion
engines? Any info on their realistic life and reliability?

TIA,

CV




  #5  
Old January 18th 06, 10:21 PM posted to rec.aviation.homebuilt
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Default Corvair conversion engines

"Ron Webb" wrote in
:

Do you have a link for the broken cranks? I cannot find anything about
broken cranks on the "Corvair authority" site.

http://www.flycorvair.com/


Click on the "Important Research Update" link for the whole story...

--
-- ET :-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams
  #6  
Old January 18th 06, 10:26 PM posted to rec.aviation.homebuilt
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Default Corvair conversion engines


See: http://www.flycorvair.com/crankissues.html


"Ron Webb" wrote in message ...
Do you have a link for the broken cranks? I cannot find anything about broken cranks on the "Corvair authority" site.

http://www.flycorvair.com/

I did find the following statement:

"I have never seen a cracked head, cylinder, case, crank or rod in the hundreds of Corvair engines I have inspected. It is a very
strong engine."

The Corvair engine has been flying since the early 1960's. Seems odd that ANY flaw would only now be being discovered.






Everything seemed OK until yesterday when I read the most recent updates on their website. Seems that the "untreated" automotive
cranks have been cracking in a very short time. Nitriding seems like the only solution. But with standard cranks cracking at
under 100 hours, what would be the expected life of a nitrided crank. Twice as long, four times as long, eight times as long?
This would still fall short of the 1500 hour TBO stated by the Corvair Authority.

Does anyone have any first hand experience with Corvair conversion engines? Any info on their realistic life and reliability?

TIA,

CV






  #7  
Old January 19th 06, 12:39 AM posted to rec.aviation.homebuilt
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Posts: n/a
Default Corvair conversion engines - cracked crank link


The issue us addressed in this page:

http://www.flycorvair.com/crankissues.html

The date on the page is 15 January 2006 - just released information.



Ron Webb wrote:

Do you have a link for the broken cranks? I cannot find anything about
broken cranks on the "Corvair authority" site.

http://www.flycorvair.com/

I did find the following statement:

"I have never seen a cracked head, cylinder, case, crank or rod in the
hundreds of Corvair engines I have inspected. It is a very strong engine."

The Corvair engine has been flying since the early 1960's. Seems odd that
ANY flaw would only now be being discovered.







Everything seemed OK until yesterday when I read the most recent updates
on their website. Seems that the "untreated" automotive cranks have been
cracking in a very short time. Nitriding seems like the only solution.
But with standard cranks cracking at under 100 hours, what would be the
expected life of a nitrided crank. Twice as long, four times as long,
eight times as long? This would still fall short of the 1500 hour TBO
stated by the Corvair Authority.

Does anyone have any first hand experience with Corvair conversion
engines? Any info on their realistic life and reliability?

TIA,

CV






  #8  
Old January 19th 06, 01:46 AM posted to rec.aviation.homebuilt
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Posts: n/a
Default Corvair conversion engines - cracked crank link

Cal Vanize wrote:

The issue us addressed in this page:

http://www.flycorvair.com/crankissues.html

The date on the page is 15 January 2006 - just released information.



Ron Webb wrote:

Do you have a link for the broken cranks? I cannot find anything about
broken cranks on the "Corvair authority" site.

http://www.flycorvair.com/

I did find the following statement:

"I have never seen a cracked head, cylinder, case, crank or rod in the
hundreds of Corvair engines I have inspected. It is a very strong
engine."

The Corvair engine has been flying since the early 1960's. Seems odd
that ANY flaw would only now be being discovered.





that dose seem like a lot of broken cranks...
  #9  
Old January 19th 06, 02:17 AM posted to rec.aviation.homebuilt
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Default Corvair conversion engines - cracked crank link



Richard Lamb wrote:

Cal Vanize wrote:


The issue us addressed in this page:

http://www.flycorvair.com/crankissues.html

The date on the page is 15 January 2006 - just released information.



Ron Webb wrote:

Do you have a link for the broken cranks? I cannot find anything
about broken cranks on the "Corvair authority" site.

http://www.flycorvair.com/

I did find the following statement:

"I have never seen a cracked head, cylinder, case, crank or rod in
the hundreds of Corvair engines I have inspected. It is a very strong
engine."

The Corvair engine has been flying since the early 1960's. Seems odd
that ANY flaw would only now be being discovered.





that dose seem like a lot of broken cranks...


Three out of five cranks cracked. All with 200 or less hours. That's a
small sampling, but not very good results.

The article does indicate that the cranks were from engines in planes
that were flying. That's the good news. But does that also mean that
the engines need a teardown and inspection as part of every oil change?


  #10  
Old January 19th 06, 05:03 AM posted to rec.aviation.homebuilt
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Posts: n/a
Default Corvair conversion engines - cracked crank link


"Cal Vanize" wrote

The article does indicate that the cranks were from engines in planes that
were flying. That's the good news. But does that also mean that the
engines need a teardown and inspection as part of every oil change?


If you are running a conversion that is different from William's
conversions, it could be a good idea. g

If people take the time (yeah, lots of it) to read the whole article, you
will notice a few things, and I will attempt to point out some of the more
significant (to me) points.

Biggest point. Do not use corvair engines outside of the recommended
operating parameters. Some sub points.

Biggest one, don't use longer prop extensions. Big time no-no.

Others include, don't use heavy props, or hand carved props. Don't
overstress the prop with some aerobatic maneuvers, or hard landings. Make
sure the crank is properly ground. Oil systems must provide for consistent
oil flow to all parts, at all times; stay away from two line cooler and
filter systems. Use low RPMs and big props, rather than smaller props and
higher RPMs. Avoid detonation, which is easy to let happen, if treated like
an aircraft engine.

Obey all points of his conversion manual. Nitrated cranks are a good way to
add an extra margin of safety, when obeying the conversion manual, but the
other examples that have followed the manual have been OK for long
operational periods, even without the nitrated cranks.

Avoid other's add ons, like extra bearing hubs, as they have not been
tested.

I am sure I missed some points, or miss stated some, but if you are using
corvair power, it would be wise to investigate what this man has to say, and
not take my word on it.

I remember saying a long time ago, that I would feel better (or something
like that) if a redrive was used to take the stress off of the crank. I
think I will still stand by those words. Of course, It would need to be a
properly researched and tested redrive, which at this time, does not exist.
--
Jim in NC

 




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