Corvair conversion engines

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

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

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.

"Cal Vanize" <forget...@nospamhere.au> wrote in message
news:Aywzf.56$7i...@fe06.lga...

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

"Ron Webb" <ron...@gci.net> wrote in message news:11stb7b...@corp.supernews.com...

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

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

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

Richard Lamb wrote:

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?

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

Morgans wrote:

Good points all.

The point that stood out most for me was the part about the crank from
the engine that William built for his own demo 601. From the article:
"This engine represents a standard installation, albeit one that was
flown at its limits by Gus"... "showed stress fractures on both sides of
the area in question." at 200 hours. "no nitride"

Note with particuclar interest the phrase "represents a standard
installation" regardless of how his pilot flew the plane (it was HIS
pilot after all). The statement goes on to say that the engine "was
flown at its limits" not beyond its limits.

What William wrote is that an engine he purposefully built himself for
his own 601 demo plane had a not insignificant crank issue. If he was
following his own recommendations, why did he use a crank that wasn't
treated?

He may be the Corvair conversion expert, but I'd like to read an
explanation as to why he wasn't following his own specs.

I have read every word on William's web site. It would appear that he
has done his homework and research. He may be the most credible source
for Corvair conversion aircraft engines. But yet, this discrepency
sticks out sorely.

\
Yes, that paragraph does seem to run contrary to the rest of the _long_
website's information. So what gives, others in the know?
--
Jim in NC

Or could it be that it's just taken a few years to rack up 200 hours?

I didn't catch a time span reference on any of the example engines.
But I thought it has been years?

First flight of William's 601 was 13 May 2004. That engine had 200 hours.

The article implies that all the engines were torn down at about the
same time. It must have been fairly recently because one of the engines
was a 2005 engine with 71 hours. The previous "crank update" was 15 August.

Good point what would a like new, best for the engine, crankshaft cost?

Replace it every year or two at annual it's still a great deal.

My read was that he was updating his policy based on new data. He even
mentioned one of his customers reminding him of a sentence in his
conversion manual saying something like "I reserve the right to get
smarter."

That is my opinion, also.
--
Jim in NC

I was a firm believer in auto engine conversions but i haven't seen many
last a long time except for the Subaru and Rotax engines.

There are many V-6's running, some significant numbers, time wise.

VW's flying all over the place.

Mercedes diesels in what, Thielert brand name?

Oh, by the way, Rotax is NOT an auto conversion.
--
Jim in NC

I bought two 3.8L Ford V6's for $150 each, bought new pistons from
Roush racing, new rings, had the best block shot peened bored and
honed, had the best crank turned and nitrided, bought new bearings,
new cam, new distributer with two sensors installed for dual ignition,
new pistons, new timing gears and chain, planed the heads, had four
new intake valves installed and new guides installed as well, new
valve springs, roller rockers, new lifters, new carburetor, old style
NWAero psru, ARP studs for the crank bearings and cylinderheads,
fabricated my own headers, and STILL spent only about $6,000.

Now, how much does one pay for a remanufactured aircraft engine of 200
horsepower?

Corky Scott

I don't think there's any dispute over the relative cost of engines.
This issue is longevity and whether one wants to fly an airplane with an
engine that might not make it to the next airport.

I agree that hanging a prop directly on the end of an automotive crank, even
if you put it on the flywheel end, is a recipe for a short tbo even at low
power and for a high failure rate at high power. (If you only use it to
push an airboat around the local swamp, you can keep a couple of bottles of
skin-so-soft in your tackle box.)

However, switching to a traditional aircraft powerplant may not solve the
problem. You really only have the full value of testing, experience, and
service history when you mate an unmodified engine to an airworthy propeller
with which that engine was certified--and preferrably in a combination used
by a large number of aircraft in regular service for a reasonably long time.
Remember the crankshaft problems in some of the Cessna 172's soon after the
change from the Continental O-300 to the Lycoming O-320. (I think it was an
early 160HP version, but have long forgotter the dash number--and the
problem was promptly solved.) There have been other "teething" problems as
well on various engines...

In the special case of a KR-2, which was the subject of at lease two of the
Corvair engines torn down and inspected, the plane sits too low to swing a
70+ inch diameter propeller; and IIRC was originally designed for VW engines
swnging 52 inch diameter propellers. I have heard that the KR-2S sits
enough higher to accept a larger prop, possibly 60 inch diameter. That
seems to negate the reduction drives, although a shaft drive, similar to the
one Steve Whittman developed for his V8 powered Tailwind, could be
interesting. BTW, the plans are still available--I think Aircraft Spruce
still sells them. Also, Revmaster (and possibly others) offers an aircraft
engine based loosly on the VW dimensions and a Jabiru could work--especially
with a 3 blade prop...

Cal, the statement I was responding to was from the guy who said that
auto engines end up essentially costing as much as an aircraft engine.
I was posting my actual costs to suggest that the costs are, or can
be, very much lower for the auto engine conversion than for a rebuilt
aircraft engine.

But I chose to do all the work, except for the machining of the engine
parts, myself. If you do not wish to put in that kind of time, or do
not have the knowledge to do so, then the options tend to be a lot
more expensive.

Buying a firewall forward package and simply bolting it in place and
connecting the wires and fuel lines will of course cost a bunch more
than doing everything yourself. Perhaps this is what that gentleman
was talking about.

Corky Scott

Why not fuel injected?

Also, is that two for $3K each?

What does that setup weigh?

Was matching a prop to your engine a problem? 3 bladed prop?

Curious...

Montblack

His recomendation of nitriding every corvair crank is NEW based on this
data and the several KR crank issues in the recent past. In other words,
nitriding was considered optional until the last week or so....

Is there any good reason to use the Ford instead of the Buick V6?
There are a lot more Buick V6s out there. Also, there is a lot of
support from the aftermarket, hot rod and racing business for the Buick
engine and apparently none at all for the Ford V6.

The other engine to look at in my opinion is the Honda/Acura engine,
because they are readily available cheap from JDM pulls. The Japanese
have laws designed to encourage vehicles to be junked or exported
young, and those that do not get bought by Australians or Brits usually
get scrapped because Japan is a RHD market.

My neighbor's son bought the back half of a Toyota MR2 in absolutely
beautiful shape-and I do mean "the back half", as in "the car was
sliced in half by a colossal bandsaw"-for $1200 when his transaxle
failed. He got a engine, trans, rear brakes, halfshafts, everything.

That said, the aluminum heads and blocks alleged to be available should make
a lighter and stronger engine. BTW, the name "Bow Tie Racing" was
mentioned, but yielded no plausible result in my quick web search.

The only word of caution to which I can personally attest (from my younger
and crazier days) is to be *very* careful of racing and hot rodding parts
designed to give you oversized ports and manifolds. As you increase the
diameter of the passages, you also decrease the velocity of the gasses;
which will result in a very "cammy" high speed engine with poor pulling
power and a poor ability to turn a fixed pitch propeller.

I didn't go fuel injected for two reasons, simplicity and safety.
Carburetors don't need an electrical system to operate and are
basically pretty simple. If you are a mechanic, carburators are easy
to diagnose and repair. Fuel injection requires a relatively high
pressure fuel pump and of course, the injectors. Both of which are
likely electrically operated. The carburetor *may* use a fuel pump,
but it's of the 5 - 7 psi variety, and with a high wing airplane,
isn't absolutely necessary in order to get fuel to the carburetor. So
if the fuel pump fails, you likely will still be running.

Plus, my entire premise was to not reinvent the wheel. Using the auto
fuel injection requires the use of the car's computer. Using the
computer requires all the sensors and sometimes faking the sensors out
so that they give the proper information. It all seemed too arcane
and difficult for me.

Carburation does not produce less power than fuel injection, but it
might be slightly less efficient, depending on how the engine is
leaned, and how much the pilot pays attention to it.

I paid $150 for each engine, and built one engine, not two.

The weight of the setup is one of those "not sure's". It likely
weighed in excess of 400 lbs, but probably not by much. The block is
cast steel, but it's a thinwall design. The heads are aluminum, as is
the timing chain cover, and intake manifold. It was the lightest V-6
being built, and may still be in it's 4.2L form.

I also used the lightweight geared starter, rather than the routine
Ford beast. The NWAero psru is noted for it's relative light weight
compared to the Blanton version, which was it's genesis.

I also used a lightweight aluminum machined flywheel, rather than the
suggested Ford flexplate. Probably no gain or loss there.

As to the prop, I bought an IVO Magnum and ran it using that while I
tested the engine.

I added largish mufflers to the header system I fabricated (header
length and diameter suggested by "Headers by Ed". Ed sizes header
tubes scientifically to promote maximum flow at the power settings
most often used and altitude at which I would normally be flying. That
required relatively small diameter header pipes (1 3/8), which is
considerably smaller than the exhaust ports in the heads (1 3/4). The
length of the headers tubes was also specified to maximise torque,
which meant that they had to be 40" long and feed into 3" diameter
collector pipes, which had to be at least two feet long each.

When I first fired the engine up, all animals in the vicinity headed
for the hills. It seemed like I was standing next to two machine guns
blasting away. Of course, I was inside the shop at the time (with the
sliding door open).

I had to add two hefty mufflers to the exhaust system in order to run
it outside the house without being attacked by the neighbors, even
though I live in rural Vermont, with lots of trees between me and my
neighbors. They were big and unwieldy and I wasn't planning to use
them in the airplane. But I was unhappy with how noisy the engine was
and was concerned about being a good citizen when flying in the area.
I tried several inserts to try to quiet the barking down some, but
nothing but actual mufflers helped. With the mufflers, you basically
only heard the soft clicking of the lifters and the hiss of the
carburator, over the whopping of the prop. As I advanced the
throttle, the carburetor began moaning/roaring and the noise of that
big prop took over with a whapping blatting roar.

I literally had to chain the test stand/engine down securely or it
would have tipped over for sure.

I had built a test stand that was basically a fully instrumented
vehical on casters. It had a battery, radiator and fuel tank. I
could have strapped it into a flatbed pontoon boat and gone air
boating.

I had the engine up to around 3,500 or so for the last run before I
shut it down and sold it and the airplane. At that rpm, lots of air
was being blown back and things like rakes and shovels were flying off
the walls of the car port. The test stand was tied down to the car
port posts, which is why the air was blowing into the bays. It was
obvious I would have needed to back off on the prop pitch a bit to get
more rpm out of the engine, if I had continued.

Corky Scott

Thank you for the report.

Montblack

You mean like a Lycoming? or an old Franklin?
>
>
>

Can't speak for Franklins. But I've never had even a skip on Lycomings
with with over 400 hours flying PIC in plances with Lyc engines nor with
any Conti with over 500 hours PIC in those. These weren't in homebuilts.

>>> 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.

>Note with particuclar interest the phrase "represents a standard
>installation" regardless of how his pilot flew the plane (it was HIS
>pilot after all). The statement goes on to say that the engine "was
>flown at its limits" not beyond its limits.
>
>What William wrote is that an engine he purposefully built himself for
>his own 601 demo plane had a not insignificant crank issue. If he was
>following his own recommendations, why did he use a crank that wasn't
>treated?
>
>He may be the Corvair conversion expert, but I'd like to read an
>explanation as to why he wasn't following his own specs.
>
>I have read every word on William's web site. It would appear that he
>has done his homework and research. He may be the most credible source
>for Corvair conversion aircraft engines. But yet, this discrepency
>sticks out sorely.

It was built BEFORE the crack issue came up and BEFORE the
recommendation to use a nitrided crank. VERY simple.

>>> Good points all.

About one year of flying - MAX.

Oh for Pete Sake...ok.

A couple of years back, I picked up an Aeronca Chief down in Florida and
flew it home. Real nice airplane, and a real bargain - because - the
engine wasn't all that great. Continental 85 with metal prop.

It had been "overhauled" by one of the club members (not A.P.) and
they (the sellers) were honest about it up front. It leaked (a bit).
And they were right reasonable on the price.
So a deal was offered, $1000 earnest money sent.
And Leo and I went down to see?/fetch?

We flew it around for a while and determined that the plane was rigged
nice and straight, stalled straight ahead, and with the 85 and a climb
prop, it could for sure and certain - climb!
The little engine ran strong.

Checking the oil level shortly after landing (yeah, I know) showed it
had indeed lost some oil, but we found it - all on the belly.

Oh well, I'm not going to have to clean it. Not part of the deal.

The seller offered to "wipe her down and top off the oil and gas".
(yeah, I know - now.)

So, next morning, oil and gas are full and we headed off for home.

It took 3 days to get home and about 12 hours flying.
Two hour legs left an hour fuel reserve for the Chief.
And the climb prop doesn't go anywhere in a hurry - except up.

This engine leaked so much oil it would embarrassed a Harley.
I mean really!

But something else was wrong.

The engine ran fine, but it felt a little sharper than normal
during climbs, but smooth out fine at cruise.

For the next three days (over swamps, timber, and once VFR on top,
I could actually hear/feel/taste it getting worse.

A little sharper at first. Then louder. Each takeoff.
Only while climbing.

On the last leg home I thought maybe an exhaust muff was opening
up maybe? And then thought - or a cracked mount?
But it smoothed out at cruise.

When we rolled out at home, I was glad to be there, because I had
decided that the engine was indeed failing and needed to be looked
over.
Very carefully.
BEFORE flying it again.

It still ran strong, but something was really major league wrong
somewhere during climb out.

When Bob (A.P.) tore it down he found the bad seals, sure, and some
other minor stuff, and one cylinder with a crack about 1/4 of the
circumference of the flange.

The crank and cam were ok. Mags ok.
A (as in one each - count it) new jug, bearings, seals, etc.
signed off major overhaul cost 4 grand.

Grandpa, the new owner, it totally tickled with his Chief.

He learned to fly in it.
Took his PPSEL check ride in it.
Took his _wife_ flying in it!
Someday his boys will have their chance to learn to fly in it.

So, what exactly is the point, you ask?

Right
Hell if I know.
But it was a fun trip otherwise...

Richard

Corky, could you tell us how successfull you were with your Ford engine.

Curious

Jean-Paul

Successful in what sense? I got it running and was just beginning my
testing of the engine when I had a kind of revelation, and sold
everything, and all aviation related tools and building materials I'd
accumulated.

The only real reason I was building the airplane was so that my wife
and I could, upon retiring, tour the area and the US at our leasure.
But she just can't fly for long without experiencing lots of pain from
the lowered pressure on her ears. Not to mention her tendency towards
air sickness.

I was at a point where the next steps in the construction would have
been pretty expensive. I had to blast and paint the fuselage, wire it
and cover it. I then had to buy and install all the necessary
instruments and deal with the cooling system for the engine. Then I
had to paint the fabric. I figured that I still had another $5,000 to
$10,000 I could put into it before it was ready to fly. Plus, then
I'd need hangar $space and in$surance. All for an airplane I'd be
mostly flying by myself, to take me to various $100 hamburger
destinations, once in a while when the weather was nice.

It just didn't seem worth it, so I sold everything last summer.

The engine went to a builder of a Bearhawk, the fuselage/wings went to
an A&P from Florida, a guy who wanted something he felt was mostly
already constructed as he's 65. So everything went to a good home.

I can't stand not building something though so I'm back at it, but in
a different venue: I'm building a cedar strip canoe. My wife and I
got out on the Connecticut River last summer in a friends beater canoe
and she powerfully pulled her weight paddling all day. Her comment
was "I can do this," and "we could bring the dogs too". We have two
dogs who don't like being left alone.

Additionally, paddling canoes means you aren't burning fossile fuels
for your entertainment, although you do burn some getting to where you
put in.

Once that's built, I'm looking at building a smallish day sailer. So
in terms of building something, I'm having a good time.

I'm also turning to woodworking to work on the house. One of the big
pluses is that I get to buy new machines, heh heh.

Corky Scott

next you'll be telling us that you are gay.

talk aeroplanes or die.

Stealth Pilot

>
>
>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.

These were also 40 year old cranks of unknown provenence, pulled out
of old car engines that may have been thrashed to within an inch of
their lives in previous "inCARnations"

New engines don't have crankshaft problems?

BWAHAHAHAHAHAHA!!!

Rich S.

However, my concerns include, reliability, maintainability, and eventual
replacement; and I think you understand my point.

At this point, the Jabiru 3300 is the only engine that really looks to me
like a promising replacement; and I really don't know its service record.
However, albeit at a higher dollar price, its features seem to preserve: 1)
similar or lighter weight, 2) similar or higher power, 3) six cylinder
smoothness, 4) reasonably slow idle, and 5) similar dimmensions. Additional
benefits are designed in dual ignition and an updraft intake system, similar
to Lycoming and Continental, which should be more resistant to ice.

Peter

Peter..........

Since you answered seriously, I will too. I can agree on the higher price
and on #1-3 and #5. I don't understand #4 - do Corvairs idle unreasonably
high? The dual ignition is good if the Jabiru 3300 truly has two stand-alone
systems. The intake direction is irrelevant if the Corvair is fuel-injected
or has a heated intake manifold. Updraft carbs are a lot better at
preventing fire as well. The small Continentals will ice up if you look at
them cross-eyed even with updraft intake.

Rich S.

Why would an updraft intake system be more resistant to ice?

Heat rises, so I would expect a downdraft system, mounted above the engine
block, to be more resistant to icing.

You are right about the small Contintals, time has gone by and I just plain
forgot.

The Lycoming approach, with the intake manifolds passing through the oil
sump are less inclined to ice up. I'm sure they can be provoked, though.

As for the Corvair's idle? I plain dunno.
I have never seen a Corvair on an airplane - in person.
ANd that kinda is the point here.

The mounted pics I have seen are on a Pietenpol Air Camper, which needs
the weight on the nose. On most other planes that's considered a
Bad Thing (tm). On small short coupled airplanes, it might qualify as
a Very Bad Thing (tm), which is obviously much worse.

Now, I've only *seen* the Jabaru on a plane.
Haven't flown one myself.
But it does look like an engine of fine merit.

Light and simple are high on my short list.

Cost is there too, of course, but it has to take a place in line with
the rest of the conflicting requirements.

The Rotax 912 (which I have flown) is a really sweet set-up.
There is the extra complication (and weight) of the liquid cooled heads.
But it's probably not that big a deal on any two-seater.

From what I've heard, the Jabaru/912 power ratings remind me of the old
Continental A-65/Lycoming 145 days. Both were rated at 65 hp, but the
Continental horses seem a little longer legged.

I'd rank most VW power estimates as Shetland ponies...
I suspect that most people expect a VW to put out like a Rotax, but it
just doesn't work that way.

In the end the final choice will depend on the airframe and the mission.

On the Corvair question...

As I said earlier the Great Plains crank on my 2180 i.e. a way massive
hunk of pure confidence. Just the way an A-65 crank compares to other
small 4 banger non-flying counterparts.

So, why can't someone turn out a new Corvair crank - built to aircraft
service requirements?

The Corvair engine is a 4 bearing block, isn't it?

There is no reason that you _have_ to have a Corvair crank is there?

Richard

Rich,

Whatchit with that BWHAAAAAAaaaaa stuff.
Scared the stuffings outta me.

O thought Badwater was back and I was going to have to spell check my
posts...

"Typically" cooling air comes in above the engine, flows down between the
cylinders, then out the bottom. This makes it colder up top, and warmer
below. There are, of course, exceptions.

--
Geoffrey Thorpe
The Sea Hawk At WowWay D0t Com

The KR-2 built to plans do have flaps. The drawings are hanging on the wall
behind me;-)
John

wish I could unload it so I could get/build a SP elegible aircraft!

>
>See: http://www.flycorvair.com/crankissues.html
>
>
>"Ron Webb" <ron...@gci.net> wrote in message news:11stb7b...@corp.supernews.com...

They are only recently flying at 115HP in 200MPH planes - which is a
totally new world. Previous engines were flying at 60HP and 90MPH
without any issues.
>>
>>
>>
>>
>>> 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
>>>
>>>
>>
>>
>

>
>"Bret Ludwig" <bret...@yahoo.com> wrote in message
>news:1137690016.4...@g14g2000cwa.googlegroups.com...
>>
>> I just think hanging a prop on a crank directly is a non-starter in
>> the first place...especially on a crank and case not specifically
>> designed for this in the first palce. Maybe a good redrive and flywheel
>> would be a better way to go?
>
>That is my opinion, also.

What isn't there can't break. That's my reson for a direct drive 'vair
insted of a geared Soob - same weight - same HP.

>When it really gets down to facts, most often aircraft engines really
>don't cost any more than auto conversions and the aircraft engine
>appears to be more reliable.
>No redrives needed, redundant ignition and lots of other things that
>makes them better.
>
>I was a firm believer in auto engine conversions but i haven't seen many
>last a long time except for the Subaru and Rotax engines.
>
>
And the Rotax is not an auto engine - it's an Aero engine - and it is
no more reliable/longlived than many conversions.

By what reasoning? Virtually all carbureted aero engines are
sucseptible to carb ice - doesn't matter where the carb is.

And updraft carbs are NO LESS dangerous firewise. They can't leak on
the top of the hot engine (but a properly designed top carb can't
either) but they have over a yard of "wet" intake manifold - if or
when the (flooded) engine backfires when starting and the battery is
low, a bottom carb engine WILL BURN.

Got ten grand? You can have a "proper" crank made - or for 300 grand
you can have a hundred of them.
As for the idle, mine ticked over very nicely at 700 RPM with a 72
inch IVO Magnum - but the Magnum was too much prop and was only able
to spin about 2450 or so. It idles fine at 750 with a 3 bladr 68" Ivo
ultralight - which is not enough prop and can be spun over 3000 at
full pitch.

Perhaps you missed the news flash, from the Corvair Authority, himself. The
'vair cranks are breaking on the new glass planes.
--
Jim in NC

The only thing that I really feel compelled to add is that, in the case of
the KR that had a complete crankshaft failure and was "substantially
damaged", the owner had been very agressive in his program to keep the
weight down. I believe that he told me it was less than 200# firewall
forward, which may have even been a record. Even presuming that the weight
excluded the cowling, that is very light, and I have no idea how harmonic
damping was accomplished on any of these engines.

Peter

Interesting. I had assumed they were originally flying with 80HP or less,
but had no idea it was that much less. Thanks.

Peter

As another poster also pointed out, my memory was faulty and it is easy to
form ice in the O-200, even though the carburetor appears to be in the path
of heated cooling air from the cylinders.

Peter

Yup, I'm aware. but the reduction box has more parts to fail. There
have been Rinker failures, and not much else in use. Lots of PSRU
failures on Soobs.
Mine's not fast, and not glass, and my crank is nitrided from the
factory.

You could find many people that would argue that low of a HP figure. I
think your 80 is closer, and in might be a few more than that.
--
Jim in NC

Original flying corvairs were the little engine - 145 cu inch, IIRC,
producing 128 ft lb gross torque at 2300 RPM. So, at 2300, 56 hp.
If run at 2700 rpm, torque approx 125 ft lb, and 64 hp.

The 164 inch engines produced up to 160 ft lb torque at 2600 or 2800
rpm depending on the engine, for 80 hp at 2600, or 85 at 2800. Mine
produces 90 at 3000.

With a fancy cam and a bit of rework they will put out closer to 170
ft lb - and at 3200 RPM with a small prop, that is 103 hp almost 115
at 3500 rpm. The factory 140 hp engine supposedly produced 140hp at
5200 rpm and 160 max torque at 3600. That means the torque dropped off
to 140 at 5200. The 110 does not breathe nearly as well at speed, so
the 14% torqe drop of the 140 would be more like 20% on a 110 - or 122
ft lbs at 5200 for 120 hp if you ran a 2:1 PSRU for a 2600rpm prop.
And that's being optimistic.

Assuming 170 peak torque at 3000 RPM (likely pretty close with OT10
cam and properly prepared for aircraft use) it is pretty close to a
100 hp engine .For the extra 10 HP there is a couple hundred dollars
worth of Camshaft etc required over and above what I've got -so I'm
satisfied, so far, with what I've got. We'll see what 90 HP does in a
Pegazair when we get it together.

My engine has 180 degree equal length headers and a short smooth equal
length intake with a 50mm carb, and it's a 140 based engine, so it
breaths a bit better than a "stock" 110 at 3000 RPM

Thanks Clare for the specifics, nice post!
John

Thanks, Clare, for a lot of excellent specifics and history.

It seems that those original engines were smaller than I remembered, and
produced less maximum torque even for their size. That shouldn't surprise
me, considering the power levels of the compact cars the Corvair was
designed to compete with and the people it was designed to serve.

I always tend to think of these little engines in terms of installing them
in go-fast machines, for their power. To me, that means turning a 52 inch
propeller about 3500 to 3600 rpm. So 95 to 100 hp may not be all that
crazy--especially with a rear drive installation such as offered by Great
Plains for their VW based engines. That is similar to Steve Whittman's V8
canversion, and presumably to his Formula-Vee racing installation as well.
Thanks to Richard Lamb for the link to Great Plains earlier in this thread.

OTOH, before someone else posts yet another recitation that more propeller
disk area equals more thrust and therefore more performance...

I took a quick look at a set of posted specs for the Pegazair, on
UltralightNews.com, and suspect that you are just about at the top of the
horsepower and rpm range for that installation. It would not surprise me at
all, using your numbers above, it the 80 hp version gave identical
performance to the 90 hp version in the Pegazair's speed range.
(Discalimer: I am not qualified to make this observation.)

Peter

Willim Wynne does not reccomend turning the Corvair engine at more than 3000
RPM, and pretty much says right out, that doing so has been shown to break
the crank, in all of the cases he has studied.

Some pretty experienced people (in VW engines) have said that the valves are
the weak link, and that much more that 45 HP will melt the valves down, if
run at that level for more than a few minutes.
--
Jim in NC

As it happens, I am really on both sides of this issue--and may not be
technically qualified on either. (Required disclaimer as I am neither a
mechanical engineer nor a mechanic)

On the "this is unadulterated manure" side: there is a dissertation
attributed to an engineer at one of the big three auto makers and posted
here a couple of times, possibly by Corky, asserting that manufacturer
testing includes a 100 hour run at full rated power--and that the failure
about which they are concerned is the harmonic dampener. That is in keeping
with articles I read more than 30 years ago in my school days, which stated
that the exhaust manifolds glow incandescent during this proceedure.
However, the colant and oil are maintained within their normal temperature
range during that portion of the testing proceedures. On modern automotive
engines, this equates to more than 1.0 hp/cid; and 100 hours is clearly much

However, my real problem with the valve assertion is that I really don't
know anyone who managed to run one of these little air cooled engines long
enough and hard enough to burn a valve. I do know of two broker cranks on
Corvair conversions (same person) and at least one, and possibly two, broken
cranks on VW conversions (same other person). Both are mentioned on the
FlyCorvair site, so I am really not adding much that is new. I am convinced
that all of the failures were torsional damping issues. The only burned
valve that I know of on an automotive conversion was on a liquid cooled
Geo/Suzuki engine and was traced to a carburetion problem--which was run at
a much higher power level. I was told that the carburetion problem was
corrected and has not recurred.

On the other hand, I strongly suspect that very high power levels equate to
accelerated wear; and I really dislike very short TBOs. So all of my own
scratch pad doodles are based on continuous power levels of less than 0.5
hp/cid, and usually significantly less.

Peter

The 140 hp Corvair engines tend to lose valve seat inserts if overheated.

Rich S.

On VW engines the problem is a lack of fin area on the heads, combined
with limitted thermal mass. Anything over 40HP produces more heat than
the heads can dissipate, and the thermal mass is low enough to limit
any operation above that level to a matter of a very few minutes.

Corvairs do not suffer this lack of fin area.

For what it's worth, I'd have to agree, with the thought that you can
operate at higher power - until - the heads are heat soaked.
Then it's 45 HP or bust.

I think the thinking is that the engine needs to turn up fast to make
maximum engine power. Which may be true drag racing dune buggies.
Grab a gear and spin that puppy up!

Fixed pitch props don't do that.

Think one speed automatic transmission - with a lot of slip.
Pure torque converter.

IIRC, and it's been a while, the VW factory specs said max rpm ws 4200?
The torque curve peaked about 3000 (?)

Swinging a propeller at 2500 to 3000 RPM puts us on the rising part of
the curve - approaching peak.
The faster it turns - the more torque it makes - the faster it turns.
That's fun!

I think that's why VW powered parasols and biplanes tend to be faster
than their two-stroke powered brothers.

For a VW to turn a propeller ~~3000 rpm means...
1600cc 54-56" prop diameter
1835cc 56-56"
2180cc 58-60"

Our little low and slow airframes lean toward the long end.
Swing as big a stick as you can.
It pays off in prop efficiency, disk area, and tip circumference.
(compared to a 66"~68" prop on a Rotax 503, VW's climb like sea slugs)

Faster airframes tend to use shorter props and throw the excess torque
into pitch to go faster! But at high cost in prop efficiency (again).

Well, like I said, for what it's worth...

Richard

Same with VW.

Probably the same with any shrink in valve seats...

Richard

You have no doubt read ditties from VeeDubber here, and one of them was on
VW engines, and how many HP they really can sustain.

Seem as though (from nearest I can remember) the amount of cooling fins in
the area of the valve guides and seats, and the cross area is insufficient
to carry away the amount of heat that is flowing through that area, if it is
run flat out with a big enough prop for very long.

Remember, heads in most auto engines nowadays, are cooled by water
circulating through the head. Flow some oil past the critical areas, and
heat can be dealt with. Air cooled engines must depend on cooling fins, and
enough metal to carry the amount of heat produced to the fins.

Perhaps VeeDubber will be kind enough to repost that treatise? <g>
--
Jim in NC

Exactly right Clare. The soob has a bulletproof interior but the use of
liquid cooling plus a drive system adds two complete failure modes that
aren't there at all with the Corvair. With the Corvair if you take care
of the systems design aspect, basically by using sound aircraft design
practices for carburation and ignition, you address the vast majority of
the reliability issue and the only open question left is how strong are
the basic mechanicals and that is something that is finally being addressed.

I'm kinda glad that these crank failures have come about because it was
always clear to me that the crank configuration should be considered
"marginal" when subjected to prop gyro loads at higher power outputs,
since simply by looking at it you see that bending loads can't be
absorbed by the 1st bearing and bending is happening. One bit of good
news is that the failure mode contains the end of the crank and does not
result in the prop leaving the aircraft.

I thought from the get go that the guys using extension shafts were
nuts. However they have unwittingly provided a service by finally
uncovering the crank's weak point in what amounted to a severe service
qualification endurance test, ending that uncomfortable sense that
nobody really knew just how strong the crank was or wasn't, or exactly
where its weak point was. It's a great credit to William that he
immediately responded by publicizing the issue and conducting further
testing. As someone with a job that provides a ringside to seat to
qualification, certification and continuing airworthiness of components
on regional jets, I found his approach to be very much like, and
sometimes superior to, the commercial world (in terms of letting it all
hang out and responding to crises).

Anyway, mistakes in calculations or engineering judgment in
certification of commercial airliner components sometimes results in
certified parts that are not up to snuff and fail in service well before
predicted (I see this all the time). Truth is, sometimes the only thing
that keeps commercial jets raining down on peoples' heads is double and
triple redundancy, not the super duper construction of their components.

There is still an unknown though. What I'd personally like to see
William do is send the fracture results and the metallurgical data on
the crank to a metallurgical and dynamic stress specialist who can
calculate the loads/cycles that it took to initiate and propagate the
cracks, then work backwards to establish the gyro forces and torque
forces required to generate those loads, then apply a safety factor and
establish safe propeller weight/length/horsepower limits for the
existing configuration with a nitrided crank (the calculated limits may
make a lot of people unhappy though). Builders need to know just where
the safety boundaries are for the existing config.

Myself I am still a big fan of the Corvair but will probably adopt the
extra bearing mod he's working on if I ever get to that point.

John Kahn
Montreal

ANY aluminum head engine can loose valve seats. The secret is not to
expect more of the engine than it can safely produce. They guy who
did mine pinned them, but I don't plan on putting the pins to the
test.

That's one thing I like about the GPASC VW is he has (as an option I think)
a heavy duty forged crank with a wider front bearing to take the loads. It
would be nice if someone did this for the Corvair with it's higher power
capability!
John

Considering the 356/912 Porsche engines have essentially the same
upper end as a Type 1 VW and they operate far higher sustained powers
than that (think a long 100+ mph Autobahn run or the military gensets
they were in designed to make 400 Hz power at continuous power
settings, depending on generator efficiency, between 55 and 70 hp), I
question this theory provided the cooling blower and baffling are
designed for the power in question. But it's easy to prove or
disprove-hang a VW on a oversized generator, hook a dummy load up, and
monitor RPM, power and CHT!

Gen seets make wonderful engine dynos.

I question whether LyCon practice, which is actually derived from
small flathead gasoline burning farm tractors- a big single barrel
updraft carb and two farm tractor magnetos- is intrinsically "Sound
design practice".

Remember when the Continental, Lycoming and Franklin engines were
introduced they were not considered sound aircraft design! Real
airplanes used P&W or Wright radials or Allison or Curtiss liquid
cooled inlines-the E-2/J-2 Cub and similar planes were considered the
ultralights of their day, and before WWII one could fly an airplane
without a license if it wasn't registered and flown only within one
state (until the states, except Oregon, outlawed it-which is why the
early homebuilders often moved there.) Nothing smaller than a Waco was
considered a real airplane.

Well, I asked about that...

Seems it would cost a bazillion bucks for some reason.

Aren't the Chinese hot rodders cutting custom cranks yet?

Simple, light, reliable is the Prime Directive, regardless of how old
the technology is. When it comes to airplanes, that is sound design
practice, when considering ass pucker levels while in climbout over a
builtup area or over a tree line. I don't care if it's made of rocks.
If it's simple, light and reliable, the fact that it's derived from
tractors is irrelevant. The big radials of the old days, when you look
at it, were also very simple, light reliable designs in relative to the
alternatives in view of the power requirements. You will note that the
"more sophisticated" liquid cooled aircraft engines never survived in a
significant way past WWII in commercial service, with one unusual
exception, the Canadair North Star airliner, which used Merlins.
Everything else was radials because relatively speaking they were the
simplest and lightest and most reliable solutions before jet engines,
even if their air cooling and pressure carbs were "crude".

This is the point. If you want to take advantage of technology like
electronic control, you have to design for complete redundancy if your
control system has a sudden potential failure mode. Not practical for
the homebuilder. The farm tractor technology engine can have its
components built with sufficient inherent robustness, or have a very
gradual failure mode, to provide the required safety without needing
duplicate systems, (like a crude but simple carb) or at least a minimal
level of redundancy.

I am a fan of auto conversions, but believe that those conversions to be
viable must be as close as possible to a traditional aircraft engine
from the standpoint of simplicity and overall design, and the Corvair
using a Stromberg aircraft carb and a dual primary points ignition comes
closest to fitting the bill of any conversion I have seen besides a
Great Plains VW. Now that the crankshaft strength issues are known and
a way forward is clear, the Corvair engine's potential is even better
than before as a conversion IMHO.

Cheers

John Kahn
Montreal

Examples of the suggestion include the Greta Planes rear drive for VW and
their derivatives as well as Steve Wittmans designs for Formula-V and the
Buick/Olds V8s. I took a look and saw that the Wittman plans remain
available from Aircraft Spruce. I have a set of the V8 conversion plans
that I purchased while he was alive, and presume that the biggest problem in
using them on a different engine might be selection of the optimum drive
shaft diameter. The obvious advantage is that the original vibration
dampening components, which putatively have been thoroughly tested in and
for automotive service, remain intact.

Just my $0.02

Peter

Drat! I can't spell either! ):-(

Peter

Mechanical fuel injection with electronic trim is within the
competence of the homebuilt community and with the existing auto
manifolding it's doable. A modified auto carburetor is also useable and
just as reliable as an aircraft one. One consideration in auto
conversions is that Detroit (or Japan) has sunk billions in reliability
engineering and testing and maximizing use of that is critical.

The simplicity of the carbureted magneto Lycoming is enviable. Its
efficiency and brute force solution of problems are not. If it were
cheap enough these could be overlooked, but it isn't and they can't.

The simple life, as someone said, isn't so simple. Let's look at the
problems with the simple LyCon engine:

1. Free air cooling worked well in the J-3 Cub and the 6:1 cr A-65
Continental engine. The Cub had about a thirty knot airspeed range,
maybe forty, and the tops of the cylinders didn't get all that hot and
a 1000-hour life was considered fantastic anyway. It was a day VFR
airplane, there was no engine management to speak of (many didn't even
have a mixture knob, including the Champ I soloed in-in the mid-80s)
and you never flew higher than cars drove in the mountains, so you
didn't miss it.

Fast forward: the Bonanza with a TSIO-550 Continental. Not a
successful concept anymore. With no speed brakes, a very clean
airframe, and the expectation of single pilot IFR at FL180 and above by
non-full-time (say the word: amateur) aircrew.....engine management and
shock cooling (most owners would never execute a power-off approach,
not with the price of cylinders what it is!) played a big part in the
Bonanza debacle that could have put the keys to the Webb Ave.plant in a
plaintiff's pocket many times over. It didn't, but GA has never and may
never recover.

Single lever power control, is rationally necessary for safe single
pilot IFR. Someday the FAA will be forced to make it so. With a piston
engine this means, as far as I can tell, either liquid cooling or a
regulated, forced fan system. Shock cooling has to be made impossible,
even with a cruise power split-S and vertical dive. ( Spare me the no
acro airspace rant...unless you think the supposed liability crisis is
from people losing their licenses instead of the family into a
hillside.)

2. Direct drive means if you land gear up (spare me the you'll get a
30 day suspension anyway rant) it's probably time not only for a new
prop but also new crankshaft as well. This in turn makes insurance for
RG aircraft much higher. Also makes insurance for taildraggers much
higher because you might put it on its nose.

A good redrive will fail a belt or quill shaft first. This is called
weak link-strong link design. Everything will fail sooner or later. You
want a known point of first failure that is accessible, inexpensive,
and of predictable consequence. If you use a wood or composite blade on
a variable pitch or ground adjustable hub the blades will go and
probably protect the hub. And because they won't last "forever' anyway
there will be a competitive market for blades. Even if the hub dies,
it's a lot cheaper than a complete major OH and new crank.

There's also a 3 through about 7 or 8. But that's a good start.

Everyone thinks there are these cheap foreign made hot rod parts. I've
never seen any, anywhere. They don't hot rod engines in Asia at
all-except a few things in Japan, for offroad use, and at very high
prices as any 240Z owner can attest! And what pieces are from Europe
are HIGH DOLLAR too. Even for VWs most everything is made in Southern
California.

I've always wanted a Ferrari V12 for a street rod....you think we can
get Taiwan to make heads and blocks and cranks? Uh unnh. They will want
a million dollars upfront for patterns and core boxes.

I drove a harvesting machine that used hydrostatic drive and a VW engine
for power. We ran it on a governer at 3950rpm 24x7 all summer. Once I
was moving it from field to field and dropped a valve when I ratcheted
the motor up to 4100 because the machine travled at the speed of growing
grass. Of course this was after about 10 weeks of continous operation so
in terms of hours it was due.... The vale seats were pretty hammered as
I recall.

Lets see, 24*7*10=1680 hours.

Dave
PDX

> for power. We ran it on a governer at 3950rpm 24x7 all summer. \\\

The fact that it ran with a governor means that it was not at full HP. It
is admirable for it to run that many RPM's for that many hours, but still,
there is no indication of how long it would run at true Wide Open Throttle,
making all the HP it could.

I suspect its life would have not been as long, if it were loaded to it's
maximum output.
--
Jim in NC

between overhauls or just between rests?

Jim
What airplane POH tells you to run your reciprocating engine at max/wot
throttle?
Most small airplanes run max hp for about 10 to 30 minutes for takeoff and
climb then throttle back to 75% for cruise. So expecting a VW/corvair to go
max for hours on end and not break is unrealistic. I personally think
either engine is viable in the proper application and treated properly. One
of the first things in your testing phase is to make sure your not
overheating the thing. It's quite well known a VW is not capable of
continuous operation at much more than 40 or 45 hp (let's see 75% of 65 (65
being about the highest you'll want to run a VW) is 49 hp) so your probably
only going to cruise at about 65% power which is not bad because you still
have that extra reserve for takeoff and go arounds!
I don't know what the max continuous of a corvair is but the same applies,
run it at the right level and you'll probably have a sweet little smooth
engine! This is homebuilt/experimental right? ;-)
John

However, also have problems with the wide open throttle scenario. I also
suspect that if we were to discuss the issue at length, we would find that
we are completely in agreement; but that we insist on using different
"phraseology."

We really don't operate our Lycomings and Continentals at their sea level
maximum output very much of the time. My best guess is that, flying with a
fixed pitch prop on a standard day, we can achieve nearly 90 percent just
off the runway and that drops gradually to less about 75 percent by around
3000 feet msl. (My recollection on exactly were this occurs is less than
perfect as I have not flown in a long time) And 75 percent, on the aircraft
engines with which I am familiar, ranges from about a low of about 0.355 to
0.357 HP per cubic inch of the low compression Lycoming O-235 engines
through 0.375 HP per cubic inch for the Continental O-200 and their new
O-240 FADEC engine, as well as Lycomings 160 HP O-326 and 180 HP O-360
engines, up to 0.420 HP per cubic inch on the 200 HP angle valve Lycoming
O-360. Those are all engines that really were designed to run that way, for
which the cooling intake and baffling requirements are well documented, and
even so many had "teething" problems which were solved long ago.

If we apply the same specific power output to a pure stock 1600cc VW as to
the smallest Lycomings, 75 percent power should equal 34 HP; which would
result in a theoretical 45 HP engine with a take-off rating that could be as
high as 60 HP, although 55 HP is more likely--based on a 52 inch diameter
prop turning about 3600 RPM. The slightly more agressive specific output of
the O-200 would give the 1600cc VW a rating of 48 HP which would equate to a
75 percent level of 36 HP.

My point in all this is that a relatively slippery aircraft fitted with a
climb prop, to conform to the ancient formula of 0.2 G static thrust
measured with a fish scale, should fly safely with an auto conversion. I
remain a fan of auto conversions, but my advocacy has its limits.

Peter