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Corvair conversion engines



 
 
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  #81  
Old January 29th 06, 12:05 AM posted to rec.aviation.homebuilt
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Default Corvair conversion engines

J.Kahn wrote:


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


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

  #82  
Old January 29th 06, 12:14 AM posted to rec.aviation.homebuilt
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Default Corvair conversion engines


Richard Lamb wrote:
Peter Dohm wrote:


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


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!


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.

  #83  
Old January 29th 06, 12:26 AM posted to rec.aviation.homebuilt
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Default Corvair conversion engines


J.Kahn wrote:
snip
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,


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.

  #84  
Old January 29th 06, 01:08 AM posted to rec.aviation.homebuilt
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Default Corvair conversion engines

UltraJohn wrote:
J.Kahn wrote:


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



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



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?


  #85  
Old January 29th 06, 01:15 AM posted to rec.aviation.homebuilt
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Default Corvair conversion engines

Bret Ludwig wrote:
J.Kahn wrote:
snip

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,



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.


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

  #86  
Old January 29th 06, 02:06 AM posted to rec.aviation.homebuilt
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Default Corvair conversion engines

---------------much snipping------------
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

In general, I agree. I wish also to advocate that, in the event that a
purpose designed crank and case/front bearing assembly do not become
available, a rear drive assembly might also resolve the problem--although it
might weigh slightly more. Or may not?

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


  #87  
Old January 29th 06, 02:11 AM posted to rec.aviation.homebuilt
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Default Corvair conversion engines

.... the Greta Planes rear drive for VW ...

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

Peter


  #88  
Old January 29th 06, 02:50 AM posted to rec.aviation.homebuilt
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Default Corvair conversion engines


J.Kahn wrote:
snip
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.


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.

  #89  
Old January 29th 06, 03:09 AM posted to rec.aviation.homebuilt
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Default Corvair conversion engines


Richard Lamb wrote:



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?


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.

  #90  
Old January 29th 06, 04:07 AM posted to rec.aviation.homebuilt
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Default Cheap Chinese Parts

Bret Ludwig wrote:
Richard Lamb wrote:



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?



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 generally agree with most of what Mr. Ludwig posts but in this
instance perhaps my knowledge of the industry could offer some insight.
Since the semi-original topic was crankshafts I will confine my
observations to these.
In fact nearly all forged crankshafts sold in this country by the hot
rod industry are forged in China. With the exception of the raw forgings
that the OEM auto manufacturers offer, I can't think of anyone who
actually forges their own cranks in the USA. Not many aftermarket
suppliers will admit to this yet it's always the same story, kind of
like the old Midas commercial 'well, we used to, but we don't anymore'.
Most of the big names still finish grind the cranks themselves.
In a broader sense, it is becoming increasingly difficult, to the point
of near impossibility, to find an independent forge shop that will do
job work. This is from the point of view of one who has actively looked.
Recently, my firm had cause to seek the services of a forge shop for
just such a type item, not a crankshaft, but similar in size, weight,
and complexity. We were prepared to provide dies. The best price I was
able to get quoted in the US, really the only quote that wasn't an
obvious brushoff, was for $500 per in quantities of 25. That is forging
service only, we were to provide the material. Several firms in China
quoted the job at $50 each. If this seems too low, think about hot rod
firms selling brand new forged Chevy cranks for $299. Due to a number of
issues, not the least of which was my unease at doing this type of
business in China, we did not proceed with the forging.
Oh yes, for those who would ask how I know about the aftermarket
industry, during my researches I approached every aftermarket hot rod
firm that I could find. When I asked them if they would certify country
of origin for all services, none would agree. In several cases this led
to very interesting conversations about the state of the industry.
Niall

 




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