Corvair conversion engines

On Thu, 19 Jan 2006 15:35:13 -0500, "Morgans"
wrote:


"Bret Ludwig" wrote in message
roups.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.

clare at snyder.on.ca wrote in message
...
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.

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

On Tue, 24 Jan 2006 22:19:55 -0500, "Morgans"
wrote:


clare at snyder.on.ca wrote in message
.. .
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.

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

clare at snyder.on.ca wrote:
On Thu, 19 Jan 2006 15:35:13 -0500, "Morgans"
wrote:


"Bret Ludwig" wrote in message
groups.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.

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

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

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?

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.

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

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.

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