Oh those CERTIFIED plane engines !!!!!!!!!!!!!!!!!

Richard Lamb wrote:
RapidRonnie wrote:

Bottom line is that if you use an auto engine made in the millions you
can research the failure rate, particularly if you pick an engine used
in motorsports run to destruction you can see where they fail first. I
would pay a premium, a big premium, to be able to fly a small block
Chevy in terms of a bigger airframe than you otherwise would, just for
that huge knowledge base.


Gently disagree, Ron.

The reason is that the prop loads are far different from anything you'll
see on the race track.


If I may be forgiven (or not) for reading about the Corvair crank
failures with rectal vision, they should not have surprised anyone.

I have never heard of anyone breaking the crankshat in their family
car,
that includes VWs. That tells me that auto manufacturers in general
and VW in particular have sucessfully designed their cranks to last
indefinately under nominal and even somewhat more adverse than
nominal conditions.

One supposes, however, that auto manufacturers do not make the
crank a whole lot stronger than needed to achieve that result.
A part that lasts indefinately is not improved by making it last
longer than indefinately when doing so would add weight which,
especially to a high RPM moving part, is generally a bad idea.

There are a lot of VW powered airplanes, and it is not uncommon
for the crankshaft to break in those.

If we make the unremarkable assumption that GM did not over-
design their Corvair crankshats any more than VW did theirs then
the Corvair crankshaft failures are quite predictable.

It is highly unlikely that any auto manufacturer is going to put
a crankshaft that is a whole lot stronger than needed into a
standard engine, don't you think?

--

FF

In article .com,
wrote:

Richard Lamb wrote:
RapidRonnie wrote:

Bottom line is that if you use an auto engine made in the millions you
can research the failure rate, particularly if you pick an engine used
in motorsports run to destruction you can see where they fail first. I
would pay a premium, a big premium, to be able to fly a small block
Chevy in terms of a bigger airframe than you otherwise would, just for
that huge knowledge base.


Gently disagree, Ron.

The reason is that the prop loads are far different from anything you'll
see on the race track.


If I may be forgiven (or not) for reading about the Corvair crank
failures with rectal vision, they should not have surprised anyone.

I have never heard of anyone breaking the crankshat in their family
car,
that includes VWs. That tells me that auto manufacturers in general
and VW in particular have sucessfully designed their cranks to last
indefinately under nominal and even somewhat more adverse than
nominal conditions.

One supposes, however, that auto manufacturers do not make the
crank a whole lot stronger than needed to achieve that result.
A part that lasts indefinately is not improved by making it last
longer than indefinately when doing so would add weight which,
especially to a high RPM moving part, is generally a bad idea.

There are a lot of VW powered airplanes, and it is not uncommon
for the crankshaft to break in those.

If we make the unremarkable assumption that GM did not over-
design their Corvair crankshats any more than VW did theirs then
the Corvair crankshaft failures are quite predictable.

It is highly unlikely that any auto manufacturer is going to put
a crankshaft that is a whole lot stronger than needed into a
standard engine, don't you think?

Automotive crankshafts are designed to take loads in predominately
torquing modes, while aircraft crankshafts have to take bending and
thrust loads, due to the fact that they have a very large flywheel
hanging on the end, which resists changes in direction.

Either engine will work quite nicely for the purpose for which it was
intended. It is when you change the mission that you had better
understand how the mission changes the operating environment vs the
design parameters.

Orval Fairbairn wrote:
In article .com,
wrote:


Richard Lamb wrote:

RapidRonnie wrote:


Bottom line is that if you use an auto engine made in the millions you
can research the failure rate, particularly if you pick an engine used
in motorsports run to destruction you can see where they fail first. I
would pay a premium, a big premium, to be able to fly a small block
Chevy in terms of a bigger airframe than you otherwise would, just for
that huge knowledge base.


Gently disagree, Ron.

The reason is that the prop loads are far different from anything you'll
see on the race track.


If I may be forgiven (or not) for reading about the Corvair crank
failures with rectal vision, they should not have surprised anyone.

I have never heard of anyone breaking the crankshat in their family
car,
that includes VWs. That tells me that auto manufacturers in general
and VW in particular have sucessfully designed their cranks to last
indefinately under nominal and even somewhat more adverse than
nominal conditions.

One supposes, however, that auto manufacturers do not make the
crank a whole lot stronger than needed to achieve that result.
A part that lasts indefinately is not improved by making it last
longer than indefinately when doing so would add weight which,
especially to a high RPM moving part, is generally a bad idea.

There are a lot of VW powered airplanes, and it is not uncommon
for the crankshaft to break in those.

If we make the unremarkable assumption that GM did not over-
design their Corvair crankshats any more than VW did theirs then
the Corvair crankshaft failures are quite predictable.

It is highly unlikely that any auto manufacturer is going to put
a crankshaft that is a whole lot stronger than needed into a
standard engine, don't you think?


Automotive crankshafts are designed to take loads in predominately
torquing modes, while aircraft crankshafts have to take bending and
thrust loads, due to the fact that they have a very large flywheel
hanging on the end, which resists changes in direction.

Either engine will work quite nicely for the purpose for which it was
intended. It is when you change the mission that you had better
understand how the mission changes the operating environment vs the
design parameters.

And, as Orval had likely experienced himself,
(dam long limber chain drives?)
PSRU's may take the gyroscopic forces out,
but can add harmonic resonance issues that
may be even tougher to deal with than a simple
broken crank shaft...

It all looks so easy on paper...

Richard

In article t,
Richard Lamb wrote:

Orval Fairbairn wrote:
In article .com,
wrote:


Richard Lamb wrote:

RapidRonnie wrote:


Bottom line is that if you use an auto engine made in the millions you
can research the failure rate, particularly if you pick an engine used
in motorsports run to destruction you can see where they fail first. I
would pay a premium, a big premium, to be able to fly a small block
Chevy in terms of a bigger airframe than you otherwise would, just for
that huge knowledge base.


Gently disagree, Ron.

The reason is that the prop loads are far different from anything you'll
see on the race track.


If I may be forgiven (or not) for reading about the Corvair crank
failures with rectal vision, they should not have surprised anyone.

I have never heard of anyone breaking the crankshat in their family
car,
that includes VWs. That tells me that auto manufacturers in general
and VW in particular have sucessfully designed their cranks to last
indefinately under nominal and even somewhat more adverse than
nominal conditions.

One supposes, however, that auto manufacturers do not make the
crank a whole lot stronger than needed to achieve that result.
A part that lasts indefinately is not improved by making it last
longer than indefinately when doing so would add weight which,
especially to a high RPM moving part, is generally a bad idea.

There are a lot of VW powered airplanes, and it is not uncommon
for the crankshaft to break in those.

If we make the unremarkable assumption that GM did not over-
design their Corvair crankshats any more than VW did theirs then
the Corvair crankshaft failures are quite predictable.

It is highly unlikely that any auto manufacturer is going to put
a crankshaft that is a whole lot stronger than needed into a
standard engine, don't you think?


Automotive crankshafts are designed to take loads in predominately
torquing modes, while aircraft crankshafts have to take bending and
thrust loads, due to the fact that they have a very large flywheel
hanging on the end, which resists changes in direction.

Either engine will work quite nicely for the purpose for which it was
intended. It is when you change the mission that you had better
understand how the mission changes the operating environment vs the
design parameters.

And, as Orval had likely experienced himself,
(dam long limber chain drives?)
PSRU's may take the gyroscopic forces out,
but can add harmonic resonance issues that
may be even tougher to deal with than a simple
broken crank shaft...

It all looks so easy on paper...

I didn't experience it myself, but I have witnessed a few less than
spectacular results. One was a Ford V-6 in a Mustang II -- very poor
job, V-belt broke and took out the ignition -- fatal.

Another two were in Stewart 51s: one was a Ford V-8 with full electronic
fuel injection, etc. The computer took awhile to set up for high power,
then took awhile for low power. It got some bent valves. Owner replaced
it with a Walther turbine after only four flights.

Another S-51 had a chain drive PSRU, which started eating up the PSRU
housing because of chain slop -- there were no tensioners on the chain.

I have also seen a few successes, too. One was the late George Morse's
Olds V-6 in his Skybolt and later in the Prowler. He found that you need
an AN water pump instead of the automotive one and that you also need a
coolant pressure indicator, in addition to temperature.

Another success (so far) is an S-51 with a V-8 (geared PSRU) that ahs
been flying here for about a year. I don't know what problems (if any)
he has had, but he is taking small steps.

As I posted earlier, you CAN fly, successfully, on automotive
conversions, but it is not for the novice and technically-inexperienced.

"Orval Fairbairn" wrote

I have also seen a few successes, too. One was the late George Morse's
Olds V-6 in his Skybolt and later in the Prowler. He found that you need
an AN water pump instead of the automotive one and that you also need a
coolant pressure indicator, in addition to temperature.

What do you mean by an AN water pump?

One of the common things people say about auto conversions, is that they are
not designed to run at the high power outputs that are needed for aircraft.

It seems, however, that most of the problems are in the stuff that is bolted
to the engine. PSRU's fail, water pumps go out, belts fly around, fuel
delivery is not up to the job, cooling is not good enough, whatever. The
engines are rarely the problem, though.

Good design and doing what other successful converters have done, looks to
be the key.
--
Jim in NC

In article ,
"Morgans" wrote:

"Orval Fairbairn" wrote

I have also seen a few successes, too. One was the late George Morse's
Olds V-6 in his Skybolt and later in the Prowler. He found that you need
an AN water pump instead of the automotive one and that you also need a
coolant pressure indicator, in addition to temperature.

What do you mean by an AN water pump?

IIRC, George meant to use a water pump such as used on Merlins or
Allisons. he found the automotive pumps to be lacking.



One of the common things people say about auto conversions, is that they are
not designed to run at the high power outputs that are needed for aircraft.

It seems, however, that most of the problems are in the stuff that is bolted
to the engine. PSRU's fail, water pumps go out, belts fly around, fuel
delivery is not up to the job, cooling is not good enough, whatever. The
engines are rarely the problem, though.

True! If you isolate the engine from unintended stresses, it will work a
lot better, but those same stresses manifest themselves in other places,
unless you are really sharp anticipating them.


Good design and doing what other successful converters have done, looks to
be the key.

True -- that is *ALWAYS* the case! Add in "good practices" also.

"Orval Fairbairn" wrote

IIRC, George meant to use a water pump such as used on Merlins or
Allisons. he found the automotive pumps to be lacking.

I was unaware that a water pump for a Merlin or an Allison would fit on an
American V-8! g

Really, though, I don't understand what he would be referring to. Is it
something like what is commonly used on racing (NASCAR) engines? What
companies make something compatible, in that design?

I had always thought that special design was needed to get the accessories
running at a slower than stock RPM, either by using a smaller than normal
drive pulley, or larger than normal accessory pulley. I would think that
better bearings would be good things for a water pump.
--
Jim in NC

wrote

If I may be forgiven (or not) for reading about the Corvair crank
failures with rectal vision, they should not have surprised anyone.

If you would read the site again, I think you will find that the breaking
problem is limited to higher speed airplanes, not stuff like aircampers,
right?

It is highly unlikely that any auto manufacturer is going to put
a crankshaft that is a whole lot stronger than needed into a
standard engine, don't you think?

Some manufacturers, at certain times in their lifespan, are less comfortable
with cutting design strength margins too closely. GM is more likely to
build hell for stout, than are many of the imports, IMHO.
--
Jim in NC

On Sun, 5 Mar 2006 14:22:07 -0500, "Morgans"
wrote:


wrote

If I may be forgiven (or not) for reading about the Corvair crank
failures with rectal vision, they should not have surprised anyone.

If you would read the site again, I think you will find that the breaking
problem is limited to higher speed airplanes, not stuff like aircampers,
right?

It is highly unlikely that any auto manufacturer is going to put
a crankshaft that is a whole lot stronger than needed into a
standard engine, don't you think?

Some manufacturers, at certain times in their lifespan, are less comfortable
with cutting design strength margins too closely. GM is more likely to
build hell for stout, than are many of the imports, IMHO.

And even more than the "aircraft" manufacturers, where weight IS the
enemy, and where change for improvement's sake is very much frowned
upon. If you change or improve something, you are admitting something
was less than perfect, and leaving yourself vulnerable to that
"unwashed horde" known as the "legal proffesion".

*** Free account sponsored by SecureIX.com ***
*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***

If I may be forgiven (or not) for reading about the Corvair crank
failures with rectal vision, they should not have surprised anyone.

If you would read the site again, I think you will find that the breaking
problem is limited to higher speed airplanes, not stuff like aircampers,
right?

It is highly unlikely that any auto manufacturer is going to put
a crankshaft that is a whole lot stronger than needed into a
standard engine, don't you think?

Some manufacturers, at certain times in their lifespan, are less
comfortable
with cutting design strength margins too closely. GM is more likely to
build hell for stout, than are many of the imports, IMHO.

And even more than the "aircraft" manufacturers, where weight IS the
enemy, and where change for improvement's sake is very much frowned
upon. If you change or improve something, you are admitting something
was less than perfect, and leaving yourself vulnerable to that
"unwashed horde" known as the "legal proffesion".

I also love to pick. However, let's also remember that improvements and
vendor changes also have a way of restarting the entire field experience
process--as has been discussed earlier in this thread, and also in AvFlash,
with regard to Lycoming...