Chevy LS2 and Trans??? any real issues besides weight

On 14 Nov 2005 13:21:23 -0800, "MrV" wrote:

just wondering if it would work so maybe just maybe i would have less
engineering work even considering the weight.

1. It has been proven several times that it does not work. Even with
relatively low power engines, it doesn't work. It was tried using a
Honda Goldwing engine. Tranny failed after a while for all the
reasons cited previously. A more powerful engine would fail the
tranny, probably more quickly.

You do have a choice though, there are several businesses
manufacturing PSRU's built specifically for high power V-8's. The
afore mentioned Geschwender folks, and also Northwest Aero, they make
a psru for a high output Chevy, or used to.

So you do have the choice of bolting on a PSRU that you know will
work, thus negating at least that piece of engineering. You will
still have to think about the driveshaft, the coupling at both it's
ends, and all the issues that plague rear propped airplanes.

Corky Scott

wrote)
The engine must pass 600 cycles without any sign of failure. We typically
run 1200 cycles and a probe test will run 1600 cycles. That's a (sic)
excellent gasket killer test. Head gaskets are the first to fail because
of the rapid expansion and contraction.


What's a probe test - that it needs to run 1600 cycles?


Montblack

Charles K. Scott wrote:
On 14 Nov 2005 13:21:23 -0800, "MrV" wrote:

just wondering if it would work so maybe just maybe i would have less
engineering work even considering the weight.

1. It has been proven several times that it does not work. Even with
relatively low power engines, it doesn't work. It was tried using a
Honda Goldwing engine. Tranny failed after a while for all the
reasons cited previously. A more powerful engine would fail the
tranny, probably more quickly.

You do have a choice though, there are several businesses
manufacturing PSRU's built specifically for high power V-8's. The
afore mentioned Geschwender folks, and also Northwest Aero, they make
a psru for a high output Chevy, or used to.

So you do have the choice of bolting on a PSRU that you know will
work, thus negating at least that piece of engineering. You will
still have to think about the driveshaft, the coupling at both it's
ends, and all the issues that plague rear propped airplanes.

If I were determined to use a driveshaft there might be a good case
for putting the redrive at the prop end and having the driveshaft turn
at engine speed. This is done in some large turboprop installations,
there is a relativly long shaft.

Pusher props are really not that great an idea. Few successful designs
used them.

When I was in Europe, I saw a Fantrainer fly. What ever happened to
that airplane? I think it started with a recip and went to production,
such as it was, with an Allison turboprop.

Your right, the manufacturers of those belts will ""NOT"" sell you one
if you even mention the application is closely related to aviation. Ya
just say is for a conveyor system or some other industrial setup. I
think the belts are somewhere around 70 bucks.

Don't tell them then.


But if I recall the Enstrom helo uses a Gilmer belt for main
transmission drive and oneother certificated helo had two or three of
them through the tailboom for tailrotor drive. I'm sure the
manufacturers knew.

On Tue, 15 Nov 2005 12:42:50 -0600, "Montblack"
wrote:

What's a probe test - that it needs to run 1600 cycles?

Not sure what you mean by probe test. The article did not use that
description. My understanding is that it was a test to uncover
weaknesses in the engine when run hard in cold weather. It seems
suitably harsh to me.

Corky Scott

Pusher props are really not that great an idea. Few successful designs
used them.


Hi all,

Not sure if this was mentionned in recent posts.
Does this document ring a bell ?

http://ibis.experimentals.de/downloa...lvibration.pdf

FWIW,

Regards,
Gilles Thesee
Grenoble, France
http://contrails.free.fr

I noticed that the hot-rod crowd is using carbon fiber tubes for drive
shafts. The advantage is light weight, extreme stiffness and strength. I'm
not sure but this might reduce torsional vibration a lot.

Bill Daniels

"GTH" wrote in message
...


Pusher props are really not that great an idea. Few successful designs
used them.


Hi all,

Not sure if this was mentionned in recent posts.
Does this document ring a bell ?

http://ibis.experimentals.de/downloa...lvibration.pdf

FWIW,

Regards,
Gilles Thesee
Grenoble, France
http://contrails.free.fr

On Wed, 16 Nov 2005 08:16:00 -0800, Richard Riley
wrote:

I read your test description a long time ago, I agree it's very
impressive. My impression is that the Sube guys are asking a lot more
out of a lot less displacement than the V-6 guys. Any comment?

I don't know a whole bunch about what they ask of the Subie engines.
I've seen some engine companies that claim what seems to be excessive
power outputs and at pretty extreme engine rpms.

I never like holding an engine at or near it's redline for extended
periods, it just makes me very nervous. Four cylinder
Lycomings/Continentals et al seem to have extremely low redlines but
they also have large heavy pistons chuffing back and forth in very
large cylinders. The power each cylinder has to produce to get
(typically) 180 horsepower is about 45 hp. A typical automotive V6
needs to produce 30 horsepower per cylinder and a V8 only 22.5. Not
only are the combustion pulses lower, the reciprocating mass is lower.

That's why smaller engines can safely rev higher for longer periods.
But I still cringe when I see the kind of high rpms necessary for the
Subie's to produce the power they claim.

Corky Scott

("Charles K. Scott" wrote)
What's a probe test - that it needs to run 1600 cycles?

Not sure what you mean by probe test. The article did not use that
description. My understanding is that it was a test to uncover
weaknesses in the engine when run hard in cold weather. It seems
suitably harsh to me.


Did so :-)

"The engine must pass 600 cycles without any sign of failure. We typically
run 1200 cycles and a probe test will run 1600 cycles. That's a (sic)
excellent gasket killer test. Head gaskets are the first to fail because of
the rapid expansion and contraction."

Was it a missing word, butchered sentence error, or is there a "probe test"
going on here?

(Here's the whole paragraph)
Thermal cycle tests are run to define engine capability under cold
weather condition. We run the engine at full throttle at 4000 RPM,
bring it down to idle, stop it, switch the coolant valves to drain the
hot coolant, pump the chilled coolant from the chiller until the metal
temperature stabilizes at 0 degrees F. Frost forms on the outside of
the block, as the cold coolant rushes into the engine. When it
stabilizes at 0 F, we motor the engine, start it, come to full
throttle at 4400 RPM, the valves switch and the coolant temperature
starts to climb. It climbs back up to 260 degrees F. It takes 10 -11
minutes to complete one cycle. The engine must pass 600 cycles
without any sign of failure. We typically run 1200 cycles and a probe
test will run 1600 cycles. That's a (sic) excellent gasket killer
test. Head gaskets are the first to fail because of the rapid
expansion and contraction.


Montblack

Copy that, Corky.

One thing that doesn't get discussed much is the idea of
direct drive auto conversions.

The VW is usually done that way, and I know of one V8 setup that
runs direct drive.

Quite a while back I sketched out a 7/8 scale Spad 13 that was
intended for a direct drive V6. The short nose on this plane makes
it possible - even necessary - to get some engine weight in there,
but this is an unusual case.

While the engine can't turn a prop fast enough to make _max_ hoss
power,
it probably could turn out something like 90 hp - with a 70 something
inch prop.
Which would be enough for the job, IMHO.

It's all about compromise, folks.

Maximize any one parameter and ALL the rest suffer immediately.

Compromise means carefully balancing all of the requirements.

Maximising horse power from an auto engine almost always means it
needs a PSRU (to turn a propeller) along with all the attendant weight,

harmonic issues, cost, complexity, and usually several single point
failure nodes.

But does the airframe _need_ that much power (need - not want - there's
a difference).

Can it stand the extra weight in the worst (ok second worst) place
(balance wise).

What does that extra weight do to the overall PERFORMANCE?
Wing area loading? Wing span loading? Stall speed - and stall
behavior?

Like it or not, (and FAA blessings aside) the aircraft engines we love
to hate
(or hate to love?)
evolved to fill that particular niche - and do it pretty well - all
things considered.

Compromise...


Richard