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

MrV wrote:

Hey guys i'm a new pilot that really wants to build his own craft. help
me with this one issue.

I want to use a chevy ls2 or ls7 as the power plant in my craft.
snip
the aircraft i want to design is a very cab foward design with a
pusher prop and the engine would be mounted approx mid craft.

i'm new at this and besides having an engineering background i really
have no exp building an aircraft so any opinions would be helpful

LS1/2/6/
http://www.v8seabee.com
http://www.seabee.info/seabee_engine_conversions.htm
http://www.republicseabee.com/Corvette_Power.html

They did all the legwork and I've seen publishied aritcles in the
aircraft magazines in regards to the Corvette engine conversions...

On Thu, 10 Nov 2005 15:01:46 -0600, Darrel Toepfer
wrote:

MrV wrote:

Hey guys i'm a new pilot that really wants to build his own craft. help
me with this one issue.

I want to use a chevy ls2 or ls7 as the power plant in my craft.
snip
the aircraft i want to design is a very cab foward design with a
pusher prop and the engine would be mounted approx mid craft.

i'm new at this and besides having an engineering background i really
have no exp building an aircraft so any opinions would be helpful

Car transissions aren't designed to take any thrust. I also suspect a
phenominon called P factor would twist the end off the tranny the
first time you started up the engine with a prop attached.

Drew Dalgleish wrote:
Darrel Toepfer wrote:

Car transissions aren't designed to take any thrust. I also suspect a
phenominon called P factor would twist the end off the tranny the
first time you started up the engine with a prop attached.

If you're going to snip out what I typed, then please remove the quote
reference to me as well...

now that would be an issue but one i would solve by attaching the
tranny to a "GearBox" attached to frame to take thrust pressuer and
that being attached to the prop. kinda similiar to a rear diff

MrV wrote:
now that would be an issue but one i would solve by attaching the
tranny to a "GearBox" attached to frame to take thrust pressuer and
that being attached to the prop. kinda similiar to a rear diff

You are trying to say "thrust bearing", I think.

Look over carefully a Soloy Allison fixed wing conversion.

Intuitively, turning a propeller is a smoother load than the diff on a
car. In reality it is not. It took the marine industry twenty or more
years to realize you could use a car ingine in a boat, but only if its
"native" conditions vis-a-vis those of heavy slow turning boat engines
were carefully looked at. Dedicated small boat engines for inboard use,
gas or diesel, have become a thing of the past as autoderivative (with
"automotive" meaning heavy truck as well as car) engines are used
exclusively up to almost 1000 hp today. The LyCon museum pieces have
been saved this fate by a confluence of arcane and arbitrary
certification requirements, legal paranoia induced by Wichita's long
misrule by drunks and bitch-ass widows, and physics-weight is
irrelevant in boats but critical in aircraft, and most autoderivative
engine cores are heavy.

"MrV" wrote in message
oups.com...
now that would be an issue but one i would solve by attaching the
tranny to a "GearBox" attached to frame to take thrust pressuer and
that being attached to the prop. kinda similiar to a rear diff

Weight, weight, weight!
--
Jim in NC

DANG! The seabee folks charge as much for their $6000 Chevy engine as
Lycoming does for their $3000 engine!

David M.


Darrel Toepfer wrote:

MrV wrote:

Hey guys i'm a new pilot that really wants to build his own craft. help
me with this one issue.

I want to use a chevy ls2 or ls7 as the power plant in my craft.

snip

the aircraft i want to design is a very cab foward design with a
pusher prop and the engine would be mounted approx mid craft.

i'm new at this and besides having an engineering background i really
have no exp building an aircraft so any opinions would be helpful


LS1/2/6/
http://www.v8seabee.com
http://www.seabee.info/seabee_engine_conversions.htm
http://www.republicseabee.com/Corvette_Power.html

They did all the legwork and I've seen publishied aritcles in the
aircraft magazines in regards to the Corvette engine conversions...

On 10 Nov 2005 12:41:25 -0800, "MrV" wrote:

Hey guys i'm a new pilot that really wants to build his own craft. help
me with this one issue.

I want to use a chevy ls2 or ls7 as the power plant in my craft.
now looking at everything including the hp/torque curves i've decided
running the engine around 3100 rpm should give me around 250 hp with
good torque now getting that power to a propeller seems to be an issue.
I'm wondering besides weight would there be any real issue using the
associated transmission locked in gear maybe 3rd/4th/5th gear whichever
is just under 1:1.

it would seem the car tranny has been engineered to convert the engine
motion into the spinning i would need to propel the propeller. plus
running the engine at 3100 rpm it would prob last longer than i will.

the aircraft i want to design is a very cab foward design with a
pusher prop and the engine would be mounted approx mid craft.

i'm new at this and besides having an engineering background i really
have no exp building an aircraft so any opinions would be helpful

Mrv, you should understand that homebuilders have been thinking that
auto engines should work fine for airplane powerplants from the very
beginning of the homebuilt era.

Not only homebuilders, but a number of qualified aeronautical
engineers thought likewise and have tried through the years, with
varying degrees of success, to convert auto engines to spin
propellers.

Toyota actually managed to get a Lexus based V-8 conversion certified
with a Hamilton prop designed specifically for it. But they withdrew
the engine from the market without attempting to put it into any
airframes, other than the test bed.

There is absolutely nothing inherently wrong with almost any auto
engine's ability to run at aircraft flight power settings for a long
time. That fact has been proven for years. What IS a problem is
fabricating a reliable prop speed reduction unit, and managing to
engineer adaquate cooling for the engine.

The litanny goes, it's not the auto engine that fails, it's everything
else. And there is a lot of everything else that can go wrong and
stop the prop from spinning.

From an aviation stand point, using an auto transmission for a PSRU is
not a great idea. For one thing, it's carrying around a bunch of
gears that add to the weight and aren't being used. That's just
crazy. Also, with the transmission in the car, the drive train is
locked solidly in place and does not impose any side loads to the
transmission at all. All it does is transmit torque as it spins.

But the propeller produces ENORMOUS side loads on the prop drive every
time you turn, hit turbulence or climb or dive. The auto
transmission, as it comes from the car manufacturers simply is not
designed to withstand that kind of side loading.

As mentioned previously, the lower gears in the transmission are
designed to be operated for only short periods. They do not have the
heft and thrust bearing support to manage sustained pressure at high
torque loads.

Finally, while belted PSRU's are fairly well understood at this point,
they tend to be marginal for high output engines. The only PSRU I'd
recommend at this point would be the Geschwender type. See:
http://www.alternate-airpower.com/ for details.

Corky Scott

"Charles K. Scott" wrote in message
...
On 10 Nov 2005 12:41:25 -0800, "MrV" wrote:

Hey guys i'm a new pilot that really wants to build his own craft. help
me with this one issue.

I want to use a chevy ls2 or ls7 as the power plant in my craft.
now looking at everything including the hp/torque curves i've decided
running the engine around 3100 rpm should give me around 250 hp with
good torque now getting that power to a propeller seems to be an issue.
I'm wondering besides weight would there be any real issue using the
associated transmission locked in gear maybe 3rd/4th/5th gear whichever
is just under 1:1.

it would seem the car tranny has been engineered to convert the engine
motion into the spinning i would need to propel the propeller. plus
running the engine at 3100 rpm it would prob last longer than i will.

the aircraft i want to design is a very cab foward design with a
pusher prop and the engine would be mounted approx mid craft.

i'm new at this and besides having an engineering background i really
have no exp building an aircraft so any opinions would be helpful

Mrv, you should understand that homebuilders have been thinking that
auto engines should work fine for airplane powerplants from the very
beginning of the homebuilt era.

Not only homebuilders, but a number of qualified aeronautical
engineers thought likewise and have tried through the years, with
varying degrees of success, to convert auto engines to spin
propellers.

Toyota actually managed to get a Lexus based V-8 conversion certified
with a Hamilton prop designed specifically for it. But they withdrew
the engine from the market without attempting to put it into any
airframes, other than the test bed.

There is absolutely nothing inherently wrong with almost any auto
engine's ability to run at aircraft flight power settings for a long
time. That fact has been proven for years. What IS a problem is
fabricating a reliable prop speed reduction unit, and managing to
engineer adaquate cooling for the engine.

The litanny goes, it's not the auto engine that fails, it's everything
else. And there is a lot of everything else that can go wrong and
stop the prop from spinning.

From an aviation stand point, using an auto transmission for a PSRU is
not a great idea. For one thing, it's carrying around a bunch of
gears that add to the weight and aren't being used. That's just
crazy. Also, with the transmission in the car, the drive train is
locked solidly in place and does not impose any side loads to the
transmission at all. All it does is transmit torque as it spins.

But the propeller produces ENORMOUS side loads on the prop drive every
time you turn, hit turbulence or climb or dive. The auto
transmission, as it comes from the car manufacturers simply is not
designed to withstand that kind of side loading.

As mentioned previously, the lower gears in the transmission are
designed to be operated for only short periods. They do not have the
heft and thrust bearing support to manage sustained pressure at high
torque loads.

Finally, while belted PSRU's are fairly well understood at this point,
they tend to be marginal for high output engines. The only PSRU I'd
recommend at this point would be the Geschwender type. See:
http://www.alternate-airpower.com/ for details.

Corky Scott

To me, it's interesting to note that in the automotive role, the engine is
isolated from the load to the maximum extent possible. In other words, the
engine is coupled to the wheels with cardan shafts that have U-Joints and
sliding splines such that engine vibrations, other than torque pulses, don't
get transmitted to the wheels and wheel vibrations don't get transmitted to
the engine. The engine just rocks and rolls in it's own rubber mounts and
transmits only torque to the drive line. The engine bearings see neither
thrust or radial loads. The vision is that everything is isolated with
rubber mounts to eliminate all possible vibrations. That seems to be a
successful formula for cars.

I'd suggest this is a good path to take in auto-engine conversions. Don't
just mount the prop to the crank or mount the PSRU rigidly to the engine.
Separate them and let the prop, PSRU and engine each live in their own
isolated vibration environment.

So, how to do this? First, think of a prop attached to the airframe turning
in it's own bearings that carry the thrust and radial loads with the bearing
carrier on elastomer mounts. Drive the prop with belts that absorb some
torque pulses and drive the belt with a pulley block mounted to the airframe
like the prop that is itself driven through a elastomer flex coupling by an
engine riding in isolation mounts. This way the prop won't see engine
vibrations and the engine won't see prop vibrations. The airframe itself
should see neither.

In drive line systems, there's no such thing as 'good vibrations'.

Bill Daniels

I've been around homebuilts and homebuilders since 1973, and have
learned much from the mistakes of others. The old guys will tell you
that you never design both an airplane and a powerplant at the same
time, and that you never design an airplane without training or
extensive research unless you are simply copying something else to a
great extent. I've met or read about fellows with odd ideas about some
"new" airframe who have either bankrupted themselves trying to make it
work, or nearly killed themselves trying to fly it. The majority of
these people weren't even pilots yet, just guys full of preconceived
notions. They spent an enormously frustrating amount of time and money
to no good purpose.
Auto engine adaptations are very time-consuming, and while
there are a few that run well enough, many of their builders wish they
had just bolted a Lyc to the firewall in the first place. Would have
been cheaper and they could have gone flying. I was also into boats for
some years, and knew a guy who did the auto transmission thing; didn't
last long at all. Those gears just won't take the high power levels for
very long. Cars don't cruise at 75% power, and that's all there is to
it. Detroit doesn't design stuff any stronger than it has to.
The OP would be wise to read EVERYTHING he can find on the
subject, which is a lot more than I had available in the '70s, what
with the 'Net and all. No excuse to make the same mistakes all over
again.

Dan