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

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.

Morgans wrote:
snip.

At every power pulse, the crankshaft winds up a little bit, and then unwinds
while waiting for the next power pulse. This can be a very large problem,
and can destroy a drivetrain. Aircraft engines get around it by making a
very stout driveshaft, but even then, some engine prop combinations are
plackered not to run at certain RPM's in continuous operations.

Do some research. There have been tons written on the subject, and even
though it does not make sense, driving a prop is way harder than a car
wheel, and avoiding the resonate problems.

Actually, aircraft engines don't deal with it very well at all. Large
radials deal with it by having a high reciprocating mass, and the 65
Continental class of engine deals with it by low impulse and again a
high reciprocating mass, but geared light aircraft engines have been
largely troublesome. The Continental Tiara was a disaster and so was
the GO-300. The planetary gear case Lycomings were a little more
successful but they were also heavy.

A good "car" engine that is suitable for ski boat use is suited to
aircraft use if 1) any resonant peaks in its internal configuration are
figured out first, (the boat will do that!) 2) a proper drive is
selected and 3) propeller loads are transferred to the airframe from
the drive and not the engine itself. Dave Blanton had no torsional
resonance problems, although he was probably a little lucky, and
careful study of Kiekhaefer's marine I/O and the Soloy Allison fixed
wing conversion (which use Allison helo turboshafts, different from
their purpose built fixed wing cousins) will be helpful.

A good autoderivative engin package solves a lot of problems aviation
users have lived with for so long they don't consider them problems
anymore, such as a prop stoppage destroying the entire lower end of the
engine, and not being able to run the engine without a prop or test
club.

"MrV" wrote in message
oups.com...
actually i'm thinking 4th or 5th gear from a 6speed manual tranny.
from the LITTLE research i've done
3rd gear is like 1.43 and 4th is like 1.2 seems like a good range
3500rpm= 2400 prop rpm
or at 1.2 3250 rpm = 2700 prop rpm.

now wouldn't the prop vibs be less than the abuse the average tranny
takes from a daily drive ?

Resonate vibration is the killer in the aircraft powerplant world.

At every power pulse, the crankshaft winds up a little bit, and then unwinds
while waiting for the next power pulse. This can be a very large problem,
and can destroy a drivetrain. Aircraft engines get around it by making a
very stout driveshaft, but even then, some engine prop combinations are
plackered not to run at certain RPM's in continuous operations.

Do some research. There have been tons written on the subject, and even
though it does not make sense, driving a prop is way harder than a car
wheel, and avoiding the resonate problems.
--
Jim in NC

"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

600 LBS,,,, Yea right........I fly a auto conversion several times a
week and it is doing fine. Don't get me wrong, it took ALOT of time to
think it through and several generations of cooling systems but,,,
boy is it a blast to fly now..

Ben
www.haaspowerair.com

"Bret Ludwig" wrote in message

Actually, aircraft engines don't deal with it very well at all. Large
radials deal with it by having a high reciprocating mass, and the 65
Continental class of engine deals with it by low impulse and again a
high reciprocating mass, but geared light aircraft engines have been
largely troublesome. The Continental Tiara was a disaster and so was
the GO-300. The planetary gear case Lycomings were a little more
successful but they were also heavy.

Agreed. Part of the solution, is like I said, stout (read heavy)
crankshaft, along with, as you stated, high reciprocating mass.

Radial engines have stout cranks, plus massive master and slave rods.

A good "car" engine that is suitable for ski boat use is suited to
aircraft use if 1) any resonant peaks in its internal configuration are
figured out first, (the boat will do that!) 2) a proper drive is
selected and 3) propeller loads are transferred to the airframe from
the drive and not the engine itself.

Part of that "proper drive" for boats also use a rubber coupling between the
engine and the transmission, outdrive, v-drive, or prop shaft. The entire
output from the engine turns the rubber, then the rubber turns the drive.
In this manner, there is no metal to metal connection of the engine to the
drive. Every one I have seen uses one, but I'll be damed if I can remember
what the correct name is, at the moment! g Old age, or time of night?

Those units tend to absorb part of the pulse energy, and leaves a way for
the torsional energy to dissipate. They do eventually wear out, and a new
one has to be installed. AMHIKT. Very careful alignment is key to the unit
lasting as long as it should.

One of the more modern solutions is use of a toothed rubber drive belt, to
slow down the prop, and allow for a prop shaft and bearings that can deal
with all of the loads the prop creates. It also allows the belt to flex and
isolate the prop from the engine. They are pretty efficient, and have a 200
hour or more life expectency.

Dave Blanton had no torsional
resonance problems,

Some would argue that! g
--
Jim in NC

"stol" wrote in message
oups.com...
600 LBS,,,, Yea right........I fly a auto conversion several times a
week and it is doing fine. Don't get me wrong, it took ALOT of time to
think it through and several generations of cooling systems but,,,
boy is it a blast to fly now..

Ben
www.haaspowerair.com

I can't tell for sure, since you didn't include some of the original post,
but I think the 600 pounds was a ballpark figure, if the OP had used a V-8,
the full auto transmission, and another drive unit to take the prop loads,
as he suggested he would.

Don't get me wrong; I am an auto drive fan. (or supporter, at least) g
--
Jim in NC

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

I can't tell for sure, since you didn't include some of the original
post,
but I think the 600 pounds was a ballpark figure, if the OP had used a
V-8,
the full auto transmission, and another drive unit to take the prop
loads,
as he suggested he would.

Don't get me wrong; I am an auto drive fan. (or supporter, at least)
g
--
Jim in NC



///////////////////////
Jim is correct there, It would weigh in at a ton....g