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

"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

wrote:
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 key is you want someone else to do the pioneering work for you.
Several autoderivative engine conversions have flown and proven to be
essentially sound. I would use one of them or at least study them
intently.

I felt at the time Blanton had essentially the right idea but should
have made his drive a two piece casting, making his own patterns and
having them poured at a nearby foundry and using automotive machine
tools to finish machine them quickly. Today I suspect a enclosed HyVo
drive or even gears-probably from an Allison truck trans-with a quill
shaft might be better. Only Blanton's pathological hatred for GM kept
him from real success in terms of volume-everyone else wants GM engines
because they are staplles of the hot rod industry.

As i stated earlier i'm an engineer and building/designing things is
something i burn to do. I've given myself 10 years to buid this thing.
My problem with airplane engines is cost they are far to costly for
what u get and are about as reliable as my lawnmower.

the tranny i'm talking bout is a chevy tremec tranny built for the
corvette. looking at the specs its about as bullet proof a gearbox as
anything i've ever seen.

now the tranny things is just an idea, use cheverolets billion dollars
of research to get something going. the only semi-const is the engine
which will more than likely be an ls2 as the ls7 i originally wanted is
up there with airplane engines in cost. well lower end airplane
engines. prob by the time i need the drivetrain it'll be cheaper.

the question is if the engine/tranny is isolated from the
thrust/sideloading/vib of the prop and besides weight would it be
reasonable to assume this would be okay. it really shouldn't be all
that difficult to completely isolate the drivetrain from the prop.


now some other details that i would like to get input on:

now the craft is essentially a kevlar covered steel tube frame. reason
being i'm good at welding but have worked very little with composites(
built speaker enclosures and spoilers for my car). but i really like
the finish of the composite aircraft. and kevlar because its cheaper
than graphite and lighter than fiberglass.

1. i only intend to run this thing at approx 50% power while i could
spin it up higher i just can't see a reason to do it. 400lbs for
200+hp seems like a good trade to me. Plus i can buy another one or
rebuild it myself for far less than the rebuild of an aircraft engine.

2. I"m not trying to build the most efficient fastest cruising thing
in the world. i want something reliable, simple kinda speedy(150 -
160kts) and without the prop, massive front end and massive instrument
panel infront of me.


3. 2 seater also maybe 3 but most likely 2.

4. also what is a good way to keep the sound of the engine/prop/gears
in back where it belongs ? massive noise in the cabin would completely
ruin the effect i'm trying to achieve.

hey guys i'm only hunting for ideas now so please feel free to respond
with anything u can come up with pro/con.

also hopefully you aren't annoyed hehe cause prob get realy frustrated
when i start asking about wing construction hehe.

It has to be said also the fastest way into the air is indeed the
museum piece Lycoming engine-securely mounted to the firewall of an
already built certificated production aircraft. Even at today's high
prices, they still are a Good Deal for most people who really want to
fly.

"MrV" wrote:

A page displaying his total lack of knowledge.

To you, I put out the following possibilities. You a

1) A kid playing on the computer. If I am wrong, stop using the text
message type of shorthand.

2) So completely ignorant of what works, what does not, and what might work,
that you need to get into the books, and/or Google, and do some homework.
The things you are proposing are ALL so far from reality, it is hard to know
where to start giving advise. I doubt you are going to get many responses,
because of this.

3) A plain and simple troll.
--
Jim in NC

yes i did and that is why i posted it here asking for comments. if u
notice a number of times i have stated this is just for info and if it
is reasonable. I'm guessing you are just an idiot that doesn't bother
to read complete post.

from the replies i've received the only thing i can see wrong with my
idea is 1 weight and 2 vibration everything else can be solved readily
with some planning. instead of posting something stupid like this why
not give reasons why i'm TOTALLY off base.

In article .com,
"MrV" wrote:


from the replies i've received the only thing i can see wrong with my
idea is 1 weight and 2 vibration everything else can be solved readily
with some planning. instead of posting something stupid like this why
not give reasons why i'm TOTALLY off base.

I think cooling was mentioned also. And, those pesky details are not
trivial. I believe you also stated that your objection to Lycon is cost.
The knowledgeable people here have pointed out that you will spend *far*
more engineering your own airplane and powerplant than you would by
buying off the shelf. I don't think they're referring to percentage, but
orders of magnitude.

And then you alluded - in a somewhat mocking tone IMO - to some new
ideas you have for a wing. I think you can understand why it might be
easy for some of us to assume you're a troll. You might be some sort of
engineer, as you claim, but without the merest hint of any background in
aviation, that isn't going to buy you much in the real world.

Now, this is RAH, so I'm not going to suggest that you're off base. But
chatting here isn't research. Go spend several thousand hours studying
the issues, and then come back with *specific* questions based on a real
understanding. Even the Wright brothers started by learning everything
they could about what everyone before them had done.

I'll give you one "out." If your objective is to design the next Moller
skycar in order to bilk investors, then of course you don't need any
real understanding of the issues at all. That's an objective that
requires a completely different set of skills.

from the replies i've received the only thing i can see wrong with my
idea is 1 weight and 2 vibration everything else can be solved readily
with some planning. instead of posting something stupid like this why
not give reasons why i'm TOTALLY off base.

Why you're TOTALLY off base:
1. Weight. You do want to fly, don't you?
2. Design. You do want to live, don't you? Get some understanding of
aircraft. It can't be solved "readily."
3. Vibration. Kills mechanisms like you are proposing. Vibration is a
science all its own, and few there are that understand it.
4. Gyroscopic loads. We haven't even touched on that one yet.
5. Money. Hope you have lots to throw away. There are plenty of people
that will take it.
6. Reality. I can't recall anyone who entered this field, non-aviation
engineering background or not, that has designed a successful airplane
and powerplant combination from the ground up. Most of them crashed a
few times and learned from that; the rest died. Since there's lots of
info available now, there's no excuse to do the macho-ego-designer
thing anymore.
7. A Lycoming is a lot more reliable than a lawnmower engine. Witness
the average age of the lightplane fleet using them: something like 35
years?
We don't want another ignorant newbie killing himself and
discrediting the homebuilt movement. Please listen up.

Dan

Smitty Two wrote:
In article .com,
"MrV" wrote:


from the replies i've received the only thing i can see wrong with my
idea is 1 weight and 2 vibration everything else can be solved readily
with some planning. instead of posting something stupid like this why
not give reasons why i'm TOTALLY off base.

I think cooling was mentioned also. And, those pesky details are not
trivial. I believe you also stated that your objection to Lycon is cost.
The knowledgeable people here have pointed out that you will spend *far*
more engineering your own airplane and powerplant than you would by
buying off the shelf. I don't think they're referring to percentage, but
orders of magnitude.

This assumes every user of a non-LyCon engine has to engineer his own
conversion from a clean sheet of paper. If you are going to apply that
standard you should insist every LyCon using homebuilder make his own
crankcase and cylinder patterns, pour sand castings himself, and
machine them. Instead of buying a reduction drive, mounts and so forth
pre-designed from a reputable supplier and attach them to an engine
core with good history of results, using plumbing and systems as other
successful operators have. That's the common sense solution. Find
someone making a redrive and mounts for a reasonable price, reflecting
only a small percentage for engineering since it's hardly a Skunk Works
project and amortizing it over many units.

The _best_ solution to auto engine cooling and cost is to buy a "real
aircraft engine" that is "proven". What does a new PT6A series P&WC
engine cost? That's a real aircraft engine, a LyCon is an overgrown
Volkswagen. Unfortunately, for me a new Pilatus PC-9 is outside the
range of affordability. (A L-39 is a third or fourth the price, and
that's too expensive by far for most of us.)

The sport boating industry exists to a large extent because of
affordable marinized auto-derivative engines and sport flying can use
them as well if some good simple engineering and common sense are
applied. In fact, it has, since the days of Bernie Pietenpol and Steve
Wittman, who flew reasonably well on commodity general purpose engines.