Differences between automotive & airplane engines

wrote in message
oups.com...
Well put.. Converting an auto engine for aircraft use is not for the
novice to try.


Neither is building airplanes. Or flying. Or driving a car. Or using
power tools... Or playing a sport... Or eating solid food...

Building the airplane involves following published
instructions. Flying involves taking lessons with someone who both
knows what they're doing and how to teach it. Driving a car is similar.
Using power tools without knowing something about how to use them
sometimes involves some hard lessons and a missing digit or two, or an
eye. Playing a sport involves rules, and we can step aside anytime if
the risks mount. The food should get gradually more solid while we
learn to eat it, but even then it's not pretty and even fatal once in a
long while.
Converting engines, for the uninitiated, seems to involve
making a prop hub and bolting it on and expecting reliability,
performance, good fuel economy and great engine life. Those of us
who've done it know otherwise; we have run into many obstacles. There
are a few really good, established conversions out there, and most
builders should buy the plans or the kit or the entire engine and stick
with that rather than assume they can easily make an auto engine fly.
Hanging around homebuilding since 1972 has taught me much, particularly
about the "fantastic" conversions that drop out of sight within a year
or two. Something like the new, improved, futuristic internal
combustion engines that Popular Mechanics seemed to have in their
magazines about every third issue back then. There's no shortage of
hype.
Geschwender sold (still sells, maybe?) converted Ford 351s
that flew all day in cropdusters like the Pawnee. That tells me
something about their credibility. A fella should look for established
machinery like that, or something close to what he needs, and build on
that experience.

Dan

Fred Geschwender has pssed on to the big engine factory in the sky.
However, the project lives on. I am not sure which of the several vendors
and developers of Hy-Vo chain based PSRUs is his direct successor; but IIRC
one of them is.

Peter

P.S.: Until further notice, the Hy-Vo chain also remains my first choice
for offset drives; although the proponents of toothed belts do raise a few
meritorious arguments.

clare at snyder.on.ca wrote in message
...
On Sat, 11 Feb 2006 09:15:06 -0500, "Kyle Boatright"
wrote:


clare at snyder.on.ca wrote in message
.. .

snip

An O200 and a Corvair weigh virtually the same (within 30 lbs), with
electrical systems, and provide virtually the same hp and thrust.

Cheaper? most definitely can be - and certainly is cheaper to overhaul
when the time comes. And the automotive engine MAY run longer between
major overhauls.
I can build a zero timed Corvair for not much more than the cost of
rebuilding one cyl on a Lycoming.

The issue there goes back to reliability. What is the reliability of a
Corvair in an aviation application with the crank and bearings taking
loads
they were never designed to deal with?

KB

They have flown thousands of hours over the years - and untill the
last couple months in high speed planes, crank failures have been
extremely rare. (assuming light weight props, no more than 3000 RPM,
and planes flying in normal category at less than 150MPH)

The cranks have not been any more problematic than Lycos or Contis.
flown within their design parameters.

As stated before, a full thrust bearing on a Corvair engine is almost
identical in thrust are as on an O-200.

An excellent point. Racers, acrobatic pilots, and some experimenters with
midified metal props have broken their share of Lycomings and Continentals.

Fred Geschwender has pssed on to the big engine factory in the sky.
However, the project lives on. I am not sure which of the several
vendors
and developers of Hy-Vo chain based PSRUs is his direct successor; but
IIRC
one of them is.

Peter


P.S.: Until further notice, the Hy-Vo chain also remains my first
choice
for offset drives; although the proponents of toothed belts do raise a
few
meritorious arguments


////////////////////////////////////////

I am very comfortable with my toothed belt redrive set up. I am feeding
about twice as much power through it as Jess@belted air advertises it
can handle. So far it shows no sign of failing. Go to my web site,
www.haaspowerair.com

and look close at the pics of the engine/redrive set up, simple,
bulletproof and not that costly.

Ben.
N801BH

wrote:
Well put.. Converting an auto engine for aircraft use is not for the
novice to try.



Neither is building airplanes. Or flying. Or driving a car. Or using
power tools... Or playing a sport... Or eating solid food...


Building the airplane involves following published
instructions.

You never seen published standards for engines? The physics involved
are well understood. All the data necessary relatively easy to come by.

Flying involves taking lessons with someone who both
knows what they're doing and how to teach it.

Who taught Orville and Wilbur?

Driving a car is similar.
Using power tools without knowing something about how to use them
sometimes involves some hard lessons and a missing digit or two, or an
eye. Playing a sport involves rules, and we can step aside anytime if
the risks mount. The food should get gradually more solid while we
learn to eat it, but even then it's not pretty and even fatal once in a
long while.
Converting engines, for the uninitiated, seems to involve
making a prop hub and bolting it on and expecting reliability,
performance, good fuel economy and great engine life. Those of us
who've done it know otherwise; we have run into many obstacles.

I agree with you 100%, and will take it one further. Building an
airplane for the uninitiated seems to involve bolting an unquantified
entity called a 'wing' to an equally unquantified entity called a
'frame' then heading off into the clear blue. Quick and easy. A few
weeks work. That's the way I thought of it...four years ago.
Fortunately, the less we know of a subject, the more we think we know;
otherwise, I might not have started.

All of your responses reinforce my point. Every endeavour we choose to
undertake, whether it be converting an engine, buiding an airplane,
playing a musical instrument, the first requirement is always to study
and understand the problem space. I believe that the only point we
disagree on is the degree of difficulty you perceive in an engine
conversion.

My argument is that an engine conversion just adds another facet to the
long list of things to learn. Which brings us back to the original
addage. If you want to build, build, even if that build involves an
auto conversion and with all the study and education that involves. If
you want to fly, buy.

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

I agree with you 100%, and will take it one further. Building an
airplane for the uninitiated seems to involve bolting an unquantified
entity called a 'wing' to an equally unquantified entity called a
'frame' then heading off into the clear blue. Quick and easy. A few
weeks work. That's the way I thought of it...four years ago.
Fortunately, the less we know of a subject, the more we think we know;
otherwise, I might not have started.

All of your responses reinforce my point. Every endeavour we choose to

undertake, whether it be converting an engine, buiding an airplane,
playing a musical instrument, the first requirement is always to study
and understand the problem space. I believe that the only point we
disagree on is the degree of difficulty you perceive in an engine
conversion.


My argument is that an engine conversion just adds another facet to the

long list of things to learn. Which brings us back to the original
addage. If you want to build, build, even if that build involves an
auto conversion and with all the study and education that involves. If

you want to fly, buy.


--

Thats whythe FAA clearly states " building a homebuilt plane is for
educational purposes" Ernest, you will reap the satisfaction when you
safely land after your first flight in a creation you built. It is a
feeling that CANNOT be duplicated. Trust us on that..Forgive me if I
didn't catch in an previous post but what are you building and how
close are you to getting in the air????

stol wrote:

Thats whythe FAA clearly states " building a homebuilt plane is for
educational purposes" Ernest, you will reap the satisfaction when you
safely land after your first flight in a creation you built. It is a
feeling that CANNOT be duplicated. Trust us on that..Forgive me if I
didn't catch in an previous post but what are you building and how
close are you to getting in the air????


I'm building a Dyke Delta JD-2. I'm at the point of skinning it, but I
keep finding little things that I'm not happy with. Lots of rework.
Like we were saying, everything looks easy until you start trying to do
it. I'm 80% done, with 80% to go. For more information:

http://ernest.isa-geek.org

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

In article ,
Chris Wells wrote:

I'm well aware of the purpose of the PSRU, I'd like to know if it's
feasible to convert an automobile (or other) engine to run at an RPM
low enough so that a PSRU wouldn't be necessary. I'm thinking a custom
camshaft would be needed, and different ignition timing, what else?

Lessee, possibilities include:
cylinder diameter
cylinder stroke
cylinder displacement
valve diameter
number of valves
valve placement
valve timing (that's the new camshaft)

You _can_ run an automotive (*not* 'automobile', BTW 'automobile' is *any*
'self-propelled' device) engine at a speed such that a PSRU isn't needed.
Doing so, however, gives a 'power to weight' ratio that can be considered
'medium dreadful' at best. If you're lugging around an extra 100 lbs
(or whatever) of engine weight, that's 100 lbs _less_ "usable" carrying
capacity.

Which leads back to the real issues:
power vs weight vs size vs longevity vs cost vs operational reliability

Balancing those 'competing' requirements is a _very_ complex and difficult
task. Taking an engine that is designed for one set of those conditions,
and attempting to modify it to a significantly different 'balance point'
is *not* terribly practical. You essentially re-design, and then 'modify'
the existing hardware to *be* the new design.

*OR*, you use the engine in the operating realm for which it was designed,
and 'adapt' the output as appropriate. Thus, PSRU 'adapters', or other
forms of a gearbox/transmission..

On Sun, 12 Feb 2006 23:11:48 -0000,
(Robert Bonomi) wrote:

In article ,
Chris Wells wrote:

I'm well aware of the purpose of the PSRU, I'd like to know if it's
feasible to convert an automobile (or other) engine to run at an RPM
low enough so that a PSRU wouldn't be necessary. I'm thinking a custom
camshaft would be needed, and different ignition timing, what else?

Lessee, possibilities include:
cylinder diameter
cylinder stroke
cylinder displacement
valve diameter
number of valves
valve placement
valve timing (that's the new camshaft)

You _can_ run an automotive (*not* 'automobile', BTW 'automobile' is *any*
'self-propelled' device) engine at a speed such that a PSRU isn't needed.
Doing so, however, gives a 'power to weight' ratio that can be considered
'medium dreadful' at best. If you're lugging around an extra 100 lbs
(or whatever) of engine weight, that's 100 lbs _less_ "usable" carrying
capacity.

Which leads back to the real issues:
power vs weight vs size vs longevity vs cost vs operational reliability

Balancing those 'competing' requirements is a _very_ complex and difficult
task. Taking an engine that is designed for one set of those conditions,
and attempting to modify it to a significantly different 'balance point'
is *not* terribly practical. You essentially re-design, and then 'modify'
the existing hardware to *be* the new design.

*OR*, you use the engine in the operating realm for which it was designed,
and 'adapt' the output as appropriate. Thus, PSRU 'adapters', or other
forms of a gearbox/transmission..

2.6 lbs per horsepower is "medium dreadful"? 235 lbs and 91 HP at 3000
RPM from an automotive power plant - including cooling system and
fluids. ANd that is NOT using a custom cam, changing bore, or stroke.
No PSRU. No valve diameter change. By changing cam I might squeeze
another 6 HP out of it.
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"Chris Wells" wrote in message
...

How are "normal" airplane engines tuned to run at a lower rpm? What
changes would have to be made to an automotive engine to shift the
power band down accordingly?


Some minor changes in valve timing, basically a bit less overlap on the
exhaust/intake crossover. You realize that you don't REALLY shift the
"power band" down. What you actually do is settle for a lot less
horsepower. Virtually all direct drive aircraft engines produce about 1/2
horsepower per cubic inch. I could probably expect about 175 horsepower
from my aviation conversion of a Chevy 350 engine at around 2700 rpm.
Most hop up mods to automotive engines are designed to let you get a bit
more RPM before they come apart or float the valves or ignition. Airplane
engines put out a lot more than their rated power if you overrev them. Of
course, they also go into automatic disassembly mode quicker too!

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )

"Peter Dohm" wrote in message
...
Some of us are mostly interested in airplanes that really need a redrive
to
get good propeller efficiency from a 40 HP VW. Others are interested in
slippery airplanes that cruise at 150 to 200 kts. My interest is in the
faster type of airplane, and the only reason the specification isn't for
something even faster is a desire to keep the simplicity of a fixed pitch
prop. Therefore, if I want to use the old formula of 0.2G static thrust
for
good takeoff performance on a 150 kt airplane, I only need to divide the
expected gross weight of the airplane by 10 to arrive at a reasonable
horsepower figure. (Since I want a static thrust of one fifth of the
gross
weight, and also since each horsepower results in 2 pounds of thrust at
the
150 kt speed--or would if efficiency was 100%) I really DON'T care about
efficiency, because I only intend to operate at low speed and high power
for
less than a minute per flight. Propeller efficiency will always be zero,
by
mathematical definition, at the beginning of the take off roll; and my
numbers work just fine with 40% efficiency during the initial climb to
clear
the obstacles. On the other hand, if your plan is to cruise at 60 kts,
with
a proportionately slower initial climb speed, then you probably need a
larger diameter prop than I do, even with a much lighter and less powerful
airplane.

We really need to look at what is workable, reliable, and affordable for
each specific application. I admit to being a long time advocate of
automotive conversions, and the various GM and D-C all aluminum 60 degree
V6s from 3.0 to 3.7 liters really do look promising; but I really would
have
to think long and hard before I trying to adapt one to an airplane that
has
already been designed around a standard airplane engine. Just making the
cooling system work reliably, with reasonable drag, would probably cause
insomnia!

Peter



I recommend Fred Weick's book on Propellor Design. I think you will find
that the thrust per horsepower is not a constant but rather decays
proportionately to the log of the RPM. The pounds of thrust per horsepower
gets pretty punk past about 2500 RPM of the prop. At 1000 RPM you get great
thrust out of 25 or 30 horsepower! At 2500 RPM you can get the same thrust
from 100 HP with a good prop! :-)

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )