Auto conversions & gear boxes

On Tue, 24 Feb 2004 11:46:41 GMT, "Blueskies" wrote:

Corky,

Do you have any details available about your engine test stand, such as how you restrain it, instrumentation, cooling?

Also, a buddy of mine was talking about an engine build he did, and how he used water to match each header tube volume,
old news I'm sure...

--
Dan D.

I fabricated the engine stand using a lot of OTLAR measurements.

I pulled some 1 1/4" tubing out of the pile (I bought a pile of tubing
for a Skybolt kit years ago and still have at least half of it left.
I always seem to find enough of what I need for projects like this. I
think the cost for the tubing worked out to something like 10 cents on
the dollar.) and welded a large rectangle. Then I welded plates on
each of the corners and scrounged up four casters from around my shop
and drilled bolt holes in the plates and bolted them on. It has two
swiveling and two that don't. They are largish,solid rubber
commercial casters and I have no idea where I found them originally
but I've had them in the shop for years. I didn't pay anything for
them, I remember that.

Then I duplicated the engine mount rails and bolted them to the
engine. I suspended the engine over the base and fitted and welded
support legs from the rails to each corner of the base. Removed the
engine and welded everything.

Then I added 3/4" diagonal tubing fore and aft between the support
legs so that the engine could not shift or sway. That REALLY
solidified things.

What I'd **like** to do is remove the instrument panel from the
cockpit and mount it on the stand and use what instruments are
necessary to monitor engine performance. That way I don't have to
fabricate two instrument panels. I have not cut any holes for
instruments yet so that's in the near future. Actually buying some
instruments is also in the near future. ;-)

I'll need: Oil pressure, oil temperature, tachometer, water pressure,
water temperature and an EGT guage. It probably wouldn't hurt to have
a cylinderhead temperature guage too. I'm leaning towards digital for
the tach and possibly the temps as well but have not made up my mind
on which of the numerous choices to use.

Or I could just use some scrap plywood since I only need the
instruments that monitor engine performance so the test stand panel
could be smallish. Or I could cut up some of the 1/8" sheet aluminum
from the huge panel I scored for free. Using that stuff takes a lot
more work than using plywood though.

The radiator is sitting below the engine at present, but I think I'm
going to have to move it a bit so that the exhaust system can clear
it. The plan is for the exhaust to wrap under and behind the engine
and tuck right behind the Griffin radiator, when I get it. But for
now, the radiator I picked up from the auto parts place will do the
job. It's a Ford Taurus radiator so I know it's adaquate for the
task. If I pick up the custom radiator before all is installed back
on the airframe, I'll likely fabricate the entire cooling duct system,
including the exhaust augmentation, just to make sure the system cools
properly.

I will leave the engine installed in the fuselage for the moment, so I
can fabricate the exhaust and make sure that it fits the airframe
properly, then the exhaust will be removed from the engine and the
engine transferred to the test stand and the exhaust system
re-installed.

I'll route hoses to the radiator as necessary and weld on a pan to
hold the battery. I'll also have a "gas tank" somewhere on the base
of the stand and will have to use a fuel pump to get the gas up to the
carburetor, probably a submerged type, or something that goes in-line
and I'll just bond on a fuel line out of the gas tank.

I've built the stand tall enough that the prop can be mounted to the
engine.

When I get ready to fire it up, I'll literally have to chain the stand
down so that it does not try to hurtle off into the woods like some
demented woods buggy run amuck.

I may lift the whole thing into the back of the pickup and drive up
into the woods to do the extended running so that the neighbors don't
complain. I'll strap it down for the trip, and for running it, of
course.

I'll probably pitch the prop so that the engine can run to it's
maximum rpm while on the test stand. This will be necessary because
I'll need to make sure the engine can manage full power for extended
periods, plus there may be some tuning and adjustments required that
show up only at full power.

The test stand is roughly patterned after the engine test stands I
worked with while training as an auto mechanic at the Rhode Island
Trades Shops. Those engines did not have props bolted to them though.

If anyone would like to see what the test stand looks like, send me an
e-mail and I'll enclose a picture and send it to you. It's in rough
form right now, not completed, but I have some shots of the engine
bolted in place so you'll get a good idea of what I'm trying to
accomplish. Plus, since it's in the unpainted stage, I can still make
lots of modifications to it, should anyone have any ideas.

Corky Scott

Bravo! Professor Lamb...
Well done! Well done indeed... Even a simple layman Like myself can understand.

Bryan

Richard Lamb wrote in message ...
Dave Covert wrote:

I notice that most auto engine conversions use a gear box between the engine
and the prop. Why is that? Is it because an auto engine's peak HP is too
high for a prop to swing? Is it because auto engines weren't designed to be
pulled around by their crankshafts and don't have proper thrust bearings?
Both?

Are there any auto/motorcycle conversions that don't require gear boxes?

Dave

Some people think aircraft engines are "old fashioned technology"
and have not kept up with developments in auto engine field.

They point out that aircraft engines haven't changed much in
over 50 years.

Some people feel that auto engines can be used to power airplanes.

To some extent, all three of these ideas are true.

Aircraft engine do not run like car motors.

Aircraft engines run at much higher sustained power settings and
constant rpm for long periods of time.

And then there is the propeller...
Turning the propeller is what it's all about.

The propeller converts the engine's power into thrust.
As always, when energy is converted, there are losses.

Moving through the air at very high speeds, the propeller
makes lift (thrust, which is power successfully converted into
forward motion) and drag (pure conversion losses).

So, propeller efficiency is extremely important.

If the propeller is only 50% efficient, half of the
power generated by the engine is wasted in losses.
Yes, literally.

Only one hard rule for propellers - longer is better.

But longer blades mean lower RPM because the tips of the
propeller blades MUST stay below the speed of sound (yep,
Mach 1, really) for any efficiency at all.

Part of the reason for this is the huge increase in drag
as the tip enters the transonic (speed) region.

It takes TORQUE to turn that propeller - not horsepower.

A given propeller needs to turn at a given RPM, which
will require a given amount of torque.

If the engine makes enough torque to turn the propeller at
that RPM, a direct drive set up may be possible.

There are a lot of other minor details that may get in the way -
Harmonic Resonance is a big one.
But, it may be possible to run this combination direct drive.

If the engine needs to turn at a higher RPM to make adequate
power, some kind of gearing would be necessary to reduce engine
RPM to propeller RPM. Notice that reducing RPM will increase
torque proportionally. Seems like a nice trade off.

Now the engine should be running at an RPM near the peak of its'
torque curve. This is for best engine operating economy.

And the (longer) propeller is running at a comfortable (lower)
RPM for good efficiency. Life is wonderful.

Except for the weight.
Auto engines are seldom as light as possible.
Then we add more weight in the form of a gearbox and such.
Radiators full of heavy (hot!) fluids.
External oil sump?
Mounting?
Propeller gyroscopic forces operating on the crankshaft?

Weight is critical to any flying machine.
(Go back and look at how birds are built)

So...
Think of it as evolution in action.

The reason our old antique Lycosourus engines are the way they
are is that they evolved into a very narrow niche.

They turn propellers to pull airplanes.

They make very high torque
at very low RPM,
and are as light as possible.
They are tremendously reliable and fairly efficient.

Prices are high because of limited production and high demand.
Simple economics.

But the economics of engine development (and risk assesment) are
anything but simple.

I have a big bore VW (2180cc) on my parasol.
That's a converted car motor.

There is a weatlh of prior art using VW engines for small airplanes
(if one is inclined to use it).

What works, and what doesn't. (eg: breaking cast crankshafts)

Mine is a very simple conversion, using high quality (GPAS) parts
built by a little German perfectinist.
I trust it - so far.

I also don't push it beyond conservative limits.

All VW engines are 40 hp engine (IMHO).
Some can make more power than that - for a while.
This one is _rated_ at 70 hp.
But will reach thermal limits of the fin area and overheat
if not throttled back (to roughly 40?)

It's a fairly expensive motor.
The jugs and pistons are standard parts, but the crank (!) and
accessories and machine work are all specialty items.
A new 2180 can easily go over $5000 with a few bells and whistles.

But the weight, power, reliability, and operating cost are all within
reason for this particular airplane.

The airplane itself can land slowly, around 35 mph.

The chances of getting down safely if the engine quits are a lot better
at 35 than they are at 53.

To me, it seems like a reasonable risk for the potential rewards.

But...

Your milage may vary.

Richard

http://www.flash.net/~lamb01


PS: I've read of a Curtiss Hawk replica that uses a direct drive Chevy
350.
It's supposed to make roughly 190 hp?
It would obviously be a heavy motor.
Not something you'd hang on a glass slipper.
But on a big old biplane with a looong prop
it seems to be just the ticket.

Bill the Grump,

Between this statement, "When I was the test pilot!". and all of your
stories, you are a legend in your own right. Or is that in your own
mind?

You are a character... LOL. We do enjoy you here, even if you are the
Grump.

Bryan


(Badwater Bill) wrote in message . ..
Nice job Richard. Nice Job.

I might just add one more comment to clear something up a bit. When
you chose a prop, you design it so the tip speeds don't exceed 0.80
Mach, or 80% the speed of sound. As the propeller tips approach
speeds over that, the airflow can become super sonic even though the
prop tip is well below Mach-1. As you mentioned, that takes a lot of
energy that is wasted and is not available for thrust to create a
shock wave and sustain it.

When I was the test pilot on the OMABP RV-6A project, we used the
Chevy Vortec V-6 engine, the PSRU was specifically designed to turn
the prop at tip speed below 80% the speed of sound. Jess Meyers also
used a reduction ratio number that was about equal to the square root
of 2 to eliminate harmonics that could have resulted in reversed
torque pulses reflecting back into the engine. By using a reduction
ratio of 1.41 (or close to it) he eliminated many sympathetic
harmonics that may have occured.

BWB

Richard Lamb wrote in message ...

Maybe we can ask Jim to design a pi detector.

That's a tough one,
A lot harder than the BS detector...

I've got a pie detector! It's right below my eyes. I can smell pies
from at least a football field away, UP WIND! Oh... You're talking
math aren't you? Damn, all you college boys make me feel
unedumacated.

Bryan "the monk" Chaisone
http://www.alexisparkinn.com/rogue's_gallery_a-h.htm#C

bryan chaisone wrote:

Bravo! Professor Lamb...
Well done! Well done indeed... Even a simple layman Like myself can understand.

Bryan


Golly! Thanks.

I didn't mean to know that much, but I came by it honestly.



Richard

bryan chaisone wrote:

Bravo! Professor Lamb...
Well done! Well done indeed... Even a simple layman Like myself can understand.

Bryan


Golly! Thanks.

I didn't mean to know that much, but I came by it honestly.



Richard

Corky Scott wrote:

On 20 Feb 2004 14:19:16 -0600, Barry S. wrote:

On Fri, 20 Feb 2004 18:08:35 GMT,
(Corky Scott) wrote:


Auto engines are tiny when compared to direct drive airplane engines.
Take a 180 hp Lycoming. It's cubic inch displacement is 360. They
turn the prop at around 2600 to 2700. The Ford V-6 in airplane trim,
puts out 180 hp also. It displaces 232 inches and makes it's power at
4800 rpm. No prop will work at that rpm. To harness the power, it
needs to be turned slower. Enter the prop speed reduction unit.

Speaking of Fords! How's your project coming?

__________________
Note: To reply, replace the word 'spam' embedded in return address with 'mail'.
N38.6 W121.4

Slowly. I have the engine assembled and is currently mounted in the
airframe. But there's everything else to do. The airframe has yet to
be blasted and painted. I think that can happen this summer. On the
other hand, we are planning some major kitchen redo's and trust me,
ALL of my attention had better be on that.

I've built an engine test stand that will allow me to wheel the engine
outside and run it, with the prop installed. I'd like to get some 30
or so hours on the engine before it gets it's final installation onto
the airframe. I decided this after listening to a crusty old DAR
speak at a local EAA meeting. It sounded to me like he'd be REALLY
unhappy with such an engine unless I could show him that it had been
thoroughly tested.

At this point, I'm being educated about headers. I was going to just
bend up a bunch of tubes, weld them to be what I need, get them jet
coated and call it good. Then I started doing some research.

It turns out that the diameter of header tubing is critical to the
performance of the engine. Larger diameter is not necessarily better.
In fact in almost all aircraft type applications, bigger is virtually
for sure not better. The exhaust header flange has openings that are
1.75" in diameter. This matches the exhaust port opening in the head.
But the tubing diameter should be 1.5", or possibly even 1 3/8" in
diameter. Also, the length of the runners should be at least over 30
inches, and 36 would be better. In addition, each tube should be as
close in length to each other as possible. Finally, the collector
needs to be about 1 78" diameter and it should be 18" long.

Reality is rearing it's ugly head. The lengths I mentioned literally
won't fit without welding the headers into loops. Not going to
happen.

I think the best I can do is get the runners as long as I can make
them and make sure they are of equal length, and get the proper
collector as that also has a huge affect on engine operation.

Why is it so important to have the runners be the same length?
Because different length runners cause different scavenging effects
within the combustion chamber. You will end up with an engine that
does not respond to ignition adjustments nor mixture adjustments as
some combustion chambers will run rich and some lean. "A series of
single cylinder engines flying loosely in formation." Quote from John
Deakin.

Many builders of the Ford V6 have complained that their engine ran
rough at maximum power. Huge effort was made to modify the intake
manifold to correct the problem. But I have not seen a single picture
of an exhaust manifold where the effort was made to create equal
length exhaust headers of the proper diameter.

I talked with a header manufacturer who told me he had heard of Dave
Blanton because a bunch of builders had asked him about headers. He
told me they all wanted to ignor his advice about tubing diameter.
They all wanted to use bigger tubing than was dictated, because they
all thought bigger was better. It's not.

Why is it so important to have the proper diameter tubing? Because
the bigger the diameter the slower the velocity of the gasses inside
it, and visa versa, up to a point. Eventually you can have exhaust
tubing in a diameter too small such that exhaust flow is restricted.
Large diameter tubing tends to cause the engine's power to peak at
extreme rpms. The smaller the diameter of the tubing, the more low to
midrange power you have.

But everyone wanted to use 1.75" tubing because that's what the
exhaust port was. 1.75" tubing would be what you would use if you
wanted flash horsepower from the engine at 8,000 rpm, like at the
dragstrip.

The header manufacturer also had a lot to say about "Zoomie" type
headers. These are headers without collectors, basically straight
pipes. Not only are these tubes also usually too large a diameter,
they leave off the collector which is crucial to the proper design of
the header system.

So with all this information, I'm taking my time with the header
design. Obviously something so important to the proper running of the
engine is not something I'm going to throw together without using
proper design criteria.

Corky Scott

Another trick that was popular on cars years ago, to bring a broad band
of peak torque into the "mid range" of 2500 to 4000 rpm; was to bring
the shortest practical header pipes which could be long enough to converge
at a reasonable included angle into collectors in groups of 3 which
would fire 240 degrees apart on six and twelve cylinder engines, or in
pairs which would fire 360 degrees apart on 4 and 8 cylinder engines.

On a V6, that would be be end of the story, and a collector having
about the same diameter as the header pipes should continue the same
inertial effect out to the exit or muffler. On V8 and in-line 4
cylinder engines, the resulting initial collectors were about as long
as the header pipes before converging into a final collector.

My expectation is that "tubing headers" made this way for V8 engines
with 90 degree cranks should be only marginally useful. However, they
should work well for all V6 engines, as well as V8 engines with single
plane cranks.

I am still (at a minimum) a couple of years away from testing this
recollection on any project. My own goal would be to achieve the
desired torque curve with an exhaust system length of 4 feet or less.

However, it appears from your post that you have found a competent
exhaust fabricator who can give you some additional guidance.

Peter

Tim Ward wrote:

"Norman Yarvin" wrote in message
...
In article ,
Badwater Bill wrote:

When I was the test pilot on the OMABP RV-6A project, we used the
Chevy Vortec V-6 engine, the PSRU was specifically designed to turn
the prop at tip speed below 80% the speed of sound. Jess Meyers also
used a reduction ratio number that was about equal to the square root
of 2 to eliminate harmonics that could have resulted in reversed
torque pulses reflecting back into the engine. By using a reduction
ratio of 1.41 (or close to it) he eliminated many sympathetic
harmonics that may have occured.

What, in order to have the ratio between the two be an irrational number?
That's not actually going to help eliminate resonances, unless you get
lucky -- and you are about equally likely to get lucky with any number of
about the same size, irrational or not.



--
Norman Yarvin http://yarchive.net

Just out of curiosity, how would you get any ratio to be an irrational
number?

Tim Ward

There is another word I don't recall. Basically, the idea is to even out
the wear in the gearbox--especially if it is a spur gear system--to give
dramatically longer life to the psru.

Peter

"Peter Dohm" -KNOW wrote in message
-KNOW...
Tim Ward wrote:

"Norman Yarvin" wrote in message
...
In article ,
Badwater Bill wrote:

When I was the test pilot on the OMABP RV-6A project, we used the
Chevy Vortec V-6 engine, the PSRU was specifically designed to turn
the prop at tip speed below 80% the speed of sound. Jess Meyers also
used a reduction ratio number that was about equal to the square root
of 2 to eliminate harmonics that could have resulted in reversed
torque pulses reflecting back into the engine. By using a reduction
ratio of 1.41 (or close to it) he eliminated many sympathetic
harmonics that may have occured.

What, in order to have the ratio between the two be an irrational
number?
That's not actually going to help eliminate resonances, unless you get
lucky -- and you are about equally likely to get lucky with any number
of
about the same size, irrational or not.



--
Norman Yarvin http://yarchive.net

Just out of curiosity, how would you get any ratio to be an irrational
number?

Tim Ward

There is another word I don't recall. Basically, the idea is to even out
the wear in the gearbox--especially if it is a spur gear system--to give
dramatically longer life to the psru.

Peter

I can see how having the numerator and denominator of the ratio relatively
prime might be a benefit. Then the same configuration would only turn up
once every product of the two numbers revolutions.
That's kind of a convoluted sentence, but I don't know how else to put it.

Tim Ward

Tim Ward wrote:

"Peter Dohm" -KNOW wrote in message
-KNOW...
Tim Ward wrote:

"Norman Yarvin" wrote in message
...
In article ,
Badwater Bill wrote:

When I was the test pilot on the OMABP RV-6A project, we used the
Chevy Vortec V-6 engine, the PSRU was specifically designed to turn
the prop at tip speed below 80% the speed of sound. Jess Meyers also
used a reduction ratio number that was about equal to the square root
of 2 to eliminate harmonics that could have resulted in reversed
torque pulses reflecting back into the engine. By using a reduction
ratio of 1.41 (or close to it) he eliminated many sympathetic
harmonics that may have occured.

What, in order to have the ratio between the two be an irrational
number?
That's not actually going to help eliminate resonances, unless you get
lucky -- and you are about equally likely to get lucky with any number
of
about the same size, irrational or not.



--
Norman Yarvin http://yarchive.net

Just out of curiosity, how would you get any ratio to be an irrational
number?

Tim Ward

There is another word I don't recall. Basically, the idea is to even out
the wear in the gearbox--especially if it is a spur gear system--to give
dramatically longer life to the psru.

Peter

I can see how having the numerator and denominator of the ratio relatively
prime might be a benefit. Then the same configuration would only turn up
once every product of the two numbers revolutions.
That's kind of a convoluted sentence, but I don't know how else to put it.

Tim Ward

You are exactly right. The remaining problem with spur gear reduction units is
that the same portions of the crankshaft pulley will always take the power
pulses--unless there is also a clutch, fluid coupling, etc. Therefore,
planetary or epicyclic drives are usually preferred unless an offset is also
needed.

Supposedly, the problems are mitigated by a hi-vo chain drive for engines of six
or more cylinders, or by a cog belt drive. Both have the advantage of spanning
approximately half of the teeth on each pulley. Unfortunately, I doubt that
some of the belt drive designers know much more than I do.

At the moment, the Geshwender drive (which is back in production despite Mr G's
death) looks like the most reliable scheme for much more than 100 horsepower,
any may still be the best value in the long run.