Diesel engine

wrote:

I'm getting set to do the ground runs on my engine and intend to run
it throughout the summer at high power settings. I don't understand
people who just bolt an engine, any engine, to the airframe and then
try to go flying without any test runs.

Corky Scott

And don't just run it on the ground. You've got to instrument that
baby. Get a bunch of temperature probes and stick one to everything you
can. Add a handful of accelerometers to measure vibration at multiple
points if you can get your hands on them. I've read that the biggest
advances in aviation power during the second world war came about due to
improvements in instrumentation. It makes sense. You won't know what
to strengthen or cool if you don't know what's hot or under harmonic
vibrations.

Someone here mentioned an adjustable strobe light at night to look for
harmonics.


--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

Ernest Christley wrote:

wrote:

I'm getting set to do the ground runs on my engine and intend to run
it throughout the summer at high power settings. I don't understand
people who just bolt an engine, any engine, to the airframe and then
try to go flying without any test runs.

Corky Scott

And don't just run it on the ground. You've got to instrument that
baby. Get a bunch of temperature probes and stick one to everything you
can. Add a handful of accelerometers to measure vibration at multiple
points if you can get your hands on them. I've read that the biggest
advances in aviation power during the second world war came about due to
improvements in instrumentation. It makes sense. You won't know what
to strengthen or cool if you don't know what's hot or under harmonic
vibrations.

Someone here mentioned an adjustable strobe light at night to look for
harmonics.

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber


Good point. Excellent point, in fact.

My engine is a VW. Not a certified aircraft engine.

Quite a bit less then $1,000,000 has been spent on detailed engineering,
testing, analysis, etc to convert this into a safe aircraft engine.

Even though haven't spent much of that million on engineering, I don't
seem to have much left for instrumentation I suspect the coffee
fund).

Accelerometers struck out - cost, complexity, and I wouldn't know what
to do with them anyway.


One thing I would like to instrument is the carburetor temperature.

Not a permenant gauge on the panel (I have one - but there's no space).
Just a low buck way of monitoring the carb temp in flight for a while to
see whazzappenin and see if pulling the carb heat knob is really doing
anything.


The carb is below the engine (KR2 style intakes manifold from GPAS)
where it is not warmed much from engine heat.

One of these days I want to make new exhaust pipes with a proper
carb heat muff.

But for now, I wonder if the air passing thru the cylinder fins would
be hot enough (too hot enough?) to work well - or not?

Only way to know for sure is to measure it.

Isn't there supposed to be a way to do that with a digital multimeter
and thermosistor, or thermocouple (what)?

Richard


PS: thanks for remembering the harmonics thread, Robert. (:it was fun

I remember thinking(back then) that I wanted to take a real good look
a the engine installation on the new plane for harmonic reactions.

I even asked around and found someone who have an old variable speed
disco strobe for the job.

But the engine wasn't ready to run back then, and I forgot about it.
Until now.

Thanks.

Richard

Richard Lamb wrote:


PS: thanks for remembering the harmonics thread, Robert. (:it was fun

I remember thinking(back then) that I wanted to take a real good look
a the engine installation on the new plane for harmonic reactions.

I even asked around and found someone who have an old variable speed
disco strobe for the job.

But the engine wasn't ready to run back then, and I forgot about it.
Until now.

Thanks.

Richard

Radio Shack has a strobe for about $20. It's cheap, and won't even give
an epiletic a fit, but it has variable timing and does flash. You just
won't be able to use it in direct sunlight. Wait 'till evening or find
an old barn?

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

In article , Ernest Christley wrote:
Another strobe that many people have in their shop is an automotive timing
light. You can wind a simple coil of a few dozen turns and put it in the
trigger clip. Then, any convenient signal source such as an audio signal
generator can be used to produce the timing signals.

good luck,
tom pettit



PS: thanks for remembering the harmonics thread, Robert. (:it was fun

I remember thinking(back then) that I wanted to take a real good look
a the engine installation on the new plane for harmonic reactions.

I even asked around and found someone who have an old variable speed
disco strobe for the job.

But the engine wasn't ready to run back then, and I forgot about it.
Until now.

Thanks.

Richard

Radio Shack has a strobe for about $20. It's cheap, and won't even give
an epiletic a fit, but it has variable timing and does flash. You just
won't be able to use it in direct sunlight. Wait 'till evening or find
an old barn?

On Tue, 27 Apr 2004 14:15:28 GMT, wrote:

In article , Ernest Christley wrote:
Another strobe that many people have in their shop is an automotive timing
light. You can wind a simple coil of a few dozen turns and put it in the
trigger clip. Then, any convenient signal source such as an audio signal
generator can be used to produce the timing signals.

good luck,
tom pettit

But what's a fella to do with the flashing light? What are you
checking and what's it all mean?

I mean the engine's going to have this 74" diameter prop on it and
it's bound to vibrate some. How do you tell what's normal and what
isn't?

Corky Scott

On Tue, 27 Apr 2004 wrote:

I mean the engine's going to have this 74" diameter prop on it and
it's bound to vibrate some. How do you tell what's normal and what
isn't?


Burt Rutan says that the prop should turn about 2600 rpm static, and that
also makes a very good cruise rpm. My setup would turn my first prop
over 3000 static, but my good prop only 2400. I use that same number
for my cruise rpm which is 5200 rpm engine speed. I know that it will
run for hours at that speed. No doubt, others will be more sophisticated.

If you do find a resonant rpm, you'll know it right away.

George Graham
RX-7 Powered Graham-EZ, N4449E
Homepage http://bfn.org/~ca266

wrote:
On Tue, 27 Apr 2004 14:15:28 GMT, wrote:


In article , Ernest Christley wrote:
Another strobe that many people have in their shop is an automotive timing
light. You can wind a simple coil of a few dozen turns and put it in the
trigger clip. Then, any convenient signal source such as an audio signal
generator can be used to produce the timing signals.

good luck,
tom pettit


But what's a fella to do with the flashing light? What are you
checking and what's it all mean?

I mean the engine's going to have this 74" diameter prop on it and
it's bound to vibrate some. How do you tell what's normal and what
isn't?

Corky Scott

I like that timing light idea. With my laptop and a simple program I
can have a lot more range than is possible with the RatShack thing I have.

Corky, the strobe will slow down any flexing due to vibrations to the
point where you can clearly see it. Sorta makes it slow motion. I
would say that if you can clearly distinquish the flexing in a motor
mount or other supporting part, then it is way too much, and you should
consider a redesign. It may not tell you anything interesting at all,
it's just an easy way to see what and where the vibration are and how
much they are shaking what. But you are right, just because it's moving
doesn't mean it's coming apart. I'll counter that you can decide what
is normal for yourself once you see it moving, and I'll bet dollars to
donuts that if you do see a lot of movement you'll be an expert on what
is normal before the engine leaves the ground 8*) (Yes, that was a long
winded way of saying, "I don't rightly know.")

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

Ernest Christley wrote:

But what's a fella to do with the flashing light? What are you
checking and what's it all mean?

I mean the engine's going to have this 74" diameter prop on it and
it's bound to vibrate some. How do you tell what's normal and what
isn't?

Corky Scott

I like that timing light idea. With my laptop and a simple program I
can have a lot more range than is possible with the RatShack thing I have.

Corky, the strobe will slow down any flexing due to vibrations to the
point where you can clearly see it. Sorta makes it slow motion. I
would say that if you can clearly distinquish the flexing in a motor
mount or other supporting part, then it is way too much, and you should
consider a redesign. It may not tell you anything interesting at all,
it's just an easy way to see what and where the vibration are and how
much they are shaking what. But you are right, just because it's moving
doesn't mean it's coming apart. I'll counter that you can decide what
is normal for yourself once you see it moving, and I'll bet dollars to
donuts that if you do see a lot of movement you'll be an expert on what
is normal before the engine leaves the ground 8*) (Yes, that was a long
winded way of saying, "I don't rightly know.")

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

"I don't rightly know", either, Earnest, but it's fun to play with.

Right on about the motion, and with the vibration of the engine
running there is visible motion.

A guitar string on a guitar that is waving back and forth will move -
back and forth. But the string is still straight. It is just waving
back and forth with the guitar - way below it's resonant frequency.

When plucked, it "bows". Flexes into a new shape. The string is
resonating at some frequency based on the length, tension, and
the string's physical properties (cross section, material, windings?)

When the moment is frozen with the strobe, you can see the curvature.


So the apparent motion of the engine mount tubes is just normal
vibration.

But if there is detectible curvature or flexing, there is a resonant
response.

The thing about the variable frequency strobe is that it makes it
easy to look at different response frequencies on the test article.

Like the choke cable where it looped around the front of the engine -
unsupported.

Dumb.


Richard

Richard,
Check this out... four K-type thermocouples and readout for $100! I
have had one for a couple years and it gets used every flight. Omega
is a well-respected name in industrial/scientific community.

http://www.omega.com/ppt/pptsc.asp?ref=HH501DK

Sid Knox
Velocity N199RS
Starduster N666SK
KR2 N24TC
W7QJQ


One thing I would like to instrument is the carburetor temperature.

Not a permenant gauge on the panel (I have one - but there's no space).
Just a low buck way of monitoring the carb temp in flight for a while to
see whazzappenin and see if pulling the carb heat knob is really doing
anything.


The carb is below the engine (KR2 style intakes manifold from GPAS)
where it is not warmed much from engine heat.

One of these days I want to make new exhaust pipes with a proper
carb heat muff.

But for now, I wonder if the air passing thru the cylinder fins would
be hot enough (too hot enough?) to work well - or not?

Only way to know for sure is to measure it.

Isn't there supposed to be a way to do that with a digital multimeter
and thermosistor, or thermocouple (what)?

Richard

sidk wrote:

Richard,
Check this out... four K-type thermocouples and readout for $100! I
have had one for a couple years and it gets used every flight. Omega
is a well-respected name in industrial/scientific community.

http://www.omega.com/ppt/pptsc.asp?ref=HH501DK

Sid Knox
Velocity N199RS
Starduster N666SK
KR2 N24TC
W7QJQ

One thing I would like to instrument is the carburetor temperature.

Not a permenant gauge on the panel (I have one - but there's no space).
Just a low buck way of monitoring the carb temp in flight for a while to
see whazzappenin and see if pulling the carb heat knob is really doing
anything.


The carb is below the engine (KR2 style intakes manifold from GPAS)
where it is not warmed much from engine heat.

One of these days I want to make new exhaust pipes with a proper
carb heat muff.

But for now, I wonder if the air passing thru the cylinder fins would
be hot enough (too hot enough?) to work well - or not?

Only way to know for sure is to measure it.

Isn't there supposed to be a way to do that with a digital multimeter
and thermosistor, or thermocouple (what)?

Richard




Thanks Sid, Very intereseting site.
And yes, that puppy just might solve my silly problems...

Richard