Today's Message Index:
----------------------
1. 12:03 AM - Re: Just a bit nippy... (Larry Bourne)
2. 12:08 AM - Fuel Tank (Larry Bourne)
3. 06:32 AM - Re: 110% duty cycle? (Richard Pike)
4. 07:08 AM - Re: Kolb-List Digest: 24 Msgs - 01/26/03 (William George)
5. 08:10 AM - Re: 110% duty cycle? (Jack & Louise Hart)
6. 08:14 AM - Re: 110% duty cycle? (John Hauck)
7. 08:44 AM - Re: 110% duty cycle? (Jack Carillon)
8. 09:41 AM - Dallas Shephards crash (Kirk Smith)
9. 09:42 AM - Re: Fuel Tank (CaptainRon)
10. 09:42 AM - Re: 110% duty cycle? (Jack & Louise Hart)
11. 09:49 AM - Re: BMEP's, RPM's, prop loading, etcetera (dixieshack@webtv.net (Mike and Dixie Shackelford))
12. 10:00 AM - Re: 110% duty cycle? (Richard Pike)
13. 10:04 AM - Re: 110% duty cycle? (Bruce McElhoe)
14. 10:06 AM - Re: 110% duty cycle? (CaptainRon)
15. 10:15 AM - Re: 110% duty cycle? (Jack & Louise Hart)
16. 12:28 PM - Re: Fuel Tank (Larry Bourne)
17. 02:49 PM - Re: 110% duty cycle? (John Hauck)
18. 03:00 PM - Prop Pitch (John Hauck)
19. 03:47 PM - Re: Fuselage tube / wing brace alignment (ZepRep251@aol.com)
20. 05:09 PM - Re: 110% duty cycle? (Don Gherardini)
21. 05:58 PM - Re:over pitching (Bill Vincent)
22. 08:12 PM - Essay-Monument Valley (Andrew Gassmann)
23. 08:39 PM - Re: 110% duty cycle? (GeoR38@aol.com)
Message 1
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| Subject: | Re: Just a bit nippy... |
--> Kolb-List message posted by: "Larry Bourne" <biglar@gogittum.com>
Good for you, Steve. I can see where George could become needed therapy
for jaded builders. (And what a great area for flying. Did you see
antelope ??) That ride was definitely a factor in jump-starting the ol'
Lar into getting moving again. GoGittin' Lar. Do
not Archive.
Larry Bourne
Palm Springs, CA
Kolb Mk III - Vamoose
www.gogittum.com
----- Original Message -----
From: "abbygirlk9" <abbygirlk9@netzero.net>
Subject: Kolb-List: Just a bit nippy...
> --> Kolb-List message posted by: "abbygirlk9" <abbygirlk9@netzero.net>
>
>
> Hey list, I wanted to write & encourage you builders out there especially
if you need a shot in the arm to keep plugging away with that Kolb project.
A few months back Big Lar reported taking a ride with George Thompson in his
Firestar II and scouting the area north of Prescott, AZ looking for
critters and such. Well I did the same last Saturday and it was a needed
infusion to remind me of why I was making a career out of building a plane
and a trailer to put it in.....it was great to finally take a hop in the
same plane that I have been constructing for the past 2 years. After
reading Big Lar's post about his hop (and seeing the pictures) I decided to
ask George for the same .....yaa, what a cool ride (actually about 35
degrees) in very calm & clear air. George's FS II was rock stable and flew
hands off, now that's what I want! The point of course is that sometimes a
person needs more than just reading the list for a boost - - get a ride and
experience the Kolb, and !
> for some it may be for the first time.
>
>
> Stephen Feldmann
>
> Glendale, AZ
>
> Firestar II 400+ hours in construction so far
>
> Firestar II custom trailer nearly done after 6 months
>
>
Message 2
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--> Kolb-List message posted by: "Larry Bourne" <biglar@gogittum.com>
A couple of weeks ago, I promised to send some pics of my fuel tank installation
to a List member. Now, I can't find the message. Sorry for my bad memory,
but Who Did I Promise ??? Confuzzled Lar. Do not
Archive.
Larry Bourne
Palm Springs, CA
Kolb Mk III - Vamoose
www.gogittum.com
Message 3
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| Subject: | Re: 110% duty cycle? |
--> Kolb-List message posted by: Richard Pike <rwpike@charter.net>
At 11:03 PM 1/26/03 -0700, you wrote:
>--> Kolb-List message posted by: "CaptainRon" <captainron@theriver.com>
>
> Now if I am told that you climb at 5800 and you level off at 5800
>and you still have a rise in egt *all else remains constant*, then its just
>magic. (and I don't believe in magic) :-)
Not magic at all, but I would question the validity of the situation
remaining constant.
Let's say you are climbing at full throttle at 5800, the main jet is
dumping in lots of fuel and the egt is normal.
Then you level off, -and at this point, all else cannot remain constant,
because if you want to stay at 5800, then you must retard the throttle, or
you will exceed 5800.
So you retard the throttle, the load on the prop goes down because you have
quit climbing, you are now running on a combination of main jet and needle
jet/jet needle, and depending on what combination of those you have, and
what notch the clip is in, your egt's can go up or down.
Compare this scenario to John H's situation of flying at a constant rpm,
raise the nose and watch the egt's fall, lower the nose and watch them
rise. (But the tach will also fall and rise as the prop load changes, so
that is not truly a constant either.)
However, if you are climbing at 5800, and then lower the nose without
touching the throttle, the rpm's will rise, the engine will unload, and the
egt's will rise also, but the situation has not remained constant because
the rpm's have risen. The egt's rise because rpm's have gone up -with an
associated increase in airflow- without a change in fuel flow.
(Despite any claims to the contrary, I have yet to see a light plane prop
for our size aircraft that was truly constant speed. The rpm's always
change with load)
Richard Pike
MKIII N420P (420ldPoops)
Do Not Archive
Message 4
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| Subject: | Re: Kolb-List Digest: 24 Msgs - 01/26/03 |
--> Kolb-List message posted by: William George <wgeorge@mountainmeadowranch.com>
Many thanks for your excellent info on duty cycle/longevity of engines in
various applications. Great stuff!
do not archive
Bill George
FOR SALE: Kolb Mk-3/Verner1400SVS/Powerfin 68" "F"
> From: Kolb-List Digest Server <kolb-list-digest@matronics.com>
> Reply-To: kolb-list@matronics.com
> Date: Sun, 26 Jan 2003 23:56:08 -0800
> To: Kolb-List Digest List <kolb-list-digest@matronics.com>
> Subject: Kolb-List Digest: 24 Msgs - 01/26/03
>
> Here are some pretty normal design parameters for IC engines in our world.
> Automotive(Car)....25%to 35% duty cycle will give the manufacturer a
> lifetime that will equal current warranty periods for the average target
> market. Your car will run....lets say, 100 mph flat out. The engine is at
> 100% duty cycle if it is approaching max rpms at that speed. If you ran it
> at that speed all the time, it wont last the 5 years or 50,000 miles that
> the manufacturer warranties it for...not by a long way. Remember how long
> that car lasted that 18 year old All- American lead footed boy? ( anybody
> remember him?..hehe!)
Message 5
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| Subject: | Re: 110% duty cycle? |
--> Kolb-List message posted by: Jack & Louise Hart <jbhart@ldd.net>
At 09:28 AM 1/27/03 -0500, you wrote:
>--> Kolb-List message posted by: Richard Pike <rwpike@charter.net>
>So you retard the throttle, the load on the prop goes down because you have
>quit climbing, you are now running on a combination of main jet and needle
>jet/jet needle, and depending on what combination of those you have, and
>what notch the clip is in, your egt's can go up or down.
>
Richard,
If you are basing this on a Rotax 2-cycle engine I do not believe "you are now
running on a combination of main jet and needle jet/jet needle" is correct for
5800 rpm. Such a statement assumes that the carburetor is sized correctly for
the engine and that when the engine is operating at top speed the throttle is
close to or wide open.
Earlier, I bought into the "how it works" Bing explanation, but then one day I
asked my self, "Why is the 447 reaching top rpm and the throttle is not close
to being wide open. That is when I made my throttle position indicator. What
I found out is that the Bing 54 carb was greatly oversized for the engine. In
my case, the 447 was running at max speed at 40% open throttle with acceptable
EGTs. This means that main jet has little to no effect in controlling engine
speed. To open the throttle further, will raise the needle and richen the
fuel mixture, and this will lower EGTs.
But if you tune for acceptable EGTs at WOT, the reverse will happen. The carburetor
is oversized, the main jet is ineffective, and so you have artificially
lowered the needle at WOT to get acceptable EGTs. After climb out you start to
reduce the throttle. In my case one has to move from 100% to less than 40%
before there is any change in the rpm. But the needle has dropped 60% with out
an rpm change and in doing so, leans out the air/fuel mixture. As result, the
EGT's float up at an alarming rate. To recover and prevent overheating, one
has two options. One can close the throttle to the 20% region to let the throttle
valve cutaway portion take over, or to advance the throttle again.
The only way out of this dilemma, is to tune for good/desired EGTs with the throttle
opened to the minimum position where engine rpm tops out at the desired
prop limited rpm. Then when the throttle position is reduced the air and fuel
are both reduced and EGT's remain stable if the needle has the correct taper.
Again, I refer you to:
http://www.thirdshift.com/jack/firefly/firefly58b.html
One must remember the Bing chart is only true if the engine and carburetor sizes
are perfectly matched. This is not the case. Therefore, one must think in
the reality of how the engine will operate if an over sized carburetor is installed.
Jack B. Hart FF004
Jackson, MO
Jack & Louise Hart
jbhart@ldd.net
Message 6
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| Subject: | Re: 110% duty cycle? |
--> Kolb-List message posted by: John Hauck <jhauck@sw.rr.com>
> Why egt's go up
> after you level off, is strange and I cannot off hand see the reason for it
> except if when you level off unloading the prop you also increase your rpm.
> Now if I am told that you climb at 5800 and you level off at 5800
> and you still have a rise in egt *all else remains constant*, then its just
> magic. (and I don't believe in magic) :-)
Ron/Gang:
Lotta magic in two smokes.
I am not an engineer. Discovered what little I
know about two smokes by using and experimenting
with them. Did a lot of flying back in the early
days of ultralighting. Much more than I do
today. Back when every flight was a test flight.
Discovered that loading and unloading the prop on
a two stroke changed EGT while playing around with
the Ultrastar. Finally, tied that in with
different pitch settings. We did not have the
convenience of ground adjustable props in those
days. Had to decide on the prop to use, usually a
two blade fixed pitch wooden prop. If it was
wrong, too much pitch, we could trim the tips to
unload it. If it was too light, we had to save
our pennies and buy another prop. Balancing props
was a contant. They never stayed balanced,
especially if you flew a lot of cross countries
and the airplane sat in the open.
Two and four stroke engines are two completely
different animals. Can not treat them the same
and they do not perform and react the same way.
Once you think you understand the two stroke, it
will do something else to get your attention.
Sorta like a piss ant kid that won't behave.
The 912S has proven to be an engine that has been
easy to get along with. Just turned 401 hours on
it yesterday afternoon. It is predictable and has
never required any carb jetting or needle
changes. I did not have an EGT with the previous
912 (1135 hrs) or this engine. Carbs are as they
left the factory with minor idle mixture changes
and synchronization. Has performed well from
extremely high temps to well below freezing and
from below sea level to 13,500 feet above.
However, I had the advantage of experience and
problems with the 912 to prevent the same problems
with the 912S. Both engines like to run warm.
Cylinder head temps at least 180F. It is
mandatory to keep the engine oil at or above 190F
in order to burn off condensation and solvents in
the oil system. During my first flight to Alaska
I encountered temps in the 40s and 50s in British
Columbia for the first time. Not knowing much
about the 912 I had a hard time determinining what
all my problems were. They were engine heat/cold
related, but I was getting indications that it was
fuel mixture related. Spark plugs were black as
soot. The following winter in Alabama, where I
could experiment more comfortably in the comfort
of my own AO (area of operation), I fould that
bringing cyl head temps up to at leat 180F and
raising the fuel needles one notch would solve my
midrange cruise power problems.
The four stroke does not care if the prop is
loaded or not. The two stroke does. Since fuel
plays a large part in cooling both the air and
liquid cooled two stroke, she is normally happy
until she gets really rich, then usually shuts
down. How do I know this? Had a main jet mixture
control on the Cuyuna ULII02. If it was set a
hair overrich it would should down as soon as the
engine got to a good operating temp or about 100
feet AGL. The four stroke will keep trying to run
even when she is bogging down in an over rich
condition.
Lean out the two stroke and she will put out a lot
more power, but shortly will burn a hole in the
top of the piston or sieze. Amazing how much
power they put out just prior to seizure.
Two strokes should be flown WOT on take off. WOT
the engine is running entirely on the main jet.
Need extra fuel to help cool it. After reaching
cruise altitude, come back on the power into a
very lean condition. The engine is now running on
the needle and needle jet. If everything is just
right there will be a big temperature spike when
the throttle is retarded to cruise power. That is
when my 582 seized, within a second or two of
retarding power. No warning, no nothing. Like I
had an engine brake. I could have probably gotten
around the problem by retarding power more
slowly. I don't really know.
Anyhow, two strokes are good engines. They are
not fuel efficient. They are designed to turn
high rpm. They need a lot of fuel to help cool.
If you fly a lot of hours you can make up the
difference in purchase price over a two stroke by
the fuel, oil, and spark plugs you save with a
four stroke. At over haul time, that is a
different story, but probably come out pretty
close. The 582 would reach 4 TBOs by the time the
912/912S reach one.
If I was a local flyer that did not put many hours
on an ultralight or light plane I would definitely
go with the two stroke.
Not asking anyone to agree or disagree with what I
have shared with you. None of it came out of a
book or off a chart or graph. It came from
everyday playing around with the engines and
airplanes. Doing one thing to see what the result
would be. Making a lot of mistakes, bad
decisions, in order to learn about my hobby. Take
it or leave it.
Ron, I think the reason EGT goes up when unloading
a two stroke is because it breaths better and the
increase in air intake leans out the mixture.
Just the opposite for loading the engine. RPM
slows down, less air injested, mixture is richer.
Nature of the beast.
Just my thoughts and experience. Thinking out
loud again............
john h
Message 7
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| Subject: | Re: 110% duty cycle? |
--> Kolb-List message posted by: Jack Carillon <pcarillonsr@neo.rr.com>
Jack, I seem to remember quite awhile back someone on the list stating
that our engines were originally designed for snowmobiles and watercraft
and turned in the neighborhood of 8000 rpm,s then derated or detuned for
our use and redlined at 6800 rpm. Could this be part of the problem with
throttle settings? Just a thought.
Jack Carillon Firestar II 503
Akron, Ohio -5 this morning Do Not Archive
Jack & Louise Hart wrote:
> --> Kolb-List message posted by: Jack & Louise Hart <jbhart@ldd.net>
>
> At 09:28 AM 1/27/03 -0500, you wrote:
>
>>--> Kolb-List message posted by: Richard Pike <rwpike@charter.net>
>>So you retard the throttle, the load on the prop goes down because you have
>>quit climbing, you are now running on a combination of main jet and needle
>>jet/jet needle, and depending on what combination of those you have, and
>>what notch the clip is in, your egt's can go up or down.
>>
>>
> Richard,
>
> If you are basing this on a Rotax 2-cycle engine I do not believe "you are now
running on a combination of main jet and needle jet/jet needle" is correct for
5800 rpm. Such a statement assumes that the carburetor is sized correctly
for the engine and that when the engine is operating at top speed the throttle
is close to or wide open.
>
> Earlier, I bought into the "how it works" Bing explanation, but then one day
I asked my self, "Why is the 447 reaching top rpm and the throttle is not close
to being wide open. That is when I made my throttle position indicator. What
I found out is that the Bing 54 carb was greatly oversized for the engine.
In my case, the 447 was running at max speed at 40% open throttle with acceptable
EGTs. This means that main jet has little to no effect in controlling engine
speed. To open the throttle further, will raise the needle and richen the
fuel mixture, and this will lower EGTs.
>
> But if you tune for acceptable EGTs at WOT, the reverse will happen. The carburetor
is oversized, the main jet is ineffective, and so you have artificially
lowered the needle at WOT to get acceptable EGTs. After climb out you start
to reduce the throttle. In my case one has to move from 100% to less than 40%
before there is any change in the rpm. But the needle has dropped 60% with
out an rpm change and in doing so, leans out the air/fuel mixture. As result,
the EGT's float up at an alarming rate. To recover and prevent overheating,
one has two options. One can close the throttle to the 20% region to let the
throttle valve cutaway portion take over, or to advance the throttle again.
>
> The only way out of this dilemma, is to tune for good/desired EGTs with the throttle
opened to the minimum position where engine rpm tops out at the desired
prop limited rpm. Then when the throttle position is reduced the air and fuel
are both reduced and EGT's remain stable if the needle has the correct taper.
>
> Again, I refer you to:
>
> http://www.thirdshift.com/jack/firefly/firefly58b.html
>
> One must remember the Bing chart is only true if the engine and carburetor sizes
are perfectly matched. This is not the case. Therefore, one must think in
the reality of how the engine will operate if an over sized carburetor is installed.
>
> Jack B. Hart FF004
> Jackson, MO
>
>
> Jack & Louise Hart
> jbhart@ldd.net
>
>
>
>
>
>
>
>
Message 8
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| Subject: | Dallas Shephards crash |
--> Kolb-List message posted by: "Kirk Smith" <snuffy@usol.com>
Something I had thought appropriate to mention about Dallas Shephards crash but
had forgotten. He had mentioned that the fuel was leaking from the the vents
on his tanks and dripping on him . He also mentioned that he couldn't reach the
master switch and I forgot the reason for that. I think it may have been a blessing
that he couldn't reach it. If the the switch was carrying current the
opening of the switch would have caused a spark to occur between the contacts.
CRS snuffy
Message 9
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--> Kolb-List message posted by: CaptainRon <CaptainRon@theriver.com>
Hi Lar'
I was interested in seeing it.
===============================
Do not archive
> --> Kolb-List message posted by: "Larry Bourne" <biglar@gogittum.com>
>
> A couple of weeks ago, I promised to send some pics of my fuel tank
> installation to a List member. Now, I can't find the message. Sorry for my
> bad memory, but Who Did I Promise ??? Confuzzled Lar.
> Do not Archive.
>
> Larry Bourne
> Palm Springs, CA
> Kolb Mk III - Vamoose
> www.gogittum.com
>
>
Message 10
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| Subject: | Re: 110% duty cycle? |
--> Kolb-List message posted by: Jack & Louise Hart <jbhart@ldd.net>
At 11:43 AM 1/27/03 -0500, you wrote:
>--> Kolb-List message posted by: Jack Carillon <pcarillonsr@neo.rr.com>
>
>Jack, I seem to remember quite awhile back someone on the list stating
>that our engines were originally designed for snowmobiles and watercraft
>and turned in the neighborhood of 8000 rpm,s then derated or detuned for
>our use and redlined at 6800 rpm. Could this be part of the problem with
> throttle settings? Just a thought.
>
>Jack Carillon Firestar II 503
>Akron, Ohio -5 this morning Do Not Archive
>
Jack,
It may have been a determining factor on carburetor size.
There is an interesting web site at:
http://www.macdizzy.com/formulas.htm
that lists equations which describe various desired 2-cycle engine parameters.
One of them is "Carburetor Throttle Bore Diameter"
The equation is as follows:
D = K x SQRT(C x N)
Where D is throttle bore diameter
K is a contant
C is cylinder displacment in liters
N is rpm at peak power
For the Rotax 447
38mm = K x SQRT(.4365 x 8000)
or K = .643
If one reduces the rpm to max rpm Rotax specifies and using the same K value:
D = .643 x SQRT(.4365 x 6800) = 35mm => 5.5% throat area reduction
If one reduces the rpm to the max torque rpm and using the same K value:
D = .643 x SQRT(.4365 x 6000) = 32.9mm => 25.0% throat area reduction
If the equation and calculations are accurate, a 32mm Bing carburetor may work
well on a 447.
Jack B. Hart FF004
Jackson, MO
Jack & Louise Hart
jbhart@ldd.net
Message 11
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| Subject: | Re: BMEP's, RPM's, prop loading, etcetera |
message of Sun, 26 Jan 2003 23:56:08 -0800
--> Kolb-List message posted by: dixieshack@webtv.net (Mike and Dixie Shackelford)
Right on John Hauck!! Common sense and logic prevail!! All goes
back to what Dad taught us when we learned to drive. "Don't lug it,
Boy!!"
"Lugging" means to apply additional fuel at any rpm without
achieving any increase in engine rpm. Just like John's hummin' Cummins.
Try driving around with a manual tranny in fifth gear doing 25
mph....push the go pedal and you'll hear and feel all sorts of
complaints from under the hood. Engine's tryin' to tell ya something.
Try driving the same vehicle on the interstate in second gear at highway
speeds......more complaints from under the hood, BUT in a different
voice.
Instead of begging you to shift down at twenty five, the ol' girl is
screaming at ya to use some common sense and shift up for cryin' out
loud.
We all apply the use and principle's of BMEP's and RPM's and duty
cycles and take advantage of Don's expertise without realizing
it...common sense and logic tells us when we're out of the "happy"
envelope with the engine. Our ears tell us, eyes and seat of the
pants, too.
By setting the prop to bump engine redline at WOT is finding the
right one gear for all around use without over-revving while at WOT or
lugging the engine in cruise. In doing so, we automatically operate in
the manufacturers design envelope.....
Ya just can't deny the benefit of John's having been there and done
that.
Reason for EGT's going up when the nose goes down is the unloading
of the prop, engine speeding up, creating a lean mix which burns hotter.
Logic. Thanks, John
Mike
do not archive
Message 12
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| Subject: | Re: 110% duty cycle? |
--> Kolb-List message posted by: Richard Pike <rwpike@charter.net>
Jack, I admire your web page, your ingenuity and your persistence, but I
think that in a couple areas you have drawn the wrong conclusions from your
data. Let me address each of them below in the appropriate paragraph:
At 10:06 AM 1/27/03 -0600, you wrote:
>--> Kolb-List message posted by: Jack & Louise Hart <jbhart@ldd.net>
>
>At 09:28 AM 1/27/03 -0500, you wrote:
> >--> Kolb-List message posted by: Richard Pike <rwpike@charter.net>
> >So you retard the throttle, the load on the prop goes down because you have
> >quit climbing, you are now running on a combination of main jet and needle
> >jet/jet needle, and depending on what combination of those you have, and
> >what notch the clip is in, your egt's can go up or down.
> >
>Richard,
>
>If you are basing this on a Rotax 2-cycle engine I do not believe "you are
>now running on a combination of main jet and needle jet/jet needle" is
>correct for 5800 rpm. Such a statement assumes that the carburetor is
>sized correctly for the engine and that when the engine is operating at
>top speed the throttle is close to or wide open.
>
>Earlier, I bought into the "how it works" Bing explanation, but then one
>day I asked my self, "Why is the 447 reaching top rpm and the throttle is
>not close to being wide open. That is when I made my throttle position
>indicator. What I found out is that the Bing 54 carb was greatly
>oversized for the engine. In my case, the 447 was running at max speed at
>40% open throttle with acceptable EGTs. This means that main jet has
>little to no effect in controlling engine speed. To open the throttle
>further, will raise the needle and richen the fuel mixture, and this will
>lower EGTs.
Yes and no. The Rotax 277 uses the same carb as the 447, and the 447 can
even be purchased with dual carbs (Both are a bit smaller than the Bing
54's however) and the 277 ran very nicely with the Bing 54, but it behaved
much as you describe, but the factory overpropped it, the Hummer was only
designed for 22 horsepower, and the 277 was too much engine. (Boy does that
sound wierd!) So they overloaded it so it would not make it's rated horsepower.
The 277 on my Hummer was propped from the factory to only turn 6000 rpm,
and it responded just as you say, changing the main jet had less effect
than changing the needle jet and jet needle, and the Bing 54 is probably
too big for the 277 when it is loaded down to only turn 6000, just as the
Bing 54 is probably too big for the 447 when it is loaded down to turn only
5600 rpm, as you indicated on your web page, you had it propped to only
turn 5600 prior to your changing to the Simonini.
But the problem is not the size of the carb, it is the excessive engine
load caused by the prop not allowing the engine to turn up.
Years ago I used to have a Suzuki 500 2-stroke twin. If I remember right,
it was turning about 6500 rpm at around 105 mph, and it would (on a good
day) hit 105 mph with both me and the Good Lookin' (much younger) Ol' Poop
on it. But if you were on a slight uphill and in top gear at about 30 miles
per hour and you wrapped the throttle around to the stop, it would just
moan like a dying cow and not go a bit faster. Were the carbs too big? No,
the load was too big at the rpm the load was applied. Kick it down two
gears (change the load factor) and it would jump right up.
That is exactly what we do when we over prop our 2 stroke aircraft engines.
>But if you tune for acceptable EGTs at WOT, the reverse will happen. The
>carburetor is oversized, the main jet is ineffective, and so you have
>artificially lowered the needle at WOT to get acceptable EGTs. After
>climb out you start to reduce the throttle. In my case one has to move
>from 100% to less than 40% before there is any change in the rpm. But the
>needle has dropped 60% with out an rpm change and in doing so, leans out
>the air/fuel mixture. As result, the EGT's float up at an alarming
>rate. To recover and prevent overheating, one has two options. One can
>close the throttle to the 20% region to let the throttle valve cutaway
>portion take over, or to advance the throttle again.
The reason that you get wildly abnormal egt's is because the engine is
artificially loaded down into a region where it is not normally intended to
run, and the carburation is trying to do something it cannot. I suspect
that the reason that most of us are not experiencing the alarming float up
of egt's (I know I'm not) is because the engine is propped normally.
As far as controlling the egt's at partial throttle positions, that is why
Bing sells needles with different cutaway shapes, and I have found that
playing with different shaped needles gives very good results to get the
egt's right where I want them at all throttle settings from partial
throttle on up.
>The only way out of this dilemma, is to tune for good/desired EGTs with
>the throttle opened to the minimum position where engine rpm tops out at
>the desired prop limited rpm. Then when the throttle position is reduced
>the air and fuel are both reduced and EGT's remain stable if the needle
>has the correct taper.
>
>Again, I refer you to:
>
>http://www.thirdshift.com/jack/firefly/firefly58b.html
>
>One must remember the Bing chart is only true if the engine and carburetor
>sizes are perfectly matched. This is not the case. Therefore, one must
>think in the reality of how the engine will operate if an over sized
>carburetor is installed.
>
>Jack B. Hart FF004
>Jackson, MO
>
>
>Jack & Louise Hart
>jbhart@ldd.net
And I would counter with the opinion that the Bing chart is true if the
engine and load are matched. If you radically change the load, and the
point where the load overcomes the engines ability to pull it, then you are
on our own.
But one thing is certain: you are truly an experimenter, please continue to
keep us posted on your efforts, you are demonstrating how to obtain
satisfactory results in areas that most of us don't normally go. (And none
of us can dispute success, even if we might argue as to why it is successful)
Richard Pike
MKIII N420P (420ldPoops)
Do Not Archive
Message 13
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| Subject: | Re: 110% duty cycle? |
--> Kolb-List message posted by: "Bruce McElhoe" <mcelhoe@cvip.net>
John,
Just a note to say how much I appreciate your contributions to the Kolb list
....and to my own flying pleasure. Your cross-country adventures lend a lot
of
credibility to your comments.
We recently completed our FireFly, and have about six hours of total time.
There have been some confusing suggestions about setting our prop
pitch.....Your recent comment makes the most sense to me....so, we have set
our prop for red-line rpm at WOT. Our EGTs are in the green in all flight
regimes. Wow!, what great performance we get....we have no desire to "back
off" (as long as we stay within allowable temperatures).
Regards,
Bruce McElhoe FireFly #88
Reedley, Calif.
>
> The Rotax engines are set up at the factory to be
> propped to bump the red line, WOT straight and
> level flight. They are jetted for this profile.
> The prop must be pitched to match the profile.
> If the engine is pitched correctly, there is no
> need to play swapping games with jets, spark plugs
> or anything else. In addition, you have the best
> of two worlds with a non-inflight adjustable
> prop: Best climb and cruise.
>
> Carb jetting and profile is also a major factor in
> changing EGT. That is why it is important to
> monitor EGT and stay out of those zones that tend
> to lean out the engine and raise EGT.
>
> Works for me....................
>
> john h
Message 14
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| Subject: | Re: 110% duty cycle? |
--> Kolb-List message posted by: CaptainRon <CaptainRon@theriver.com>
Well I am kinda getting bored with this subject Old Boy.
But I'll make some additional observations, and then off I go to make a
buck.
first I do have some familiarty with 2 cycle motors and in many ways I see
them as a much less complex machine than the 4 cycle version.
See John I have been messing around with those contraptions mostly in the
theoretical part since I was 8 years old. Just say for lack of better stuff
to read. :-)
My hope was that from my last post the understanding would be that the key
to the rise in egt had nothing to do with jets, magic, ballony, or Santa,,
but **everything to do with looking at you tach when you level off**. I
guess next time I should spell it out.
So next time John wheather you are in your Rotax 912 chariot or a lowly 2
cycle one, **do** notice that if you turn level from a climb without
adjusting either your prop or throtle your EGT's **will go higher**. It has
to do with thermo dynamics John, and not the Easter Bunny!
And now I am going to let that castrated old bull alone. :-)
========================================================
1/27/03 9:13John Hauck
> --> Kolb-List message posted by: John Hauck <jhauck@sw.rr.com>
>
>
>> Why egt's go up
>> after you level off, is strange and I cannot off hand see the reason for it
>> except if when you level off unloading the prop you also increase your rpm.
>
>> Now if I am told that you climb at 5800 and you level off at 5800
>> and you still have a rise in egt *all else remains constant*, then its just
>> magic. (and I don't believe in magic) :-)
>
> Ron/Gang:
>
> Lotta magic in two smokes.
>
> I am not an engineer. Discovered what little I
> know about two smokes by using and experimenting
> with them. Did a lot of flying back in the early
> days of ultralighting. Much more than I do
> today. Back when every flight was a test flight.
>
> Discovered that loading and unloading the prop on
> a two stroke changed EGT while playing around with
> the Ultrastar. Finally, tied that in with
> different pitch settings. We did not have the
> convenience of ground adjustable props in those
> days. Had to decide on the prop to use, usually a
> two blade fixed pitch wooden prop. If it was
> wrong, too much pitch, we could trim the tips to
> unload it. If it was too light, we had to save
> our pennies and buy another prop. Balancing props
> was a contant. They never stayed balanced,
> especially if you flew a lot of cross countries
> and the airplane sat in the open.
>
> Two and four stroke engines are two completely
> different animals. Can not treat them the same
> and they do not perform and react the same way.
> Once you think you understand the two stroke, it
> will do something else to get your attention.
> Sorta like a piss ant kid that won't behave.
>
> The 912S has proven to be an engine that has been
> easy to get along with. Just turned 401 hours on
> it yesterday afternoon. It is predictable and has
> never required any carb jetting or needle
> changes. I did not have an EGT with the previous
> 912 (1135 hrs) or this engine. Carbs are as they
> left the factory with minor idle mixture changes
> and synchronization. Has performed well from
> extremely high temps to well below freezing and
> from below sea level to 13,500 feet above.
>
> However, I had the advantage of experience and
> problems with the 912 to prevent the same problems
> with the 912S. Both engines like to run warm.
> Cylinder head temps at least 180F. It is
> mandatory to keep the engine oil at or above 190F
> in order to burn off condensation and solvents in
> the oil system. During my first flight to Alaska
> I encountered temps in the 40s and 50s in British
> Columbia for the first time. Not knowing much
> about the 912 I had a hard time determinining what
> all my problems were. They were engine heat/cold
> related, but I was getting indications that it was
> fuel mixture related. Spark plugs were black as
> soot. The following winter in Alabama, where I
> could experiment more comfortably in the comfort
> of my own AO (area of operation), I fould that
> bringing cyl head temps up to at leat 180F and
> raising the fuel needles one notch would solve my
> midrange cruise power problems.
>
> The four stroke does not care if the prop is
> loaded or not. The two stroke does. Since fuel
> plays a large part in cooling both the air and
> liquid cooled two stroke, she is normally happy
> until she gets really rich, then usually shuts
> down. How do I know this? Had a main jet mixture
> control on the Cuyuna ULII02. If it was set a
> hair overrich it would should down as soon as the
> engine got to a good operating temp or about 100
> feet AGL. The four stroke will keep trying to run
> even when she is bogging down in an over rich
> condition.
>
> Lean out the two stroke and she will put out a lot
> more power, but shortly will burn a hole in the
> top of the piston or sieze. Amazing how much
> power they put out just prior to seizure.
>
> Two strokes should be flown WOT on take off. WOT
> the engine is running entirely on the main jet.
> Need extra fuel to help cool it. After reaching
> cruise altitude, come back on the power into a
> very lean condition. The engine is now running on
> the needle and needle jet. If everything is just
> right there will be a big temperature spike when
> the throttle is retarded to cruise power. That is
> when my 582 seized, within a second or two of
> retarding power. No warning, no nothing. Like I
> had an engine brake. I could have probably gotten
> around the problem by retarding power more
> slowly. I don't really know.
>
> Anyhow, two strokes are good engines. They are
> not fuel efficient. They are designed to turn
> high rpm. They need a lot of fuel to help cool.
>
> If you fly a lot of hours you can make up the
> difference in purchase price over a two stroke by
> the fuel, oil, and spark plugs you save with a
> four stroke. At over haul time, that is a
> different story, but probably come out pretty
> close. The 582 would reach 4 TBOs by the time the
> 912/912S reach one.
>
> If I was a local flyer that did not put many hours
> on an ultralight or light plane I would definitely
> go with the two stroke.
>
> Not asking anyone to agree or disagree with what I
> have shared with you. None of it came out of a
> book or off a chart or graph. It came from
> everyday playing around with the engines and
> airplanes. Doing one thing to see what the result
> would be. Making a lot of mistakes, bad
> decisions, in order to learn about my hobby. Take
> it or leave it.
>
> Ron, I think the reason EGT goes up when unloading
> a two stroke is because it breaths better and the
> increase in air intake leans out the mixture.
> Just the opposite for loading the engine. RPM
> slows down, less air injested, mixture is richer.
> Nature of the beast.
>
> Just my thoughts and experience. Thinking out
> loud again............
>
> john h
>
>
>
>
>
>
Message 15
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| Subject: | Re: 110% duty cycle? |
--> Kolb-List message posted by: Jack & Louise Hart <jbhart@ldd.net>
>
>But one thing is certain: you are truly an experimenter, please continue to
>keep us posted on your efforts, you are demonstrating how to obtain
>satisfactory results in areas that most of us don't normally go. (And none
>of us can dispute success, even if we might argue as to why it is successful)
>
>Richard Pike
>MKIII N420P (420ldPoops)
>
>Do Not Archive
>
Richard,
It is fun to have a good conversation.
Jack B. Hart FF004
Jackson, MO
Jack & Louise Hart
jbhart@ldd.net
Message 16
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--> Kolb-List message posted by: "Larry Bourne" <biglar@gogittum.com>
OK, Ron. The plane's up in the high desert now, and I won't be up there
till the weekend. I'll take the pics then. Lar.
Larry Bourne
Palm Springs, CA
Kolb Mk III - Vamoose
www.gogittum.com
----- Original Message -----
From: "CaptainRon" <CaptainRon@theriver.com>
Subject: Re: Kolb-List: Fuel Tank
> --> Kolb-List message posted by: CaptainRon <CaptainRon@theriver.com>
>
> Hi Lar'
>
> I was interested in seeing it.
>
> ===============================
>
> Do not archive
>
> > --> Kolb-List message posted by: "Larry Bourne" <biglar@gogittum.com>
> >
> > A couple of weeks ago, I promised to send some pics of my fuel tank
> > installation to a List member. Now, I can't find the message. Sorry
for my
> > bad memory, but Who Did I Promise ??? Confuzzled Lar.
> > Do not Archive.
> >
> > Larry Bourne
> > Palm Springs, CA
> > Kolb Mk III - Vamoose
> > www.gogittum.com
> >
> >
>
>
Message 17
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| Subject: | Re: 110% duty cycle? |
--> Kolb-List message posted by: John Hauck <jhauck@sw.rr.com>
> Jack, I seem to remember quite awhile back someone on the list stating
> that our engines were originally designed for snowmobiles and watercraft
> and turned in the neighborhood of 8000 rpm,s then derated or detuned for
> our use and redlined at 6800 rpm. Could this be part of the problem with
> throttle settings? Just a thought.
>
> Jack Carillon Firestar II 503
Jack C/Gang:
I realize you addressed your comment to Jack Hart,
but I would like to also reply to it.
True, our two stroke engines evolved from hobbies
other than flying. But that has been many years
ago. I am thinking about cleaning out 20 years
worth of aviation mags that I have collected since
I got started in civilian aviation, primarily
ultralights. In those stacks of mags somewhere is
an article about Eric Tucker, Big Daddy of Rotax.
IIRC it was when he was in the process of
configuring Rotax snow machine engines for use in
ultralights. Probably 1983 or 84. These engines
were not only derated from a much higher HP
application, but also engineered to work in a
continuous duty environment with a prop hung on
the end of it.
They have come a long way since then. But one
thing has not changed since the last time I flew a
two stroke. That is where the engine comes up on
the pipe. In the area of 5,200 to 5,500 rpm. Two
strokes don't have valves and camshafts like four
strokes. They rely on other methods to get the
job done. We have straight piston port engines
like the 447 and 503. Intake and exhaust timing
is controlled by the position of the ports in the
cylinder. We have rotary valve and piston port
timing in the 532 and 582, and we have reed valves
in conjunction with piston port timing in the
engine that Jack Hart is experimenting with. On
top of that, the exhaust system is used to enhance
performance, which is usually in a much narrower
band in the two stroke, than the four stroke. In
a 447 you can feel it "come on the pipe" at
5,200-5,500 rpm. From there to 6,500 rpm is the
power band. It is where it wants to run. I doubt
we get any more power out of it after 6,500 to the
6,800 red line. That's why I came back yesterday
and recommended pitching for 6,500 instead of
6,800. That's it gents. That is where the Rotax
engineers tuned all their two strokes to perform,
after it comes up on the pipe. Before it comes up
on the pipe it is not getting much benefit out of
the exhaust system/expansion chamber or its
piston/ports and valves (if it has them). It was
not designed to. It is the nature of the engine.
When the engine is propped and operated as the
engineers intended it to be operated, there is no
problem with EGT, fouled plugs, or lack of power
and longevity. When we try to re-engineer the two
strokes to make them do what they were not
designed to do, we get into a grey area where only
true adventurist (dare devils???) should roam.
Screw with the way they were designed to operate
and they will come back in an instant to bite you,
usually with little or no warning.
The beauty of the two stroke is instant overhaul.
Can do one in a day.
If they went to nicoseal or some other coated
cylinder instead of the cast iron liner, might
make for a better engine. We just had a 4 stroke
thumper cylinder recoated at Langcourt in Auburn,
AL. This is part of a company out of Great
Britain. Cost to bring the cylinder back to new
specs was $149.95. That process would take care
of scored cylinders caused by stuck rings and
seizures. If the damage got worse than that, they
can weld them up, then recoat. Do beautiful work.
Again folks, these are my own ideas, thoughts, as
they come spewing forth after two trips to the big
city of Montgomery today and a pot of coffee.
Take what you want and leave the rest. If it
bores you, hit the delete key. If you are that
smart and been around that long, I probably don't
have much to offer you anyhow.
john h
Message 18
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--> Kolb-List message posted by: John Hauck <jhauck@sw.rr.com>
> We recently completed our FireFly, and have about six hours of total time.
> There have been some confusing suggestions about setting our prop
> pitch.....Your recent comment makes the most sense to me....so, we have set
> our prop for red-line rpm at WOT. Our EGTs are in the green in all flight
> regimes. Wow!, what great performance we get....we have no desire to "back
> off" (as long as we stay within allowable temperatures).
>
> Regards,
>
> Bruce McElhoe FireFly #88
> Reedley, Calif.
Bruce/Gang:
Congratulations on your new bird.
Wow! Ain't it amazing how well they perform. I
love to fly the Fire Fly. To me, it is a Sling
Shot slightly scaled down. Feels and flies about
the same. A real hot rod.
Thanks for the kind words.
Take care,
john h
DO NOT ARCHIVE
Message 19
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| Subject: | Re: Fuselage tube / wing brace alignment |
--> Kolb-List message posted by: ZepRep251@aol.com
Ed, they sent me Firefly inner wing rib for one sideof my firestar.Big
difference so far as drag strut alignment goes.You might check for that.
Message 20
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| Subject: | Re: 110% duty cycle? |
--> Kolb-List message posted by: "Don Gherardini" <donghe@one-eleven.net>
Jack C....I dont know about the rest of the engines...but I have an old
Snowmobile out in the barn with a dual carb point ignition 503 in it. Still
runs jus fine too...tach shows redline of 6500. I also used to have a 440
scorpion with a Cayuna in it, and it also was a 6500rpm redline on the tach.
Don
Message 21
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| Subject: | re:over pitching |
--> Kolb-List message posted by: Bill Vincent <emailbill@chartermi.net>
John, I agree with you.
A few years ago at the Oshkosh EAA, I spoke to Ivo Zdarsky about his
then fairly new in-flight adjustable prop.
Ivo told me it was working out very good but ... he said he was having
trouble with people who would over pitch the prop on their 2 cycles to
try and get more speed; causing the plugs and engine to carbon up
extensively.
Bill Vincent
Firestar II
Quinnesec, Upper Peninsula of Michigan
DO NOT ARCHIVE
Worst thing in the world for an engine is to
hammer it down, i.e., overpitch.
The above applies to gasoline as well as Diesel
engines. I used to think Diesels liked to get
lugged down until they stalled, but found out they
are just like most other engines. They have an
operational rpm they like to operate in and it is
not below their max torque producing rpm.
Message 22
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| Subject: | Essay-Monument Valley |
--> Kolb-List message posted by: Andrew Gassmann <a1929gassmann@earthlink.net>
Group,
found this:
http://midamerican.homestead.com/BruceStory.html
Good photo essay of your proposed trip to the same location.
Andy
Do not archive
Message 23
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| Subject: | Re: 110% duty cycle? |
--> Kolb-List message posted by: GeoR38@aol.com
In a message dated 1/27/03 9:33:37 AM Eastern Standard Time,
rwpike@charter.net writes:
>
> However, if you are climbing at 5800, and then lower the nose without
> touching the throttle, the rpm's will rise, the engine will unload, and the
>
> egt's will rise also, but the situation has not remained constant because
> the rpm's have risen. The egt's rise because rpm's have gone up -with an
> associated increase in airflow- without a change in fuel flow.
> (Despite any claims to the contrary, I have yet to see a light plane prop
> for our size aircraft that was truly constant speed. The rpm's always
> change with load)
>
> Richard Pike
> MKIII N420P (420ldPoops)
>
But you didn't say the punchline Richard...namely that the increase in
airflow with no increase in fuel flow constitutes leaner mixture. The only
thing that blows my mind is ....why can you say that the fuel flow has
remained the same....doesn't the carburator automatically keep the mixture
the same? I thought that was the function of it.
George Randolph
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