Today's Message Index:
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1. 08:10 AM - Re: My Firestar Project Update (Richard Pike)
2. 10:03 AM - Re: My Firestar Project Update (Bill Berle)
3. 08:58 PM - Re: My Firestar Project Update (Richard Pike)
Message 1
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| Subject: | Re: My Firestar Project Update |
Nice looking exhaust. Does it have a flex fitting in it anywhere?
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Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0
Forgiving is tough, being forgiven is wonderful, and Grace really is amazing.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=476841#476841
Message 2
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| Subject: | Re: My Firestar Project Update |
First, before any of this was built, I consulted with a real live aircraft engineer
who is an expert on material stress, metallurgy, etc. None of this was just
me making assumptions or guesses. It is of course completely experimental,
and may need mofidications, but the point is that there were a lot more brain
cells on the job than mine :)
Second, what is shown in the photo is the PARTIALLY completed exhaust, tack-welded
together. There will be another "L shaped" pipe with a 90 degree bend added
at the bottom, and that bend will go into a "Swiss Muffler" of the type described
by Tony Bingelis in his Firewall Forward series of books. The Swiss Muffler
has been proven to work extremely well and provide the least back-pressure/power
loss.
So with that said, yes the exhaust will indeed have a flex fitting at the bottom
betweem the part you see in the photo and the "L bend" section I mentioned.
The exhaust will be mounted solidly to the engine at the top, bolted to the exhaust
flanges on the cylinders, AND welded lugs a few inches away that attach to
bolts on the engine case. Having these two solid attach points near the top
will prevent any twisting or flexing at the exhaust flange.
At the mid-point of the exhaust we will fabricate some sort of a "restraining collar"
mounted to the airframe, that will prevent the two exhaust pipes from moving
rearward toward the propeller. But this collar is not a "solid" mount at
all, it will allow the exhaust pipes to expand, contract, and move slightly side
to side. This side to side movement will be necessary because the engine will
"rock" left and right (parallel to the roll axis of the aircraft).
At the bottom of what is shown in the photo, where the two pipes join, there will
be a short section of pipe that turns rearward underneath the tailboom. That
is where the flex pipe or ball/spring joint will be. At this location the exhaust
pipe will end, and slip-fit into the front end of the muffler .
The muffler will be mounted to the tailboom with some sort of muffler hanger hardware
and rubber blocks. Perhaps I can find some sutomotive hardware that will
work. Perhaps I will have to fabricate some parts. But in general, I plan to
use large diameter aircraft grade (rubber padding) Adel clamps around the tailboom
tube, and similar Adel clamps around the muffler (4 inch diameter), and
then some sort of flexible coupling between them. The intention is for the muffler
to have significant range of movement, so the bottom of the exhaust can swing
back and forth.
"Why the heck didn't he just use the OEM exhaust system that came with the HKS
engine???"
Trust me, I started with that. But it simply would not fit on the Kolb airframe.
The HKS exhaust would prevent the wings from being folded, there was solid interference
between the HKS system and the Kolb aileron torque tubes. The only
way it would fit is if I raised the engine up a few inches higher on spacers.
From reading the Kolb list I learned that it is very well worthwhile to have
the engine thrust line as low as possible. I believe that it will be worth the
effort that this custom exhaust required, because I was able to mount the engine
on 2 inch spacers instead of 4 or 5 inch spacers.
Anyway, sorry for the long message :)
Bill Berle
www.ezflaphandle.com - safety & performance upgrade for light aircraft
www.grantstar.net - winning proposals for non-profit and for-profit entities
--------------------------------------------
On Thu, 12/28/17, Richard Pike <thegreybaron@charter.net> wrote:
Subject: Kolb-List: Re: My Firestar Project Update
To: kolb-list@matronics.com
Date: Thursday, December 28, 2017, 8:10 AM
Pike" <thegreybaron@charter.net>
Nice looking exhaust. Does it have a
flex fitting in it anywhere?
--------
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0
Forgiving is tough, being forgiven is
wonderful, and Grace really is amazing.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=476841#476841
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Message 3
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| Subject: | Re: My Firestar Project Update |
I hate to sound critical because I always have to redo all my stuff 3 times before
I can get it to work right, so that says a lot for my eyeball engineering...
(Starting the redo on the gap seal for the forth time tomorrow) And meanwhile
all your work in those pictures is way ahead of anything I can do in terms
of quality control. So I feel like a shade tree mechanic telling a pro how to
do his stuff.
But - just looking at your pictures, if it was me, I would have your two exhaust
pipes come together right behind the rear main fuselage tube, because that is
almost exactly aligned with the center of pivot of the engine on its motor mounts.
Yours extend down way beyond that. If it were me, I would terminate them
there with a Y into a ball joint.
By doing that, all the radial movement of the engine would sort of focus at that
point. So if you had your ball joint there, with just one pipe going down to
the rest of the exhaust assembly, now you have isolated the engine movement from
the main mass of the exhaust system, and taken a lot of stress off the upper
exhaust pipes. And possibly eliminated some vibration, because you have also
removed some exhaust system mass from the engine and it's associated movements,
and what movement there is, is now minimized by having it aligned with the
center axis of the motor mounts, at which point you have a movable ball joint.
Worth what ya paid for it...
--------
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0
Forgiving is tough, being forgiven is wonderful, and Grace really is amazing.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=476847#476847
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