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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
|
 Posted: Wed Jun 21, 2006 5:09 pm Post subject: FireFly Wing Swivel Joint Repair |
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Hi Jack:
| All I am trying to do is improve the swivel joint so that it will
not
| experience significant wear in the way I believe Homer and/or Dennis
| intended the joint to be used. It may take another 200 or more
hours to
| determine if I have indeed made an improvement or not.
Did not realize there was a problem in this area. Anyone else
experiencing wallowed out holes and worn bolts in the wing fold
universal joints?
| In spite of your good luck at hard bolting, I am not comfortable
with the
| concept. If things are not matched up perfectly, it is possible to
induce
| hidden stress by hard bolting.
You are way over my head on the above. Once before when I shared with
the Kolb List the way we welded steel bushings in the lift struts to
fit snug and bolt down tight, you mentioned the "induction of hidden
stress by hard bolting" phenomenon. Do not have a clue what you are
talking about.
Most everything on my airplane is riveted hard or hard bolted to keep
it together, to prevent vibration damage. Please explain in
"layman's" terms what you are talking about. After 2500+ hours on the
mkIII I am afraid I am going to lose a wing because I used bushings
and bolts on the lift strut and snug the bolts down on my universal
joints on the drag strut.
Thanks in advance.
john h
mkIII
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_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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Eugene Zimmerman
Joined: 10 Jan 2006
Posts: 392
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| Posted: Wed Jun 21, 2006 5:32 pm Post subject: FireFly Wing Swivel Joint Repair |
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|
Thanks Jack,
I understand your explanation and rationale. We are fortunate to
have conservatively designed Kolb planes to fly and tinker with.
I have certainly done my share of modifying too. I suppose it is
normal for each guy to prefer his own modifications over someone else's.
Please do keep sharing your ideas and EXPERIMENTS.
That is what this sport is all about.
The fun we have flying our little EXPERIMENTS is just one of the
consequences. ; )
Gene
On Jun 21, 2006, at 3:54 PM, Jack B. Hart wrote:
| Quote: |
<jbhart(at)onlyinternet.net>
At 12:52 PM 6/21/06 -0400, you wrote:
>
> <etzim62(at)earthlink.net>
>
> Jack,
> The main concern I have is your ,,,,, "If I had it to do over again,
> I would try this approach on the cage pivot stud." ,,, web page
> diagram.
> Why do you think that would be an improvement?
>
Eugene,
I have used this method to get all of the play out of the aileron
control up
next to the stick. The reason, I believe, it would be better is
that it is
simpler than what I have done. The trick is to make the chamfer
just large
enough so that when the nut is compressed up to the plate the "O"
ring is
completely contained in the chamfer space. This gives some
compliance for
the "O" ring to keep the clevis centered on the stud, but does not
keep the
clevis from being rotated. And better yet, as the mating surface
between
the clevis and the cage wear, the "O" ring acts as a compressive
spring and
maintains joint tightness. Also, if the "O" ring keeps the stud from
touching the hole ID, there can be no wear between the stud and the
clevis
hole.
The thing to remember is that during flight these two vertical
surfaces are
in compression (drag force) and most of the lifting force is
handled by the
main spar connector and the struts, so it takes very little
compressive "O"
ring force to keep the rear spar centered/located.
Jack B. Hart FF004
Winchester, IN
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ulflyer(at)verizon.net
Guest
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| Posted: Thu Jun 22, 2006 10:13 am Post subject: FireFly Wing Swivel Joint Repair |
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|
Jack,
Instead of rubber o-rings, might metal (wavy) spring washers be better?
jerb
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jbhart(at)onlyinternet.ne
Guest
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| Posted: Thu Jun 22, 2006 4:38 pm Post subject: FireFly Wing Swivel Joint Repair |
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|
At 01:27 PM 6/19/06 -0500, you wrote:
| Quote: | NOTE: ............. However, let it be noted that his procedure for
taking slack out of the wing fold universal joint and wing attachment
to the fuselage is certainly not a "normal, safe, recommended" method
of maintenance.
.......................
|
John & FireFlyers,
I know I am not an expert, and flying an ultralight vehicle I do not have to
consult one. But if the FireFly was "experimental" someone would have to
sign off on the re-worked swivel joint. So, I asked an A&P to look at what
I had done. His comment was that it was a "big improvement".
Jack B. Hart FF004
Winchester, IN
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ceengland(at)bellsouth.ne
Guest
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| Posted: Thu Jun 22, 2006 5:51 pm Post subject: FireFly Wing Swivel Joint Repair |
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|
Jack B. Hart wrote:
| Quote: |
At 01:27 PM 6/19/06 -0500, you wrote:
>
>
>
................
>NOTE: ............. However, let it be noted that his procedure for
>taking slack out of the wing fold universal joint and wing attachment
>to the fuselage is certainly not a "normal, safe, recommended" method
>of maintenance.
>
>
........................
John & FireFlyers,
I know I am not an expert, and flying an ultralight vehicle I do not have to
consult one. But if the FireFly was "experimental" someone would have to
sign off on the re-worked swivel joint. So, I asked an A&P to look at what
I had done. His comment was that it was a "big improvement".
Jack B. Hart FF004
Winchester, IN
|
Good move getting a 2nd opinion, but it should be noted that once an
experimental-homebuilt is signed off for flight, *anyone* can work on or
modify it. Legally, the work must be logged, but no degrees,
certificates, etc are required to perform & log the work. The only
requirement is that if it's considered a 'major modification' (changes
to structure would meet the definition), then a return to 'phase one'
flight test is required, typically for 5 hours. The details of the
procedure to return to 'phase 1' & back to 'phase 2' depend on when the
operating limitations were issued. There have been at least 3 versions
over the last 10 years.
The only time certificates & degrees come into play is the annual
'condition inspection' which must be logged by either the holder of the
'repairman's certificate' (the builder) or someone holding at least an
A&P ticket (no IA is required for experimental-homebuilt inspections).
Charlie
currently on my 4th homebuilt (all purchased), 3 of which had major mods
while I owned them
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jbhart(at)onlyinternet.ne
Guest
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| Posted: Thu Jun 22, 2006 6:05 pm Post subject: FireFly Wing Swivel Joint Repair |
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|
At 01:07 PM 6/22/06 -0500, you wrote:
| Quote: |
Jack,
Instead of rubber o-rings, might metal (wavy) spring washers be better?
jerb
|
Jerb,
I believe they would work. McMaster Carr sells disk springs and belleville
washers. I have easy access to "O" rings. Since I use them in compression,
I do not worry about them breaking. If one would fail, things will get
loose but nothing is going to fall apart. The trick is to confine the "O"
ring in compression so it cannot break.
Jack B. Hart FF004
Winchester, IN
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