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From: "Alister Yeoman" <
yeoman@voyager.co.nz>
To: "Murphy Rebel" <
murphy-rebel@dcsol.com>
Subject: Re: strengthening for O320 and spring gear; floatreinforcement?
Date: Fri, 13 Nov 1998 15:13:52 +1300
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Hi Dave Bangle
Hope you dont mind me jumping in here, you have raised some interesting
points.
You have obviously been through the mill in regards to landing gear!
If I read your message correctly you regard the spring gear as the
potential problem rather than the attachment or load dissipation.
I have been concerned about the mounting system ( and load dissipation) for
a while, as can been seen by the number of times I have metioned this topic
in this forum, I now have reason to be even more concerned.
I have just removed my wings to do some 'mods' to the fuse as previously
discribed, and I found damage to the mounts that would have resulted in the
loss of the right hand gear within a very short period of time.
The damage is to the forward stradle bolt mounting on the right side, the
main carrythrough member has cracked right thru' to the outside leaving the
bolt loose to work and eventually pull thru'.
I remember thinking while mounting the gear that it seemed underdone in
this area, the rest of the carrythrough has been beefed up with plates on
top except the area that needs it most, and the edge clearances if you
follow the manual are not great.
The forces on this front bolt and surrounding mounting area are very great
under braking and rough ground etc.
I possibly could take a bit of the blame in that I did not retighten the
gear bolts until I had done about 20hrs, I believe it should be done
regularly over the first few hours of use ( hindsight of course!).
It is early days yet in regards to how I 'fix' this, but I think what I may
do is run reasonably heavy piece of 4130 steel down the wing attach bracket
across and down the forward carrythrough and also along inwards to meet up
with the top plates.(4130 may be a little easier to work----who cares about
the weight if it holds!!)
I am considering welding another piece of 4130 around the stradle bolt hole
as a doubler so that the bolt wont break out again with the limited edge
clearance available. I will be replacing the stradle bolt with 3/8" as in
the elite and increasing the diameter of the inboard bolt.
As you can see Dave, I am very sensitive about this area as you are, but I
see the potenial problems as more in the design of the mountings rather
than the gear inself which at this stage I consider to be more than
adequate.
Do you have any info that may make me want to reconsider my opinion?
What area's in the nose area do you consider need more strenght?
Cheers
Alister
----------
From: subersys <
subersys@nidlink.com>
To: (Murphy Rebel) <
murphy-rebel@dcsol.com>
Subject: Re: strengthening for O320 and spring gear; floatreinforcement?
Date: Friday, November 13, 1998 4:58 AM
Bob,
I dare to differ. I believe through 2 complete gear failures that the
spring
gear is probably a better system, stronger, safer, if used right out of
the
box. Having been the reason for the safety cable AD was the first
failure. And
a ground loop being the reason for the second. Had the gear stayed
together in
the ground loop incident I would not have spent the next 9 months
rebuilding.
Yet.........in getting and starting the mod for the spring gear the same
feeling
of nausea (and much greater in strength)overcame that actual
installation.
Everytime I have had that little voice induce nausea in my brain it was
for good
reason. That is why I sent the spring gear back and rebuilt the original
gear
out of chromemoly. Yes it is heavier than the aluminum gear, but I won't
be
rebuilding the airplane every other year. Twice is enough. In regards
to the
aluminum spring gear visualize this. Touch down on a rough mountain
strip and
encounter a gopher hole. I see bolt heads popping and the creation of a
retractable gear. Yes, the Murphy demos have not had a problem, but keep
in
mind who has been flying the demos. Robin hasn't made a lot of bad
landings
lately. A drop test is fine and strainght down it will come through
every
time. Try a drop test while encountering that gopher hole at 30 mph.
Food for
thought.
I do agree that the bungee gear is better, but only after mods. I also
reinforced the fus between the front and rear attach point with 2" square
tube.
No more wrinkling of skins in the door area.
I believe that any area of the airplane that is cause for concern needs
to be
looked at really hard, as I have had problems with every area that has
ever been
a concern. Don't consider that since Murphy designed it it must be okay.
The
design testing is a result of years of use. More AD's will come and go
as
weaknesses are discovered. Better to look ahead and visualize the
trouble
before it happens.
The float fix. That became apparent right away after the groundloop.
The
rivets sheared full lenght of the door post, the windshield shattered,
the
engine almost left the firewall. I believe the nose area needs major
strength
mods. Just my own personal feelings. Created through experience.
Don't think I don't love the airplane. It is wonderful and I would build
another in a heartbeat. What a joy to fly.
Dave Bangle
Bob Patterson wrote:
Alister,
I had another look at the "floatfix" bulletin, and it doesn't
mention the extra rivets - maybe just being updated now ??
All the more reason to check with Tech Support directly - there
may be other recent additions as well.
I agree completely - if you're still building, ADD THE MODS !!
Even if you don't plan floats !
There is no question that the bungee gear is stronger, better
triangulated to spread the loads, and MUCH more effective in energy
dissipation (the friction of hundreds of strands of rubber, rubbing
over each other !). It is also 28 lb. lighter, and about $700 cheaper !
BUT - the spring gear looks sexy, and "Cessna did it, so it
must be good" ..... Murphy bowed to customer demand.
You're right about the problems with Cessnas - ask anyone
who's owned one for a while about the inspections and problems with
the gear box structure . Again, these are things that the general
public DOESN'T hear about - they only hear the good bits. ALL aircraft
have problem areas (the fuel system on the Aeronca Sedan comes to
mind !! - horrible !!)
Please keep us posted on progress ....
Thanks ! .....bobp
--------------------------orig.--------------------------------------
At 07:56 PM 11/8/98 +1300, you wrote:
Hi Dan,
I see Dave has sent the address to pick up the floatfix bulletin, (
Thanks
Dave!) but remember that Bob mentioned that there has been an addition
to
that very recently, that is, the addition of more and larger diameter
rivets down the doorposts.
Bob suggests to contact Murphy for details on this, it sounds like a
good
idea and I am certainly going to make a move in this area.
This is a quote straight from the Murphy crowd, ' even though you're
not on
floats its obvious that its only a matter of time before this ( the
floatfix problem) will affect you'.
I think all Rebel owners should take note of this whether they intend
to
fit floats or not.
Cheers
Alister
----------
reinforcement?
to
which
get
that
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