strengthening and spring gear; float reinforcement?

Mike Davis · Post by **Mike Davis** » Fri Feb 17, 2012 4:51 pm

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To: <murphy-rebel@dcsol.com> (Murphy Rebel)
From: Bob Patterson <bob.patterson@canrem.com>
Subject: Re: strengthening and spring gear; float reinforcement?
Message-Id: <E0zfvBt-0006kZ-00@mail2.toronto.istar.net>
Date: Tue, 17 Nov 1998 19:09:50 -0500

Hi Dave !!
Good to hear from you - sorry I'm slow replying - really busy now with
Y2K upgrades !!

From what we're hearing here, even out of the box, the spring
gear isn't as good .... Glad you agree that the bungee gear is a good
way to go, albeit with mods.

I agree completely with your description of the situation after
encountering a gopher hole !! Have considered this myself - of course,
Robin makes MUCH better landings than I do ! The real world is showing
us the weaknesses ...

The original idea of most parts of the Rebel was to 'preserve
the pilot' - towards this end, much of it is designed to crumple
progressively to absorb energy.
I believe the idea of the gear was to have it fail, rather than
injure the pilot or airframe. If the gear were a lot stronger, then
major fuselage components (like the 'cage' structure) would be damaged,
making for an even larger, more difficult repair. In this regard, I think
a landing problem with the spring gear is much more likely to result in
a difficult, expensive repair.
I know of several Rebel builders who have ripped off part of the
bungee gear in 'incidents', and been back flying again in a week or
so !! Have seen the spring gear on a Citabria fail - VERY messy, with
a BIG groundloop, damaged wing & tail - all because the large U bolt
fatigued ! We made replacement of these bolts a mandatory 100 hour
procedure (heavy use towing gliders - 6-10 landings/hour).

There are at least TWO Rebels up here that have followed your
lead & built bungee gear out of 4130 steel - but even they haven't escaped
unscathed - one snapped in a major groundloop. Seems no matter how strong
you build 'em, they can still be broken !

All of your suggestions are much appreciated - everybody needs
to know what fixes work ! Thanks !

I'm sure, through the combined efforts of all of us, and the
factory, we'll end up with a better Rebel !! Not that it isn't already
GREAT !!!!! ;-)

.....bobp

------------------------------------orig.-----------------------------
At 07:58 AM 11/12/98 -0800, you wrote:

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

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reinforcement?

to

the

which

get

will

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