I think "the third one" would definitely say that the die springs
DID bottom. That has always been my concern - suspect the bungees
would have absorbed that one a bit better - but still might have
ended up with a bent tube. Maybe longer springs would be better -
but the ride would likely suffer .... Not worth fiddling with - this was
an unusual circumstance, combined with poor judgement, and
.... not likely to be loaded that way again, at high density altitude,
at too low an approach speed. Should have added a bit of power -
or just started higher ... Fortunately, it only took a couple of
hours for a field repair, and we were on our way.
The die springs definitely give the best ride of all the gear
combinations.... the spring gear 'waddles', while the floor flexes,
and the bungees are stiff - given that they are only supposed
to move to prevent damage to the fuselage. Big, soft tires -
Dico/Carlyle 800 x 6's - help that ! For the lightest weight, use bungees.
Everything about the Rebel was designed to crumple progressively,
to absorb energy and protect the pilot and passenger(s). It does
that VERY well - I've seen some spectacular crashes where everybody
walked away with small scratches. Looking at the wreck, you would
not believe that ! Ask any knowledgeable insurance company -
they don't like the cost of repairs, but Rebels CAN be completely
rebuilt - BUT they LOVE the fact that nobody has ever been killed
or seriously injured in a Rebel !
I totally agree with just leaving it the way it was designed, as far
as the gear goes - any beef-ups can result in what Wayne calls
"the bigger bandage syndrome" - it will just break elsewhere !! ;-)
Particularly concerned with replacing legs with steel - have
seen early failures because of this - and more damage !!
--
......bobp
bobp@prosumers.ca
http://www.amway.ca/BobPatterson
http://bpatterson.qhealthbeauty.com
http://apatterson2.ordermygift.com
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On June 30, 2010 08:29:00 am Ken wrote:
Don't know for sure but I believe that two of those incidents did not
bottom the gear. The third one got into sinking air and ended up hitting
the lip at the pavement threshold. Don't know if he bottomed but there
was no obvious indication that the spring bottomed and no damage other
than the bent leg.
One fellow who switched from bungees to springs would like to dampen the
bouncing somehow so it will be interesting to see how yours work out. I
believe Wayne has delivered some struts with double springs which is
likely similar to what you built. (half spring rate, twice the movement
and twice the energy absorption) Don't recall anyone posting comments on
them though.
My good fortune may be that all the firm pastings that my aircraft has
done were wings level with little sideways drift so that the forces were
shared on both wheels with little tendency to twist the fuselage.
Ken
bransom@dcsol.com wrote:
Very interesting to hear this Ken ...thank you, we're all better off. In
my limited flying experience, although half on semi-rough terrain, a bit
of power is always a friend ...not that I don't need the reminder.
(Rusty me.) In my many hours of thinking about landing gear design, one
thing that often pops to the forefront is that improving anything just
moves the weak link somewhere else. So now, other than pilot error if
you will, the weak link may be the main gear struts themselves ..the
simple stock square tubes. Geez.
One could opt to upgrade those further. On the other hand, it seems the
failures proved to be almost the best possible of outcomes ...well at
least two of the three. I have 16 more feet of that 1.25" tube and had
thought even when I ordered it that I'd plan to keep a piece in the back
of the fuse (spare main). ;)
I wonder if those mains bent when/if the springs bottomed out. I know
the calculated max loads on the tension struts but will check back to
the numbers for the mains out of curiosity, if nothing else.
On 6/29/2010 2:00 PM,
klehman@albedo.net wrote to rebel-builders:
The two incidents of bent and one incident of broken main gear struts
that I am familiar with had nothing to do with the bungees or die
springs Ben.
All these involved heavily loaded aircraft, unfamiliar airports, and
elevated density altitude. Two of the three had no other damage other
than the bent main gear leg. (except one of those did bend enough to
mess up the fairing)
The third did a bit of a ground loop after the gear leg broke and a fair
bit of fuselage damage occurred. There was a 90 degree crosswind at the
time.
Perhaps planning to land with some power on may be a good thing in such
unfamiliar situations.
I have Wayne's die springs and am happy with them.
My only landing gear concern is that I am a bit suspicious of the amount
that the main gear leg can twist. I know that the bolt holes in the
bottom of my drag links elongated a fair bit over about 600 landings.
That allowed a surprising amount of twist (wheel toe change) at
touchdown and at brake application. It may be worth occasionally
monitoring how much one can twist the wheel and strut by hand. I would
hope to improve that part of the design if I remove the floats.
Ken
bransom@dcsol.com wrote:
gear
or
of
after
simple
on
to
my
spirit
politely
his is
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