Hi! Fred.
Thanks for your input. I'm mostly convinced that the break was due to
overlaid layers of bungee trapping the under layers .
There is evidence of further damage at measured intervals indicating that
the "Vee" trap on the Mono strengthening members was trapping the bungee and
therefore not allowing it to slide and equalise loads in each "fall of rope"
even to the extent that it had probably never been allowed to equalise any
differing loads during application.
As for measuring the "break" weight of the complete assembly I used the
Europa digital balance (used for weight and balance checks ) Just stood the
nose wheel onto it and pulled down on the prop. (yeah.yeah with the mag
switches off! )and read the weight at which the nose leg started to compress
and so extend the bungee.
I also put two ferrules on for extra insurance.
But when I asked the factory what to do with the stretched excess bungee
they
said "might as well put some extra "falls" on the system" then you still
have the ends available if you should need to retighten it !!!! Herein lies
my demise coupled with the blessed "Vees" , I am sure going to have to make
a PERMANENT decision to do away with the Mono OPTION on my CONVERTIBLE
!!!!!!!!!
Regards
Bob Harrison. G-PTAG
-----Original Message-----
From: owner-europa@post.aviators.net
Sent: 30 July 2001 14:56
Subject: Re: Trike Nose Leg Bungee Breaking.
Bob, your original message didn't come thru to me, but I get it in
context. I avoided overlapping by substituting 1/2" bungee. Doing a
leverage and math problem, and testing the #'s pull per % of stretch,
came out enough loops to appear to do the job, so maybe the math
method wasn't dumb, as a check.
It's easier to pull the thinner supplied bungee toward it's design
limit, and perhaps the overlaps caused concentration of stretching at
some point due to friction. It may have been stretching in service,
like maybe too loose total, locally at the limit (it's not supposed to
stretch in normal service). How'd you determine 350# tension at the
nose wheel? Lakeland said push down quickly and hard on the engine,
in a maneuver like a gymnast mounting the horse. Not very scientific,
but else?? I scored only 9.2 :)
On topic, I doubled the diameter of the safety cable, using plastic
coated comm'l cable. Yeah, I know, not aviation grade, but 4X the
area, as there has been breakage on hard landing I hear. The plastic
I figure will help prevent chafing of the frame, causing rust in
places you cannot inspect so easy. I also swaged on 2 ferrules for
extra safety.
Regards,
Fred F., A063
Bob Harrison wrote:
> Hi! Guys.
> Further to my message yesterday on this subject.
> We are not sure that in fact the safety strap/cable actually was the
> culprit.
> It just may be the frame being a monowheel strengthened frame with
> the additional support members (the aircraft being convertible) that
> overlaying members of bungee due to restricted space have severed the
> lower bungee members by pulling them into the "Vee" and crushing them.
> Never the less a close inspection would be well in order for trike
> owner/operators.
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