Bob
> Do you mean your bird specifically or in the fleet generally
Our bird. I was aware of the discussion re your accident two years ago.
> The factory did load tests and gave assurances as to the adequacy of the
arrangement.
As far is I am aware what the factory tested was the adequacy of the roll
pin to retain the spindle. What is called into question this time is the
bending of the spindle.
> simple load tests do not represent real time operation and because of the
prising action of the friction assembly the stresses can far outweigh the
dead weight factors.
I agree with you here. On the three examples I have examined there is
evidence of loads on the roll pin that I would not have expected. This is
on the forward lower side and may compressed the casting. This marking
indicates stress but far below what would be required to shear the pin.
> BTW the application of Loctite was part of the original assembly procedure
anyway.
That is not what David Person (who makes the unit) said. The three I have
examined did not use Loctite or similar.
> The solution you proffer
I am reporting what David Person is now doing. I believe this is an
improvement and I have no evidence to suggest a second roll pin is needed.
> These forces "out of vertical plumb" also go to cause the prising/opening
action of the friction device against the
castellated adjustment nut holding the whole assembly together.
Basically I agree with this analysis. As I understand it, it is this action
which is allowing the bending to occur. I think we have very limited
understanding of the loads applied to the components in the real world of
potholes and wheelbarrow landings.
G-IANI has damping grease applied to the friction plate. As a result the
castellated nut does not need to be very tight to provide the necessary
damping friction. Under shock loads this means the spindle can move a short
distance vertically against the spring washers. I have speculated that this
may be what allows the bending to occur. Taking this to its logical
conclusion, it would be best to eliminate the spring washers. The question
is how to do this and provide and maintain the anti shimmy damping required.
So:-
1) The point of may article was to prompt owners to keep a close watch on
their nose wheel.
2) If there a better man/woman out there, who can come up with an improved
design for the nose wheel, I am sure we will be pleased to hear from them.
What we want is proper trailing link springing, controllable anti shimmy
damping, no weight increase etc.
PS) The longer spindle does not have a Mod number at present but it probably
should have. I will discuss this with Roger when I have time.
Ian Rickard G-IANI XS Trigear, 250 hours
Europa Club Mods Rep (Trigear)
e-mail mods@europaclub.org.uk
or direct g-iani@ntlworld.com
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