Hi! Craig.
I should say I was the first to experience this problem and I'm not
ashamed to admit, it had a fair share of wheel barrow jobs. Firstly you
need to regularly inspect the castor spindle fixing in the aluminium
nose wheel yoke/stirrup casting. Unfortunately a nose wheel spat must be
removed to do this adequately. If the castoring facility needs regular
tightening you will probably have the problem. If the said castor
spindle is not plumb into the yoke, either bent or leaning backwards,
you need a new spindle and may need a new yoke. My yoke compressed
behind the spindle and I now know that the miniscule gap at the front of
the friction device is indicating a problem further down.
My fix was to have a 1" extended spindle made to project 1" further into
the yoke. I utilize a new roll pin in my new yoke AND a second roll pin
1" below the original but 180 deg out of alignment with the first. All
suitably loctite applied.
ON reflection if I did this again I would have the entire spindle solid
instead of bored. ( I accept that the core of the spindle does nothing
to improve the bending stress but it does facilitate better continuity
of hole for applying the blessed roll pins)
I also use the friction grease on the friction damper and to date the
fix has worked satisfactorily.
Please note that any over lubrication of the pivot area will migrate
through the rubber "o" ring mod and so lubricate the friction damper
needing still more adjustment /tension applied to the castellated nut
and bingo you are on a fools errand tightening the nut still further to
get friction and so pulling on the existing inadequate roll pin.
The Europa Flyer Mag. contains an item on this problem but still
advocates only one roll pin and damn loctite on their own!
Regards
Bob Harrison G-PTAG (going where supposedly none went before !)
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of craig
bastin
Sent: 18 April 2009 00:20
Subject: RE: Europa-List: Trike nose wheel castor spindle and yoke
failure. Europa Flyer Mag.
<craigb@onthenet.com.au>
I have come in on the end of this conversation. From the descriptions
and
examination of the nose gear
yoke etc, am i right you are all referring to the shaft in the yoke
being
pulled out the top of the fork that
holds the wheel. There is no mention of any work needed to fix this
issue on
the europa site, I can see how
a wheelbarrow landing could create such loads. Could some one point me
in
the right direction for the orginal issue.
thanks
craig
VH-XSV
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com]On Behalf Of Robert C
Harrison
Sent: Friday, 17 April 2009 8:06 PM
Subject: Europa-List: Trike nose wheel castor spindle and yoke failure.
Europa Flyer Mag.
<ptag.dev@tiscali.co.uk>
Hi! Ian,
You quote :-"This was something of a surprise as, to the best of my
knowledge, we had not had an accident with the nose wheel"
Do you mean your bird specifically or in the fleet generally?
Where were you when I tried to give a "heads up" to trike operators two
years ago about my incident of nose wheel/yoke departure? Everyone I
highlighted this self same issue to seemed once again to put it down to
"Bob Harrison Syndrome." The factory did load tests and gave assurances
as to the adequacy of the arrangement so how come we are needing to
revisit the matter? My claim was that 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 don't need "brownie points" but I do have a conscience for other
flyers lives.
Now to return to the main points of engineering:-
I think you may well find that aft of your yoke spindle hole the metal
is beginning to be compressively distressed if the spindle has been
bent.
Your roll pin seems to indicate that movement has taken place so there
will also be compressive distress in front of the spindle hole at its
lower forward reaches. (BTW the application of Loctite was part of the
original assembly procedure anyway.)
The solution you proffer is to put an additional 1" of spindle into the
Yoke as I did but may I suggest that you also insert a second roll pin
1" below the original and still use Loctite but also applied from the
bottom of the hole.
As to the cause of the failure and pot holes etc. the possibility of a
"wheel barrow" landing also adds loads from forward of the spindle
centre line and I posted a message only last week on the Matronics Forum
in a debate about Bungee/Springs and suspension only supposed to be by
flexing of the nose leg. 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.
Much more attention is needed to be applied to inspection and the
loading applied by the castellated nut. I had re-set my friction loading
only 10 days prior to the incident but unbeknown to me the assembly was
being pulled apart by the adjustment loading.
BTW let me know the mod. number for the longer spindle when you have it
!
Ignore all this at your peril.
Regards
Bob Harrison G-PTAG
Checked by AVG - www.avg.com
16:38:00
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