REFLECTOR: Fixed Gear Nose Gear Shock Replacement

[Andy Millin]

For those of us that fly with the gear "down and cured"  .

 

If you have worked on the nose gear of the FG, you probably know there is a
rubber bumper used as a shock absorber on the nose gear.

 

Like several other parts, this was a "found part."   It is an automotive
engine mount that seemed to fit the bill.

 

I have not flown yet, so I can only relate what I have been told.  The
rubber portion of the mount is sandwiched between plates of steel.  When
compressed, the steel will deform and does not relax to the original shape.
The bent steel introduces slop.  Over time, possibly a lot of slop.

 

I am told that Velocity has recommended replacing the shock, or shimming
from behind.  Shimming will remove the slop, but not the original problem.
The steel may deform even more.

 

A small group of builders/owners has taken up the task of finding a new
option.

 

The original research was done by Jorge Bujanda.  http://www.jbujanda.com 

 

He located an industrial bumper.  It is not a sandwich.  It is a rubber pad
mounted to a steel plate.  Jorge's son is an engineer and ran the numbers
for suitability.  His analysis showed it would be an excellent replacement.

 

Since it was not a proven solution, we didn't think it wise to recommend it
to anyone.  We wanted to get our hands on it and try it first.

 

The new part was ordered and installed by Kevin Steiner (SELW/FG) and Bruce
Topp (XL/FG).  The new part mounts vertically on the canard bulkhead.  The
retaining strap on the current bumper is discarded.

 

The pad is hard but flexible.  Taxi tests revealed the new shock must be
installed under compression.  Both Kevin and Bruce fabricated shims and
adjusted the force so the gear leg would stay firmly held with a two
passenger load in the front.  Kevin did this by standing on the canard
bulkhead and checking for any gap.  I couldn't to this.  I'm pretty sure I
would shoot a knee cap across the shop.  I'll have to find another way.  :)

 

Once installed, the new shock has taxied, flown, and landed beautifully.
There has been no sign of deformation or slop.  It appears to be just the
right thing.

 

The manufacturer of the bumper is an industrial supplier.  Unfortunately,
the smallest run they make of the product is in the thousands.  At the time
the part was located, they had just 17 left on the shelf with no plans to
make more.

 

Gary Paxton (SE/FG) ordered the last of the bumpers this weekend.  He
reported back that the manufacturer said this has become a "hot item" and
they were going to tool up and make more.  :)  There should be enough for
anyone that wants one.

 

Jorge spoke with Scott Swing and they will be getting one.  If they see them
same results, this might become the standard part.

 

I will be installing mine soon.  I will try to post pictures of the
installation on my site.

 

If you are interested in making this modification, here is the info:

 

ADVANCED ANTIVIBRATION COMPONENTS

2101 Jericho Turnpike

New Hyde Park, NY  11042-5416

Tel: 516 328-3662

Description      Rectangular Bumper

Part Number     V10Z 7-1011

 

Their catalog can be found here:
http://www.punchtools.com/PDFSupplies/V100.pdf  (6 MB download)

 

The part is listed on page 126.  There is a picture.  Dimensions are also
given.

 

You can call and order it directly.  The cost is around $50 (including
shipping).

 

Andy

 

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