Fixed Gear Replacement Bumper

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.

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

Desc:  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 Millin

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