On Fri, 20 Nov 1998 17:23:12 -0600 Reed Coleman
>Gentlemen & Ladies,
>… A very easy fix (which I’vebeen doing for quite a few years) is to
take the Spectra sock and
>completely and thoroughly soak it with Vaseline(or other petro jelly)
>before donning on the foot module and applying the cover. Apply the
>cosmetic foot shell, and trim sock to the top of the shell. This has
>worked to eliminate 99.9% of the noise and it lasts and lasts and
>lasts and lasts and then lasts some more!! Give it a try and I think
>you’ll be more than pleased with the results.
>
>E.Reed Coleman, C.P.
>Advantage Prosthetics & Orthotics
Very interesting advice. I will have too experiment with this one.
The Spectralon fiber sock is a College Park invention. We had noises
early on related to the foot components sliding across the inside of the
urethane foam shell. This method was then adopted by other companies,
like Flex Foot. Spectralon is an interesting material. It is
essentially High Molecular Weight Polyethylene (UHMWPE) stretched such
that the polymer chains arrange in such a way that the fibers have
excellent tensile properties, while retaining the inherent lubricity of
UHMWPE. The fibers are woven into socks.
Elimination of noise in prosthetic components is a never ending task. We
are simply not a smart as God, as we have not been able to design but
crude analogs to the body. The human body has an incredible number of
mechanical interfaces that run noise free except for a popping knee or
ankle occasionally. As an amputee, I have experienced most every noise
imaginable. Pylons, 3S latches, feet, sheels, shoes, socket interfaces!
It’s enough to drive one nuts sometimes! I now have a much, much lower
incidence of noise, having spent the last few years working on just such
an issue, noise abatement on our feet. As a result, I had to get all the
other noise makers to stop too, like pylon set screws and tube clamp
adapter/tube interfaces. Hard to make the foot better when there things
are making a racket! I now know how to make pylons shut up, latches,
feet, shoes, sockets, etc., most of the time. Had a really stupid one
pop up the other day. I had a small popping noise at heel strike. What
the…? I finally figured out the zipper I put in my pants to give fast
access to the leg (all my pants are thus) was slapping against the side
of the shoe. If it can make noise, it will!
The use of Vaseline on the spectra sock is not something I’ve considered.
A few of our customers have in the past adopted use of talcum powder in
the shell, but we advise against it, as powder may cure the noise
temporarily, but then causes noise down the road. I recently took a tech
call wherein the customer was going nuts trying to diagnose the noise. I
almost gave up when then there was mention of powder. Bingo! Powder was
completely removed, a fresh sock installed, no more return to office with
noise after a few weeks.
We recommend the sock be inserted into the shell dry. With our new
improved Spectra sock, we now have pretty much no complaints in this
area. The old sock used to get holes in it. The contact of hard foot
components against the shell could cause a groaning noise, particularly
on inversion/eversion. The Flex Foot is a different design, so I don’t
know what is causing the noise there and why Vaseline may help. I would
think Vaseline may attract and retain dirt. What has been your finding
there? From a theoretical standpoint, why do you think the Vaseline is
helping? In other words, what is the true cause of the noise and why
exactly does Vaseline stop it? Thanks for sharing your idea, I will
check this out.
Chris (CJ) Johnson, Director of Engineering,
College Park Industries, Inc. http://www.college-park.com
(810) 294-7950 (at CPI), (616) 664-4173 (home office)
