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Dennis Johnson
Joined: 10 Jan 2006
Posts: 89
Location: N. Calif.
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 Posted: Sun Apr 20, 2008 9:13 am Post subject: Grommets |
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Hi Jeff,
I just can't imagine any circumstance where expansion/contraction could cut a grommet completely in two. It might cut a grommet mostly in half, but it seems like at some point as the grommet failed, the pressure on it would be released and the grommet would stop failing and remain in place. To find them lying on the floor, cut in half, is really baffling. But I'm interested in hearing your conclusion, because I always enjoy learning something new.
I wonder if the grommets were manufactured by bonding two pieces together and the grommets failed by splitting apart on the bond line due to a manufacturing defect?
Dennis Johnson
[quote][b]
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khorton01(at)rogers.com
Guest
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| Posted: Mon Apr 21, 2008 1:06 am Post subject: Grommets |
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I would expect proper aviation grommets to be OK, as long as they
were installed in proper sized holes. These grommets are made to
military specifications, and should have been well tested in aviation
environments. The ones with narrow grooves are certainly intended to
be installed in thin sheet.
Putting a grommet in an undersized hole (as the original poster did)
is using the grommet in a way that the designer never intended. In
this case, all the design work and testing that the manufacturer did
is is no longer relevant, as is the previous service history. You
now are on your own, and have to do your own testing to establish an
envelope of conditions under which the grommet functions properly.
The original poster has learned that one type of non-aviation
grommet, installed in an undersized hole, is not appropriate for
aviation use.
--
Kevin Horton
On 20 Apr 2008, at 14:45, Ken wrote:
| Quote: |
Another product that may be suitable is the plastic snap bushings
such as Spruce 04-05730. I never liked putting soft grommets from
any source in very thin metal.
Ken
Jeff Page wrote:
>
> Two of you both thought my grommet problem so absurd that it must
> be a prank.
> I wish that were true, but my T hangar is locked.
> They were exposed only to cold air, darkness, time and my
> installation.
> When I get to the hangar next, i will be taking a close look at
> all of them, to see if the ones remaining are partly torn, or if
> some of them are perfectly intact.
> I will also try to do some tests with some still in the box to see
> if I can tear them like that.
> Sure is weird though. We install grommets to protect the wires,
> so they should be tougher than the insulation.
> Jeff
>> Are you sure someone didn't cut them off, just to play a mind
>> game with
>> you??
>>
>> Roger
>>> Just a guess but exposure to solvents could breakdown SBR. I
>>> cannot
>>> imagine that hole size alone is the issue.
>> I will chime in and comment.... This is really hard to believe
>> they spli
>> t all by themselves. Are you sure someone didn't remove them and
>> split t
>> hem with a razor and them drop them on the floor as a joke/ prank
>> etc...
>>
>> Ben Haas
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