Cherokee Strut Access Plugs

We have been having trouble getting decent replacements for the above, which
pop into the holes in the top of the wing to allow the main gear struts to
be pressurized. Our mechanic uses 1 1/2" plastic (Polypropylene, I think)
hole plugs from McMaster Carr, but they don't seem to stay in our wing.
We've lost two over the past couple of years. When we lost the first of
our original Piper ones, we got a replacement from Wentworth. While we were
waiting for that to arrive, we put one of the plastic plugs in as a
temporary measure. It was gone on the next flight. The replacement from
Wentworth turned out to be a well used (i.e. rusty) steel knockout cover
from some electrical supply. I painted it, and it seemed to work OK. The
other day, that disappeared. Back to the black plastic plugs. Gone again
on the next flight. These seem to work well in other Cherokees, including
the school's rental planes, but for some reason, they don't stay in ours.

I found some better quality plastic (Nylon) from Heyco, and got some black
samples (the minimum order for the white "standard" color ones was 26,000!).
These seemed promising, but are just a bit too deep to lock in securely.
Has anyone found an acceptable substitute for the Piper part? I may have to
go back to the steel knockout plugs, or machine my own design (I have a
lathe and milling machine, fortunately).

--
Bob (Chief Pilot, White Knuckle Airways)

On Fri, 6 Oct 2006 10:37:40 -0400, "Bob Chilcoat"
wrote:

We have been having trouble getting decent replacements for the above, which
pop into the holes in the top of the wing to allow the main gear struts to
be pressurized. Our mechanic uses 1 1/2" plastic (Polypropylene, I think)
hole plugs from McMaster Carr, but they don't seem to stay in our wing.

I've been trying to avoid losing mine by gluing them in with silicone.
A bead of white silicone isn't noticeable on a white airplane, and
it's easily breached if someone really needs to get the plug out to
service the strut. It also helps keep water out.

I had to replace one plug with a Piper part. It came with a little
rubber O-ring that disintegrated after a few months, and I noticed
that the area around the strut valve was flooded with rainwater.
That's when I started gluing them in with silicone. I haven't lost any
since.

RK Henry

I lost one of mine, and IIRC I bought a chrome replacement one from the
Certified Aviation Parts section at the local Lowes home center.

-Cory



--

************************************************** ***********************
* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

wrote:

Certified Aviation Parts section at the local Lowes home center.

I thought they only had that section in my local store!

Bob Chilcoat wrote:
We have been having trouble getting decent replacements for the above, which
pop into the holes in the top of the wing to allow the main gear struts to
be pressurized. Our mechanic uses 1 1/2" plastic (Polypropylene, I think)
snip
I found some better quality plastic (Nylon) from Heyco, and got some black
samples (the minimum order for the white "standard" color ones was 26,000!).
These seemed promising, but are just a bit too deep to lock in securely.
Has anyone found an acceptable substitute for the Piper part? I may have to
go back to the steel knockout plugs, or machine my own design (I have a
lathe and milling machine, fortunately).
sig snip

On the later PA28's (can't remember about the 140's, 180's etc, been
too long), the plain-jane knock-out plug has an internal snap ring
inside the "fingers" that shoves them "out" with a little more force
after the plug is snapped into the hole in the wing skin.

I would procur a suitable replacement knock-out plug and source a
suitably sized snap ring to put inside it. The problem is finding a
relatively thin snap ring that has a large enuff ID.

Makes it a little trickier to get it snapped into the hole (and pried
back out for that matter), but helps keep the little sucker in place...

TC

We have been having trouble getting decent replacements for the above, which
pop into the holes in the top of the wing to allow the main gear struts to
be pressurized.


The originals were aluminum and are impossible to find. You can get
plated steel ones from the local ACE hardware (or equivalent chain
store). But, even if painted, these will eventually rust around the
fingers. I hate siliconing them because they usually look bad and don't
stay on any better. Don't use electrical knockout covers. They look
horrible and don't stay in.

I found that bending the fingers out on the steel ones a little before
installation keeps them in. I just get new ones every 2-3 years, paint
them, bend the fingers, and put them in. You can also bend a couple of
the fingers to have a more radical bend in them before painting. That
helps too. Also, you must "work" them in to be sure they are fully
seated. Sounds silly, but it does make a difference.

I have not lost one in about 10 years. But, if anyone finds aluminum
ones, please post the source.

Good Luck,
Mike

Bob Chilcoat wrote:
We have been having trouble getting decent replacements for the above,
which pop into the holes in the top of the wing to allow the main gear
struts to be pressurized.

Some ideas... Caplugs http://www.caplugs.com/ has plugs in a variety of
materials. The places I've used them don't get exposed to your kinds of
airspeeds, but I have found that the tapered kind stay in a little better.

We've lost two over the past couple of years.

Is there any good way to "leash" them to the plane, or would this be a
bad idea? I'm thinking something like drilling a hole in the center of
the plug, using a self-locking nut and bolt to bolt a wire, bead chain,
or similar to the plug, and then securing the other end down inside the
wing someplace. On the other hand, the way it is now, if the plug comes
out it's just gone, while with a leashed plug, it's free to dance on the
surface of the wing and beat up the paint and the metal.

I found some better quality plastic (Nylon) from Heyco, and got some
black samples (the minimum order for the white "standard" color ones
was 26,000!).

Mouser http://www.mouser.com/ carries a few Heyco plastic plugs and will
sell in small quantities; a plug for a 1.5" hole (Heyco 2763/DP-1500) is
25 cents quantity one. This is probably black nylon.

These seemed promising, but are just a bit too deep to lock in securely.

Does the bottom of the plug stick down too far and hit something inside
the wing, or is there too much room between the locking tabs and the top
flange of the plug? For the former, maybe some sandpaper or notching
the plug to fit over the obstruction would help. For the latter, maybe
a thin rubber gasket around the plug would take up enough of the slack
to make it grip in better. The hardware store may be able to help, or
ask your dentist for a sheet of rubber you can cut to size. Another
thing I have seen done with these type of plugs is to use a bushing
(hollow plug) in the hole first, and then put a smaller plug in the hole
in the bushing. Sometimes the bushings are made a bit stiffer than the
plugs and stay in the hole a little better.

I don't know the official name of this part, but there is a thing that
is meant to temporarily plug pipes and is also sometimes used on boats.
Basically it's a thick rubber washer between two steel washers with a
bolt running through the middle. You tighten a nut on the bolt (or turn
a cam handle on the bolt), which squeezes the steel washers together and
expands the rubber washer. This would leave more stuff sticking out in
the air stream, though.

_If_ you can get to the hole from somewhere else, how about this: at the
hardware store, buy a PVC pipe reducer - the kind with a flange, big OD
(possibly threaded), and small threaded ID. Also get a PVC pipe plug to
fit the internal threads of the reducer. From the bottom, put the
reducer through the hole so the flange is against the wing, and glue it
down. (Alternatively, get a reducer with a threaded OD, and from the
top, screw down a "nut" cut from another fitting over the threads. Use
PVC solvent to make sure the nut stays put.) From the top, install the
plug. You can use the tapered threads to secure the plug, or maybe use
a cotter pin, Loctite, etc. This also assumes that you can tolerate the
reduction in hole diameter that the pipe reducer will give you.

I am less sure about this one, but I _think_ I've seen some nice flat,
threaded covers on the tops of motorcycle fork struts. They usually
have a flat top with holes for a pin spanner and I _think_ they have an
O-ring on the underside. Again, you might have to to be able to get to
the underside of the hole to attach the part it screws into (which you
may have to cut off of the top of a junk fork), but once you have a
threaded plug, tricks like Loctite can be used.

Further afield (and possibly showing that living in Oklahoma is rubbing
off on me), an older-style outdoor electrical outlet cover has a couple
of nice hinged, gasketed covers on it that are spring-loaded closed.
You'd probably have to cut most of the plate itself off and figure out
a way to attach the rest of it to the wing.

Matt Roberds

"B A R R Y" wrote in message
...
On Fri, 06 Oct 2006 23:16:32 GMT, wrote:

Land based radio shops are under "two-way radio" in the yellow pages,
or you can ask your local fire dept., police, public works dept.,
etc... for the name of the shop who installs their radios and strobe
lights. The rubber plugs are usually less than a buck.

They come in limited sizes (3/8", 3/4", 7/8" and 1-5/16") because those
are the only size holes we punch in cars for 2-way antennas. They are usually
plastic. In general, they stay in well, seal well, and last for a year or two.
A good source is Tessco.com

Here is a link:
http://www.tessco.com/products/heade...&searchField=1

Vaughn





Your local installer of truck and construction equipment accessories
who sells strobes and warning lights may also have them.