Help With Leak Test Results

jcarlyle wrote:
I did some research on this subject. Turns out that the proprietary
term is "elastrator ring", ......
...... Apparently there are two materials that they are
made from, with latex "expanding 170% more and gripping tighter" than
whatever the normal material is. I found no information about size;
It's a long time since I've seen them, but IIRC the hole is about 4.5mm
(3/16") and the ring is about 3mm (1/8") thick.

They all stretch a lot. As Todd says, they are also used to remove
lamb's tails and so must stretch far enough to be easily slipped over
the tail + wool in it. At a guess that means they will stretch to an ID
of at least 25mm (1"), so even the non-latex variety should do as the
tubing clamp.

In the USA you can find them at at veterinary and farm supply firms,
see ( http://shop.store.yahoo.com/animalme...re/cassup.html ). One
potential problem is that they are so cheap ($1.20 for 100) you might
run into a minimum order size problem if you mail order them.

If the applicator is not too expensive, you buy that to bulk up your
order. The ones I've seen have four wires coming out the business end
and bent at right angles to the plane of the grips. The wires are
normally all touching and a ring slides snugly over them. Squeezing the
grips separates the wires to expand the ring into a stretched square so
you could use it to place rings onto the tube.

You'll need something to stretch a ring so you can push the tube through it.


--
martin@ | Martin Gregorie
gregorie. |
org | Zappa fan & glider pilot

In message , Eric Greenwell
writes
Robin Birch wrote:


I would also recommend putting springs over the silicone pipe if
there is any chance of a sharp bend coming up as it can collapse and
effectively seal the tube.

That doesn't seem necessary with the tubing I have, unless it is quite
sharp; for example, bending the tubing in a "U" that is 1.5" (measured
at the center of the tubing) across doesn't cause a problem. It has a
maximum temperature rating of 500 F, so cockpit temperatures won't be a
problem! The McMaster-Carr label on the bag it came in is says

Vanguard Products
Size: 3/16" (ID) x 5/16" (OD)
Material: translucent, 50 Duro silicone


Other types might be more prone to collapse, but this one seems quite
resistant.

Well I know to my cost that the standard silicon tubing you can get in
the UK suffers from this problem. Especially if you don't secure the
pipes in the shapes that you want them to follow.

I've also known them to temporarily compress if something moves behind
the panel in severe turbulence.

Robin

--
Robin Birch

jcarlyle wrote:

What I'm not sure of is the optimal ID and wall thickness. I picked
5/16" OD so they would easily roll over the tubing above, and 3/32"
width because it would be slightly stronger than 1/16" while still not
much more expensive. However, a 1/4" OD with a 1/16" width would surely
hold tighter - but might it distort the tubing to the point of leaking?
I don't know - opinions?

-John

I'm a big believer in the experimental method :-)) You can pick up a
variety pack of o-rings at most hardware stores (even the so-called
"tools section" at Walmart). I'd try a couple first before buying in
volume. My guess is that 5/16" ID with a thicker wall (ie. width)
would work fine; the barbs on the fitting tend to increase the
effective OD of the tubing, but not so much to cause a problem.

If you're in the US of A, try your local ACE Hardware if you have one.
If it's anything like mine, they actually have a good-ole-fashioned
"hardware" section with bins of O-Rings. I feel kind of sheepish (no
pun intended based on earlier tone of this thread) walking up to the
register with 3 o-rings totalling 15 cents, but hey...

P3

Whoa- normal "O" rings? CAUTION! The rubber compounds used in many so-called O rings is not up to the task, UV, Temperature and standard gaseos compounds will break them down in just a few weeks.
If you cant do a test on the ring, like leave it on the cockpit seat for a month or two, stick with a proven thing!

This would be the case for "normal" Buna-N O-rings. It would not apply to
Viton, EPDM "normal" O-rings (g).

If you go into a hardware store and ask for an O-ring, you'll likely get
handed a Buna-N. They do petroleum oils well, but not weather and ozone.
EPDM does DOT brake fluids and resists weather/ozone etc.

bumper

bumper

"bagmaker" wrote in message
...

Whoa- normal "O" rings? CAUTION! The rubber compounds used in many
so-called O rings is not up to the task, UV, Temperature and standard
gaseos compounds will break them down in just a few weeks.
If you cant do a test on the ring, like leave it on the cockpit seat
for a month or two, stick with a proven thing!


--
bagmaker

Actually the donuts I've got for my instruments look like the bands used to
castrate male cows and I assume that's what they were originally for. You
can but a big bundle (100's) for cheap. They're easy to use, but just watch
out where you put them ;)

Doug

"jcarlyle" wrote in message
oups.com...
Here's a leak testing article that I found helpful:
http://www.borgeltinstruments.com/Leaks.pdf
Sure, it's commercial, but it gives a nice detailed procedure for leak
testing.

Note paragraphs 3 and 4 near the front. Mike recommends using rubber
donuts to prevent leaks (I thinking these donuts are similar to the
grommets used for feeding power cables into metal boxes). He also
concurs with Doug that cable ties or twisted wire are not good for
pneumatic systems.

-John