Doug Miller fired this volley in
Those are not "tube fittings". They're mechanical adaptors that are
probably custom-made by the company making the chair/table/tent/whatever
into which they assemble.
They are called "plastic aluminum tube joiners".
What were they part of? The manufacturer of the original device is
probably the best source for them.
I've never seen a name for them. It looks like something from a
medical mobility assistance device.
For temporary use would chain link fence post tee joint clamps work?
The smallest size is 1.315" top rail, called "1-3/8."
A fence company would have a much better selection than the big-box
Ian Malcolm wrote in
Thanks to all who replied. I think this will put me on the right track.
Yes, I could get them from the manufacturer of the parts in the photo, but I need them sooner
than I'm likely to get them that way. If I can't find a local source, I need to make my own.
Fence-post fittings are too large; the tubing in the photo is 7/8" OD.
"Guv Bob" wrote in news:NO-
Force a 7/8 OD wooden dowel inside a 7/8 OD aluminum tube?
Yes, the wall is pretty thin, but it's not zero. Somehow, I don't think that's going to work very well.
Martin Eastburn wrote in news:PUzGv.194874$ne6.53439
No, it won't. Aluminum expands about 12 parts per million per degree Fahrenheit. It would have
to be heated to over 800 degrees F to increase the ID by just 1% -- and that's not nearly
enough to make the ID as large as the room-temperature OD.
We won't even talk about what that would do to the wooden dowel...
What type of expansion is that? Volume ?
Try linear expansion. around the circle. It is a long ring. A ring
will expand more.
Think wagon wheel expanding the wheel band in a fire and then sliding it
onto the oak frame of the wheel. cool with water and it fits tight.
one of the experiments in thermo labs is to take a ring and a ball that
have the same outsides. Heat both in a flame and the ball slides easily
through the ring. Volume is less than linear of the ring.
Martin Eastburn wrote in
No, linear expansion.
No, it will not. The diameter and the circumference increase by
exactly the same proportion.
Related thought experiment: suppose you have a string wrapped
tightly around the surface of the earth. How much longer does that
string need to be, if you want to put it on one-foot-high
standoffs all around the planet?
I understand how that works. Do you understand that it's not *at
all* the same situation? Fitting a steel band over an oaken wagon
wheel requires only that the ID of the band is less than the OD of
the wheel at ambient temperature but greater than the OD of the
*wheel* when heated -- *not* that the ID of the band when heated
exceeds the OD of the *band* at ambient.
Do the calculations. Assume an aluminum tube with 0.875" OD,
0.050" walls, and therefore 0.775" ID, at 75 deg F. To what
temperature must the tube be heated to increase its ID to 0.875"?
About 8" (two feet / pi).
Related thought experiment: Suppose you have a mile of railroad track. Supp
ose it gets really hot and the track expands (in length) by one inch. Suppo
se that, due to the expansion, the track buckles in the middle, forming an
isosceles triangle. How high will the bump in the middle be?
yeah, well, haven't finished the morning coffee yet. Besides, by the time t
hey finished building all those little standoffs, I'd have been paid and sp
ent the money. So sue me ;-) And it's all a trick question anyway: EVERYONE
knows the earth is flat.
uppose it gets really hot and the track expands (in length) by one inch. Su
ppose that, due to the expansion, the track buckles in the middle, forming
an isosceles triangle. How high will the bump in the middle be?