Extruded tubing has a wide tolerance range so finding something off the
shelf that fits nicely with your 2 1/2 boom is unlikely. For my 3" booms,
I had to machine couplers on a lathe and I left around .010" clearance. DX
Engineering now sells tubing in some sizes with a .120 wall which should
telescope.
John KK9A
To: towertalk@contesting.com
Subject: [TowerTalk] Concentric Tubing and Piping
From: "L L bahr " <pulsarxp@embarqmail.com>
Date: Mon, 25 Aug 2014 21:52:38 -0400 (EDT)
I'm gathering parts to build a 40 meter Moxon. The boom will be 24 foot
long.
I happen to own some 6 foot sections of 2.5 inch OD tubing with what
appears to
have 1/16th inch wall thickness. (The stuff has never been used but I have
had
it a long time. I think I bought it surplus from Hy-Gain a zillion years
ago.)
That means the ID is most likely 2.375 inches. I sure would like to use this
tubing as I already own it. I need to find some pipe or tubing to fit inside
this existing tubing to join 4 sections together. I looked for 2.375 OD
tubing
and can't find any. However, 2 inch aluminum schedule 40 pipe has a 2.375
inch
OD.
Would the 2 inch schedule 40 pipe bought in 6 foot sections slide and go
inside
my tubing? My idea is to stagger the joints of the joiners to the joints of
the outer tubing. Maybe even have double wall throughout the entire 24 foot
boom. Would this work? I have heard telescoping tubing actually has some
gap
between the telescoped parts, so they can telescope. But, I am not sure this
is true when you mix tube and pipe. That's my concern.
Can anyone educate me on all this?
Lee, w0vt
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