2.0 od into a 2.5 od with a nice slip fit means the 2.5 tube has 1/4
wall thickness! If these are your parts (it seems unlikely), you need a
.25 wall 2" od internal splice tube. 0.058 wall isn't anywhere near
strong enough to splice 1/4" wall tube. If it really is 1/4" wall then
buy a 2" fiberglass rod (McMaster) for internal reinforcement and sleeve
the outside with 2.75" od by .120 wall. DX Eng can supply this tube.
On-Line metals might have it.
Regarding overlap, 4" would be about minimum each side, so you can bolt
at 2" and 3" from the splice at 90 deg angles, with 1/4" SS bolts.
Since the antenna has failed once, you might consider buying "yagi
mech" stress analysis from DX Eng and checking all of the design for
wind load and reinforce as needed. It is pretty easy to use and can do
the calcs for sleeved sections, it assumes they are a snug slip fit as
is the case with 0.058 and 0.120 wall thickness tube. FWIW 0.62" and
0.125" wall tubing usually won't telescope, unless the larger size has
the 0.058 or 0.120 wall.
Grant KZ1W
On 9/5/2011 5:26 PM, Robert Chudek - K0RC wrote:
> I am rebuilding an old Telrex 40m dipole that was damaged in a recent
> windstorm. One side of the dipole buckled slightly from excess force. It
> didn't break, rather it crumpled on the leeward side and the element was
> about 20 degrees out of straight.
>
> Is there a formula for how far a smaller diameter tube (not pipe) should
> be inserted into a larger tube and still retain the full strength of the
> smaller tube?
>
> In my particular case, I have a 2.0" OD 6061-T6 tube, 0.058" wall
> thickness that will slip into a 2.5" OD tube. The larger tube has the
> proper wall thickness so the smaller tube is a "nice" slip fit.
>
> I am wondering if 4" is adequate, but that's just a SWAG.e
>
> 73 de Bob - KØRC in MN
>
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