[Top] [All Lists]

[TowerTalk] material testing Re: 2" OD pipe.. again

To: "Tower and HF antenna construction topics." <>
Subject: [TowerTalk] material testing Re: 2" OD pipe.. again
From: jimlux <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Sat, 20 Mar 2010 07:48:22 -0700
List-post: <">>
Steve, W3AHL wrote:
> In my opinion, there is no way to do any stress analysis of pipe
> without a material testing lab, and then the results only apply to
> the specific batch of pipe sampled, at best.  Pipe is not a
> structural element.  Even if you know the yield strength of the
> steel, the manufacturing process does not result in a predictable
> structural component.  Ask a P.E. to certify a mast using "pipe"....
> Hundreds of hams use pipe successfully for years.  But it isn't a
> sound practice that I would ever recommend to others as "safe enough,
> most of the time".

Actually, one doesn't need a full-up lab, if you know what you want to 
measure and have some ingenuity.  For instance, you could buy your piece 
of pipe, and test just that piece of pipe as a single instance in a 
purpose built jig.

For instance, you could set up a piece of tower or some blocks of wood 
with holes in the appropriately places horizontally with sand 
bags/concrete blocks to hold it down, shove in your would-be mast, and 
hang weights on it to simulate the antenna loads and measure the deflection.

One can even "proof test" by overloading it.

This is pretty common when you don't have enough information about 
material properties, or where the properties vary a lot (e.g. hand layup 
of composites).

High performance experimental sailboat masts get tested this way (attach 
them to the wall, hang weights), as do composite airplane wings and 
such.  There's an interesting video on youtube (I think) of a full size 
wing being tested under load.

However, designing the test to meaningful also requires some cleverness 
and knowledge.

TowerTalk mailing list

<Prev in Thread] Current Thread [Next in Thread>