[TowerTalk] Straightening Bent Aluminum Tube

[Bill Coleman AA4LR]

On 6/28/00 1:28 PM, Jeff Maass at jmaass@columbus.rr.com wrote:

>Is there a preferred procedure for straightening-out aluminum tubing,
>to minimize the possibility of weakening, kinking or breaking?

If the bend is gentle enough, you may be able to coax it out. The tubing 
was already weakened when it was bent, you can't make it much worse by 
unbending it. (Once. If you bend and unbend, you'll work-harden the 
aluminum, which will lead to fracturing and eventually cutting the tube)

At the Atlanta Expeditionary Force (a group of four guys building 
Nieuport 11 (WWI Biplane Fighter) replicas), we regularly bend tubing 
into all sorts of interesting shapes. The preferred bending jig is 
nothing more than two closely fitting blocks of wood screwed to a 
workbench. 

Place the tube between the two blocks, making sure it is snug. The blocks 
should be at least as tall as the thickness of the tube. Bend slowly, 
sliding the tube to a new position between bends. Note that most aluminum 
will hold about 2/3 of a bend (it springs back 1/3). Don't try to take it 
all out at once. For straightening, roll the tube on the workbench or the 
floor to figure out where the bends are. 

If the bend is so sharp you kink the tubing, or cracks develop in the 
surface of the aluminum, scrap it and buy a new tube. (Cut off the bent 
portion and recycle it. Use the remaining straight portion for repairs or 
future antenna projects)

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@radio.org
Quote: "Boot, you transistorized tormentor! Boot!"
            -- Archibald Asparagus, VeggieTales


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