At 10:58 30/07/2001 -0500, you wrote:
>On a related topic--
>
>I have some commercial wingrod I'd like to bend for a couple of projects
>I'll be working on. The 1/4" wingrod material is "case-hardened" (North
>East Sailplanes, I think) and the 5/16" is "Ultrarod" from DreamCatcher.
>What I want to do is bend these wingrods (12-14" length) with a central
>bend of 10-15 degrees.
>
>Would it be do-able to bend the hardened wingrod?
>
>Otherwise, I have some 1/4" music wire I can use instead.
>
>--Bill
Bill I don't think that you would have case hardened material supplied as a
wind joiner
as it wouldn't work. Case hardening is just that ... the internal material
is still soft and
only made out of S1214 or similar. You can use a higher carbon content
material such
as K1045 and harden it to use as a wing joiner but I would bend it before
hardening.
Spring steel or music wire that is usually used and is available from model
shops is
normally bent cold. but don't over bend it as suggested below or very
quickly it will over
bend in use again.
What happens when you bend material is that the molecular structure gets
distorted (work
hardening) and tends to move on bending into a locking position .... if you
over bend and
straighten it back again the molecular structure unlocks and it becomes weaker.
This is the reason that they no longer reform coil springs in cars.
Bend it only to the angle you need.
Now this is the way to bend material.... I use a piece of 1" thick hard
rubber sheet, placing
the rod to be bent flat on it. On top of the rod place another say ...
1/2' dia rod and press it
down until the joiner reaches the correct angle.
This method produces a very localized bend (good for wing joiners) in the
material.
I use a small press but if you have a 4 to 5" vice you can use that with
the rubber sheet vertical.
>>4) Bend about 5-10 deg PAST the intended angle. Then bend back
>>to the intended angle.
>>
>>
>>Note 1: The reason for going "too far" and then returning is to relieve
>>the huge residual stresses (about 1/2 of yield stress!) in the steel which
>>would otherwise remain. The bend will be much stronger then.
Eddie the Eagle
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