On Fri, 19 Jun 2015 18:15:00 +0800, Techman wrote:

I need to replace a broken light duty torsion spring and need some
advice.

It's broken right at the bend, I may be able to buy a new one but it
will have to come from the UK to Australia and I need it ASAP.

https://dl.dropboxusercontent.com/u/...ring%20(1).JPG

https://dl.dropboxusercontent.com/u/...ring%20(2).JPG


The spring returns an aluminum flap through and rotates through an angle
of around 90°.
The wire diameter is 4.5mm and the overall length of the spring is
around 24".


I can get some 3/16" diameter "piano wire" (4.76mm) or 5/32" (4mm) from
my local hobby shop. Will piano wire work OK as a spring in this sort of
application?


Will I have trouble cold bending the ends?

I was thinking of drilling a 5mm hole through a heavy piece of metal and
using pipe, then a hammer, applying the bend. I would try to leave a
more generous radius than the on the original.

Thoughts?

What everyone else has said, except that to bend it I'd put it in a vice,
pointing straight up, with a couple of bits of 1/16" thick soft aluminum
on the bend side to act as a sacrificial one-time wire bending tool.
Bending it down onto the aluminum (instead of across the sharp jaw of the
vice) should give you a reasonable radius.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com