On Fri, 19 Jun 2015 20:59:45 -0500, Martin Eastburn
wrote:

I have a Z bend for those piano wire wires we used in RC flying.
It was used cold and pressed a z with square corners. So rounds
especially using a mandrel would be nicely done.
Martin

I used to build "U" control planes and as I remember it I bent nearly
all of the wire - landing gars, push-pull rods, etc., by hand or
perhaps with a pair of pliers. If you use two pair of pliers the
distance between then tends to govern the radius of the curve.

On 6/19/2015 6:31 AM, John B. wrote:
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?


Thanks guys.

I've made a number of springs from music wire and they seem to work
pretty well. and yes, a bit more generous radius on the bends will
probably last longer.

I would think that you could bend 3/16" by hand, or perhaps a couple
of pairs of pliers, so a fancy jig shouldn't be necessary, and I
wouldn't hammer on the bends as it might work harden then even more
and could cause them to fail.
--
cheers,

John B.

--
cheers,

John B.