On Wed, 12 Aug 2009 08:44:36 +0100, "N_Cook"
wrote:

In preparation for the next time (if) I do another one, as many thousands of
turns I don't fancy doing another one, to explore this anomaly.
I successfully wound my first 0.05mm wire guitar pickup rewind, but one
curiosity- anyone know the reason?

This sort of rewind needs winding on a demountable former and transfering,
as a hank of wire, into a trough. On demounting, there is a distinct banana
shaped bowing to the hank
Hank is about 65mm long , place onm a table and the ends are , equally,
about 8mm off the table.
Possible reasons , I can think of
1/ there must be a twist in the
wire on the spool , despite pulling the wire off the supply spool
tangentially rather than
axially.
2/ some bias on left hand traverse versus RH traverse on the coilwinder
machine.
3/ For this sort of very fine wire,
instead of a final delivery pulley I use a tiny PTFE lump on a small bar. A
hole in the PTFE squashed to form a sub-mm slot. Then a 15 foot run back to
the spool (and a light felt slip clutch) to allow for any snatching. Because
of room arrangement , to get a 15 foot run , the winder and so PTFE is set
at an angle of 25 or 30 degrees rather than straight fore-aft. Perhaps that
puts a set on the wire.

My totally uneducated guess (I am not a professional coil winder, I
deal with 12-GA and 14-GA solid...) is that there are residual
stresses on the wire from when it was wound onto the spool.

You might want to use a set of pulleys in series as a Straightener
after the supply reel (and felt clutch) to gently work the stress out
of the wire - you put five or seven pulleys in a sawtooth pattern so
the centerlines of the groove are only a few degrees off a straight
path, which makes the wire bend back and forth ever so slightly as it
goes through them.

One set of pulleys for vertical, then a second set for horizontal.
Then go through your PTFE slip block and onto the coil winder.

Oh, and is there any problem with putting a drop of varnish onto the
finished coil in several spots while it's in thew winding bobbin, let
it wick through and set, then remove it from the bobbin form?

Pick a resilient varnish that won't eat into the insulating varnish
on the wires and cause shorted turns (ask the wire manufgacturer for
suggestions, they probably have several...) and it'll be a solid form
coil but it could be bent if you need to without going "Sproing!"

-- Bruce --