On Thu, 10 Jun 2004 12:35:51 +0100, "Wally"
wrote:

Trevor Wilson wrote:

Duly noted. Are there any particular patterns that are preferable,
or is a neat side-by-side lay-up okay?

**Here's where you really should talk to someone who REALLY knows what
they're talking about.

All I need to do is find one...


Side by side is fine, AFAIK. Then lay the next winding on top.

Yup, that seems doable.


**Sure. As long as you can drop your lathe down low enough in speed,
I don't see a major difficulty.

Just timed it - 10 turns took 18 seconds - 30-odd rpm.


Big wire demands very low winding
speeds.

Should be okay - it's quite torquey.


Thin wire requires enormous care.

That'll be the fiddly bit, then. My thinking is to rig up a reel in front of
the lathe and feed the wire on by hand while wearing cotton gloves.


**Good luck. At worst, it will be entertaining. Whilst there are
probably lots of books around, you might try to secure a copy of the
Radiotron Designer's Handbook. I don't have one, but I'll betcha
transformer winding is covered therein.

I'll see if I can track it down.

I used (back in the '60s) in a place where we had an old chap who
wound transformers for us. He was some sort of wizard - we would give
him a spec with plenty of different windings and voltages (or
impedances for audio) and the next day we would be handed a work of
art.

I remember his technique, and I had many a chat with him about it. The
first windings would go on very slowly, and he would guide them
tightly alongside each other with a piece of polished wood. Each
winding would then be hammered down. He explained that it was
transformer death to allow an air gap in there - it would make the
windings buzz. Each layer was topped with kraft paper, then the next
was started.

I tried fitting the laminations once, and when I had fitted as many as
would possibly go into the gap, he took over and fitted another three.
"More buzzing, I'm afraid" he said.

Finally the whole thing went into a vat of molten lacquer, a lid put
on and the vat was evacuated. It stayed there for about two hours.

So don't be put off, but don't forget the bits of wood and the hammer.
Oh, and take some time to plane a piece of wood that fits snugly
through the centre of the former while you are doing all this,
otherwise you will smash it.

d
Pearce Consulting
http://www.pearce.uk.com