DC Coil Secondary Winding
|I wound the secondary on a length of 80mm PVC
drainpipe from Mr Mitre10, my local hardware emporium.
I'd had a look around for suitable secondary formers I
might be able to scavenge and all the ones I came across
in skips and so on were really beaten up and manky, so I
thought I'd go with a brand new fresh piece. Of course it
comes in 3m lengths and you can't buy just the bit you
want, but it wasn't too expensive.
I had to remember to take along a hacksaw so I could get it home though - I can't fit 3 metres of anything in my car. Drainpipe's not heavy, I suppose I could've walked it back. But people look at me funny already.
I cut it to length, sanded off the lettering printed along it, fitted it into my rudimentary winding jig and gave it a coat of polyurethane varnish. The winding itself was done with 0.4mm diameter magnet wire, for a wound length of about 520mm - so I guess there are approximately 1300 turns. Once the secondary was wound it had another 2 or 3 coats of polyurethane (still on the winding jig, so I could continue turning it as it dried and prevent too many aesthetically displeasing drips or runs in the coating)
The secondary's mounted in the closest-fitting pipe endcap I could find, which is bolted down to the baseboard of the coil. The endcap didn't really fit the drainpipe all that well, so I epoxied some wedge-shaped pieces of perspex to the sides of the secondary former to make for a tighter fit. I also fitted a long nylon bolt that passes through holes in the side walls of the endcap and the bottom of the secondary former and stops the secondary from lifting out.
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