Warming dynamo field coils.

I too read this but many years ago. The trick is to pass a current latge enough to produce useful heat but at a voltage low enough not to stress the damp insulation. It's a procedure used on electric motors that have been got wet etc. Google drying motors and you get this

John

Umm....

Do you want it as the manufacturer made it. I guess so..Or do you want it to work reliably...Next post.. :-)

Now, the old stye wire (not cotton) had a sort of shellac coating Which cracks and degrades quickly,. New style has a PU coating which is reluctant to crack and degrades more slowly...

Spect you want it as the manufacture made it, So, you want it dry....I wouldn't pass a current thro it, I'd make sure it was dry in the first case. Yes, It will get wet / damp later, but let's build a platform.

You need cotton coated wire thats dry and wont short. Test it first..

So. Step 1) Dry the wire gently -- unspool, electric oven gas mark

0.5, leave, check regularly make sure hasn't gone crispy. ( half an hour should do it ) - nb. gas ovens produce water so possibly not the best.

Please don't even think about mcrowaving it... :-)

You now have dry wire. Rewind. There used to be a product (Holts Igniotion Sealant?) that cured most ills, consider a light spray of this every turn.

Won't do any harm, might help..

But,

If you want your ccurrent oils dried. Electric oven. Minimal setting. . Day or so.

Problem is that cotton will attract water...

If they've been indoors for 8 months, then they will be as dry as they are going to get.

Tracking is usually only a problem on Magnetos which work at considerably higher voltages.

Your bigger worry is the physical security of the windings etc. I'm thinking about getting some of my old stuff re-dipped (via our friendly transformer maker) so that everything is securely bonded.

We also have air-drying dipping varnish here for the small bits and pieces, you're welcome to a dip if you call round....

Peter

-- Peter A Forbes Prepair Ltd, Rushden, UK snipped-for-privacy@easynet.co.uk

It was called "Damp Start" which was a big No No as it didn't dispel water so no use spraying it over wet electrics. It was actually a laquer which may be what you want. It's still available. Google produces a number of suppliers.

John

Thank you, gentlemen.

The main windings were securely wrapped, it was just the supply leads to them that were frayed and req'd re-wrapping. I bought a reel of modern cotton(?) wrapping at an autojumble a while ago with this in mind. After double wrapping and securing with small cable ties, I liberally soaked them, trying to avoid the coils, with black anti-tracking varnish.

Thanks for the offer of a dip, Peter. I had the armature dipped to prevent any further deterioration to the winding wrappings and to try to increase the insulation reading. I maybe should have had the coils dipped as well.

Page 6, Para 4.2 of the pdf is pretty much the same as that which I read.

Would the "Safe Insulation Chart" zone lines hold true for a 32v. dynamo?

Regards, Dave.

Dave... I should imagine a meg would more than ample at 36 volts , due to the low voltage the coils would have to be really screewed to brake down I would not bother with current heating just bring them indoors in the airing cuboard for a while. I have just finsished rewinding an old lister dynamo which was a dead short from the comm to the armature it was as if someone had been pouring oil away in there , the field coils where perfect though. I have 5 liters of red antitrack paint if you need any to paint the inside of the frame to give extra protection to the coils.

Regards bob