Variac Lubrication

[coil1234]

Hello,
I was given a Claude Lyons Variac of about 10 Amp Rating a few years ago by a work colleague. I found however that it was hard to turn due to the center spindle binding in the frame.
I tried to free it using WD 40 but this appeared to make things worse, I ended up having to completely dismantle it and tap out the spindle, which resulted in it breaking.
The spindle was repaired using Araldite and after a smoothing down with wet and dry paper went back together OK and ran freely, however it doesn,t get a lot of use and I've just tried it again after about a year of not being used it appears to be getting stiff again.

From memory the spindle is a hollow tube about 1 1/4" dia made of SRBP or Paxolin and the frame it runs in is a diecast aluminium.

After the previous experience I'm loathe to try WD 40 again, could this really cause this material to swell ? At present it is stored in an unheated garage, could a slight amount of dampness cause the problem ?
What did the makers recommend for lubrication ?

Many Thanks Mike Andrews

[Leon Crampin]

A very good question - I've a similar Claude Lyons variac (beautifully made) which is also very stiff. Has anybody any words of wisdom?

Leon.

[Hermit6345]

I bought a Zenith Variac many years ago, it was an eight amp unit and I put it in my garage, which is always a bit cold and damp feeling. When I came to use it, it was more or less seized solid. I dismantled it and did all the things you do under these circumstances but it was never as free as I would have liked. I subsequently moved it indoors into my test gear cupboard through which runs my hot air central heating duct so it's always nice and warm in there. When I needed it again I found it to be absolutely and perfectly free. I wonder if the insulation material is hygroscopic to a degree and swells up when damp. Perhaps a spell in the oven at a low temperature might effect a cure for your sticky Variacs? (That's if you can sneak it past HTMBO)

[tvden]

Originally Posted by Leon Crampin

A very good question - I've a similar Claude Lyons variac (beautifully made) which is also very stiff. Has anybody any words of wisdom?

Leon.

I have one of these but I have always kept it in a warm dry environment and have never had any probs you can almost spin it round

[Leon Crampin]

Thanks for the comments. I'll give mine a holiday in the airing cupboard for a few weeks and see how it goes. Another possibility might be to apply DC to the windings for a few days to warm it up a bit.

Leon.

[Mike Phelan]

WD40 can cause more problems than it resolves. It is not a lubricant.
My guess is that moisture has penetrated the SRBF or SRPB and caused it to swell. When I ever lubricate similar materials, I find that petroleum jelly (Vaseline) is quite good.

Mike
I'd just try keeping it in the warm for a week or two.

[coil1234]

Thanks for all the replies, looks as if I need to bring it indoors, I knew the accumulated wisdom of the forum would come up with an answer.

Regards Mike A

[Sean Williams]

If you feel the need to strip it again a coating of cellulose lacquer would help seal it against further damp....

[murphyv310]

Hi.
I certainly would suggest a good drying out in a warm room, WD40 is good for some things but perhaps not this.
I also wouldn't use cellulose lacquer as you will seal in any residue dampness and also the layer has a finite thickness.
I have "repaired" this type of assembly before and after the drying process it is a good idea to polish the spindle with 1000 grade wet & dry dipping in oil (3 in 1 or light engine oil) after this cover the spindle and bearing in good quality silicone grease this should now last for years, i've not had a bouncer in 20 years.
Trevor

[Aerodyne]

In my experience the paraffin-based WD40 should be kept well clear of all thermosetting plastics products such as valveholders as it can cause more problems than it solves. Bakelite - and resin-bonded paper products such as Paxolin tubing, PCBs etc - are hygroscopic and will swell under damp conditions, given time. This mechanism is a well-documented cause of the destruction of Bakelite cabinets by expanding the wood flour filler, producing a rough surface texture that cannot be levelled properly and will no longer take a polish, no matter how firmly the Brasso is rubbed!
I'd certainly go along with Mike's petroleum jelly lubricant (useful stuff, I'm told ) or Trevor's silicone grease.
-Tony

[Oldtimer74]

I agree with all the replies but have found that silicone grease is fine for glassware joints but is not such a good lubricant where metal is involved. I use Castrol CL grease for anthing which you want to keep the damp out of (getting it dry first of course). Usually available at Halfords.

[coil1234]

Happy to report after a few weeks indoors my variac is much easier to turn Thanks again to all who have contributed advice.

Mike A

[mastermanx2001]

What about graphite grease, many years ago my friend's father who was Technical Manager of Vitavox told me to use Graphite grease where items need lubrication that will last. It worked great on nuts and bolts on cars to stop them seizing. I found that years later the nuts and bolts would still be free. Even if used on manifold nuts where the heat would burn off the grease, some of the graphite was still there to lubricate.

I think I remember when WD40 first came out it was called Rocket WD40 and there were some problems with it and some plastics. I seem to remember that it would make them swell. It was a long time ago though.

[mikelect]

Originally Posted by mastermanx2001

What about graphite grease, many years ago my friend's father who was Technical Manager of Vitavox told me to use Graphite grease where items need lubrication that will last. It worked great on nuts and bolts on cars to stop them seizing. I found that years later the nuts and bolts would still be free. Even if used on manifold nuts where the heat would burn off the grease, some of the graphite was still there to lubricate.

I think I remember when WD40 first came out it was called Rocket WD40 and there were some problems with it and some plastics. I seem to remember that it would make them swell. It was a long time ago though.

Graphite is conductive not a good thing to put on a Variac

Mike

[mastermanx2001]

Good point, safety first of course. no problem if used sparingly on metal bearings. I am not familiar with the design of the variac.

[GMB]

I use MDS grease where I would previously use graphite grease. I think it works better and it too is based on a solid lubricant (molybdenum disulphide) and so works in the same way as graphite.

[mastermanx2001]

Originally Posted by GMB

I use MDS grease where I would previously use graphite grease. I think it works better and it too is based on a solid lubricant (molybdenum disulphide) and so works in the same way as graphite.

Yes, Moly grease probably better in this application, on old cars, over many years, my experience was that the graphite grease did a better job of stopping nuts and bolts seizing than moly. I know that there are things like copper loaded grease for this sort of purpose as well, but these cost much more and did not really seem any more effective.

[FrankB]

I purchased several of those Variacs (R) and they had the shafts "frozen" for peanuts.

I finally had to drive the center shafts with a drift- very carrefully.

Polishing down the shaft with fine sanding paper and then lubing with silicone grease solved the problem.

The shafts on mine were all Bakelite, and the original lubricating grease in the bearing hole had caused the Bakelite material to swell up.

[GMB]

lubing with silicone grease

Be very careful with silicone compounds on anything electrical. They are highly insulating and have the property to creep along surfaces and if they get onto contacts they can cause a lot of trouble.