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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 8th Dec 2019, 4:34 pm   #41
ajgriff
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Default Re: Damaged vintage variac

Have just read some of the earlier posts again and looked at the time lapsed section of JW's video part 3. Am I right in thinking that it's the grub screws holding the collar to the insulating tube that you've been unable to shift? I wonder if these are the things on which to concentrate your efforts. If the collar can be freed it'll be much easier to remove the rotor from the top end of the tube. Just thinking aloud really.

Alan
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Old 8th Dec 2019, 4:54 pm   #42
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Default Re: Damaged vintage variac

I will make the decision on replacing the brush nearer when it comes to re-assembly, which may be some time yet as everything needs to be cleaned thoroughly and re-painted before it can be re-assembled. This will give me some time to think about it, although I am now inclined to go with the 'leave well alone' advice until proven otherwise.

The top plate and rotator are made of aluminium/mu-metal or similar. The insulating material I think is phenolic resin. I initially thought it might be Bakelite, but not sure.

I seem to remember PlusGas being mentioned before. I don't have any, or anything similar, so just used what I had to hand. I did wonder about thinning some cycle oil with with white spirit? Regarding PlusGas, which to go for: the spray can or the 'oil can' with the nozzle? I am inclined to go with the the nozzle as that would make it easier to direct the fluid rather than using a spray can, but I am a little worried about the potential for spillage if the consistency is as thin as WD40? Sorry but I have not used PlusGas so am not familiar with its properties.
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Old 8th Dec 2019, 10:08 pm   #43
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Default Re: Damaged vintage variac

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Have just read some of the earlier posts again and looked at the time lapsed section of JW's video part 3. Am I right in thinking that it's the grub screws holding the collar to the insulating tube that you've been unable to shift? I wonder if these are the things on which to concentrate your efforts. If the collar can be freed it'll be much easier to remove the rotor from the top end of the tube. Just thinking aloud really.

Alan
Alan, I had no problem removing the grub screws from the collar. Just as well as the ones holding the 'steering wheel' knob to the top of the shaft will not budge. Once the two screws in the collar were removed, the shaft complete with knob came away from the insulator. The collar does seem stuck solid and it didn't even occur to me that it can come off. If it does and the insulator can be pushed through the top plate then that might indeed make things a bit rather easier. The top plate is firmly seized on insulator as well so this is going to be a challenge!
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Old 8th Dec 2019, 10:32 pm   #44
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Default Re: Damaged vintage variac

Plusgas is a similar viscosity to WD40 - it has to be so that it can creep.

To be honest though, the reason it has gone tight on the shaft is probably due to the phenolic shaft swelling - be warned that this may well end up going horribly wrong if too much force is applied.

a proper puller is best, you can apply a constant pressure to the shaft, and hopefully this controlled method will be kinder to the parts.
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Old 8th Dec 2019, 11:18 pm   #45
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Default Re: Damaged vintage variac

I have a couple of these 8A jobs. One came very corroded, and the 'plastic' tube in the middle had swollen and gone very tight - I think they swell if they are stored anywhere other than dry. It lives outside in a shed now and is going a little tight again. The grub screws came out on mine and the steering wheel pulled off, but as I remember it was a bit of a nervous moment. Your brushes look a lot newer / less worn than anything I have - I suggest they're fine.
cheers
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Old 8th Dec 2019, 11:27 pm   #46
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Default Re: Damaged vintage variac

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Originally Posted by WaveyDipole View Post
The collar does seem stuck solid and it didn't even occur to me that it can come off. If it does and the insulator can be pushed through the top plate then that might indeed make things a bit rather easier. The top plate is firmly seized on insulator as well so this is going to be a challenge!
The collar definitely comes off (see part 3 of video). Unfortunately JW doesn't show it being removed or replaced. It just magically reappears in the time lapse reassambly clip. If you remove the grub screws completely a bit of waggling and twisting might free the collar. If that works you could then try drifting the tube out as you did with the bottom plate.

Alan
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Old 9th Dec 2019, 1:04 am   #47
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Default Re: Damaged vintage variac

Worth noting that the top plate should just slide off (in theory!) once the collar is out of the way but the rotor is held in place by more grub screws as it has to rotate with the tube. I think you will only be able access the grub screws once the top plate has been removed. This would explain why it's not possible to shift the rotor towards the bottom of the tube. Might not need the penetrating oil after all.

Alan
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Old 9th Dec 2019, 11:38 am   #48
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Default Re: Damaged vintage variac

The attached sketch illustrates how I think the whole thing goes together and comes apart. You will notice that drawing was not one of my better subjects at school. Hope it helps anyway. Good luck!

Alan
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Old 9th Dec 2019, 2:28 pm   #49
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Default Re: Damaged vintage variac

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Plusgas is a similar viscosity to WD40 - it has to be so that it can creep.
I expected as much and those cans with tips do not appear to be supplied with a cap? The aerosol seems significantly cheaper but does not appear to come with one of those thin applicator tubes. The only place I can find the stuff is on Amazon.

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To be honest though, the reason it has gone tight on the shaft is probably due to the phenolic shaft swelling - be warned that this may well end up going horribly wrong if too much force is applied.

a proper puller is best, you can apply a constant pressure to the shaft, and hopefully this controlled method will be kinder to the parts.
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Originally Posted by mark_in_manc View Post
I have a couple of these 8A jobs. One came very corroded, and the 'plastic' tube in the middle had swollen and gone very tight - I think they swell if they are stored anywhere other than dry....
Mark
I didn't think that kind of material could well, but that certainly might explain a lot. The residues would seem to indicate that it has been somewhere damp at some point but perhaps not extremely so. I share your concern about things going horribly wrong, bit with the insulating shaft and the metal components. I did have a puller somewhere but I have not done any work on cars in a long time. I'm not sure whether I still have it, but I will try and dig it out and see if it can be put to good use.

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The attached sketch illustrates how I think the whole thing goes together and comes apart. You will notice that drawing was not one of my better subjects at school. Hope it helps anyway. Good luck!

Alan
Thanks for that sketch. After you mentioned the collar, that is how I now see it. Hopefully I might have some time later to have a crack at it.

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Old 9th Dec 2019, 4:38 pm   #50
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Default Re: Damaged vintage variac

I think it might well be the case that phenolic materials could swell or even be embrittled by agents like WD40 or Plusgas. Certainly, cracks in many materials (all?) can be made worse by wetting the tip of the crack.

As for the question of which is the best releasing agent, I suspect no one can supply some hard data on that matter? I've got cans of the traditional WD40, the newer WD40 penetrating stuff and a tin of Plus Gas. I have no strong inclination to say that any one is better.

B
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Old 9th Dec 2019, 6:03 pm   #51
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Default Re: Damaged vintage variac

Another problem I've seen in association with damp and variacs is that the winding doughnut often sits on a ring of insulating fibre material against the base frame (seems like a sort of dense compressed card, though it may even be an asbestos-type gasket material with bigger or older ones). This can absorb moisture if it's kept in damp conditions and eventually the enamelling fails in places and results in problems that can result in write-off, such as shorted turns and fusing, or nuisance such as leakage to earth or serious corrosion. They really are devices that ought to be kept in dry conditions.
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Old 9th Dec 2019, 6:43 pm   #52
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Default Re: Damaged vintage variac

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Heat might be an option as well - not sure what the materials are here, but running it through the kitchen oven (after the roast's out !) might help.
I am beginning to wonder whether that might be a good idea...

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I think it might well be the case that phenolic materials could swell or even be embrittled by agents like WD40 or Plusgas.
B
I fear this might have been proved right.... I can't move the thing at all now! Not sure whether this is down to the WD40 or being stored in the shed for a couple of days. I would add that the shed is very dry, but obviously it is damp outside. I placed it next to the heater in the shed for a while but that didn't help so I will keep it indoors for a couple of days to see whether that loosens it up a bit again.

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Originally Posted by turretslug View Post
Another problem I've seen in association with damp and variacs is that the winding doughnut often sits on a ring of insulating fibre material against the base frame (seems like a sort of dense compressed card, though it may even be an asbestos-type gasket material with bigger or older ones). This can absorb moisture if it's kept in damp conditions and eventually the enamelling fails in places and results in problems that can result in write-off, such as shorted turns and fusing, or nuisance such as leakage to earth or serious corrosion. They really are devices that ought to be kept in dry conditions.
Thank you for the heads up on this. I have now removed them from the shed and brought them inside into the warm and dry!

I dug the puller out but unfortunately it will be of no use for now. Having had another look today, I realised that the top end of the isolator is wider than the bottom end by about 5mm. It seems that the tube has been moulded with a lip (and narrower inner diameter) at the top end which would make it impossible to remove the top plate and rotor via that end of the isolator tube. Even if it were possible, there is only the tiniest of gaps below the collar and some insulating material, the presence of which also makes applying any leverage impractical as the material would almost certainly get damaged.

It would therefore seem that the only way the parts can be removed is along the full length of the tube via the bottom end.
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Old 9th Dec 2019, 7:03 pm   #53
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Default Re: Damaged vintage variac

A long bolt straight through the centre of the insulator, with appropriate oversized washers (at the bottom), and something like a very large 'socket', big enough to clear the diameter of the metal collar at the top, could be used as a 'puller' - that's how we used to 'pull' new small-end bearings, or some gearbox bearings, into / out of place on older motorcycles.

Nuts at each end can be just tightened to provide a controlled 'pull', possibly with the aid of oven heat, and penetrating oil. If the insulator is phenolic, then 100C shouldn't damage it, but may be enough to expand the metal sufficiently to free it off...
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Old 9th Dec 2019, 8:27 pm   #54
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If the insulator is phenolic, then 100C shouldn't damage it, but may be enough to expand the metal sufficiently to free it off...
Maybe the trick would be use a hot-air gun (paint stripper), or perhaps a gas torch, to heat up the metal quickly while trying to avoid getting much heat into the phenolic.

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Old 9th Dec 2019, 8:49 pm   #55
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Having had another look today, I realised that the top end of the isolator is wider than the bottom end by about 5mm. It seems that the tube has been moulded with a lip (and narrower inner diameter) at the top end which would make it impossible to remove the top plate and rotor via that end of the isolator tube.
In view of the lip at the top it does now look as if removing the top plate and rotor by sliding them to the bottom end of the tube is the only way to proceed. I also realise that the rotor is effectively upside down in my sketch which means that you do in fact have easy access to the grub screws. All very frustrating but I'm sure you'll get there in the end. I think I would have resorted to brute force and ignorance by now, probably with disastrous consequences.

Alan
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Old 12th Dec 2019, 7:01 pm   #56
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Default Re: Damaged vintage variac

Its out! The PlusGas arrived today so I gave it a try. It did loosen the rotator after it got stuck again when using WD40. I managed to wiggle it about an inch forward using the PlusGas, applying it, leaving it to soak and then wiggling a bit more, but then it got stuck again. Still, an inch was now enough to get my fingers though and use both hands.

I clamped it to a workbench and again using the PlusGas and wiggling managed to get it to within 2 in or so of the bottom end. At this point it needed more drastic action so out came the socket and hammer. I took my time using generous squirts but not overflowing of PlusGas and managed to get the rotator off, but not before a bit of damage occurred (see photo).

At this point things got rather worrying as I still needed to get the top plate off and didn't want to do any more damage. I tried the PlusGas on it but this only moved it a little bit and I could move it no further by hand, brute force seemed the only way was brute force again, but this time I tried using a piece of wood between the insulator and socket. This worked and I got the tube down about 3 inches of the way which was enough then to get the puller on. The puller did the rest.

Now can begin the work of cleaning up!

Fortunately the damage does not look too severe and it should still rotate when re-assembled. I was hoping that the single piece that came off can be glued it back on with either superglue or epoxy adhesive and got back down to original thickness using some fine sandpaper? Or should I just leave it off?

Hindsight is a wonderful thing and perhaps I should have used the piece of wood in the first place. In my defence, I tried every option before resorting to brute force. Although I would have preferred to have gotten it out intact, things could have been much worse and I am content with getting this far.
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Old 12th Dec 2019, 8:24 pm   #57
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I'd say that was a pretty good outcome . Also sounds like you'll be joining the PlusGas fan club?

B
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Old 12th Dec 2019, 8:43 pm   #58
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Well done indeed. I'd be inclined to use super-glue on the small chip but don't think it'll matter much if you decide to leave things as they are. All plain sailing from now on.

Alan
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Old 12th Dec 2019, 9:44 pm   #59
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I'd say that was a pretty good outcome . Also sounds like you'll be joining the PlusGas fan club?

B
Thanks. I did try heat incidentally but that seemed to make things tighter. Not sure why. The PlusGas was certainly instrumental so a big thanks to Paul Sherwood for suggesting it. I am sure that the outcome would have been much worse without it. It was certainly much better than WD40 for this particular job.

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All plain sailing from now on.
I hope so!

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