rewinding tractor starter motor

[AJH]

I had a mishap this week when the main terminal on a tractor starter motor became loose and rotated allowing it to contact the motor winding terminal, while the engine was running. I didn't notice anything until the damage was done.

As this is an old ford industrial engine the starter is going to take a while to arrive so I thought I'd see if the old one could be made functional again.

The armature seems okay, no shorts to the iron core and the commutator and brushes are serviceable.

One of the 4 stator coils has shorted and burned off its wrappings, the others seem fine, the copper is so large a cross section it is not possible to discriminate the resistance as it is so low but the copper rectangular section looks sound.

Now looking on you tube if anyone has the time to watch some old school workmanship:

at 2 minutes the guy is cutting some insulation sheet, anyone any idea what it is and if it is avalable?

Later at 4:20 he wraps with a tape, any ideas what it is and where I can get some?

At 5:40 a paint is used to cover the wrapped coil, is this likely to be anything special?

[GB]

How hot does this thing get in normal use? I suspect that the guy in Pakistan is just using ordinary PVC sheeting. However, as we don't know for sure, why not use some oven liner?

Sellotape? :)

However, to avoid potential problems use high temperature tape:

Lots of high temperature paints available.

I gather you have a new starter on order, so this is a temporary stop gap solution. I'm not sure what the downside is if it fails? Will it bork the engine, or just put you back to square one?

If the downside risk is small, I'd just use ordinary plastic insulator and ordinary tape and paint. If you want to be sure it's a good repair, then spend 20 quid on high temp bits to fix it.

And whichever route you go, you NEED to spend another 20 quid on PPE before you burn the existing insulation off. Life is cheap on the sub-continent.

[JNugent]

Not seen that before (unless, as suggested by another poster, it's PVC).

We used to use Kraft <sp?> for layered insulation.

For example:

That looks like a woven insulation tape, a bit like this:

[But completely wrapping stator coils was not common in the armature winding world.]

I can see the bright colour, but suggest that that is a varnish rather than a paint. The purpose (maybe among others) will be to hold the coil turns firmly and prevent abrasion of the wire's own insulation by reducing vibration "chatter".

[jon]

Or even PTFE tape.

[The Natural Philosopher]

'insulation sheet'; on old kit would be something like phenolic resin impregnated paper - a sort of bakelite lookalike - but that looks alarmingly like simple plastic sheet. Which will melt at high temperatures.

You can buy stuff like that at any model shop. Oh thinking, I'd use ptfe.

Almost anything would do. Back in the day it might have been cotton or linen.

I wouldn't use nylon - cotton 'webbing tape' is probably best these days.

Typically old electric wire was insulated with shellac. French polish to you.

That looks like 'any old muck'. Its only there to stabilise the tape.

For the authentic Awful Smell on overload, why not use shellac?

[Brian Gaff (Sofa]

Well some coil rewiinders tend to pot the winding if there is room to achieve this, it often last longer than the traditional vanish approach. Brian

[Brian Gaff (Sofa]

We used to use Mica, but the bend radius needs to be quite obtuse. There is also mylar film that is often used in a tape form, its often yellow, what colour is it in the video? Brian

[Chris Green]

Nice one! :-)

[nightjar]

The sound it makes while being is the same as some very thin phenolic resin sheet I used to have, but that was brown.

It looks like asbestos tape and if that is being done in Pakistan, it might be. However, there is a wide range of safer alternatives;

As others have said, that looks more like a varnish than a paint. The same web site offers these:

[AJH]

Well it gets pretty warm as it is 50mm from the exhaust manifold and it looks like the nearest one to that is the one that failed however I'mloathe to use what has not been used for this before and am surprised not to find someone who has done this in the past here.

That looks suitable though what's on there on the remaining coils looks like a cotton cloth tape.

Yes on order but no acknowledgement on when it might arrive and the machine is stuck in a wood, I may have to take another tractor to drag it out and then bump start it. If I can fix this before the other arrives it needs to be good enough to last as it's an awkward job to fit in a tight space.

No need to burn anything off the shorting out did that.

As in plumber's tape, I'd think it not strong enough.

[AJH]

Thanks I wonder how that differs from the oven liner.

Yes looks about right

I wondered what that smell was.

[AJH]

Good find but one page says sold only in the Swedish market.

[nightjar]

I didn't see that, but it was the first hit I got on a Google search for motor rewinding supplies. There are plenty of motor rewinders in the UK and they must get their supplies from somewhere.

[AJH]

Thanks for taking the trouble to look. In the meanwhile I have ordered a sheet of 0.5mm PTFE, the adhesive PTFE covered fibre glass tape and some exhaust paint. The PTFE won't be here till June and I hope the new motor will be fitted by then, so I will do a repair at my leisure.

[newshound]

Full marks for considering a fairly out of the normal repair. That's one job I have never done myself (although having seen from YouTube how it is done, I realise it is not quite so daunting as it appeared when I was a cash-strapped youth).