Centrifugal switch bakelite broken problem.

Hi, I have an old Brook Motors induction motor (1440RPM) driving a circular saw. It's probably early 1930s. I was cleaning off a build-up of old grease, and stupidly dropped the centrifugal switch, and a woodrough key shaped part of the disc broke off.

So I degreased it and blew off the solvent with compressed air, and used (slow) araldite to stick it back together.

It would be nice to reinforce it, perhaps by putting a metal ring around the outside of the disc (imagine a section cut from a tin can), retaining it with araldite and folding the edges down to help it stay on. Something like that. However, I can'r fins ant tins of a suitable inside diameter (the disc is 2" diameter, by vernier calipers).

Does that sound a reasonable idea? Any suggestions, or anything else to do?

What about looking for a tube or pipe of suitable size or one which could be bored out ?

Just an idea. I have used rings like this for similar jobs.

If the part that broke off is not a working part of the switch you could remove the same amount of material from the opposite side to keep the mass balanced.

To answer your question trepan a ring from paxolin/tufnol including a recess with smaller diameter than the switch so it will support the existing plate when araldited back in.

Emgee

New switches are available, at a reasonable cost. The design has not changed much over the years.

Regards

Gray,

Make a ring. Turn a piece of material of correct dimension and wrap apiece of tin strip or coper wire round to form shape. Then cut ends across square and solder together.

David

What about a worm drive clip, used to be called Jubilee clips.

Reinforce the switch with fibreglass tape and a coat of resin. Its lightweight, strong, will stick to the switch and does not conduct electricity. Available from some hardware stores.

Or a simple solution. Bind the switch with string or wire and coat with epoxy glue (Araldite, etc)

Edited By Paul Lousick on 10/07/2022 13:05:20

Thank you. I would bore out a piece of tube, had I one suitable, but currently no lathe.

Adding a new ring over existing is an interesting idea and might be possible via careful electric drill bodgery.

Usure about new switches. Again, possibility I will have to look further into. The shaft is 3/4". Would a 19mm one go on, I wonder? The problem I had when looking is that they seem to be 1500RPM ones generally. The motor's plate says "Full Load speed 1410". I certainly don't want to damage the motor!

I had wondered about making a ring by soldering. Perhaps I could cut some copper sheet or even flatten some copper tube and use that.

Unfortunately I don't think there's room for a Jubilee clip, the button that the disc presses is not ver high and I think the clip would foul it.

I'd also wondered about filing a groove in the edge of the ring and soldering or guluing that.

I'm going to see if I can add a link to a pic. Fingers crossed! EDIT (again) I hope I hgave not broken the rules. I will scurry off to look them up and find out about psoting pics (Edit, edit, got there in the end, easy when you know how)..

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If all else fails, you can bring out the switch pair and use a push button switch ( NOT a bell Push) and YOU do the switching yourself. Mount the push switch in a substancial plastic box, very close to your existing power switch, insulate the pair with some glass tubing and remember how to use it to start the motor. Not the best idea but needs must, Brook Crompton Parc are not what they used to be when in Huddersfield, apparently owned by a holding company in PRC. John

I wonder if a piece of fibreglass circuit board material, say 1mm thick unclad could be glued on and still fit in the motor?

Instead of a section of an old tin can, how about filing a little groove around it, deep enough to accept a length of wire (stainless, copper, whatever) then inserting the wire - twist the ends together for added strength. Then covering it with Araldite - sort of like reinforced concrete. I've successfully repaired several hard plastic items using this technique.

Having had a centrifugal switch fail I replaced it with a timed relay that powered the start winding long enough for the motor to run up to speed.

No further problems.

John

Get a new switch from any motor rewinding co.

Roy

I used to start a Brooks 1HP circular saw motor for years like that with no problems.

John

Back when you could get inside motor starter switches I wired a second relay to the start button. Hold the button down and it energised the start windings, let go and it de-energised the start, but the run stayed latched in. Worked a treat.

Hi Duncan, I like that idea, reminds me about the old star/delta starters with the lever for start and then run.

Regards Nick.

The days when rewind shops would even consider single phase stuff have long gone, just so expensive, unless its a very special motor.as fitted to some top quality high speed wood working machine. Sad to say, generally speaking single phase is a throw away job, cheaper to get a new one. from PRC or their agent. John

Having had a think, and a rummage, I see I have some old white (and some very old, brown!) electrical junction boxes, as well as a fascinating collection of other obsolete things (like the light-bulb socket adapter so that you could plug your vacuum cleaner into the lighting circuit..., anyway, I digress).

What do you think these old junction boxes are made of? The brown ones may be bakelite, the white ones...? They're the hard sort, that bits snap off, not flexible at all.

I could use the flat lid of one of those, maybe... any thoughts?

Heatshrink comes in 82mm flat-width tube = 50mm dia. - maybe a narrow 'tyre' with a small overhang either side would pull itself tight over the edges of the rim?