Mains motors in the workshop

[Adrian Brentnall]

Hi All

Until last week I was using a little (probably 1/3hp) electric motor to power a combination diamond saw / grinder / polisher unit. I guess that the original motor was ex an old washing machine.

Anyway - last week, said motor gave a gasp and died. Now all it will do is buzz weakly - and won't turn - mains lights in the workshop dim while it's buzzing (not a good sign, I think).

So - bright idea time ! Saw something on the web about using a cheapie bench grinder as a motor - found one in Homebase, and lo & behold the pulley fitted in place of the grinding wheel. Result !

Sadly not - the new little motor is perfectly happy to spin its own grinding wheels - but refuses to start when faced with the effort of spinning the combination unit - it now sits and buzzes weakly..... darn !

The new thing's rated at 150Watts - which is probably a bit on the light side - but any idea why it'll happily spin up its own wheels but not my combo unit....?

Alternatively - what's the chance or fixing the old motor - no magic smoke escaped - so I'm hopeful....

Thanks Adrian Suffolk UK ======return email munged================= take out the papers and the trash to reply

[Roger Mills]

Does the original motor have a starter capacitor? If so, there's a fair chance that that's failed, and gone something akin to short circuit. If you replace that, the motor will probably work.

[meow2222]

Some motors deliver little torque during starting, some produce lots. So not all motors are suited to all loads.

Total rank bodge time:

1. wrap string 10 times round the driveshaft, ensuring that each layer is firmly on top of previous layers so the string grips. Pull string medium-hard at same time as throwing the switch. Very crude but effective.

1. If a washing machine motor has a shorted winding, running it in series with another load will get it going. Now and then you'll find it wont self start unless turned, if it stopped on the dead spot. Unfortunately this bodge cant be used in a washing machine, as the motor must start many times per wash cycle without manual assistance.

NT

[Adrian Brentnall]

HI Roger

Thanks for the reply

I've uploaded some photos of the motor - they're at

little cover over the electrical connections has a schematic which seems to show a capacitor - would this be the starter capacitor ?

If so - do you know where it is ? - do I have to undo the long bolts which appear to hold the two end castings together - and then does it all become clear ??? (or do I end up with a bag of bits )

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[Adrian Brentnall]

So it seems. I even thought I'd get smart (always a mistake!) Tried fitting the pulley to my older bench grinder - it's rated at

300W rather than the 150W that the new ones have.

Still no joy - it just won't start under load..

Didn't actually try with the string - but spinning the grinding wheels by hand didn't do it - it refused to pick up..

I don't really want to have to 'kick-start' this one either

Some photos at

you have a moment... I'm wondering... looks as if it might have a starter capacitor - but I can't see it at the moment - guessing that it might be mounted beneath the paxolin panel with the mains connections on...

Guessing further - looks as if I need to undo the long bolts that hold the two end castings on to get inside - does that sound about right to you ??

Despite having played and worked around electric & electronics all my life I've never really got up close & personal with the innards of one of these before - and don't want to withdraw the two long bolts just for it all to go 'ping' and bits fly everywhere......

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[Tim Morley]

"Adrian Brentnall" wrote in message news: [e-mail]...

Looking at the top picture, is that a shiny wire link between terminals z and a at the top? If so then its wired as the RHS of the 3rd picture. This is marked TS 43-58. I assume that this will be stamped on the motor nameplate. I suspect then that (assuming both above correct) that it will use a start winding with a centrifugal (spelling??) switch. I guess the contacts have gone and not powering up the start winding. Follow that bit of metal coming off the live terminal post, think you may find something there.

Hope I have helped a bit!

[Roger Mills]

I think the schematics on that cover plate show two alternative configurations - one with a strap between A and Z (which is what you've got) and one with a capacitor (which would be external if it existed). So it looks as if you haven't got one - so much for that idea!

Is there anything readable on the larger plate (curved round the main casing)?

[Adrian Brentnall]

Oh - bother I was looking forward to replacing a £1 capacitor and it all bursting into life again..... shucks !

Just been out to the workshop..

It reads Crompton Parkinson Insulation Class E BS170 A73 AC Motor Spares Cat A3 No TS4543H BHP 0.166 RPM 1425 Volts 220 / 240 Amps 1.6 PH 1 Hz 50 Rating Cont

Don't know if that helps ??

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[Roger Mills]

It doesn't give *me* any clues as to its mode of operation, I'm afraid - but I don't claim to be the world's leading expert in these matters.

If you feel like doing a little experiment, you could remove the A-Z strap, and fit a strap between A and S instead - and see whether it works when you tell it to go backwards. It might just use a different set of internal windings in this mode, and they might be ok.

Could you still use it if it rotated the other way - maybe by fitting the belt in a figure of 8 or something if your machinery minds which way it turns?

[Adrian Brentnall]

You & me both !

Now that's an idea.... good thinking.... I was (mis) reading the diagram on the cover plate as being (left side) rotation one way and (right side) rotation 'tother way - but, on re-reading it, it does advise swapping yellow & blue leads to rotate the other way.

Maybe I'll give that a try tomorrow..... (if you hear a loud 'bang' then draw your own conclusions

Oh yes - the motor is mounted on a wooden baseboard - so it can easily be rotated through 180-degrees and all will be fine (until the other winding blows !)..

I'll give it a try and report back - many thanks....

You'd think that there would be a fair few of these things kicking about - but a quick trawl through eBay shows very few of them. I did read that modern washing machine motors are not as 'usable' as thes old-fashioned ones, as they need their controller box to be useful.... progress, eh ??

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[meow2222]

that can be bodged around, but I dont have any decent solutions.

the string will give you at least 10x the speed, it may be worth a try.

I doubt it has one by the look of it. A cord grip would be wise.

Not really, that would separate bits you dont want to separate. Can you get the curved side cover off? If its a brushed motor that would get you access to brushes, and hopefully you could find some other brushes to replace them. But there's not much else you can do in there, assuming youre not looking to rewind the thing.

you would need to be able to put it together again

Its probably a wound stator wound rotor brushed universal motor, meaning it has no separate starting circuit and high start torque. If so, attention to brushes may fix it, and string starting wouldnt. But I cant be sure thats the type of beast it is, so the string is worth a go. Its odd the diagram shows a cap tho.

NT

[Clint Sharp]

In message , Adrian Brentnall writes

You might find that a cheap tumble dryer motor is more what you're looking for.

[robgraham]

I had a single phase induction motor of unknown origin that I used to drive a circular saw. It functioned fine for 25 years until the smoke got out ! But during that 25 years it would regularly do exactly what yours is doing because sawdust got into the centrifugal switch. It was not a sealed motor and on occasions a bit of sawdust would end up between the contacts when the motor was running down and consequently it would go into the 'buzz' mode the next time I started it. Immediate switch off the power. I was fortunate in that I could just push a spring plate through the slots on the motor end with a screwdriver and the problem was solved and away it would go when the power was next applied.

In time however the damage to the insulation accumulated such that the smoke got out as I said. The cf switch operated a capacitor fed starter winding.

I've now got a 3hp motor out of an old pressure washer which is sealed and has an electronic timer for the starter; interestingly the saw is quite a different load from a pressure pump and the machine ate fuses until I got the timing right.

I may be wrong but I think starter caps for cf switched starter windings are smaller than those for constant run ones. Having looked at your pictures, I'm wondering if there is a cf switch under the end plate with 3 screws - I don't think there would be any problems taking off that cover plate and having a look. What I would discourage you from doing is putting poer on to it until you've found the problem as each time you do so you're weakening the insulation in the widings.

Replacement may not be so easy as this is a four pole motor to give

1500 revs - most inexpensive motors of this type are 2 pole and hence 3000 revs. At one point Screwfix had motors and I think Machine Mart did too.

Rob

[Andy Wade]

Sounds flipping dangerous to me.

Bzzzt. It's very clearly a spilt-phase induction motor - the type with an auxiliary starer winding connected via a centrifugal switch (& no capacitor). Tim Morley probably hit the nail on the head a few articles ago, but no-one seems to be listening.

Adrian, I think you'll need to strip the motor down and inspect/clean the switch. Take the long through studs out, get the front end-plate off and withdraw the armature from the front, and the rest should be fairly obvious. Alternatively a local rewinds place (see YP) could probably repair it for a lot less than the cost of a new motor.

[John Rumm]

If you need a new on, machinemart have a reasonable selection.

[Thomas Prufer]

I'd start with the metal cap next to the terminals. Three screws, and much likely to be easy to put back together than taking the motor apart (though it may still come to that). That's about where I'd expect a centrifugal switch to be, too.

Thomas Prufer

[Adrian Brentnall]

Yes indeed - well spotted

Last night in the dark I read it as TS4543 - but the nameplate's been bashed about a bit so I'll take a closer look today in daylight !

When the motor worked, there was a definite 'clunk' as it spun up to speed - that would have been the centrifugal switch, perhaps ??

Yes thanks ! Now I need to get 'inside' this motor to see what's going on..... The only obvious things I can see holding it all together are the four long bolts - unless there's something clever holding the covers on underneath the mounting feet - I'll have another look & report back...

Many thanks - I missed your post last night and it wasn't unti some kind soul pointed it out that I read it.....

Thanks Adrian

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[Adrian Brentnall]

Just about do-able - but not really how I'd like it to work

I'd missed Tim's post until you pointed it out - just read it - makes sense - thanks..

OK - I'll have a look. As I just replied to Tim, there was a definite 'clunk' as it started (when it worked) - so that bears out the centrifugal switch theory.

The motor was very second-hand from a friend - think it cost me a tenner - so if a cost-effective 'DIY' repair is possible then that'd be great.

I use this kit for slicing up & grinding / polishing my kiln-fused glass work - and I've got another 'fair' coming up next weekend - so if it's possible to get it flying again sooner that'd be great....

I'll take a look and report back - many thanks !

Adrian

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[Adrian Brentnall]

I did quickly whip this cover off - all I could see was the end of a bearing and 3 or 4 felt pads delivering oil to it.

I'll take another look in a bit before I start the big dismantling effort ! Thanks Adrian ======return email munged================= take out the papers and the trash to reply

[Adrian Brentnall]

you'd think that Screwfix would supply a can of magic smoke - so's you could 'refill' things like this ??

OK - interesting

Right

I'm a bit cross with myself over this 'bench grinder as a motor' thing

- I was concerned that the pulley would fit on the shaft - never thought that the darn thing wouldn't have enough torque to start up ! Ah well - they were only 12.99 each When we get moved to our new house I shall mount them all on a workbench - the old one and the (two) new ones - won't that look impressive

Don't think so - but I'll take another look in a mo.

Spoeed isn't a big problem - I've got a pair of stepped pulleys - so I can get the right speed regardless of the motor speed (within reason !)

Thanks - if all else fails....

Regards Adrian ======return email munged================= take out the papers and the trash to reply