Belt Sander Motor Problems

[Mathew Newton]

I dug my cheap belt sander out today having not used it for several years, and indeed not used it all that much back then either. Shortly after starti ng it up whilst it was running there was a distinct smell of burning and su re enough smoke started pouring out...

I pulled the plug and took the cover off expecting to find either a build-u p of sawdust or perhaps dry bearings. I found neither but did find that the smoke seems to be coming from the windings or the brushes as seen in this video:

(Apologies for the quality - I'm using a crappy camera that I keep in the w orkshop)

Any ideas what's wrong? I'm no expect but the brushes seemed fine when I re moved them, and indeed I cleaned and filed them up just in case. As you can see towards the end I gave the motor a spin to show that it is moving free ly. There's certainly a lot of hot generated by whatever's happening - the motor remains hot for quite some time afterwards.

Any thoughts as to what's wrong?

Mathew

[Bill Wright]

Is it meant to run on UK mains voltages? Has oil got on the commutator?

Bill

[Mathew Newton]

Yes, definitely a UK tool.

I don't think anything could have got on the commutator - it's been in big toolbox (admittedly with a bunch of other power tools) and showed no signs of anything having dripped on it.

I can't remember how 'powerful' it was when I last used it but my first thoughts when turning it on today was that it ran slower, and noisier, than I seem to recall.

I'm wondering if the insulation on the windings might have perished with age and I've got a short? Could this explain slow(er) running and the smoke?

Mathew

[meow2222]

, and indeed not used it all that much back then either. Shortly after star ting it up whilst it was running there was a distinct smell of burning and sure enough smoke started pouring out...

Its buggered

age and I've got a short? Could this explain slow(er) running and the smoke ?

I reckon so

Sometimes its poss to get such motors going by running in series with a 3kW heater. But in your case Im not optimistic. Rewind it if you've endless pa tience and no money, or bin it.

NT

[John Rumm]

Yup, in technical terms, its shagged.

Looks like the insulation has failed somewhere in one of the motor windings. Hence the lack of speed and the rough running. A short in a winding also draws much more current - hence the heat, magic smoke, and complaints from the brushes.

You can get new armatures for some of the more high end tools, but its unlikely for a cheap one. Probably not cost effective to have it rewound either.

Look for a nice second hand Makita on ebay?

[John Rumm]

Yes, yes and yes, would be my guess.

[meow2222]

Some of the pawn shops do a good line in tools. With inconsistent pricing there are sometimes bargains.

NT