Food mixer repair

Universal motors are not precision devices. If you look at the balancing gouges, you can see that some are not done to a high level of engineering accuracy. The imbalance is never zero. If the motor is operated in isolation, with no mechanical impedance it will reach speeds well beyond the design rating and a negligible in service imbalance will become quite severe.

If you have run it on mains, fine. But it isn't wise if there is a low Voltage supply to run it up on first.

Your initial question suggested you were unfamiliar with the practicalities of that type of motor, I was just trying to help.

I had an episode with a vacuum cleaner motor a few years ago, it was only

Malc

May self destruct

I'd have thought, if it was a brushed motor then the actually commutator was now toast after all that sparking, so might well be unrecoverable, even if new brushes were fitted, capacitors changed etc. Brian

Exactly, which is why I said, its been run in the fault mode too long. The contacts on the motor itself are probably knackered by the stuck brush. Brian

Yes, but I had one in a drill, that even then would not work well, turned out to be shorted turns in one of the coils on the rotor itself causing the rather interesting pong. A junk item. Always need to expect the unexpected with mass produced devices. Brian

A shorted turn (or turns) is the 'expected' not the 'unexpected'. All my mains motor failures with symptoms as described here have been shorted turns or other armature failures and not brush/commutator problems.

If the failure happens 'suddenly' then it's almost certainly a shorted turn and not worth trying to fix.

No. The RPM of a motor is determined by the need to generate back emf that matches the applied voltage. That emf is a linear function of the turns number, the RPM and the flux in the field windings. The flux in the field windings on a shunt wound motor is limited by the applied voltage and the inductance - it is load insensitive. If the motor is series wound then under no load the flux drops anyway, also self limiting. If you grind through some tedious mathematics, you will find that the ratio of the volts lost to resistive effects is why a motor slows down under load as the current increases. A typical motor with say 70% efficiency will therefore only be perhaps 50% faster off load than on.

Most mains motors are better than that.

Often worth fixing with a new armature if readily available at a cost not equal to that of the whole machine.

I replaced one in my Makita SDS - cost about £25 for the part IIRC.

My Stayer SDS which has lasted me a good 20 years so far and looks likely to last at least the same again cost less than that for the whole thing.

Anyway I suspect that a new armature for a food mixer or similar will either be unobtainable or cost more than a new mixer. Spares for such as Makita are *supposed* to be available as Makita are 'professional' and a price of £25 isn't too silly for a tool that has cost considerably more than that.

Any spares look like hens' teeth?

You would think so.

I would not rely on the fact there was a fault to prevent overspeed.

Like everything else, there is a slim chance of injury, but some effects are not reversible. A bit like a universal motor :-)

Anyway, the only thing that will cause a stink is either contamination, like a dollop of stray batter, or a winding. I would have thought Tim would have found that by now.

I assume he has not actually removed the armature yet, if he hasn't identified the duff coil.

It still does not excuse not taking every care to prevent injury though.

Malc

yep. HM510 simply a model no one cares enough to keep going

And no one is even selling em on ebay. Not even for spares.

You can test the armature for earth shorts with a resistance meter, but its most likely that some mains rated cap has popped - they do after about 30 years. Or the brushes are shot or jammed. I cant remember what the original fault report was, but when you can replace the whole shooting match for under a £100 one has to wonder if the place for this isn't in the bin

Bin it. Work on something worth doing,

NT

I think it is worth trying new brushes if they can be obtained. They are are always much longer than you think.

Thanks for looking. I?ve had a closer look at the armature now in good light and it?s got some decidedly ?toasted? looking insulation on the enamelled wires at the opposite end from the commutator. I got distracted by all the sparking at that end and hadn?t looked properly at the other end. ;-)

As other have said, only really fit for the bin. I was looking at it for a friend. The owner has had it for many years and didn?t want to dispose of it if it was repairable.

Tim

Not quite. I've run kit in that state easily before using the series method.

NT

Feel free to rake through my bin...

Tim