Numatic Henry (year 2001?) stopped, fixed.

[Chris Bacon]

Well, I thought it was about time I took the vacuum cleaner around, it's about that time of year... so I used it for 5 mins, then got a phone call. After that, Henry would not start.

The problem turned out to be that the brushes, which were very tight in their brass housing. I pulled them out (had to bend up the brass end closure on the housings and pull quite hard on the brush leads), and scrape the sides of the brushes a little with a knife, then put them back in & bend the tabs back).

Normal service resumed. New brushes are only a fiver, but did not need them.

[Harry Bloomfield, Esq.]

Chris Bacon formulated the question :

I fancy our Henry has the same issue too - It has suddenly begun running rough, amid lots of sparking and runnung normally for a bit. I have had carbon brushes stick in their holders before. I find it best to rub the sides on sand paper

[GB]

When this happened to ours (1998 vintage), it didn't occur to me that the brushes were just jamming like that. I bought new ones, and the old ones were only a quarter of the length.

When they get pretty short, maybe they jam like a drawer that's in crooked?

[newshound]

I've needed to "cut down" oversized brushes a few times when the right size was not available, I usually "finish" them on medium-fine emery cloth or paper. That removes material quickly, but maintains almost flat surfaces. Similarly for brushes that are binding.

[Chris Bacon]

They might, but these were hardly worn at all. I suspect damp and lack of use allowed some sort of "corrosion" on the inside of the holders. The brushes were hard to remove, they were tight in the housings. Still, it's back to normal now.

[alan_m]

I don't know about the Henry as I haven't had to replace brushes yet but when I had a Hotpoint washing machine the brushes were still very long when worn out. Initially I assumed with so much of the brush left that it couldn't be the cause of the motor intermittently stopping spinning. It wasn't until I purchased replacements and found the brushes to be 3x longer than the ones in my machine that I realised that the problem was with the brushes.

If the brushes in the Henry have been sparking the assembly is likely to have got hot and there would have been a lot of hot carbon dust fired back into the housing.

[Jim Jackson]

I had a hotpoint washing machine for 25+ years and replaced the brushes several times. I have a hotpoint vacuum bought in 1989 and used all the time, and never had a motor problem - will the motor be brushless? Or have I been lucky?

cheers Jim

[Brian Gaff (Sofa]

So to what do you suggest the fault was due to? Is it the mere age of the cleaner, some change in the properties of te brush assembly making it not spring onto the comutator or what? Brian

[Harry Bloomfield, Esq.]

Jim Jackson was thinking very hard :

You have been lucky - there wasn't such a thing as brushless back then. Only the high-tech battery vacs have brushless even now.

[Harry Bloomfield, Esq.]

Brian Gaff (Sofa) laid this down on his screen :

I wonder if age and moisture might cause the carbon to swell up in the holder?

[Jim Jackson]

I had sort of guessed. So since I've brought this up - tomorrow it's going to fail :-(

The other half wants a new vac anyway. Jim

[The Natural Philosopher]

Course there was. synchronous and squirrel cage style motors/ Problem was they are one speed motors or low torque motors :-)

Hardly high tech these days. I've been flying model planes on cheap brushless motors (but not as cheap and nasty as the Dyson ones) since around 2007

You can get a motor and controller for less than £20.

[The Natural Philosopher]

No. Shouldn't do.

People think that brushes are worn out because there is no brush left, but it is probably better to design the thing to run out of spring first, or to have the push and a tube tapered, so that the brushes jam before they are totally worn out....

smashed up brush remains jammed between commutator and brush carrier = not so good

[Harry Bloomfield, Esq.]

Harry Bloomfield, Esq. used his keyboard to write :

I have just pulled it apart to have a look. The brushes were absolutely fine, almost no wear, but the suction side bush or bearing has a lot of sideways play in it. I tried to remove the impeller cover, to take a look at the bush/bearing, but it was too tight to get off without destroying the motor - the cover did just seem to be a push on fit.

I didn't actually find anything fixable, but apart from the bearing grumble at start and end of the run - it ran absolutely fine.

[Chris Bacon]

I think there may have been some slight corrosion on the inside of the brush holder. Perhaps the brushes themselves might have been slightly tapered, but I rather doubt it. I had to pull quite hard on the braided wires of the brushes, and worried they might break or pull out, they were that tight. There were marks on the sides of the brushes where they scraped as they came out. The commutator was in good condition. The brushes were scarcely worn. The springs were fine, no sign of anything getting hot.

[Chris Bacon]

I replaced the brushes on my vehicle's alternator. They had worn out, and the stub of the brush was prevented from rubbing on the slip ring by the length of brushes's wire, which was soldered into the end of the brush holder. Replacement was a matter of desoldering, making the hole in the end of the holder a little bigger, to get the wire from the new brush in, then holding the brush "extended" (with the spring around the wire...), and soldering the wire back. There was a mess of carbon and copper particles in there, one slip ring in particular had been badly worn.

This shows the procedure:

(I didn't break off the little plastic bit though :) )

Same bloke does "how to change the slip rings".

[The Natural Philosopher]

'new' motors are between £16 and £50 on e.g. ebay I think they come complete with the fan/vacuum assembly

Probably mot much point in trying to recon them

Rumbly bearings will use more power and generate less suck until the runout is large enough to case the motor to jam

suggests that you really cant get at the main bearing, and that jammed brushes due to presumably dirt are not unknown

[Harry Bloomfield, Esq.]

The Natural Philosopher submitted this idea :

They would not be classed as 'brushless' :-)

[Harry Bloomfield, Esq.]

The Natural Philosopher explained :

+1

[The Natural Philosopher]

In fact they *are* classed as brushless

A 'so called brushless' motor is simply a synchronous motor fed from a variable frequency supply