The dual-motor central vac unit started smelling funny tonight. Burning phenolic is the best description I can muster.
The motors are typical good quality Ametek-Lamb units; they fluttered a bit while running, but there was no bearing noise. I haven’t opened up yet to have a look. They’re about eight years old.
Any suspicions? Brushes maybe? (I’m hoping that’s what it is.)
Thanks.
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Replies
>>>How many miles on
>>>How many miles on it?
Tons.
I'll open it up and have a look. Thanks.
Did some reading.
Might be brushes, but the hot phenolic smell can mean some armature damage, so I'll take it to a trusted pro repair shop that can install brushes, check the armature, and dress the commutator. Hopefully around $100.
Then it should be good for five or six more years. After that it's time for new motors, which I can easily do. (Easily do, that is, for around $800!! View Image)
Suckin' up dirt can be an expensive proposition.
When the brushes burn you will get some overheating of the commutator -- that's mainly what produces the smell, I suspect. (Arcing by itself will produce more of an ozone smell.) Whether the commutator then needs to be turned depends on how bad the arcing/overheating got, how much the commutator is worn, and, frankly, how picky you are. Turning the armature will (maybe) make the brushes last a little longer, but it's often a significant expense, and it can (depending on multiple factors) cost you in terms of total lifetime for the motor.
Does turning the comm. involve removal and work with a lathe-like apparatus? If so I'll need to hire it out.
Generally for dressing or turning the commutator the rotor is removed. Depends, though, on what's meant by "dressing", how big the motor is, and how much access there is. Most motors can be dressed in place if there is sufficient access to the commutator, and I'm guessing that the really big motors can be turned in place.
You can do a degree of "dressing" yourself, in place, and it's reasonably difficult to FU badly. First, use a pencil eraser to clean the commutator as you turn it. (You many need to unscrew one or both brush holders to gain clear access.) That may be all that's needed to clean things up nicely, and you'll be better able to see the condition of the commutator. Then, if there are just scorch marks and maybe some very light pitting and roughness, you can smooth the commutator with fine emory paper. SOP is to cut a long, narrow strip of the paper, work it around the commutator, and work it back and forth like a cable saw, or you can remove the rotor to do this.
If the commutator is badly pitted or scored, though, it probably needs turning.
(Of course, there's some possibility that you'll get in there and discover that this is an induction motor with no brushes. I've never worked on a whole-house unit, so can't say, but the smaller vacs I've worked on have all been "AC/DC" units with brushes.)
involve removal and work with a lathe-like apparatus
Before I had a metal lathe (like 35 years ago <G>) I turned armatures in a drill press with a file and steady hand.
Always worked OK for me, still have a couple of drills I fixed like that.
First thought on the OP post was the filter has a hole and dust getting thru to the motor.
Have seen dc commutator mmotors with brushes totally gone and the spring burned off from running with the spring as the brush and the commutator with an 1/8" groove - pretty much do need a lathe for that (or long time with the file) if the commutator is thick enough.
Found the culprit. The
Found the culprit.
The first pic is the lower motor, with a somewhat "normal" commutator.
The upper motor's comm. shows obvious signs of distress.
I'm not certain what caused this, as the brushes appear to have some meat left on them. Either way, I don't have the equipment to turn it, so it's off to the shop.
Thanks for the help.
Scott.
Even though the brushes seem to still have some "meat" as you say, often what happens is that they become constained somehow -- perhaps because the wires that connect them have pulled taut, perhaps because the springs are fully extended. In one case I found that the brushes had gotten short enough that they twisted slightly in their guides and jammed. Once the brushes start making poor contact the commutator erodes fairly rapidly.
In any event, that commutator is indeed worn enough that it merits turning, or at least heavier "dressing" than you're apt to achieve with simple means, so it's not unwise to take it to the shop.
(I'd probably just clean it up and replace the brushes, but there's a little bit of JunkHound in me.)
Excellent excuse to buy a nice little tool, and save the shop visit cost!!
On sale at $499 at HF - ps: no, I do not have HF stock, dont even know if publicly traded.
View Image
>>>Excellent excuse to buy a
>>>Excellent excuse to buy a nice little tool,
Thanks Bud, I like the way you think, but $499 for a lathe ain't in the budget right now. Besides, I'm really not much of a metal worker.
I'm guessing I'm in for about $150 for one armature turned, one set of bearings, and carbons all around. Might do bearings on motor #2 too, but I'll leave that up to the tech.