Does anyone know the failure mechanism of an induction fan motor?

Can you determine how many leads are used for the motor, excluding an earth ground lead?

Is there a low value capacitor assocated with the motor wiring? The capacitor may possibly be more than one value, such as 2uF and 4uF.

A grinding noise may be unintended contact of moving parts. I would inspect the motor's interior, and the blower section for signs of contact of moving parts.

A low frequency growling noise may actually be a result of mildly worn bearings.. a sort-of chatter that takes place as the shaft rattles in the bearing I.D.. there is a specific term for this type of chatter, but I can't remember it. For a Hunter air cleaner that I use daily, standing the unit on it's side eliminates the noise, which I'm certain is due to slightly worn bearings. I've been using it for about 5 years, and it was neglectfully used when I bought it.

With the motor shaft in a horizontal position, notice that the motor shaft has a certain amount of axial movement (end play). At a point near the center of this axial movement, apply radial force finger pressure to the shaft or blower wheel to see if there is any significant amount of movement. Any movement geater than barely noticeable, is bearing wear.

Small motor temperatures often seem to be exessive when checked by hand contact. A thermocouple or other type of contact measuring device would indicate if the motor is actually overheated.

In many types of air moving appliances, the air flow path passing over/thru the motor provides adequate cooling if the motor vents and passages are clear. Additionally, most consumer appliances use motor designs with internal temperature protection devices.. a self-resetting, temperature sensitive, bi-metal type switch that will open at a temperature level below a dangerous temperature. A label on the motor generally states that the motor has temperature protection.

Because the pass-thru air flow cools the motor, this also means that the motor bearings are exposed to fine dirt that gets past the filter elements in normal operation. Periodic internal cleaning of the appliance and a drop of very light machine oil to the bearings will go a long way to extend the effiiency and useful life of the appliance.

Fine dust around bearings, even ball bearings, tends to wick the lubrication out of the bearings.

I'm not saying that your motor doesn't have a thermally induced and/or shorted turn fault, but conclusively finding out if it does, isn't a simple matter. If a capacitor is associated with the motor, that could be a more likely source of the problem.

-- Cheers, WB .............

Bad sleeve or ball bearings will cause the problem you are experimenting. If they are worn out, they will allow the rotor to rub against the armature as soon the armature gets hot and expands a little, thus causing the grinding noise and slowing the entire motor.

In the other hand a winding failure is an one time event: once a shorts develops in a coil the entire winding gets burnt.

I do, but, it was the bearings. I don't know about the air cleaner you mention, although Oreck advertised very heavily on radio programs I used to listen to.

Can you turn off power and rotate the fan blades with a finger? Plainly, they should coast.

I won't discount your hypothesis about a shorted turn, though.

A while back, I bought a very-popular Honeywell-branded three-speed tabletop fan, a Vornado knock-off, and its bearings had run low on oil. It has an alloy steel shaft, probably a variety of Ni Cr, and porous bronze self-aligning bearings surrounded by oil-reservoir wicks; they were "dry".

The motor normally ran hot, est. 125 or 150 C. I tried every lubricant I could easily obtain except synthetic car-engine oil, and none lasted more than maybe (at most) a week. Apparently factory lube was a high-tech synthetic with very low volatility even when hot. I do hope that such a lube is available in small quantities, such as 3 oz or 100 cc (probably not equivalent, btw.)

One summer night, I had the fan on, and awoke to the odor of overheated insulation. The bearings had "frozen" (they could still be disassembled and cleaned), and a thermal fuse inside the windings had opened. It was near the surface, but covered by the insulation.

I decided that it would be foolhardy to try to use the fan any more, and put most of it out for recycling, but saved the rotor, shaft, and bearings just for kicks. (Nice specimen for explaining commonplace tech. to somebody who hasn't seen such things. I feel that we don't tend take apart unwanted stuff any more, although I'm heartened by transparent plastic housings that let us see innards. a rather-new trend).

Interesting that this fan is so popular that the dies for injection- molding the blades have eroded badly enough to unbalance the blades significantly. I also saved the blades, which were nicely balanced. I have no confidence at all that if I returned one of these fans for excessive vibration that doing so would cause them to do something about it, other than to send me another with the same problem.

Fwiw, I was given a Nidec-Torin Alpha V square computer-type fan rated for 240 V operation. It has advanced plain hydrodynamic (surely not "hydrostatic"?) bearings, in which motion probably drags the oil into narrowing cylindrical wedge-like cavities so there's no metal-to metal contact. The lubricant (and seals) must be simply superb. Run at 120V 60 Hz, the motor has a whopping amount of induction-motor slip, but of course it runs at cucumber temperature. I know that it will outlast me (I'm 73), even if I last like Andres Segovia or Dan Schorr, God bless him.

I use it at night while sleeping as a very-gentle, very quiet circulator, so that I don't re-breathe my own stale air.

After it's been running, the coast-down is so long that you'd swear that it has ball bearings.

Btw, those 3-speed induction-motor fans have tapped windings, with taps very carefully chosen so that the curves of motor speed and torque correlate with fan drive torque vs. speed; both just have to be nonlinear. Remove a fan blade, and the motor runs at all speed settings with low slip, but different torques; you can use your fingers briefly as a load brake if the shaft is smooth and it's a small fan. (I don't try to slow it to half speed or so; just get an idea of running torque, or else grip the shaft tightly enough to stall it, then switch on. Of course, stall torque differs.)

(Slip? I do hope there's a good explanation somewhere. Try Wikipedia on electric motors. I'm not ambitious enough just now to explain it properly; it's the difference between synch. speed and operating speed of a squirrel-cage induction motor, the kind you find everywhere; they run quiet, and not especially fast.)

HTH!

=+=+=

As to the HP printer: I used to work in a very small computer store, sales and service, run by a guy so generous-spirited I considered him to be a "prince by [virtue of] merit". More about that, some other time.

A fellow brought in an HP inkjet of the 600 or 700 series, and its main printhead/ink cartridge (HP lingo: "pen") carrier sliding bearing had run dry. My boss used WD-40, against my gentle advice. Surely enough, it had the same problem, one day later.

(Perhaps WD-40 is one of the most-misused products since 3-in-1 oil was based on vegetable oil that polymerized into varnish, like linseed oil.)

I ran the store while he worked as a sysadmin., and called HP printer service. They stonewalled fanatically. When I told HP he'd used WD-40, he gave a classic "eeeeuuuuuwwww". No more info. When the p. by m. came in at the end of the day (or else next chance) he called HP and gave them the blazes. He had HP cert. for laser printers (he loved LJ 3's -- wonderfully built), and was therefore, in a sense, an insider, at least regarding printers. HP, contrite, sent about four syringes of an Anderol synthetic lubricant, and it worked marvelously.

Talk about "secret lubricants"!

Yrs trly wants to get a small quantity of grease for plastic mechanisms, but hasn't really looked.

--
Nicabod =+= Waltham, Mass.

.

Thank you every one for replying!

Does anyone have a schematic for the Oreck XL Professional Air Purifier?

Regarding bearings:

I, too, learned the hard way about the ills of WD-40. I found Singer Sewing Machine oil to work very well and if mixed with lighter fluid it seemed to have the same penetrating power of WD-40 [without the varnish effect later] *and* the naptha would evaporate with time leaving nice consistency oil.

The fan is a horizontal squirrel cage in a separate compartment from the motor. Without power the fan can be spun by hand and takes a great deal of time to coast to a stop. Also, spinning makes no sound. With power [and the light grounding noise] the fan is spinning, and has noticeable torque when the fan is stopped with my hand.

*****ARRRRG!!!!!

Nothing more valuable than experimentation! Just now I purposely stopped the fan and could hear the grinding noise continuing. Just for 'some reason' I touched the butt end of the motor to find it was still turning with the fan stopped! This motor drive path has a CLUTCH!!! to the fan [may be NOT on purpose]. The noise is the sound the 'clutch' makes as it's slipping!

That also explains why there is only one speed. At higher speed setting the grinding moves up a bit in pitch but the fan never speeds up, because, again, that clutch is slipping!

This may not be a clutch by design, but rather a rubber 'alignment' shaft. When new, the press fit kept the fan and motor locked together, but with age and rubber deteriorating from actions of oil, the press fit is slipping. Now to lock the fan to the motor shaft???

Thank you all.

Should I use super glue on the rubber?

Robert

No. Superglue is brittle and will crack loose the first time the fan hits something. Start by tearing the rubber shaft (clutch?) apart and cleaning it and the shaft. Remove all the old oil and goo. Use alcohol to make the rubber swell a bit. Make sure the shaft is clean and oil free. There should be enough friction to make it work. If not, try some rubber belt no-slip compound used for improving the friction in tape recorders, record players, and other rubber parts. Avoid xylene (dimethylbenzene) based "rubber restorer" solutions as they will soften the rubber but also probably make the shaft slip.

For high temperature lubricant, use a SOLID lubricant, not liquid. Yeah, I know it doesn't penetrate, but that's the price you pay for high temp. See:

for clues on different types. If you're lazy, try graphite lock lube (the powder variety, not the messy stuff mixed with light oil). Keep the lube away from the rubber "clutch" as it will make it slip.

I do some HP LaserJet printer repairs. The older models (LJII, LJIII and LJ4) required some grease on the drive gears and a few metal gears on shafts. When needed, I used lithium white auto grease, which is probably not the right stuff, but worked well. However, all the other nylon gears were self lubricating. The best way to make a huge mess was to lube all the gears. I'm not 100.0% sure, but I believe that current HP printers (LJ42xx, 43xx, etc) do not require any lubrication. I sometimes use "rubber restorer" on the paper feed rollers, but only if the paper is slipping and I don't have a replacement roller or foot.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

some trimmed

The problem you are describing sounds more like failing pre oiled bronze bearings. They loose the oil impregnation and then gall, re-oiling them once they have galled and begun grinding has no effect.

I have encountered these many times on air cleaners and item that run for long periods built with cheap motors that really were never rated for continuous duty.

There was one exception I ran into, it was one that used a squrrel cage that had a bearing on it that supported the end away from the motor and it was bad like a motor bearing.

The only solution is replace the motor or the unit and the motor generally costs more that the unit.

Gnack

Tight clearances on the rotor, heat expands it, and it binds? I'd guess it gets hot because of a shorted turn in the stator, but that's a guess. And, how did you eliminate the bearings from the equation? Does the motor spin freely when hot?

Next time try light high-temperature wheel bearing grease. The stuff I have is blue in color, flows reasonably well, works wonderfully, doesn't burn off, and lasts.

As you note: oil just plain doesn't work. I've also tried synthetic motor oil, and didn't have good results with it either. The only thing that works for me is that wheel bearing grease. (look for some that says 'good for disk brake wheel bearings' or something similar.

Doesn't the Oreck have some sort of super-long warranty? Its products are so expensive there wouldn't be much point buying them otherwise.

Thank you for your reply. Great suggestions. Especially the rubber belt dressing to increase friction.

The 'light grinding' noise comes when the motor shaft starts slipping in the rubber transfer to the fan. It seems there are four small ridges on the metal to help 'bite' into the rubber. So, when it starts slipping it makes a noise.

Here is the failure scenario to date: System does run fairly cool at around 60C [This is based upon my experience at not being able to hold my finger on metal above 60C for more than 10 seconds]. All bearings are smooth and oiled, also running cool. Fan whether hot or cold turns easily coasting slowly to stop. Oil however migrated from the motor bearing, along the shaft, and into the rubber transfer and that is now slipping.

I tried to remove the fan from the motor shaft, but could not. I completely lifted the motor/fan out of the unit, yet the rubber won't slide off the end of the motor shaft allowing access to clean all out. If there is a retaining clip of some kind, I can't see it, and worse, not be able to get access to it. Since the fan is squirrel cage, there is no way to gain access to a clip inside the 'cylinder' with my tools.

Can I still try cleaning with alcohol? Will that dissolve any of the oil residue inside the rubber/metal junction?

Change of subject: Not for this problem but for other 'clean out old oil' problems, did you ever try transmission fluid? I once had a mechanic tell me "to flush an oil system with one quart of transmission fluid mixed in the oil to remove all the ill effects of someone using STP. He said, don't drive it, simply heat the engine up and change the oil mix out, and replace with oil, heat up engine again, and replace with oil. That will clean all gunk out."

But, transmission fluid is a high temperature oil isn't it?

Robert

some clipped

Yes transmission fluid is a grade of oil and is safe for neopreme Orings not regular rubber.

Your Oric sounds a lot like some Sears branded electrostatic cleaners that I had once the fan was what is refered to as a reever style about 8 inches long and mounted in a bronze bearing block on one end and a heavy rubber grommet on the other. The rubber is simply to allow easy alignment between the motor and fan, A flex coupler if you think about it so that the case alignment is not critical.

The bearing on the end of the fam was what failed since it was quite small

7/16" ID (had I known this before it failed oiling would have saved it) Like your case the fan would run at low speed for a short period before locking up but woul not run at any speed higher than low.

You probably have a bad beaing on the end of thr fan away from the motor Robert. Here is what happens with sleve bearings that are "oillite" bronze used in most places. They exhaust the actual impregnated lubricant and gall. This is not apperent until the friction heats up the bearing or the fan tries to run beyond the point where friction balances torque. ( this effect is most often seen in chesp computer cooing fans that rev up to about haf or less of rated speed and start squealing and slow down).

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e quoted text -

That description is exactly correct. Except the bearing is so good that hot or cold spinning the fan and powering off takes a long time to coast to a stop. Bearing is in good shape.

However, the motor bearing oil migrated over to the rubber grommet. And I can't disassemble it to clean it.

Robert

White lithium grease is fine for those parts. That's what Canon use themselves for that purpose.

I use acetone (or nail-polish remover) to take the 'shine' off paper rollers, which gives you years more life out of them. It's also good for the separation pad in the paper pickup assembly for laser printers & the document pickup assembly in faxes.

--
    W
  . | ,. w ,   "Some people are alive only because
   \\|/  \\|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

I've been told that cooking the bearings & dunking them in light oil fixes that, but I've never actually tried it myself, so YMMV.

Another trick with worn phosphor-bronze bearings is to build up the bronze with a coating of solder, which has worked well for me when it hasn't been possible to replace the bearing.

--
    W
  . | ,. w ,   "Some people are alive only because
   \\|/  \\|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

Thanks. I wasn't sure it was the right stuff.

Nope. I've had problems with acetone warping the plastic spindle under the rubber feed rollers. It works, but is far too strong a solvent. If the rubber is impregnated with oil (to keep it soft), the acetone will dry it out, causing the rubber surface to get hard after about a month or two of use. I switched to a xylene based solvent:

which doesn't have the problem. One problem is that it's a really foul smelling cleaner. I have to do the cleaning outdoors, and store the can inside two zip lock bags. I threw some towel paper with some of the stuff on it, and it stunk up the office for days.

There are also some nasty health effects for Xylene, so I user rubber gloves and plenty of fresh air. I've had dizziness and nausea from the stuff when I wasn't careful:

I don't think it will make much difference for the rubber clutch in this motor. Alcohol or whatever is probably sufficient to clean it.

Also, it didn't take much to find a replacement motor:

However, no sign of the rubber clutch.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

If you're warping the spindle, you're using too much acetone. Dip a coarse rag in the acetone, & rub the roller with it. You do need to be careful to keep it away from the plastic.

That's never been a problem for me. I've serviced a heap of printers under service contracts, & never had any of these fixes come back to haunt me.

You're not kidding. No way would I go near that shit. I'll stick with acetone, thanks all the same.

--
    W
  . | ,. w ,   "Some people are alive only because
   \\|/  \\|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

FINALLY!

Simply removed the grommet, cleaned under it, put some tacky glue stick on the shaft, reassembled, and VOILA! Working great now.

Removing the grommet was the key. The fan comes out easily, but remains attached to the motor shaft, so remove the mounting screws for the motor and tilt the assembly up out of the mounting points. Then DON'T PULL instead use a pair of plier tips to gently wedge the rubber off the retaining ring and PUSH the fan away from the motor. For me, it popped right off, probably due to all that oil in there. That allowed me to clean the squirrel cage fan blades in a sink of detergent and wipe off the motor shaft. After sliding paper towel rolled up to the size of the shaft through the rubber several times [a lot of residue came out] I then used the only tacky stuff around, a glue stick, rubbed it on the shaft, reassembled, and let it set a few hours. Compared to before the friction between the motor and the fan was now incredible. So turned it on. And all works well. Very quiet, too.

Thank you to all who jumped in to help. And especially thank you about suggesting acetone on my HP DeskJet rollers.

Robert

Glad we could help.

-- W . | ,. w , "Some people are alive only because \\|/ \\|/ it is illegal to kill them." Perna condita delenda est

---^----^---------------------------------------------------------------

Bob,

Most helpful to know! Many thanks. I have an older HP LJ (7?) that won't pick a single sheet. There have been refurb kits, but I haven't been keen on following through; access is from the back, and judging by the online (poor quality) images, it's quite involved. It would be easier, I'd expect, to resurface than to replace parts.

=+=+=

I once helped a friend (a lady geek) clean her Oki impact dot-matrix printer. The print head drive motor was mounted with the print head (!), and a pinion engaged a clear plastic rack that extended across the operating space inside. Thinking that isopropyl alcohol (but, rubbing alcohol, which contains other stuff) would be OK to clean the rack, we were both amazed and horrified to see the plastic craze and disintegrate

*as we watched*!

As I recall, she contacted the regional Oki rep., and he sent a free replacement, which was easy to install. Credit Oki for being decent.

--
Nicabod =+= Waltham, Mass.
who really should properly dispose
of that metal can of Freon TF; it\'s
never used any more. Was nice stuff...