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170CFM blower - oiling?

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BlakeN (Jul 04, 2001 12:12 a.m.):
bump this is a great topic

After 3 days of "liquid wrench" and trials I still hadn't managed to get the teensy set screw loose. Hoot says he does NOT ride a horse , so I can't claim my failure is due to that. (But the original Hoot did ride a horse, didn't he?) So I grabbed the SOBn little wrench with pliers and put my whole arm into the effort. The flimsy wrench twisted a quarter turn, like a torsion bar, without the screw budging in the least. But I wasn't about to be deterred. I gave a healthy grunt and the threw my whole body into it. Then a loud POW! and no resistance at all. In that instant I knew I had busted something and was filled with remorse over my impetuous nature. I should have given it a fourth day. What would I do now? But no, the screw had turned, undamaged, and the blower cage slipped off easily. A testimonial to the Loctite corporation, I guess. Who knew some fool would actually want to take it apart?

Disassembling the motor only requires removing a couple of nuts. (no DANG Loctite!)

I see now why the brushes squeak so bad ; they are made out of copper. The only brushes I am familiar with are carbon (graphite?), which has some lubricating properties. The brushes only have wear marks on a part of their contact surface, so a couple of hours wear has not been enough to completely seat them.

The wires I planned to use are too fat - too much insulation- and don't look like they will go into the exit hole without squeezing, which may defeat the whole purpose. What I think I am going to do is gob around the rope caulk and see what it does. The real way to do this is to remount the brush holder platform with rubber instead of rivets, but I am not up to that.

Real life is interfering with my hobby and it may be a while before I can put more time into this.
 
The brushes are not pure copper. They are a mix of copper and graphite, perhaps sintered. Still, that is not the genesis of the squeak. They slide somewhat loosely in their guides. My bet is they are vibrating against the guide walls, even under spring tension. Not that you can do a lot about it. They have to be loose enough in the guides to assure they won't seize up as they progress towards the rotor, with wear. Obviously, the motor design did not give much thought with regards to the brush noise, but then it was intended to run full-tilt. Under that condition, it's hard to hear the brushes over the rest of the noise. ;D
Kudos for your persistence on the set screw. That was how it went for me also. POP! If you pull the rotor out, mind the magnets. They're strong. It's a bit tricky expanding the brushes to reseat it also. Don't remount the end where the brushes are mounted, rotated 180 deg as the motor will run backwards then. That, having been said. Running it backwards a while helps break in the brushes evenly.
In case you're wondering, they did not go for a brushless design because of the current consumed by the windings. On the rare occasions when I have my system put back together and sitting under the computer table, the brush noise is not nearly as objectionable.

Hoot
 
Hoot (Jul 04, 2001 01:37 p.m.):

>If you pull the rotor out, mind the magnets. They're strong.
For a while I thought there was some sort of mount holding the rotor in place.

> It's a bit tricky expanding the brushes to reseat it also.
Yes, you have to get the rotor by itself first. Then seat the shaft as best you can. Then use a narrow tool to pry each brush back in turn while wiggling the rotor; repeat until the commutator slips in between. Make sure you hold the shaft in place when you slip the armature over it, so it doesn't pull the rotor out and ruin all your effort.

> Don't remount the end where the brushes are mounted, rotated 180 deg as the motor will run backwards then
I was baffled for an hour wondering why the air flow was so feeble. Then I figured out the cage was going backwards. Then I tried to figure out how a DC motor knows which way its supposed to start up, but my feeble intellect could not untangle the mystery. There was only one thing I could try : rotating the brush end 180. I still don't get it.

I rerouted the red wire so that it did not contact the case, the idea being to decouple the vibration. I squished Mortite around the platform mounts and the exit hole bushing, using a small drill bit as a pusher. Then more Mortite all around in between the case and the brush platform. Then I molded a thin coat of Mortite around the red and black wires. The idea of this is to damp vibrations and resonances. It also adds mass, which lowers the amplitude of the vibration and decreases the resonant frequency, high frequencies being the most irritating.

I'm pleased with the result. It is silent compared to what it was, although in absolute terms, it is easily audible. It makes less noise than an isolation mounted 120mm 100cfm fan. I wanted to see how it was before I spray the rubberized automobile undercoating on the sheet metal. Since the motor cools itself through the case, I don't think its is a good idea to coat it with anything. The motor should be decoupled from the blower housing, but it also needs to be mounted very firmly, which limits how good the decoupling can be. Maybe some Mortite between the housing and the motor case will not all squeeze out.

You can lower the noise of a case fan by mounting it so it is decoupled from the case. I have my 120mm fan hanging from insulated number 14 electrical house wire.
 
What about making a box with sound insulation fot the blower to go into and puting a hole for entry and exit, than running duct fork to the case inlet. You sould even insulate the duct work to reduce noise and put a small inlet duct with a elbow in it that had some sound absorbing material to dampen the blower noise.

When I start tweeken I am a snowball rolling down that tall Tibeten mountin, haha. I usualy go way to far, so I'm glad I found this place, makes me feel at home.
 
CalCoolage (Jul 02, 2001 09:30 a.m.):
Part of my day job is doing maitenance on pellets stoves which use fabco and comair rotron motors. .... Wow I guess my 9yrs in that industry is paying off LOL
Thanks for the oiling info. What happens? Does the oil get on the wires and cause shorts?

Are any of these motors quiet blowers that put out about 80 cfm, and cost less than $75?

It doesn't cause shorts. My Understnading is the escess oil "gums up" and causs problems. Since I never "rebuild" blowers/fans I don't know for sure. Just been told by several who have more years on the job than I have been alive, so I trust their judgement.

The VAST majority of "blower/fan noise" is air movement/contact with the blades. As faras "quiet blowers" let me give you an example. On woodstoves teh most common blower is a 140-170 CFM "squirrel-cage" type blower that is pretty noisy when trying to watch TV in the same room. There is one woodstove company that uses a 700CFM fan that is WAY too big but when turned down to the 150 CFM range is almost silent. That is how you quiet them down. All the blowers we sell are in the 200 dollarrange. Not because they are worth it but because there are too many layers of distribution involved. Any 500-800 CFM fan running on AC can be plugged into a typical wall outlet and be spped adjusted by a rheostat. Hope that helps.
 
Froggy (Jul 05, 2001 02:35 a.m.):
[.

>Any 500-800 CFM fan running on AC can be plugged into a typical wall outlet and be speed adjusted by a rheostat.

Since people are actually doing this, it must be OK. As mentioned before, I have always been told lowering the voltage causes it to overheat. The AC version of this blower (2C647A) only uses 60 watts and a current of .65 amps. That is well within what a light bulb uses, so I wonder if a light dimmer switch would work for adjusting the speed?

AC blowers are a lot easier to find than DC.
 
I was toying with that idea myself. The best approach is a triac based Pulse Width Modulator. It varies the frequency of the AC and since the motor speed is sync'ed to the frequency, it can be varied that way. I did try lowering the AC voltage with a variac and though the motor speed varied a little, it was not enough to have an appreciable impact upon the noise.
Wall mounted bathroom fan speed controls can be gotten from Home Improvement stores. They use the PWM approach, but are no where near as inexpensive as light dimmers. I may pick up a light dimmer and give it a try this afternoon. Will let you know how it works out.

Hoot
 
CalCoolage (Jul 05, 2001 07:45 a.m.):
Froggy (Jul 05, 2001 02:35 a.m.):
[.

>Any 500-800 CFM fan running on AC can be plugged into a typical wall outlet and be speed adjusted by a rheostat.

Since people are actually doing this, it must be OK. As mentioned before, I have always been told lowering the voltage causes it to overheat. The AC version of this blower (2C647A) only uses 60 watts and a current of .65 amps. That is well within what a light bulb uses, so I wonder if a light dimmer switch would work for adjusting the speed?

AC blowers are a lot easier to find than DC.


They are partially right on both counts. Being fan motors are inductive loads, they will draw more cuurent and may overheat because of that. But they have small fans that go on the shafts of the motor to cool the motor to deal with this extra heat. Also I know that the actual motor part of 95% of the blowers controlled by a rheostat and used on wood/gas/pellet stoves are not your run of the mill motor. I will do a little research and find out what kind of motor they are using, because they must be using this type because it can handle being run as low as 50 volts AC for prolonged periods of time.
 
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