Please help me spec alternate footwell blower motor

[rusnak]

I've been watching this thread, 'fraid I'm not much help. I took one of my footwell blowers to an electric motor rebuild shop and the guy just looked at it and shook his head.

Ian, all I can offer is moral support. I hope you don't give up!

Russ Nakata

[Monza_dh]

can anyone tell me just how much resistance the cage should have if properly lubed on the stock footwell blowers? I took mine out and cleaned them up and they spin but not without manual help. Is this normal?

[CatSkynr]

Originally Posted by Monza_dh

can anyone tell me just how much resistance the cage should have if properly lubed on the stock footwell blowers? I took mine out and cleaned them up and they spin but not without manual help. Is this normal?

Are you saying manual help when power is applied?

I will assume you mean when not powered. The motor is a magneto, so there is magnetic resistance; they do not free-wheel. They will however spin with help when no power is applied, level of free-spin is dependant on applying force. You can feel the locking points in the turns where the magnetic collar will grab, it will feel lumpy.

There should also be no wobble in the shaft. (meaning you need to remove the squirrel cage and inspect the motor itself) If there is, the coil comes in direct contact with the magnetic collar and stops the polar inversion, which makes the motor spin. This resistive contact with the collar is also the cause of the dreaded screech, be it shot bushings or just dirt itself. Also check the clearance between the cage and the motor to make sure they do not come in contact. Mind this when re-installing the cage onto the motor shaft.

To test the motor, just apply 12Vdc.

[Monza_dh]

Catsyner,

great info thanks. It looks then to be just the magnetic resisitance from your description. One motor turns much more after testing but the other is still a little rough so I may bring it to a shop

Another quick question: how the hell does the cage come off? I have yet to apply force.

Thanks again.

[ianc]

Another quick question: how the hell does the cage come off? I have yet to apply force.

Apply force. It's just pressed on.

This resistive contact with the collar is also the cause of the dreaded screech, be it shot bushings or just dirt itself

Catskynr,

I'm interested to hear you say that. I remember asking about what causes the screech some time ago but nobody had a good answer. When I removed mine and bench tested it, it would not make the noise, but it always would when installed in the car, which made it quite difficult to troubleshoot. Can you explain the mechanics of why the armature touching the magnets would cause the squealing noise?

ianc

[JFairman]

your noise may be high frequency chattering of the slightly worn dry motor bushings that desperately need oil.
It needs to be cleaned but it mostly needs oil after 20+ years.

[CatSkynr]

Catskynr,

I'm interested to hear you say that. I remember asking about what causes the screech some time ago but nobody had a good answer. When I removed mine and bench tested it, it would not make the noise, but it always would when installed in the car, which made it quite difficult to troubleshoot. Can you explain the mechanics of why the armature touching the magnets would cause the squealing noise?

ianc

With the motor outboard, the weight on the shaft is no longer there, especially if the squirrel cage is removed; no centripetal force or rotational mass. With the unit outboard, you also have much less resistance in airflow on the squirrel cage, which is also centripetal force.

From worst to best - With the coil coming in contact with the collar, you now have a squealing metal tire as the coil should float, not contact; the function of the shaft and bushings. You get a distinct gring with this also. Eventually your magneto is burned out (dead short and destroyed windings) and no more motor. If the bushing allows the shaft to contact the case, you have the squeal; the shaft should ride in the bushing. If the bushing is binding the shaft from turning, same effect, but you’re on your way to destroying the bushing. This is why you want to clean and check the tolerance of the shaft. If the shaft is loose, fix it before disaster strikes and destroys your windings (coil).

[Wcb4]

I converted my 71 to use two of the foot well motors. Living in Northern Michigan I needed a good bit more hot air. To the point I picked two aftermarket blowers. They were less than $100.00 ea and new. That was back in 2005. Let me think on it and I will rember in a couple of hours.

[Wcb4]

I purchessed the blowers from World Pack or World Pac in Sacramento. And they were Bosch units for alot less then getting them thru Porsche.

[ianc]

Due to Catskynr's comments, I again enlisted the aid of a couple of beers in removing (yet again) the footwell blower from car last nite. The motor is a little dirty, but my first step in attempting to cure this was to oil and grease the bushings. They have no discernible horizontal movement at all; very tight. There is some axial movement of course, but this is controlled by the small clip at the brush end. The motor spins freely while out of the blower assembly and does not rub. The brushes have plenty of beef on them.

It was quite difficult to get the motor out of the housing, so after awhile I speculated that this tightness may be warping or bending the motor when it is pressed back in the plastic housing and causing it to rub. I took a dremel and ground down the ribs on the inside of the housing to loosen up the fit of the motor and then it was quite a bit easier to put back. I replaced the fuse and the motor runs, but it is still noisy. Not a squeal, but almost a noise like the cage is rubbing on the housing, although my pre-installation inspection showed plenty of clearance, and I could see no evidence of rubbing, either on the cage or the housing.

I'll let it go for a bit and see how it gets on, but it is quite hot here now, so I probably won't be needing them for awhile...

I'm leaning more toward the Dayton motor conversion at this point however. The extra boost in the air movement might be nice, but I'm concerned about how much noise these motors would make in the cabin; the stock motors (driver's side at least) are very quiet. Perhaps I should check in with that fellow over at Rennlist to see if he's bothered with the noise level...

ianc

[CatSkynr]

As I mentioned before, you want to use a “dry lubrication”. (Gun stores will carry this if you cannot find it, such as Otis and TriLube) Oil and stuff like silicone spray and especially WD-40 attract dirt. You can use these as a penetrating cleaning agent, but make sure you displace all this oil; otherwise you will attract dirt and you will be in the same boat as before.

Also, on your axial movement, you want to ensure when you reinstall your squirrel cage, you have checked your clearance to take this into account. As the motor turns the cage, it will have lift, like a toy helicopter, trying to pull the shaft from the motor. You will be, at this point, to the far end of your slack.

Most likely, if you have a rattling vibration noise it is not the motor itself, but the cage itself because of balance. This is why most cages you will see clips on the blades; like your wheels and weights, to balance the spin. You do not want to mess with these clips unless you have equipment to balance such things..

[MattKellett]

I have my footwell blowers on my bench, they do work but are noisy!!! although they do rotate fairly freely.

I'd like to lube them, to help with noise and obviously keep them working.

I'm just not sure where I should be lubing them. Any experts out there who can tell me what i should be lubing? - oh and answers in verrrrryyyyyy simple terms alway appriecated

Many thanks

Matt

[ianc]

I'm just not sure where I should be lubing them. Any experts out there who can tell me what i should be lubing?

Well, the obvious place to start is the top and bottom bearing\bushing that the shaft rides on. Notice that the top has a felt pad which should have oil or grease added to it. HTH,

ianc

[CatSkynr]

Just soak the entire motor in a dry lubrication. Let it sit for at least an hour and sling the remaining out by running the motor. Not only will this lubricate everything, but it will displace any dirt and grime. When I say ‘dry lubrication’ I mean that it dries, dry. It starts its life as a liquid. Tri-Lube Teflon is a good one. Ottis is also a very good one. Both of these are penetrating oil that is dry. Gun stores (or sportsman’s stores that have a gun department) carry these and are your best bet for finding these.