phase converter quieter when vertical...

I have a homebuilt RPC. It is a 10HP Baldor motor running 1760 RPM, using a start capacitor and run capacitors. It runs my mill, lathe, surface grinder just fine.

However it is noisy. Compared to a commercial unit, very noisy. I have been messing with insulation and isolation. And on a hairbrained whim I set the motor on its butt so the spindle was vertical and it was *significantly* quieter.

Two questions:

1) Is this indicative of bad bearings?
2) Assuming sufficient clearance for airflow, is there any reason I can't just run it in the vertical orientation permanently?

I haven't cracked the case on the motor. The heritage of the motor is unknown but it is rust free and appears in good shape. No real runout and spins up like a champ. $50 on Craigslist from a guy who said he was saving it for a project that never happened, pulled from working service.

thanks

philip

hahnpv said:

I have a homebuilt RPC. It is a 10HP Baldor motor running 1760 RPM, using a start capacitor and run capacitors. It runs my mill, lathe, surface grinder just fine.

However it is noisy. Compared to a commercial unit, very noisy. I have been messing with insulation and isolation. And on a hairbrained whim I set the motor on its butt so the spindle was vertical and it was *significantly* quieter.

Two questions:

1) Is this indicative of bad bearings?
2) Assuming sufficient clearance for airflow, is there any reason I can't just run it in the vertical orientation permanently?

I haven't cracked the case on the motor. The heritage of the motor is unknown but it is rust free and appears in good shape. No real runout and spins up like a champ. $50 on Craigslist from a guy who said he was saving it for a project that never happened, pulled from working service.

thanks

philip

Click to expand...

Well. dunno what TYPE of motor your idler is, but MY idler is an "Open, Drip Proof" Fan-cooled Weg.

Given the intake grill for the fan is pierced holes in the ass-end, s**t metal, sitting it on its "butt" would prevent air reaching the fan, so yea, quieter.

Hafta say that's in the same league as stopping PMS by getting the gal pregnant.

Eventually, there are OTHER consequences?

thermite said:

Given the intake grill for the fan is pierced holes in the ass-end, s**t metal, sitting it on its "butt" would prevent air reaching the fan, so yea, quieter.

Click to expand...

It is propped up to allow for airflow. Still quieter.

This motor: M3313T - Baldor.com

-philip

hahnpv said:

It is propped up to allow for airflow. Still quieter.

This motor: M3313T - Baldor.com

-philip

Click to expand...

Just a guess then, and at two things. Audio industry background, Deaf old 'nam vet, I own and rely on a cheap "Sound Pressure Level" meter for quieting-down my gen set and such - not on my own damaged ears. Bad days and good days, but there's lots of stuff i can't hear, period, some of it hazardous.

- Is it ACTUALLY emitting less noise? Or is it simply projecting the same amount in a direction away from your ears - attenuated by the time it comes back to you? No foul. A benefit is a benefit. You can use that. Perhaps several among us can use that.

- do the bearings permit a slight end-float when the shaft is horizontal, and load onto only the one when vertical? That's OK, too IF the motor is listed for continuous running all orientations, or at least vertical operation.

Not ALL are so rated, believe it or not. Some will suffer reduced bearing life.

That data may be off in the maker's "family" of a given motor's specs, not necessarily shown on each individual motor IN said family poop-sheet.

Even so . bearings are cheap enough. So long as replaced BEFORE they hard-fail, not after!



2CW

Toning Down A RPC Idler

It's likely, on a used motor that your bearing grease is dried up, and they are running dry, metal to metal. All the grease has been pushed to the side, and is no longer flowing. Turning the motor on end puts a bit of axial thrust on the rotor, and allows the bearing balls to touch some of the side grease, for a while.

Putting in a fresh set of bearings, and some vibration isolator feet, would go a long way to keeping the noise down, for the long haul. The starting torque when standing it on end, may cause it to roll over, or twist around.

From the motor tag, in the link you provided, these are the bearings you would need, lower end units, but you don't need high quality ones, for an unloaded motor, just ones with fresh grease. $25 bucks would get you fresh bearings and vibration isolators.

Bl Radial Ball Bearing, PS, 35mm, 6307-2RS 6307 2RS/C3 PRX | Zoro.com


Bl Radial Ball Bearing, PS, 30mm, 6206ZZ 6206 ZZ/C3 PRX | Zoro.com

Zoro Select Vibration Isolator, 60 Lb Max, 5/16-18 2NPG3 | Zoro.com



SAF Ω

I bought a NOS Boston Gear 5 hp TECF motor on eBay for my first RPC. It was very noisy when first started. It also squealed from time to time. I ran it for a while and also noticed that it was getting very hot.

Upon disassembly (four long, thin bolts) I discovered that the sealed bearings were Ka-Ka. A trip to the bearing store and a few minutes with my bearing puller and all was well. It's now not only reasonably quiet, but actually emits rather a pleasant sound and runs at a proper heat.

Check your bearings.

hahnpv said:

I have a homebuilt RPC. It is a 10HP Baldor motor running 1760 RPM, using a start capacitor and run capacitors. It runs my mill, lathe, surface grinder just fine.

However it is noisy. Compared to a commercial unit, very noisy. I have been messing with insulation and isolation. And on a hairbrained whim I set the motor on its butt so the spindle was vertical and it was *significantly* quieter.

Two questions:

1) Is this indicative of bad bearings?

Click to expand...

Maybe.
Do you have a bearing puller? Replacing motor bearings is usually not too hard.

hahnpv said:

2) Assuming sufficient clearance for airflow, is there any reason I can't just run it in the vertical orientation permanently?

Click to expand...

As long as your fan is working and cooling it.
You could mount standoffs to get clearance for airflow, but honestly I’d try to figure out what the noise source is and rectify it.

Checking/replacing bearings is not a bad idea.
Is the motor well balanced?
Does it have a shaft? Keyway? Balance it or cut the shaft off.
Are the fan blades all there? Bent? Balanced?

It's not unusual to have a horizontal motor generate less noise in vertical operation, and all the above notes about grease and bearings are true, but here's a big reason why it happens:

When the plane of the motor's rotor is horizontal, and the motor is sitting on a flat surface, that surface becomes a 'speaker', converting motor vibration into sound pressure. Doesn't matter what the surface is, if it's getting vibration transferred from the motor, you're gonna get noise.

By standing motor up on end, rotor vibration occurs on an axis perpendicular to the mounting surface, so motor vibrations are not directly coupled to that surface. The end result, is much less amplitude from the flat surface, hence, less noise.

The problem you'll run into with running the motor vertically, is that the motor's shaft bearings are not designed to tolerate loading of vertical suspension.

IF you choose to mount it vertically, one way to accomodate that, is simply to replace the bearings, but to use a bearing rated for lateral load, and install it in proper orientation to accept the vertical load. Another way is to put a thrust bearing on a fixture on the end the shaft to accept that end-loading.

After all, the rotor is not doing any real loading... you're just supporting it against gravity.

DaveKamp said:

It's not unusual to have a horizontal motor generate less noise in vertical operation, and all the above notes about grease and bearings are true, but here's a big reason why it happens:

When the plane of the motor's rotor is horizontal, and the motor is sitting on a flat surface, that surface becomes a 'speaker', converting motor vibration into sound pressure. Doesn't matter what the surface is, if it's getting vibration transferred from the motor, you're gonna get noise.

By standing motor up on end, rotor vibration occurs on an axis perpendicular to the mounting surface, so motor vibrations are not directly coupled to that surface. The end result, is much less amplitude from the flat surface, hence, less noise.

The problem you'll run into with running the motor vertically, is that the motor's shaft bearings are not designed to tolerate loading of vertical suspension.

IF you choose to mount it vertically, one way to accomodate that, is simply to replace the bearings, but to use a bearing rated for lateral load, and install it in proper orientation to accept the vertical load. Another way is to put a thrust bearing on a fixture on the end the shaft to accept that end-loading.

After all, the rotor is not doing any real loading... you're just supporting it against gravity.

Click to expand...

Thanks, Dave!

Thank you, double, hahnpv, for bringing it to the top of the office in-tray!


Wish I had seen this several years ago. Or figured it out meself. As I SHOULD have,

What with having a PAIR of the highest-grade anechoic chambers and Bruel & Kjaer test gear available as weekend playtoys. Designing speaker enclosures with a 20+ patent holder as mentor?

Brethren? Yah know when we go a'scouting for bargains on 3-P motors to use for idlers?

How many among us have given surplused vertical shaft PUMP motors a miss?
Already equipped just the way we need them. Quite often going begging in the used or NOS market as too specialized for general-purpose needs.

Damn. Cudda saved a few sheckels and had a quieter RPC into the deal?

Sure got THAT shot bass-ackwards!

UPDATE:

"Curses. Foiled again."

Yazz. Vertical shaft pump motors were found at very, very, favourable prices per HP.

Sadly, I do not need, nor can I feed ... 500 HP.. 150 HP... 100 HP .."idlers".

Back to the drawing board...

DaveKamp said:

When the plane of the motor's rotor is horizontal, and the motor is sitting on a flat surface, that surface becomes a 'speaker', converting motor vibration into sound pressure. Doesn't matter what the surface is, if it's getting vibration transferred from the motor, you're gonna get noise.

Click to expand...

This of course is very true.

The other test I did was place the motor hoizontal to the ground, start it up and then press against the end of the shaft with a 2x4 applying some load much like gravity would if it were vertically oriented, and again it got quieter. Maybe this is indicative of the bearings being an issue.

I'll try giving the bearings an inspection / replacement.

thanks all
philip

hahnpv said:

The other test I did was place the motor hoizontal to the ground, start it up and then press against the end of the shaft with a 2x4 applying some load much like gravity would if it were vertically oriented, and again it got quieter. Maybe this is indicative of the bearings being an issue.

I'll try giving the bearings an inspection / replacement.

Click to expand...

There should be a wavy spring washer on the shaft that exerts a force on one of the bearings. Usually it is between the back shell and the back end bearing.
There might also be a straight washer next to the wavy washer. A few times I increased the thickness of my straight washer by stacking some smaller washers
together and assembling the motor back together and testing. A few thousands more in thickness made a difference for quieter operation. Then I machined a new
washer with the new dimension.

If the bearings do not have rubber seals then you can soak them in lacquer thinner and dissolve the old grease. Then palm in new grease. That means you can
hold the bearing in your palm and force new grease with your fingers. You can also use a bearing pack tool which doesn't cost much or make one.

RPC motors run quieter and vibrate less when they are balanced correctly with the right amount of run capacitors. That is when the target motor is powered.
When the RPC motor is running by itself then it should be louder and vibrate more because you would have balanced it when running a target motor.

hahnpv said:

And on a hairbrained whim I set the motor on its butt so the spindle was vertical and it was *significantly* quieter.

Two questions:

1) Is this indicative of bad bearings?
2) Assuming sufficient clearance for airflow, is there any reason I can't just run it in the vertical orientation permanently?

Click to expand...

I had done this years ago with a 5Hp motor and noticed that the noise was reduced. It does not appear that the bearings would wear evenly and that
if the orientation was changed to horizontal I might hear more noise.

Instead I use a small torch flame on the cases before unseating the bearings.
Only use totally sealed bearings.
Do a static balance of the rotor.
If this is a RPC motor the balance capacitors are added to get 1-2% voltage change from phase to phase.

The best thing that I did to quiet down my RPCs was to use rubber pads under the frame. Although the motors were fairly quiet, the rubber mounts helped to further quiet them down.

rons said:

There should be a wavy spring washer on the shaft that exerts a force on one of the bearings. Usually it is between the back shell and the back end bearing.
There might also be a straight washer next to the wavy washer. A few times I increased the thickness of my straight washer by stacking some smaller washers
together and assembling the motor back together and testing. A few thousands more in thickness made a difference for quieter operation. Then I machined a new
washer with the new dimension.

Click to expand...

I took off the back end and this is correct - wavy washer to apply axial load. The bearings were essentially dry and noisy when spun by hand. There was some blue grease off to the side - zerk feeding to feed grease in to the side of the bearing by the wavy washer. Palm greased and reinstalled for now.

I need to remove the sheave before I can assess the other end, and then I'll likely order new bearings.

rons said:

RPC motors run quieter and vibrate less when they are balanced correctly with the right amount of run capacitors. That is when the target motor is powered. When the RPC motor is running by itself then it should be louder and vibrate more because you would have balanced it when running a target motor.

Click to expand...

Once I get rid of the mechanical noise, this is next. Thanks,

philip