Wicked dumb motor question

[Mojo]

Bobbin:

I have a new clutch motor that your welcome to have. I will never use it myself. I will donate it to your new business. You pay the shipping. :)

Chris

[Darren Henry]

I should probably just junk it, but my father loaned me the money to buy it when I broke and then returned it to me when I'd paid him back in full.  So I have a sentimental attachment to that machine.  Isn't that silly?

You know how I am about sentimental and old,especially lately; We'll fix 'er. I own a 31K20 with a rolling foot and have driven a of couple of 15's and 19's. My '20 is back home in Ontario, so I'm working from memory.

The motor turns on and does its usual wind up to full speed (although the pitch of the hum is different).  But instead of moving the machine's handwheel in the normal direction (counterclockwise) it powers it in a clockwise direction.

.

Unless the leather belt up to the machine got loose enough to turn into a figure 8 instead of an oval (and you would have already checked that) ; It's either an open neutral (white wire) or brushes/internal windings on the motor. Those motors are cheap like borscht.

[fragged8]

i don't know much about American electrickery but can you plug in those crazy 2 pin american flat pin plugs the wrong way around ??
That would probably reverse the polarity,

you can't get english power plugs the wrong way round :-)

[Allan]

Unless there is a faulty motor you cannot normally reverse the polarity of an AC motor by reversing the plug wires
Not all AC motors are reversable and this is normally done internally in the motor
DC motors are a different matter

An electrician amongst us may be able to clarify this

Allan

[gene]

i don't know much about American electrickery but can you plug in those crazy 2 pin american flat pin plugs the wrong way around ??
That would probably reverse the polarity,

No, but if you spread apart a bobby pin and put each end into one of the two holes in that cazy 2 pin american flat pin plug, and make sure you are standing bare foot, feet?, footed?, feeted?,  in a puddle of water, and your other hand is clutching the end of the Christmas tree lights... Merry Christmas!


In regards to sOfad's link:

1. if there is an external 'potential relay' there will be a button or switch that you can push. Check to see if there is such a button.

2. If there is an internal centrifugal switch that got stuck:

Turn the motor on several times without the fan belt to make sure that it is consistently spinning in the wrong direction. If yes, then with the motor off, hit the motor sharply with a metal hammer several times. This will very often free up this switch and when you turn the motor on it will spin in the correct direction. If it does, then you know the problem. Any motor repair company can repair the motor.

If the motor spins in both directions at random it's the centrifugal switch also.

gene

[sofadoc]

Any motor repair company can repair the motor.

Another business that has "Gone the way of the Dinosaur".

I used to have 3 or 4 electric shops within 1/2 mile to choose from. Now, I suspect that if you can find one, it'll cost dangerously close to the cost of a new motor.

Back to polarity.........as a kid, I remember some really old appliances that would shock you (mild, tingly shock) if you touched any metal part of them. When this occurred, you had to unplug it, and turn the plug over, and plug it back in. If Bobbin's motor came with the 3115, it's probably pretty old, and came from the same era when they hadn't yet completely conquered reverse polarity.

[bobbin]

It's so funny that this question popped up at the head of the list today.  I just called Ace Mechanic who's been gone for a week and will call me back.  I did try rotating the plug 180 degrees, no luck.  I tried by-passing the extension cord.  Nada.  Ditto the attempt at another outlet. 

I have two potential organ donors in my shop (atelier?).  One is a 1/2hp 3450 (US Blindstitch), the other is a 1/2hp 1725 (Nakajima 380, cylinder bed).  Having just converted my overlock machine to a servo motor I'd be all over converting the Nakajima to one, too.  I could then use its lower rpm motor for the 31-15.  As I said, the 31-15 is not something I would use a lot, but it is a simple bottom feed, lockstitch and could prove useful in a variety of applications, esp. given the number of feet and attachments I have for it. 

My brother will probably be here for T-day and I bet we could have some laughs farting around with the old motor.  I am certain he will find your comments and suggestions interesting.  Sofa. is correct, the motor is an oldie.  I wasn't able to find a date on it anywhere, but the traditional black paintjob, the official Singer plate and the look of the specification tags lead me to believe it dates from at least the '40s, possibly earlier.  It came with the machine when I bought it, but is not likely original. 

[gene]

Another thought is to take the metal frame apart and pull the motor out and blow it with air and vacuum and wipe with alcohol wipes or Windex.

I mentioned awhile back how dusty my motors were.

This may give the old motor a new lease on life.

gene

[bobbin]

Gene, this one made me laugh.  My 31-15 sat unused for the better part of 7 years until I decided (on a whim) to haul it out, clean it up, and fire it up.  Part of that was hooking up the air hose and blowing the daylights out of the motor!  I've owned the machine for 30+yrs. and never did a thing to the motor.  The oily crap that spewed forthe was beyond belief.  My guess is that there was close to 50 yrs. of accumulated dust, grease, thread trimmings, etc. in the motor's housing. 

When the motor spazzed out the first thing I thought was that I prolly shouldn't have taken the compressor to it, and should've left well enough alone!

[Mojo]

There is only one way to reverse a motor and that is by changing the leads inside the motor itself. By doing this it will change the rotation.

Flipping the plug wont do it and can actually damage the motor.

I am curious as to why this machine is running backwards so I am going to bring in the expert, Bob Kovar.

Chris

[Toledo Mach. Sales]

I can't offer a reason except that I've had that happen before with that style of motor so I think the starter windings are going bad causing this if you spin the motor the correct way it's supposed to run & turn the switch before it stops spinning it'll run the correct way.

[Darren Henry]

[quote Part of that was hooking up the air hose and blowing the daylights out of the motor!][/quote]

That is quite likely what caused the damage to the windings or brushes. Those same motors are used for everything from bench grinders (the old ones with a drive belt) to barn fans to .....Up here, I'd say go to Princess auto or Canadian tire. Not much help to you for U.S retailers. Keith??, June??,anybody, got an idea where to send her?

[byhammerandhand]

How US electricity works:

60 Hertz (cycles per second) alternating current

For nominal 120 V circuit, when wired correctly, the white wire is "neutral" and has no charge.   The black "hot" wire carries the current that alternates from positive to negative, the white wire responds by doing the other direction.    All outlets and some plugs are polarized, meaning there is a white side and a black side.    This is common on a lot of things and important on, say, lamps where the black wire should go up the middle and the white wire to the socket.   This is to reduce the chance of shock by touching the socket by mistake.  Likewise, correct wiring to a light, etc., should be black from circuit box to switch, white directly back to circuit breaker box.   Depending upon where the wires come in you might need to have a white wire that is "hot" when switched on.  Then you're supposed to mark it black on the ends, signaling it may be hot at times.

Some plugs are non-polarized, that means they fit either way.    If you look carefully at a lamp wire, you'll see one side has ridges.   This is supposed to be the white wire.

Green (or bare) are ground wires and are not charged unless there's a problem.   Then it provides a safe out.


240 v circuits have two "hot" wires that are 180 degrees out of synch with each other.  So when one is +120V the other is -120V, thus making a differential of 240V.   Then they switch in a sine wave pattern and in 1/120 of a second, first becomes -120V and second +120V.   These also have a ground wire for the same reason.    240V outlets have a different configuration so that you can't plug in a 120 appliance (though one of my customers had one of these in his new warehouse and I fried two hair dryers before I found this out.)


Some motors, like my table saw, can run either 120 or 240.  You have to switch some wires inside the control box according to the chart printed there.   One advantage of 240 use is that for the same motor it will draw half the amps (Ohm's law), so it's kinder on the wiring as there's less voltage drop.   It uses the same watts (what you pay for), so there's no operating cost advantage.


I don't know a whole lot about DC motors, but they're supposed to be better for variable speed motors.  None of my stuff has them, for one reason, they're a lot more expensive.


There are "motor shops" around and places like Grainger sell them in all configurations.

[Darren Henry]

As we were "divying-up" dad's tools yesterday, I asked my niece's husband (certified electrician) about your problem and he was confident that it was most likely the brushes in the motor. Dead easy fix---once you find the parts down there. I'd just call your local farm supply and ask them who would have the brushes and or motors. I'm sure they would know.