Another motor reversing attempt

[Jason Rodgers]

Dang, I just can't be happy with the direction of rotation on the motors I have! Here is my latest motor reversal frustration...

The wiring directions say: 120V - OG TO ONE LINE, BU & YE TO OTHER, RD & BK TOGETHER (translation: orange to one line, blue and yellow to other, red and black together)

And here are the leads in the motor...

And here is a diagram, for clarity...

I've tried swapping the orange, yellow, and blue, but it doesn't change direction. I've googled for diagrams (old motor, serial and model get no hits), but I'm no electrician, and I can't make heads or tails of the various color coding, T-1 T-2 T-3 coding, and various references to poles and leads and whatnot.

Is there a simple swap of leads to turn this bugger the other way?

[David King]

Jason,

You have two wires going to the field and two wires going to the armature (via the brushes).
One field wire and one armature wire get connected together (in series it looks like).
All you need to do to change direction of spin is reverse one set of leads or the other, either the armature leads or the field leads (but not both or you will end up spinning in the same direction again). If you have a meter or can see into the back side try to figure out which wires are going to the brushes and then swap those.

You can reverse the motor with an external switch if you want. It takes a DPDT with jumpers connecting the opposite corner terminals of the switch to form an "X".

Your complication here is that you have an extra wire for 120 or 240 V operation.

Read this thread over at Practical Machinist forum for more… http://www.practicalmachinist.com/vb/ge ... or-146198/

[Jason Rodgers]

Brushes? This motor ain't gots no brushes.

I pulled off the back cover and see that it's all potted and sealed up with some sort of black resin goo, so I think I'll just try the DPDT method. If I go digging around I'll surely end up with a pile of inert metal.

[David King]

There are Brushless DC motors and there are Universal motors but I've never heard of a brushless universal motor. Check again for brushes.
If it has no brushes then it's a very odd bird indeed. There are brushless DC motors that use electronics to time the pulses to get them and keep them running. These are a recent development and they cost serious money.

http://en.wikipedia.org/wiki/Universal_motor has a pictorial diagram showing the commutator in series with the field. The field has a tap shown.

[Jason Rodgers]

I dunno. This is AC, and is intended to be so, but only the ball bearings at each end touch anything on the shaft.

I wired up a DPDT, and it doesn't change direction. I have the motor wired into one end (1, 4), criss-crossed to the other end (3, 6), and power in the middle (2, 4). Is that right? Or is it power at the end, criss-crossed to the other end, and motor in the middle? I've also seen a diagram on the interwebs with power on one side (1, 3), criss-crossed to the other side (4, 6), motor in the middle (2, 5), but jumped again to the bottom (3, 6). WTF?!

[Jason Rodgers]

David, I read through some of that wiki article, but didn't understand much. There were a few things I picked up, though:

- The core (is that the cummutator?) on my motor is a solid cylinder, with no visible coils, unlike the picture shown in this wiki. And I'm pretty sure there are no brushes and the core floats inside the coil. There is what I think could be a small capacitor that the black and orange wires connect to/through.

- This type of universal motor described in the wiki is used in appliances and is very loud. The motor I have is very quiet.

- The AC version of the motor described in the wiki has a wiring that allows it to turn in one direction, regardless of the arrangement of the power wiring.

- The type of motor described in the wiki has high running speeds. I grabbed this at an estate sale because I saw its 3000rpms and thought it was unusual. Then, just a couple weeks ago, I was talking to an acquaintance who happens to be an electrical engineer about my lathe project (see the discussion "Mini lathe: mega cheap"), and I told him about the motor. He said, "3000rpm, at 60hz? Shouldn't it be 3600?" I shrugged my shoulders and later texted him the photo above of the housing. He replied, "Isn't it curious that it says 3000rpm for both 50 and 60hz!" Again, I have no idea what he's talking about, as I've not had an opportunity for a followup conversation.

Anyhoo, I didn't think I had such a curiousity!

[David King]

I'm really baffled but I think you'll just have to run it 180º around so that it effectively spins backwards.
It's not the kind of universal motor I'm familiar with and would seem to be a capacitor start induction motor that by nature should run at a multiple of 60Hz. If it runs at 3000 RPM then it might be a http://en.wikipedia.org/wiki/Shaded-pole_motor Shaded pole motor. According to that wikipage they can be reversed by turning the outer armature (field) around 180º i.e.flipping the end caps and shaft end for end.
These will respond to SCR dimmers as speed control. They tend to run very hot -inefficient in my limited experience.

[Jason Rodgers]

Here are a few more shots of the motor's guts.

The core. No brushes.

The guts, viewed from the back end (drive end shown above). As mentioned, everything is potted and glued in place. The orange and black wires come together with some sort of silver component (capacitor?) about the size of a Dentyne chewing gum tablet (out of sight, stuffed down in one of those tubes on the right). The yellow and red seem to be joined, as well, possibly with a coil lead.

[David King]

OK then..
I do think this is just a two pole induction motor which normally should run at 3500 or 3600 RPM. A start capacitor would normally be bigger (1/2 roll of pennies) and there would also be a centrifugal switch to disconnect the starting cap once the motor gets up to speed.

It could be a shaded pole but i don't see the thick copper wire the article mentions. Either way reassemble it with the stator flipped around and see what happens.

[Jason Rodgers]

I'll give that a try. The coil section of the motor is symmetrical, so the core and end caps should fit either way. Since it's fan cooled, I'll need to carefully pull the fan off with a gear puller or something.

Thanks, again, Mr. King!

[Bill Raymond]

That appears to be a motor made by a company called Universal Electric, not a universal motor. It's probably a shaded-pole motor, as David surmised, but I don't see the shaded pole winding either. However, notice that the pole is segmented as would be a shaded-pole motor. I'm not quite clear about the "fan cooled" property you mentioned. If there's a small fan blade mounted on the shaft within the motor housing, I would think you should perhaps just leave it in place when you reverse the rotor.

[Jason Rodgers]

Weeellllll, the good news is the motor is spinning in the other direction. With a little work, the core was flipped and it ran beautifully.

The bad news is, this cute little motor, about the size of a fat soup can, has NO TORQUE! (Where's the forehead-slapping emoticon when you need it?!) I don't know what this thing did in its original life, but it certainly did not turn anything very big/heavy.

Sooo, time to search for a new motor. My mini lathe just got a little less mega cheap.

Oh well. If anything, perhaps this thread can offer others some info on motor types and arrangements.

[David King]

Well you can pick up fraction HP motors for $25 on CL so I'd start there. I have a little stash of them here usually but it's been a while since I looked through the pile.

That motor was undoubtedly for a fan or blower. Spinning it backwards may have upset the timing and reduced the torque and efficiency. That said you don't need a lot of torque to turn pen blanks.

[Jason Rodgers]

I've already begun looking. How small a fraction would work? 1/4hp or even 1/6?

[David King]

There's a fellow in Eastmoreland that has three 1/2hps for sale in the tools section of CL today starting at $10. that might seem overkill but it can't do any harm. You can always repurpose it later .

[Bob Hammond]

I don't know your application for these motors. Will the motor drive a shaft via a belt and pulleys? If so , there is a mechanical way to reverse the direction of rotation. Plan on using a longish belt, and mount the motor so that its shaft is at a right angle to the driven shaft. When you twist the belt one way, the driven shaft will turn clockwise, and when you twist it the other way the driven shaft will turn counterclockwise.

if this seems confusing, here's a way to see it. Make a loop of string ~18" long, and put it around your wrists. Hold your arms at right angles, and rotate one wrist and watch the direction of rotation of the string over your other wrist. Then twist the string the other way, and you'll see that it rotates in the other direction.

[Jason Rodgers]

Thanks, Bob. Yes, the motor (or eventual motor) will turn the shaft on my mini lathe. I have an old Emerson 1/4hp lump that would turn it, but I'm trying to keep the size (and weight) of the whole kit to about the size of a jeweler's/watchmaker's lathe. Right now, I have it all bolted to a piece of plywood 18" x 12", and the approx 5" x 5" motor that is the subject of this discussion sat perfectly in that footprint. I'm looking for something else now, maybe a 1/6hp furnace blower motor or the like.

[David King]

Many watch lathes run on glorified sewing machine motors. Those tend run a little fast 7-8000 rpm but you can reduce the speed with pulleys and they take well to being run in reverse or on most types of speed control; PWM, sewing machine pedal, rheostat, router speed control, dimmer etc. the best thing about sewing machine motors is that there are many, many of them in Good Will stores or for free.

[Jason Rodgers]

I may need one with a little more oomph than your standard, run-o-the-mill, household sewing machine, then: I remembered today that I have a sewing machine motor, complete with on/off switch and pedal, that I pulled out of my wife's old machine when it died a whike back (something mechanical, not electrical). It would spin the spindle, but only with a very loose belt. Any tension considered normal would stop it.

A "glorified sewing machine motor," as you describe is correct, though out of something more commercial/industrial. I found a discussion on another forum on this same topic. A guy said he was turning a small lathe with a sewing machine motor, but needed to clarify that it was from a bigger machine.

[David King]

You'll need to run that motor at full speed and belt it down 4:1 or 5:1 to get any kind of torque out of it. You can't expect much running it at low speeds.

Commercial sewing machines use big motors (1-2HP) that run full speed all the time and are driven by a slip clutch that's actuated with your knee. The acceleration is very impressive on those. I used to work in a sail loft. You could sew a 30 foot seam in a few seconds with one provided you had a "puller", basically a power feed to get the 20 lbs of cloth moving.
What about using a DC treadmill motor. Plenty of free treadmills around. Also lots of cheap portable drills, hand mixers etc.

The main issue with blower motors is that they are open (so dust gets in) and need a lot of air blowing over them to keep them cool under load.