Monday, August 1, 2016

An Antique Wagner Electric 1/2 HP Electric Motor

I picked this up from a guy on Kijiji for $20.00.

It's a bit of an antique. I didn't realize how much of an antique until I got it home, and read the I.D. label, and compared it to a modern Marathon Electric 1/2 hp motor. Here's a view of it next to the Marathon motor.

The motor is huge. The Marathon weighs about 15 lbs. The antique weighs about 45 lbs.

Here's a shot of the old motor's I.D. plate.

Following is a transcription of all the I.D. plate data:
  • TYPE RPI ['might be RP1]
  • H.P. 1/2
  • R.P.M. 1725
  • CY 60
  • PH. 1
  • FRAME 67Y
  • VOLTS 110/220
  • AMPS. 7.7/3.8
  • HRS. CON 50° C
  • SPECIAL DATA [blank]
  • MODEL 248R168
  • SERIAL 127
  • H.E.P.C. CODE P56 04 23-12-790 5003
Following are some notes on the above:
  • Parts of the above transcription are a little iffy. The vertical registration of the data printed on the I.D. plate's grid is poor, and some characters were difficult to be certain of.
  • "REP START" is short for 'REPULSION START'. That's something new to me, and I'll try to learn more in a practical sense. What I've seen on the internet so far looks a bit thick and dense to me.
  • Wagner Electric as an independent manufacturing entity is no more. Here's the Wikipedia entry on Wagner Electric.
  • "CONVERTED TO 60 CYCLES..." says that this was originally a 25 cycle motor, so it's very old indeed. As I recall, conversion to 60 cycles in southern Ontario, Canada occurred in about the early to mid-1950s.
Does It Run?

Yes, it does. It starts and runs quite nicely. It's currently wired for 110V operation. The wiring diagram for voltage conversion inside the connection box's cover is still in fine condition, like so.

The diagram doesn't mention reversibility, so I guess that's not doable. That's ok, though, because the motor's direction of rotation is correct for the application I have in mind. (It's CW, viewed shaft-end-on.)

The shaft has about 0.027" of end play to it, which strikes me as a tad excessive, but it doesn't appear to be a cause for concern. As the motor reaches full speed, the shaft biases itself outward, and seems to be quite happy there.

An Application

I have an ancient Sears Craftsman 8" table saw that I'd like to be rid of. I have other motors for the saw, but if this one will fit the stand I've made for the saw, it would be ideal to go with the saw. We'll see how that goes.

A Trial Fitting

Using this motor with the Craftsman saw appears to be doable.

I'll have to add new motor-mounting tee-nut locations, and possibly get a shorter v-belt, but it looks like it'll work.

I'll put a blade in the saw, clamp the motor in place, wire up the motor temporarily and try the motor under load. If that proves out, then I'll go ahead and make the adaptations to use this motor on the Craftsman saw.

It Works

I put an old thin-kerf blade in, changed the v-belt from 38" to 37", wired it up, clamped the motor in place and gave it a go. It starts up and cuts wood. So now, here's my list of things to be done:
  • Get the pulley off and clean it up, along with the motor's shaft.
  • Remount the pulley and position it closer to the motor's frame. That will minimize belt tension leverage effects on motor bearing load.
  • Establish new mounting bolt locations.
  • Install 1/4"-20 tee-nuts for the new bolt locations.
  • Reassemble everything, tension the belt, wire up the motor and cut some more wood to really give the thing a trial. Fortunately, that existing armored cable that's part of the stand will fit perfectly.
  • Put it up on Kijiji and get it out of my workshop and my life.
Pulley and Shaft

Here we are with the shaft and pulley cleaned up, and the pulley better positioned than it was.

The pulley wasn't badly seized on the shaft, but I did have to use a puller to get it off. The pulley is 5" diameter. The shaft is 5/8" diameter, with a 3/16" keyway.

The keyway had a binding spot in it that I had to file in order to obtain a free-sliding key fit. I think the binding spot was from someone once having tightened down the setscrew with no key in place.

Using the motor as its own lathe, I steel-wooled the shaft and the pulley. The outcome was reasonable. I wasn't after pristine perfection -- I just didn't want the thing to look like it had sat in a barn for the past twenty years.

I gave each bearing oil-hole six drops of 3-IN-ONE SAE 20 motor oil.


I got the new mounting hole locations marked out, drilled, counter-bored  and fitted with 1/4"-20 tee-nuts. Here's the arrangement with the motor in place and properly bolted down.

The motor's mounting bolt slots provide a fair bit of adjustment range for belt tensioning. That's a good thing, because belt tension changes depending on the saw blade's elevation, and has to be readjusted accordingly. I've set the belt tension with the saw blade fully elevated, since that's my usual way of operating a table saw.

That saw has a tilt feature, but that will be inoperative with this motor mounting arrangement. Construction of a motor mount that would allow for saw blade tilt would involve a level of engineering skill that's frankly beyond me, so this saw is going to be strictly a 90° cutting angle affair.


The wires that emerge from the motor are stranded, like so.

There were wire nuts on those connections that I can re-use for connecting to the incoming armored cable, but I'll want to tin those stranded wires first. When using wire nuts on stranded wire, I prefer to tin the ends of the wires.

And here we are with that done.

Four nicely tinned wire ends that won't shed strands.[1]

A Ground Connection

This motor is from back in the day when armored cable didn't include a separate, bare copper ground wire; the cable's aluminum sheath and a thin strip of aluminum were the only ground continuity guarantors.

Modern armored cable includes a bare copper ground wire, but there's no provision on the motor for connecting it. What I'll do is add a 10-32 stud to a wall of the connection box, and that will serve as a ground terminal.

- - -

And here it is.

That hex nut has an internal tooth lockwasher under it for good measure, and I scraped off paint from under screwheads as required to ensure ground continuity. The motor's frame will absolutely, positively be grounded.

Here's the armored cable installed, the ground wire connected and the line connections ready to receive their wire nuts.


With everything buttoned up, I gave the saw a brief trial.

The motor takes a full second to get up to speed, which seems a bit long to me -- I'm accustomed to seeing motors reach full speed much quicker than that. Perhaps it's a normal characteristic of a repulsion start motor.

I did a few crosscuts, and one rip cut on a short piece of 2x4, and the motor's power is impressive. I'd say that its 1/2 hp rating is a conservative one. It could probably handle a 1/8" kerf blade easily.

* * *

Update -- WEDNESDAY, JUNE 21, 2017

The saw didn't sell, so I've stashed it away against the day that I maybe enable its arbor tilt feature. We'll see.

I decided that the motor deserved to be better looking, so I tore it down and gave most of it a gloss black paint job. Following is an outline of that whole process and what it revealed of the motor's architecture.

- - -

Two 10-32 thru-bolts hold the motor together. With those removed and the motor disassembled, here's what all we have.

The Wiring-End Bell

It's a lightweight alloy casting with sleeve bearing and capped oiler. I've stripped the paint off it, and I've left it unpainted. It won't rust, and it looks fine unpainted.

Note the round screw-head in a recess at about seven o'clock. That's the head of a screw that fastens the brush carrier angular restraint prong in place for the repulsion-start commutator. More on that in a bit.

The I.D. label on the end bell is the original, from when the motor was a 25 cycles per second machine. Here's a close-up view of that.

That label is also an inspection port cover. It can be swung up for a peek at the repulsion-start commutator. I'll show that when I've got the motor reassembled.

Here's the inside of the wiring-end bell.

Note the rectangular prong sticking up alongside the bearing housing. That's the brush carrier angular restraint.

The Output-End Bell

It's a steel casting with sleeve bearing and capped oiler. I've given it a gloss black paint job.

The Frame/Stator

That got a gloss black paint job as well.

What an unwieldy thing that was to manipulate for painting preparation. Anyway, the outcome is pretty good, except for one little flaw that I'll have to touch up.

I had the frame outdoors for a spell so the sunlight and free-moving air could age the paint and harden it. When I fetched it back in, I noticed a nasty little blemish on it. It's right at the centre of the following photograph.

I have no idea what it is or where it came from -- a wee spatter of bird poop, perhaps. I suppose that's the risk you take with leaving a painted object outside for the paint to harden.

Here's a view of the end of the stator inside the frame.

The stator has a total of thirty-six poles.

The Armature/Rotor

And here we have a repulsion-start/induction-run rotor.

It has twenty poles. The commutator has thirty-nine segments. I don't pretend to understand that.

Here's a view of the rotor's other end, with the centrifugal switch flyweights.

When the flyweights trip outward at sufficient rotor speed, two things happen:
  • The brush carrier is lifted away from the commutator, so the shorting brushes are no longer riding on the commutator.
  • The rotor's segments are shorted together, so the rotor becomes a squirrel-cage rotor.
It's the first I've ever seen of such a start/run arrangement for an induction motor.

Reassembly In Progress -- FRIDAY, JUNE 23, 2017

Here we are with the output-end bell on and the rotor in place, awaiting installation of the wiring-end bell.

Note the groove in the brush carrier at six o'clock. That groove accepts the prong on the inside of the wiring-end bell that anchors the brush carrier against angular motion.

And here's the motor back together, waiting on its thru-bolts and an operational test.

I think that looks fine, with the one end bell bare metal.

- - -

All Done -- MONDAY, JUNE 26, 2017

And here we are with the motor ready to go into service.

I mean to sell it, so I've given it a temporary 18 AWG line cord that's adequate for demonstration purposes. And if I don't get a buyer, that's ok; I'll have a fine, spare 1/2 hp motor on hand that I may find a use for some day.

- - -

Sold It -- THURSDAY, JULY 6, 2017

An ad on Kijiji got results. 'Got my $50.00 asking price for it.

* * *


[1] See this post for some information on wire connection best practice.

# # #

# # #

1 comment:

  1. I have one running my bench grinder i like the sound it makes starting up kinda a 2 stage whine