Oder unisaw motor potential problemo

I'm sure I'm not the first one to have this happen to, but my 1950's model unisaw with the 1hp motor is slow to start. Kinda like it's not getting enough power. Sometimes the motor hums but the blade won't spin. Other times it takes a moment of "hum" and then starts up. Once it is started, it works fine. But it does seem to be getting worse. Thoughts? SH
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I am not a motor expert, but I would do a few things:
1. clean up the motor 2. check and clean the brushes 3. check the start capacitor for leakage
--

Greg


"Slowhand" <I'm@work> wrote in message
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I am not a motor expert either but I would add
4. Check starting capacitor (there should be one on top of the motor. If it is HOT when you are trying to start it, that might be part of the problem.
Some of our electricians out there can probably tell you how to check it with a multimeter.
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Probably not a serious problem but after 50 years it deserves a good clean and check. Take it to a good rewind shop and have it checked out. While in the shop have them pop a new set of bearings in it ( you may be amazed at how little they cost). With everything checked, cleaned and replaced as necessary the motor will probably out last you. Earl Creel

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Replace the motor start capacitor. It is the hump on the motor case. First, uncover it, and then short a screwdriver across the leads to discharge it. You don't want a nasty shock. Of course you do this with the saw unplugged. If that doesn't do it and you feel comfortable taking the motor apart you take the bell off the end opposite the shaft. There is a centrifugal switch assembly in that end that has points. You need to clean the points. max.

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From the OPs diescription, it sounds like this is an RI motor. It probably doesn't have a capacitor. The cleaning & dust removal is a good idea in any case.

--

Larry Wasserman Baltimore, Maryland
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Don't go trying to change out the cap start onna 'count of there isn't any and you'll only make yourself crazy trying to find it. It's Repulsion/Induction and has brushes. This is a good thing because they guard against any of the magic smoke getting out.
That aside, take the oval (actually elliptical) access covers off the end of the bell and look inside. Underneath one you'll see a lock screw and a brush holder. On the brush holder there will be a letter L, a center line and a letter R. Dependent upon which way you want the motor to rotate you set it to R or L. Disregard the center line mark. It must never be spoke of aloud otherwise you could let out the magic smoke.
Back to the matter at hand. More than likely the lock screw has loosened and the brush holder has shifted slightly. Loosen the lock screw (or not dependent upon how loose it is already) and shift the bracket to where the R or L (in this case more than likely the letter most closest to the notch) align with the notch in the motor housing (towards the outside of the motor case. It should be just a case of shifting that to where it wants to be and you're set for the next forty years. You might have to go this way or that with it but it's not rocket science and besides, if you don't feel good about it there should be a competent motor man near you who will do it for an extremely small fee.
I don't know much about 'lectrical things and motors but I do know I love my R/I (Less Than A Horse) Unisaw motor.
UA100
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It ain't always how much you know, it's often what you know.
--

-Mike-
snipped-for-privacy@sprintmail.com
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Mike Marlow wrote:

Try telling that to a couple/few of the regulars. They'd argue the point and the next thing you'd know is they be off making chalk lines on the wall and dropping their trousers.
Oh, getting back to your comment, I've also come to understand that having the answer isn't always important but knowing where to find the answer, priceless.
UA100
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The answer is generally somewhere in Wisconsin, when it comes to old iron.
Patriarch
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Thank you UA. Not to discount the other people helping at all but I know you do own the older style unisaw and was hoping you would chime in. Just curious but how do these older 1hp motors line up with the newer 3 and 5 hp motors as far as power goes? SH
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Ours at school seems every bit the equal of a 3 HP. Of course the 1/2 HP RI on the shaper will take almost any cut you have the courage to make. I think the spiral design of the core gives more continuous push than the windings on a regular induction run motor.
Torque!

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Slowhand wrote:

The R/I motors are very "tourquie" (pronounced torky) and as far as I'm concerned you can keep your 3 horse Baldors. This is not to say that a 5 horse isn't more powerful but I wouldn't hesitate to buy a Unisaw with an R/I motor.
So, did your problem get fixed/is the machine going whirrrrr better now?
UA100
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"Unisaw A100" axed:

Heh, heh. Indeed it is. And I thank you profusely. It took me a bit to figure it out but once I cleaned up the R and L area, I figured it out. You ever seen a unisaw run backwards? I did. <LOL>. I set the R with the notch and turned the saw on. I thought, cool. I actually fixed a saw motor. I went inside and told my wife how great I was. Told her she had to come see how well the saw was running. Hold my beer honey and watch this. I took a piece of scrap to show her how well this works now and that piece of scrap was grabbed from my hands and flung to the back wall.
She says "Is it sposed to do that?" I was busy scratching my head as I have NEVER had that happen before. Then I started wondering if I had set the R and L thing wrong. Back into the motor I went and set it to the L. Wala! Unisaw moving forward again.
I'm just curious but what do the R and L settings stand for? I figured if I had a right tilt, it must be needed to sit on the R. I guess the R must stand for Reverse! Anyway, I big time thank you as the saw has never run this well before. SH
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About 10 years ago I bought a Yates 18 inch tablesaw made in 1933. A beautiful saw with less run out than my new Rockwell unisaw at the time. It had a three phase direct drive motor. I bought a static phase converter and a Forrest 16 inch WW11 that was made specially for me. When I finished hooking it up I tried to run a piece of ply through it. To my utter amazement it grabbed the piece of wood and shot it across the shop. The motor was spinning backwards. I reversed the wires and all was well. max

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Slowhand wrote:

The six worst words to be hearing from your wife at a time like that.

Right and Left, as in rotation.
That same(ish) motor with a standard mount was once upon a time used in the Heavy-duty shaper. Those motors had a lever on the bell end to reverse the rotation. You reached inside the cabinet and flipped the lever. That was all there was to it.

Real Unisaws tilt right hand only. When your machine was made there were no l*ft h*nd tilting Unisaws.

Sounds like it's ready for the next fifty years?
UA100, who would have hated it if you'd not have asked and figured the motor was toast and we all know where that goes...
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(I know nothing about Unisaw specifics)
Generally the older motors have as much power as they claim, and the newer motors have some large fraction of what they actually claim. I've heard this described as the difference between mechanical output (old measurement) and electrical input (modern), but whether that's an explanation or an excuse, I don't know.
What the old motors (RI rather than cap start) do have is higher torque at startup. This is the real reason why you can have "the same saw" with an old motor that's apparently a tiny rating compared to the new one, yet appears to do the same job.
If you're looking at maximum power, that's the torque they can deliver at near operating speed under a heavy load. Remember that _all_ motors under these conditions are only rated for a certain duty cycle. Modern power ratings are taken at shorter duty cycles than older motors, which is another way to massage the figures.
[digression] A squirrel cage motor (and the switched equivalents when they're running above the switched speed) relies on "slip" to generate current in the armature windings. The armature rotates more slowly than the field in the stator rotates. This difference appears as a rotating field in the armature, inducing a current in its windings. The stator field is a constant speed, so as the armature slows under load this slip increases and the induced current goes up. I^2.R and there's your extra heat source when you load up the motor.
If you hammer your saw with a huge rip, then let it cool down afterwards before feeding it another heavy cut. For a modern motor (minimal mass in the frame and laminations) then you might leave it running off load for a minute to keep the fan circulating. NB - Stand by the saw while you do this - you shouldn't leave the whirling blade unattended, even if it's not cutting anything.
--
Smert' spamionam

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THank you to all who responded. I appreciate it. SH

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I bought a 1 1/2 hp Unisaw about 25 years ago and it acted the way you describe. In the case of this saw it had been wired 240v but had a regular 120v plug on it. Something to check.

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