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?
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.
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.
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.
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.
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.
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?
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.
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
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.
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.
The six worst words to be hearing from your wife at a time
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
(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.
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.
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