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Unisaw repulsion/induction motor issue

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Forum topic by NorthernMaple1 posted 09-21-2020 11:30 AM 303 views 0 times favorited 4 replies Add to Favorites Watch
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NorthernMaple1

5 posts in 37 days


09-21-2020 11:30 AM

Topic tags/keywords: unisaw motor issues delta table saw

Hello lumberjacks. I’ve been coming here lurking for years and finally had a reason to post. I’m restoring a 1951 unisaw with the bullet repulsion induction motor. I’ve replaced the bearings, cleaned the carbon out and cleaned off the commutator. The shorting necklace spring seems to be nice and tight. Running the motor with no belts on it and it just free spinning, it fires right up and after timing the brushes you can hear it kick into the induction after about 1.3 seconds. However, after putting the belt and blade on, it bogs down and won’t even cut when trying raise the blade through a new zero clearance insert.

Based off the tag the motor looks wired correctly for 220. Tomorrow I’m thinking I will pull the wire nuts off and make sure the wires are not corroded. I may also bypass the switch to make sure there is no issue there. I’m running out of ideas and any help would be appreciated before I have to drive 2 hours each way to a motor shop.


4 replies so far

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CaptainKlutz

3722 posts in 2377 days


#1 posted 09-21-2020 12:49 PM

Have you checked the commutator mica?
Are the springs pushing on brushes properly?

http://wiki.vintagemachinery.org/Unisaw-Bullet-Motor-Repair.ashx

Have a couple RI motor experts posting in various RI threads over at the OWWM.org forums that might be able to help. Be sure to register for OWWM to get access to all the forums and posts, as search engines don’t index those materials.

Best Luck!

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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NorthernMaple1

5 posts in 37 days


#2 posted 09-22-2020 03:15 PM

Being it was my first post here and I didn’t realize it had to be approved I though I was doing something wrong since The topic it didn’t initially
post. So I had pretty much given up at that point on the motor and actually posted at owwm about upgrading the motor and different speed motors and which pulley I would need. While answering that they encouraged me to try and not give up on the RI motor yet and guys have been walking me through trying to diagnose to old stock motor. So I have been diving into it again and It’s a head scratcher for sure. I may just have to go with a new lesson.

It’s starting up no problem. With no load it fires up and sounds great.
With the belts installed tight it dosnt want to power up. With the belts fairly loose it will fire up but seems to hesitate or almost stutter when trying to go into induction.

Carbon was cleaned out. (There was a lot) New bearing installed. Commutator and shorting necklace contacts were cleaned and brushes are all contacting when it was put back together. Shorting necklace is nice and tight. I’ve had this thing apart about 5 times checking and double checking. The guys at the owwm agree it looks wired properly.

I’m not opposed to upgrading to a 2-3hp motor especially now that a member over there posted how it looks after removing only a little bit of the cabinet to make it fit. I was hoping initially that original motor would work because I would add a cabinet saw for nothing more than arbor bearings, motor bearings and a nice blade guard but that may not turn out to be the case. At this point All that other stuff is installed and I’ still have a nice cabinet saw with a good fence, but I’ll be quite a bit invested into it with the addition of a new motor.

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CaptainKlutz

3722 posts in 2377 days


#3 posted 09-23-2020 02:28 AM

Saw the OWWM thread.

As long as the winding resistance values are close in value, and don’t have hidden damage to a winding;
I agree with OWWM folks regarding brush positioning as potential source of problem.

Only rebuilt one RI to date, and getting a proper brush contact patch on cummuntator, and angular position can be tricky.

Best Luck!

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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NorthernMaple1

5 posts in 37 days


#4 posted 09-23-2020 08:42 PM

Captain,

I agree and thought the Same. The way I currently have it I cannot time it any better with the brushes. I’m currently working on various end bell positions and a continuity test. If this thing never works again, I’ve at least leaned far more about old notepad that I ever wanted to. Haha. I’ll update with progress.

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