Unisaw bullet motor starting problem

[Zachary Hoyt]

I have a late 40s (I think it's 1948 if I remember right) Unisaw with a 1 HP bullet motor. I bought it from a school auction last spring and set it up for 120v and it has run fine and been in regular use since then. Tonight I cranked the blade tilt to about 35 or 40 degrees, and when I tried to turn it on the motor didn't sound like it came up to speed all the way, and had no power. I tried tilting it back to 90 degrees and had the same symptoms.

I'm wondering if I should be trying to fix this myself, or take it to a repair shop, or buy a newer motor. I've been happy with the amount of power it has. I have some electrical knowledge but not that much. I was able to rewire the motor from 240 to 120 and I have changed bearings and capacitors in motors but that's about it. I found a motor shop 67 minutes away and another 91 minutes away that seem like they might be able to work on it, but I'll have to wait till tomorrow to call and ask them. I don't know if a newer Unisaw motor will fit in the cabinet. I've been doing some reading about how to repair these motors, but I am doubtful as to what is the problem with mine. I'll be very grateful for any advice.

[Ron Selzer]

I would try a new starting capacitor first.
Check the start switch in motor next if capacitor didn't fix it.

[Marc Fenneuff]

The bullet motor is a repulsion start, induction run motor. So no caps. You may have a broken shorting spring. I will suggest you ask the folks at owwm.org for troubleshooting steps.

[Zachary Hoyt]

I feel kind of dumb, but I'm happy to say that it's back up and running after less than an hour's work. I pulled the motor out this morning and found that the 3/16 square key that holds the pulley on the shaft had fallen out. When I bought the saw it was missing, and I bought a foot of key stock. I will get some Loctite for the set screw if it does it again. This time I drilled a dimple in the top of the key so the setscrew could go down into it and am hoping that may help.

[Marc Fenneuff]

Simple fixes are the best! Keep the old girl running!

[Bill Dufour]

If there is enough depth, use two setscrews one on top of the other. The outer one can extend out a bit beyond flush.
Bill D

[John TenEyck]

Glad it was a simple fix. If the bearings in the motor have never been replaced you might want to think about doing so. Bearings typically are good for 25 years or so, whether or not it's run much, and you're well beyond that. Keep your ears attuned for any change in sound or if it keeps spinning for a long time when you turn it off. In any case, keep that motor. Those bullet motors have amazing torque for their rated HP.

John

[Earl McLain]

Glad it was a simple fix. If the bearings in the motor have never been replaced you might want to think about doing so. Bearings typically are good for 25 years or so, whether or not it's run much, and you're well beyond that. Keep your ears attuned for any change in sound or if it keeps spinning for a long time when you turn it off. In any case, keep that motor. Those bullet motors have amazing torque for their rated HP.

John

That part i italicized above was the best lesson i learned on a RAS forum. Sounded counter-intuitive first time i ever read it--but the long spin time is a sign of needing grease in the bearings.

Congrats on getting your saw "running" again!!
earl

[Zachary Hoyt]

Thank you all for the advice. There's only enough threads for one setscrew, but at some point I may look for a different pulley since this one is a bit worn in the ID. I didn't know that about spinning for a long time when turned off. What is considered a long time? This saw hasn't changed noticeably since I bought it, so I will time the duration of the spin and at least have a baseline.

I do want to replace the arbor and motor bearings, but have been hurrying to get the house repairs completed and still keep making enough instruments to have some income, so they will likely wait a few more months unless they get worse. I could hear a little grindiness in the arbor bearings when I spun the blade with the motor out, but it doesn't seem like an acute problem yet.

[Zachary Hoyt]

After letting the saw run a few seconds at full speed I turned it off and it took about 9.5 to 10 seconds to stop. I don't know if that's a long or a short time. I can't remember the other saws I've had and how long they took.

[John TenEyck]

Take the belts off the arbor and just run the motor. If it takes 10 seconds or more to stop the bearings likely need to be replaced. 20 seconds and it's time right now. Hearing grittiness in the arbor bearings is bad. While you have the belts off push/pull on the arbor. If you feel any movement or more grittiness, the bearings need to be replaced. It's not too hard a job to change them, but it will chew up a day if you've never done it before. I don't mean to cry wolf, but bearings are easier and less expensive to replace than the arbor and/or what it fits into. Sorry, I can't remember the name of that part.

John

[Zachary Hoyt]

Thanks for the advice. I did check the arbor bearings this morning by trying to wiggle the blade, and was not able to feel any movement, but the bearings don't sound great. I'll have to look into where I can get new ones. I test ran the motor tonight as you described, and it took 54 seconds to stop. I guess it's either a miracle, or an impending disaster, or maybe both.

[Bill Dufour]

Bearings are simple off the shelf items. Get rubber sealed. I believe they are both the same. Only warning is to push direct on the casting do not use it as a lever. Some try to push from the far end and snap the arm off.
My remarks are for much newer machines yours may vary? ebay no name 6203 bearing will be under $10 for two
Bill D.

https://sawmillcreek.org/showthread.php?181412-Need-help-replacing-arbor-bearings-on-unisaw

[Zachary Hoyt]

Thanks. I should need the earlier style bearings with the wider inner races, and they're also widely available on eBay and such but at a bit higher cost since they're less common for other jobs, I imagine.

[John TenEyck]

Thanks. I should need the earlier style bearings with the wider inner races, and they're also widely available on eBay and such but at a bit higher cost since they're less common for other jobs, I imagine.

I'm pretty sure that's correct as I remember them being different when I did them on my 1954 Unisaw. You need an exploded view of your saw to corresponds with its serial number. The accompanying parts list will give you the bearing number. If you don't have it I'm sure you can get it at OWWM's website.

I can't remember how I removed the bearings, but I do remember heating the new ones to install them on one part, probably the arbor, and chilling all that to install them into the casting. I think. I'm sure you can find the process well documented.

Yep, those motor bearings are way beyond toast. Install new ones or send it to a motor shop and have them go through it. My advice is not to wait until something goes wrong, or the repair can get very expensive. That loose set screw was a good thing.

John

[Bill Dufour]

The bearing grease is more then 70 years old so it should be replaced. far easier to replace the entire bearing rather then try to pull the shields and reinstall them. Is the vee belt 70 years old as well? Might be a good time to replace it while things are apart. As I remember there are two arbors the older one used special bearing with extended inner races and maybe a spacer.
The newer version the arbor is bigger diameter in the middle so the bearing can not get too close together. Or maybe the spacer is just a bit longer so regular bearings work.
Bill D.

[Zachary Hoyt]

I ordered the old style arbor bearings this morning, assuming they'll be correct. If not I should be able to get the regular ones through NAPA in town faster, if I take the arbor apart and find it's not the origina typel. The V belts look nearly new, though I have been running them for a while and they were on the saw when I bought it. They're the greenish kind of heavy duty rubber and there are two instead of three but that seems to be plenty for the size of the motor.

I took the oval covers off at the end of the motor and looked in, and I would say the motor looks like it was rebuilt not too long ago. The windings are blackish with age, but the wire going to one of the brushes was visible and it looks as shiny as new, and the commutator is fairly clean. Also the paint on the gray cylinder part of the motor is a different color gray than the cabinet, and looks newer. I can't feel any end or axial play in the bearings and the motor runs very smoothly and quietly, so I will continue running it. If anything changes I will re-evaluate, or if there is a catastrophic failure I will certainly post about it here right away.

[John TenEyck]

That's a logical approach, but 54 seconds for the motor to stop spinning strongly suggests the grease in the bearings has dried out. Keep your ears tuned.

John

[John Lanciani]

54 seconds is about 44 seconds too long. Replace the bearings before you do permanent damage to the motor.

[Bill Dufour]

When those motor bearings freeze up they may scour the endbell bores beyond repair or they may scar the arbor shaft the same way. Yes there is spray welding and remachineing, but a new motor will be cheaper.
That galling and friction welding can occur in just a few seconds under power.
Bill D