Unisaw bullet motors?

[M. A. Espinoza]

I'm kicking around buying a used Unisaw.

Is there any information/opinion regarding the old 1.5 hp bullet shape motors? Are they comparable to current 1.5 hp ratings or was there a different standard back then?

Any info appreciated.

[Jim Becker]

Anecdotally, many of those older motors perform more like higher horsepower machines do today. Good efficiency and quality was a hallmark.

[Pete Bradley]

These motors were built for Delta by Marathon and they were very high quality. They'll deliver at least the nameplate rating at speed, and I suspect somewhat more. The rotor is very heavy, which give you a lot of momentum to power through if you hit something hard. The single phase ones are Repulsion start-Induction run (aka R/I) which means that starting amp draw is far lower and starting torque is much higher than a comparable induction motor today.

A good quality modern industrial motor of the same rating will deliver horsepower in the same ballpark. Of course, there are plenty of optimistically rated motors available too. No modern 1.5HP induction motor has the rotating mass of the bullet.

I don't have a lot of experience with this motor in a tablesaw yet, but I generally hear that it's got plenty of power. I've got a 1HP Marathon R/I motor in my 1949 20" band saw and the only time I'd ask for more is in full height (13") resaws in logs.

You also get the classic R/I growl when it's running and the scritch of brushes as it stops, if you appreciate that sort of thing. Single phase bullets are in demand. If yours is a 1.5HP R/I motor, there are plenty of people happy to pay you as much as a new one would cost.

Pete
(who coincidentally just did a bearing replacement on a 1940 bullet this week)

[Jim Holman]

I have a 1948 Unisaw with the original 1.5 HP bullet shaped motor. Great saw with plenty of power to rip 2" hardwood. Mine is very quiet and smooth passing the dime test easily. The motor is honestly rated at 1.5 HP and will produce at the rated HP for as long as you care to push wood through the saw.

[Randy Ferguson]

I am very lucky to have my grandfather's 1945 Unisaw with the original R/I motor.

When I started using it about 8 years ago I took the motor to a local shop to have it gone thru, it's still going strong.

I have been slightly more satisified using a thin kerf WW II blade.

Randy

[M. A. Espinoza]

Given the age, replacing bearings and possibly motor service is a concern.

Seems you have some experience servicing older equipment. Any ballpark figures for bearing replacement or motor service?

I also have a lead on a 3 hp Uni that has recently had its arbor bearings replaced. It came from a school shop so I figure the motor is on borrowed time. Could last ten years or ten days.

Thanks for the info.


These motors were built for Delta by Marathon and they were very high quality. They'll deliver at least the nameplate rating at speed, and I suspect somewhat more. The rotor is very heavy, which give you a lot of momentum to power through if you hit something hard. The single phase ones are Repulsion start-Induction run (aka R/I) which means that starting amp draw is far lower and starting torque is much higher than a comparable induction motor today.

A good quality modern industrial motor of the same rating will deliver horsepower in the same ballpark. Of course, there are plenty of optimistically rated motors available too. No modern 1.5HP induction motor has the rotating mass of the bullet.

I don't have a lot of experience with this motor in a tablesaw yet, but I generally hear that it's got plenty of power. I've got a 1HP Marathon R/I motor in my 1949 20" band saw and the only time I'd ask for more is in full height (13") resaws in logs.

You also get the classic R/I growl when it's running and the scritch of brushes as it stops, if you appreciate that sort of thing. Single phase bullets are in demand. If yours is a 1.5HP R/I motor, there are plenty of people happy to pay you as much as a new one would cost.

Pete
(who coincidentally just did a bearing replacement on a 1940 bullet this week)

[Pete Bradley]

I also have a lead on a 3 hp Uni that has recently had its arbor bearings replaced. It came from a school shop so I figure the motor is on borrowed time.
Thanks for the info.

If it's got a bullet, it's 3 phase, since they didn't make single phase bullets in that HP. If you don't have 3PH you'll want to figure out the price of conversion and take that into consideration. It's hard to fit a single-phase motor other than a bullet into these cabinets without cutting the cabinet. Bullets do come up on Ebay, but a VFD might also be an option.

With new bearings, the expected lifetime of a 3PH motor is virtually unlimited.

Pete

[Steve LaFara]

I restored a '39 Uni last winter that has the original R/I bullet motor and it runs great. Bearings are easy to replace for under $20 and if the armature needs to be trued, any local motor repair shop should be able to handle that fairly easily.

[M. A. Espinoza]

I'll have to look into that. I assumed it was a r/i motor due to the vintage but it could have been replaced. It is supposed to be a 110 motor. The cover is on the saw so couldn't see for sure, its the egg-shaped cover. Due you know when they stopped making this style?

Thanks for the info., I'll need to get a little more information before I make a decision.


If it's got a bullet, it's 3 phase, since they didn't make single phase bullets in that HP. If you don't have 3PH you'll want to figure out the price of conversion and take that into consideration. It's hard to fit a single-phase motor other than a bullet into these cabinets without cutting the cabinet. Bullets do come up on Ebay, but a VFD might also be an option.

With new bearings, the expected lifetime of a 3PH motor is virtually unlimited.

Pete