# 3ph Motor Install, Need Recommendations



## chevydyl (Jan 1, 2016)

I have an Atlas 12" underneath drive, and pretty much since I have owned it I cant use the top 2 speeds, it vibrates pretty bad from a sprung pulley. I have however made a pulley for just one of those speeds, number 3. I have a 1.5hp 3ph motor that I want to install and use my vfd to control speed, partially. Still want to use pulleys for the torque advantage. The new motor is a Baldor inverter rated 1755rpm motor, i was wondering what size pulleys i should use, or how i should do the drive, i was thinking of deleting the step motor pulleys, what size would i replace those with? i also thought of driving the countershaft with the motor, and having 2 or 3 steps at that point, basically for a low and high range. let me know what you guys think, thanks.


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## kd4gij (Jan 1, 2016)

That motor is quit over size for an atlas. They came with either a 1/3 or 1/2 hp motor.


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## Ulma Doctor (Jan 1, 2016)

it is a larger motor, but shouldn't be too big an issue unless you crash the lathe repeatedly- 
it will get expensive to put humpy dumpty together again!
you are free to do as you'd like, but if i could..
i'd see if i could somehow keep the stock motor drive pulley, or approximate them on a homemade pulley-
you'd be better off.
that way you can utilize the lathe with intended speeds, then use the frequency control to fine tune the speed you'd like to operate at.
you could gain a lot of mechanical advantage in backgear, with pinpoint rpm control- a very useful thing.

i may suggest limiting your vfd's output, as to not over speed the lathe.

good luck.


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## chevydyl (Jan 1, 2016)

to be truthful, the lathe also has had a broken motor pulley, so I bought a single v pulley to put on the stock motor, for high range of speeds. One issue that I have is the 3ph motor is a bit longer than the stock one, which to mount it I would have to cut into the cabinet, that would be to retain the original drive configuration, not sure if I could make a deep dish pulley to move it close to the cabinet wall so I could move the motor over without having to cut into the cabinet.
on another note, whats the max rpm you would run the lathe at? im thinking 2750 for short durations of around 5mins would be ok

it currently has a 3/4hp motor


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## Nitmare67 (Jan 2, 2016)

Thats a really big motor. Youre going to find a hard time finding an appropriate frame size 3 phase motor in that hp... basically you wont find one. thats probably a 143 or 145 frame size and you need something much smaller. I would strongly suggest running a 3/4 or 1hp motor and setting the drive up for vector control as compared to volts over hz. You will have peak torque at 20hz just like you do at 60hz. Then just set the lathe up on a middle of the mill belt drive speed and overspeed the motor if you need high rpm and still use the back gear for threading. Basicaly you would end up being capable of prob 25% more top spindle speed and still be able to run 25% of the charted speed and still have full torque for any range selected.

I would suggest something like an AB Powerflex 40 VFD.


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## chevydyl (Jan 2, 2016)

Lol you guys, I don't need to hear how much too big the motor is, I don't care, I'm putting that motor on my lathe, end of story. All I wanted to know was what I should do with the pulleys as far as having the listed speeds, currently I mostly thread in direct drive on low speed of high range.... I know what my lathe can handle, just because I'm putting a bigger motor on it don't mean I'm gonna take bigger cuts, cause it simply can't handle anymore than what I do now.
Number 1, I will NOT have adjustable motor pulley steps. Single V or serp.
Number 2, I will install that 1.5hp motor, and use a mitsubishi 3hp vfd
Ps, I already run the motor belt loose, and I've stalled the spindle on heavy cuts where I've had to tighten it up to get through the job then put it back, all part of knowing the limits, but knowing there is a little more there if I need it.


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## chevydyl (Jan 2, 2016)

Oh yeah, I also have a 1.5hp DC high torque treadmill motor I could use, it has about a 5000rpm range, problem with that motor is it has a screwed on pulley, that's a serpentine type belt drive, that's my other option, I could use that instead of the 3ph motor. I think that one would need some underdrive pulleys to use so I would stay in the range of lathe speeds, with some extra speed for polishing or whatever


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## Ulma Doctor (Jan 2, 2016)

chevydyl said:


> to be truthful, the lathe also has had a broken motor pulley, so I bought a single v pulley to put on the stock motor, for high range of speeds. One issue that I have is the 3ph motor is a bit longer than the stock one, which to mount it I would have to cut into the cabinet, that would be to retain the original drive configuration, not sure if I could make a deep dish pulley to move it close to the cabinet wall so I could move the motor over without having to cut into the cabinet.
> on another note, whats the max rpm you would run the lathe at? im thinking 2750 for short durations of around 5mins would be ok
> 
> it currently has a 3/4hp motor



if you have a broken pulley and do not have room for a suitable sized multi pulley, i'd suggest picking the larger motor drive pulley or something that closely approximates it's size.
you don't really want the motor going much past 1800 rpms with a stock sized pulley- the lathe was not constructed for high speed operations
going slower is fine for short periods of time


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## chevydyl (Jan 2, 2016)

With the current pulley configuration the lathe goes 2025 right, I don't remember exactly, but all my high speed range is intact except the sprung countershaft pulley which limits me to the two lower ranges, the top two ranges create massive vibration where the tool post shakes like a money maker

I wouldn't be spinning the 3ph motor all that fast anyway, as it is now I don't use freq control on my mill, I just use the vari speed


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## wa5cab (Jan 3, 2016)

1-1/2 HP 3-ph motor is 'way too large for a 12" Atlas, even the Commercial.  The max recommended is 3/4 HP.  If you use a surplus (Chinese made) tread mill motor, it would probably be OK, as the mainland Chinese usually grossly overrate their motors.


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## chevydyl (Jan 3, 2016)

lol, again with that, I know that motor is a lot, but its what I have, and I will not be purchasing any other motors for it. forget the HP number, its a 3ph .5hp motor now, what would you do with the pulleys, being that I DONT have good stock pulleys, and with VFD control can get away from most but NOT all belt changes..... but I don't want to buy stock type pulleys, I want different pulleys, the motor will not have steps, but the countershaft can have a max of 3 steps, or maybe, just maybe the motor has 2 steps, for hi and low, and the countershaft has 2 steps for hi and low, with the freq control to make up the rest.....


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## chevydyl (Jan 3, 2016)

oh yeah one more thing, VFDs have an amp output limit control.....


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## wa5cab (Jan 3, 2016)

True.  But you said that you were going to have to butcher the cabinet to install the huge motor.  The Commercial cabinet is pretty strong but it won't be if you cut half of the right wall out.  I'll bet that if you got on CL and said that you had a 1-1/2 HP 3 ph motor that you were willing to trade for a 3/4 HP 3 ph one, you'd quickly enough get a taker.  It's your machine and you can do whatever you want to it.  But using that motor just makes no sense.


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## chevydyl (Jan 3, 2016)

I'm in alaska, most people see or hear 3 phase and run lol. I'd only have to cut the cabinet if I chose to use the stock motor pulleys cause they stick out kinda far away from the cabinet wall. That why I mentioned using a deep dish pulley in an earlier post as it would move the motor over several inches, or I could run the motor shaft out the side of the cabinet, where the big pulley is at... no cutting.
I'm not interested in what anyone else would or wouldn't do, I'm only interested in the pulleys, and sizes YOU would run given you had this motor to install and there were NO other motors


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## wa5cab (Jan 3, 2016)

OK.  Now I understand what you meant by "deep dish" pulley.  If you do that, before you install the pulley, you need to "remote" the oiler as it is just barely accessible as it is.  As an out of place afterthought, hanging that heavy a motor 'way in the back of the cabinet is going to be "interesting" (no room for a helper).  So don't forget to install the motor pulley before you start installing the motor the FIRST time.

What is the motor's shaft diameter?  What is the motor's maximum continuous duty rated RPM?  What is the motors minimum continuous duty rated RPM @ 1/2 HP?


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## chevydyl (Jan 3, 2016)

Not sure on the rpms, the power graph from Baldor says it makes 0% of rated output at 1700rpm, and 150% @1735rpm, the rated speed is 1755rpm I have a hard time believing that I would be able to stop it by hand at 1700rpm since the graph says it would be making zero hp..., it has an .875-.8745 (7/8) shaft. 145TC frame, flange front mount or foot mount TEFC
The motor on my mill doesn't seem to care all that much when I've cut with it at half rpm/hertz


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## John Hasler (Jan 3, 2016)

chevydyl said:


> Oh yeah, I also have a 1.5hp DC high torque treadmill motor I could use, it has about a 5000rpm range, problem with that motor is it has a screwed on pulley, that's a serpentine type belt drive, that's my other option, I could use that instead of the 3ph motor. I think that one would need some underdrive pulleys to use so I would stay in the range of lathe speeds, with some extra speed for polishing or whatever


Chuck up the screwed-on pulley and turn it into either a V-belt pulley of the proper size or an adapter to put a v-belt pulley onto.  If the fan is integral with the pulley/flywheel use a muffin fan to cool the motor.  If you use either a multigroove or 3/8" cogged belt you can put quite a small pulley on the motor.


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## wa5cab (Jan 3, 2016)

There must be something wrong with the graph.  That makes no sense at all!  

The maximum rated RPM is needed because at some point it's going to fly apart from centrifugal force.  The minimum is needed because the slower it runs, the less cooling the fan will provide.  You don't want to burn it up.  On the plus side there, you don't need to get but about 1/2 HP out of it.

Without those numbers, I can't say which would be better but where I was headed was this.  If the motor will run safely (not overheat) at 575 RPM, and you use two pulleys the diameter of the faster set on the 2-step motor and first countershaft pulleys, with the speed controller set to run the motor at 1725 RPM the 4-step cone pulleys would give you the four higher speeds shown on the chart on the lathe.  With the motor set to run at 575 RPM, you would get the four slower speeds.  I seriously doubt that the motor will safely run at 5175 RPM, which would be the other option of those two.

Or, once you know how fast you can conservatively run the motor, you could re-do the speed chart and go for something in between.  

But in any case, a hollow (deep dish) pulley is by far the best way to solve the motor mounting problem.

Back to hanging the motor, and its weight, when I originally set mine up in 1982, I hung the 3/4 HP TEFC the hard way, holding the motor up with one hand.  But that was soon to be 35 years ago.  I don't recall why at the moment but last year I decided that I needed to slightly reposistion the motor.  So I made a saddle of wood that I bolted to the top of a scissors jack and used that for all the heavy lifting.


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## mksj (Jan 3, 2016)

The motor is way oversized, which is actually to your benefit (and quite common with VFD equipped lathe/mills which usually have a 10 fold operating VFD speed range usually with 2 manual speed ranges Lo/High) as you will have rated Hp output that you had before at much lower RPM. You should have full toque down to at least 15Hz or lower. Since the motor is way bigger than you had, it is very doubtful that you will have any cooling issues with the motor even running at 10-15Hz (300 RPM and above). TEFC motors start to have cooling issues at speeds below 15Hz and over 90Hz, possible exception might be running it at full load continuously, not going to happen.  I do not know the safe upper speed for on this lathe, probably something under 2000 RPM. I would determine the pulley sizes based on the maximum expected RPM you want to achieve with the motor at 90Hz or approximately 2500 RPM (this is a safe and acceptable upper bound for the motor per most manufacturer's for this type/size of motor).  You need to determine the lathe maximum safe operating speed and then work out the pulley ratios.


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## John Hasler (Jan 3, 2016)

chevydyl said:


> Not sure on the rpms, the power graph from Baldor says it makes 0% of rated output at 1700rpm, and 150% @1735rpm, the rated speed is 1755rpm I have a hard time believing that I would be able to stop it by hand at 1700rpm since the graph says it would be making zero hp..., it has an .875-.8745 (7/8) shaft. 145TC frame, flange front mount or foot mount TEFC
> The motor on my mill doesn't seem to care all that much when I've cut with it at half rpm/hertz


I think those numbers are for 60Hz operation.    Zero doesn't make sense but the other numbers are reasonable.  Do you have a link to that table?

[Edit] If the graph you have is like the one posted by mksj you aren't reading it correctly (It's admittedly confusing).


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## mksj (Jan 3, 2016)

Should develop full Hp, usually drops off in a linear fashion below the base speed. Motor graph example below.
	

		
			
		

		
	



	

		
			
		

		
	
 .


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## chevydyl (Jan 3, 2016)

I like the idea of only 1 pulley set, with 2 steps for high and low, stick the motor shaft out the side of the cabinet where the original motor driven pulley is on the jackshaft
Here's the manual for my actual motor, except on the plate of my motor after looking at it again it's 1740 rpm


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## chevydyl (Jan 3, 2016)

Dbl


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## John Hasler (Jan 3, 2016)

chevydyl said:


> I like the idea of only 1 pulley set, with 2 steps for high and low, stick the motor shaft out the side of the cabinet where the original motor driven pulley is on the jackshaft
> Here's the manual for my actual motor, except on the plate of my motor after looking at it again it's 1740 rpm


Each of those curves goes with a different one of the vertical scales on the left.  Look at the key at the top to tell which goes with which.


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## chevydyl (Jan 3, 2016)

right, that's how I made the conclusion that is makes 0% of rated output at 1700rpm


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## wa5cab (Jan 3, 2016)

OK.  Based upon what mksj wrote, you can do what I suggested above, that is, use new pulleys the same size as the larger step on the existing 2-step ones.  The rated top speed of all Atlas 10" and 12" since the early 1940's has been given as 2072 with a nominal 1740 RPM motor.  So running the 3-phase motor off of 58 cps with the spindle belt in position 4 should yield that.  At 90 cps, you would have around 3100 RPM.  Unless you plan to do a lot of wood turning on very small diameters, that should be much faster than you would ever want to run.  And of course, slowing the motor down and using the 4 steps on the cone pulley would get you down to the slowest speed.  Plus there are still the back gears.


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## wa5cab (Jan 3, 2016)

But don't stick the motor shaft through the side of the cabinet.  Unless you also want to have to fabricate a new belt cover to avoid a serious safety hazard.


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## chevydyl (Jan 3, 2016)

I wouldn't have to fabricate a belt cover, the stock one is great....


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## John Hasler (Jan 3, 2016)

chevydyl said:


> right, that's how I made the conclusion that is makes 0% of rated output at 1700rpm


The RPM curve starts at just under 1800 RPM at 0% of rated load and slopes down to the right, reaching 1735RPM at 150% of rated load.  The bottom curve is torque, which goes to zero at zero load (as it has to).


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## chevydyl (Jan 4, 2016)

I see what your looking at john, I was looking at the torque line not the rpm line on the graph.


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## mattthemuppet2 (Jan 4, 2016)

If the 3ph is going to be tricky to fit, go with the treadmill motor. You'll get most of the same controls (variable speed, reverse) and it should be easier to fit. As for the pulley fan thing you have 2 options. 1, ditch the current pulley, put your own on and rig up some kind of fan. either stand alone fixed speed or attached to the shaft somehow - the 2nd one is what I did with my Atlas 618 treadmill motor. 2, turn a V pulley into the current pulley or turn it down and press on an appropriately machined V pulley. This is what I'm going to do for the treadmill motor on my drill press. Then cut/ grind a flat or two on the shaft and secure it with a set screw.

As for motor size, for a treadmill go as small as you can and still wrap a belt around it. You want to be running it at 1/3 speed or above, whatever spindle speed you're after, and as they're typically 4000rpm motors that means you'll need to gear it down a lot with the motor pulley (or a much bigger counter shaft pulley). Notched V belts work better on small pulleys than standard V belts and the link belt I'm using on my lathe works well too, although some don't like them.

I'm very happy with the 1hp treadmill motor on my 618. You can hear it slow down a touch on deeper cuts, but as long as the motor speed is 1/3 (ideally 1/2) of max the belts will slip way before the motor stalls. Being able to vary speed during a cut is awesome too. I was able to go from ~70rpm to ~250rpm facing a 4in back plate from the edge to the center.


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