mounting lathe motor on the floor?!

JonathanK

JonathanK

New member
I know many including my self have had lathe vibration issues, most of which it seems can be isolated to the motor (usually 240 single phase) mounted directly to the base of the machine. I and many others have been able to correct a lot of the issues by isolating the machine from the motor with rubber/cork. I have been thinking about this issue and ways to correct it, one possible way I have come up with is to completely isolate the motor by removing it from the base of the machine. I have thought of mounting it to the wall, building a separate stand for the motor, or mounting it directly to the floor and using a long belt to connect it. I currently use V-link belts on my machines and I think this may work for the long distance but may not. I have been thinking of using long timing type belts if need be. Let me know what yall think. Is it a good idea? Is it a bad idea? How can I make it work if at all. Any suggestions will be greatly appreciated, and any criticism is welcome
Jonathan Kuykendall
 
A lot of the old lathes, like southbend and hendey, used a setup like that. Some were rear driven some were overhead. Also all the lineshaft machines worked on the same idea. Try it.
 
Most vibration issues come from having crappy or worn out pulleys, belts, or in some cases, a crappy motor. The first two are not a real big deal unless they are some sort of variable speed setup. Then, the pulleys are probably not readily available, and the belt somewhat expensive. Still, if you need it, you need it.

If the motor is out of balance, then it was a piece of crap brand new. It should run smooth as glass with no connected parts. Try that first. Then, put on just the pulley, if it's out of balance, replace it or fix it. If the belt makes it vibrate, replace that.

Belt tension will affect this. Belt age. If the belt sat at one spot for a couple years, that set in it will make it vibrate. Even just being old will make the belt less flexible and that will create vibration.

I'd recommend finding the vibration first, then fixing it. I can't see moving the motor being a solution.
 
Mounting "off site" could help if the motor is out of balance. I think your dealing with a transmitted vibration from the pulses of the 60 Hz electric motor starting/stopping 60 times a sec. It may look like a continuous pull to us but it not. DC motors are continuous pull. I don't know about 3 phase but maybe they are also.

I don't see how you can eliminate a single phase motor power pulses jerking on the belt 60 times a sec. I'm probably not 100% correct it has been a long time since 8 grade science but I think i'm close. Maybe someone with an electrical background can help me with what i'm thinking (or dreaming).... joe
 
It may look like a continuous pull to us but it not. DC motors are continuous pull. I don't know about 3 phase but maybe they are also.
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If you're talking about a conventionally commutated motor, all end up with some form of pulsed power consumption/demand. That still doesn't mean it isn't smooth. DC motors with brushes lets say, they put power to one winding, then, mechanically commutate to the next winding by having the brushes touch a new spot on the armature. Still, it's plenty smooth enough it should not be noticed, whether dc or ac. Various types of AC motor work under the same principal, even if they don't need brushes.

Odds are this guy is talking about a conventional AC motor, and honestly, they should still be very smooth. When you have a fan running in your house, does it vibrate due to the motor commutation? Ehh, not likely.

All of these discussions get muddy if you start talking about variable drive systems though. Those typically will have active torque control and curve smoothing when they apply power. They are pretty slick about the way they maintain speed, and some do re-calculations 100's of times per revolution. Some under no load, and without something connected to cause imbalance, are near silent.
 
I have been helping a fellow benchrest shooter get started fitting barrels with his new Grizzly G0709. It has a nasty motor vibration which can be felt through the headstock. The motor is mounted with no rubber isolation whatsoever. The vibration causes a distinct chatter pattern on the workpiece. I have been using a Jet GHB 1340 for over 10 years. I felt the headstock for vibration with the motor running and it was very slight. I looked at the motor mounting and it appears the same as the Grizzly, except that it has rubber washers between the motor base and the mounting bracket. I think reducing and isolating the motor vibration by any means possible will help. Can't see any reason not to try mounting the motor separatly from the machine. It may require some trial and error; possibly an idler or two. The idea is not new by any means. In the case of my friend's Grizzly, we intend to start by trying rubber cushioning between the motor and the mount.

Scott
 
I have already isolated the bracket with rubber and it made a huge difference. The machine produces pretty nice smooth finishes now but I can still feel that 60 cycle hum(with the pulley and belt removed) a little bit on the carriage and quite a bit on the headstock. I would like to get a way from the 60hz issue with a 3 phase or DC motor eventually, but I also think that where the motor is located(right on the frame) is another issue.
 
4Mesh said:
<snip> When you have a fan running in your house, does it vibrate due to the motor commutation? Ehh, not likely. <snip>
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Please no offense but the analogy is a very poor one at best. Let me state up front I have an eight grade education and I am unarmed in a battle of wits.

For me and i'm probably wrong but I can see the 60Hz pattern in Jonathan's machine work- it's as plain as day for me. Now Jonathan can see it also and it's gonna drive him nuts until it's gone. I would be interested in the outcome. From what 4mesh says it looks like one of those variable drives will be the answer.

Don't mean to come up with such a "left field" idea but I really think that's what were seeing- but just maybe a remote mt motor will solve the issue.... joe:confused:
 
I would take a careful look at the pulley on the motor..... check with indicator..... look for cracks in pulley...... is motor shaft bent...???...also a bad drive belt will create bad vibes....
bill larson
 
jGEE said:
Please no offense but the analogy is a very poor one at best.

For me and i'm probably wrong but I can see the 60Hz pattern in Jonathan's machine work- it's as plain as day for me.
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I'll begin by saying I have rather a lot of experience using motors, right down to actually making the drives themselves from scratch, for several types of motor. In my experience, motors that don't run smooth are a poor design. Ok, moving it might be a nice band aid to the problem, but the solution to it is to find the imbalance. It might be as simple as fixing a pulley or belt. Not often do you see motors that are manufactured with the rotating assembly out of balance. It just ain't good business sense. And for the commutation of the motor to be an issue, it would have to be under enough load that the motor would decelerate significantly between phases. Honestly, lathes don't often operate under any significant load. It's not often I bog one down, but when I do and I hear it, the last thing I'm worried about is surface finish.

Maybe you're right, maybe it is a lot smaller than I'm thinking and it is under a lot of load. I just don't think so. Theres guys here have lathes that run on 60hz lines. (single phase). With the right motor, there should be no trouble.

If the motor is so small as to have very little mass and then, very little rotor inertia, I suppose your right. But, 1HP or more... I'd really doubt it. How big is the motor?
 
Mr 4mesh thanks for not bashing me- part of my theory comes from knowing the Chinese to sell attractive products price wise- they have learned how to trick a lot of items that look real but leave out the American quality and usually leave out the finesse and safe guards that were "engineered in" from an era now gone past.

I bought a China Lathe 2 years ago because of my very limited budget. It's a great lathe for the money and I wondered how the old American lathe could cost as much 5 -6 times as much. Two years later now i'm beginning to understand the value of American iron. I would bet the electric motors on some of the old 10- 13" lathes probably cost as much as my lathe in dollar for dollar value.

I have a tired old 1936 9" South bend still runs with the original GE motor- I don't think they were much over 1/2 hp but in comparison of todays motors it is almost twice as big in size. I always wondered why- maybe the guys back then didn't know what they were doing..... now I understand a lot more about long life of machine tools. i'm not a machinist never even been inside a machine shop. One day I would love to whittle on a piece of stock on an old Hargtin (sp)lathe or another of the old timers...... joe
 
Success will still depend on the amount of isolation between the motor and lathe. But I think separating the machinery is a good idea if the motor can't be sufficiently isolated in its blueprint location.

A floor fan at the opposite end of a large room shows up on the dial indicator at the lathe.
 
My 12X36 Jet used to make the nicest Damascus patterns when it had an Tiawann AC motor. I converted it to DC, motor is still mounted to the machine with no rubber isolation, and now there is zero "chatter"

I find the less expensive gear drive lathes to be really poor at surface finish. I think a good link belt drive removes most of the issue on the lighter weight lathes.
 
Jonathan,

That is exactly what my old buddy Homer Strickland did to his 13" MSC (aka 'Prince') lathe. He removed the motor mount from the base and re-engineered it to be bolted directly to the concrete which totally isolated the lathe from any motor harmonics. It worked like a charm. He took some very detailed pictures of this conversion. I will see if I can dig them up and bring them to you.

Kris Whitman
 
4Mesh said:
If you're talking about a conventionally commutated motor, all end up with some form of pulsed power consumption/demand. That still doesn't mean it isn't smooth. DC motors with brushes lets say, they put power to one winding, then, mechanically commutate to the next winding by having the brushes touch a new spot on the armature. Still, it's plenty smooth enough it should not be noticed, whether dc or ac. Various types of AC motor work under the same principal, even if they don't need brushes.

Odds are this guy is talking about a conventional AC motor, and honestly, they should still be very smooth. When you have a fan running in your house, does it vibrate due to the motor commutation? Ehh, not likely.

All of these discussions get muddy if you start talking about variable drive systems though. Those typically will have active torque control and curve smoothing when they apply power. They are pretty slick about the way they maintain speed, and some do re-calculations 100's of times per revolution. Some under no load, and without something connected to cause imbalance, are near silent.
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Single phase motors all have electrically induced torsional vibration of the shft. It can be minimized with flywheels (nobody does that), soft coupling (v-belts help) and high intertia running gear (like big heavy chucks) but it's always there to some degree.

Three phase motors don't have it, or so little of it it's almost indetectable.

And yes, the torsional vibration, torque pulsing, is there on the shaft of your single phase household fan, but it's damped by the fan's inertia (large with respect to the ability of the fan motor torque to accelerate and decelerate it which is why fans take so long to accelerate to speed) to the point of being almost indetectable.

Fitch
 
It would seem to me that if anyone gets smooth cuts, on a lathe with a single phase motor ( a picture would help), then others may be able to accomplish the same thing, if all of the details are correct. What would it cost to have a motor rebalanced, or is the cost prohibitive for small motors?
 
Looking at the newer better lathes many are mounting the motor in the base close to the floor likely for stability and reduced vibration transmitted. I found a 7.5 hp 3ph motor; it came off a news paper printing machine. It has to be the smoothest motor I have ever seen. Looking to use it to replace the china single phase in another lathe I picked up using a VFD.
 
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Awesome Kris, that would be great!

Kris Whitman said:
Jonathan,

That is exactly what my old buddy Homer Strickland did to his 13" MSC (aka 'Prince') lathe. He removed the motor mount from the base and re-engineered it to be bolted directly to the concrete which totally isolated the lathe from any motor harmonics. It worked like a charm. He took some very detailed pictures of this conversion. I will see if I can dig them up and bring them to you.

Kris Whitman
Click to expand...
 
Boyd Allen said:
It would seem to me that if anyone gets smooth cuts, on a lathe with a single phase motor ( a picture would help), then others may be able to accomplish the same thing, if all of the details are correct. What would it cost to have a motor rebalanced, or is the cost prohibitive for small motors?
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Well, first, you have to determine if the motor really is out of balance or if something else is the cause. Then if you did determine it is the trouble, the question is, where do you take it to get a dynamic balance for 3000 rpms? Even as recent as 5 or 10 years ago, the cost of the motor would have made balancing a viable option. But now, you can get decent motors for so little money ya gotta wonder if its worth messing with the old one.

F21sh has the right idea. Find a nice motor and don't look back.
 
The old 9" and 10" South Bends were known for smooth finishes and they had single phase AC/DC motors and ran thru belts and a jackshaft.
 
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