Correct AC motor for turning sculpture

MisterBill2

Joined Jan 23, 2018
13,704
Half inch will work very well, quarter inch would be adequate for that application, but less forgiving to work with. The stuff I am thinking of is also used for lining chutes that metal parts and chips fall through in industrial machinery. What is handy is that you can machine it with woodworking tools. It is also referred to as UHMW, (ultra high molecular weight PE) Ordinary PE is not as tough, but it could work in this application.
 

Thread Starter

mxabeles

Joined Apr 25, 2009
257
Half inch will work very well, quarter inch would be adequate for that application, but less forgiving to work with. The stuff I am thinking of is also used for lining chutes that metal parts and chips fall through in industrial machinery. What is handy is that you can machine it with woodworking tools. It is also referred to as UHMW, (ultra high molecular weight PE) Ordinary PE is not as tough, but it could work in this application.
The sheet of plastic (its a cutting board made with the material you described) and the pillow blocks were delivered same day, and it was simpler to just bolt the flange onto the top of box and test. It worked! As a first attempt I'm happy. The motor itself is not level because I was just eyeballing everything, thus the pole is at an angle. But it's surely turning with ease and as a proof of concept I can claim it as a success. Thanks again!
 

MisterBill2

Joined Jan 23, 2018
13,704
Now I am wondering about the actual speed that the motor and the sculpture are turning. One more thought is that with the sculpture being a very light load, that you might possibly get away with longer operating times. .
So you could run the motor for a few minutes and feel the electrical portion of the motor after switching it off. If it has not become hot, try it for ten minutes and see. The one-minute time may be for the full load rating.
 

shortbus

Joined Sep 30, 2009
9,754
The sheet of plastic (its a cutting board made with the material you described) and the pillow blocks were delivered same day, and it was simpler to just bolt the flange onto the top of box and test.
Your much better off with the pillow blocks instead of a part made of plastic. The plastic will not do anything to support the weight of your sculpture. The pillow blocks while working for rotation also have a good deal of thrust(the weight of your sculpture downward) handling capability. There is no thrust capability to a piece of plastic with a hole in it.
 

shortbus

Joined Sep 30, 2009
9,754
@mxabeles Another thought. since you have a female 1/2"NPT in the bottom of the sculpture and that doesn't match up to any pillow block inch or metirc, you could get a 1/2"NPT bushing and drill out the pipe thread in the bushing to make a standard size rod instead of the pipe. that way you don't need to mess around trying to make a pipe work in the pillow blocks.

A pipe bushing like this -
1669998571700.png
And drill the center to fit rod.
 

MisterBill2

Joined Jan 23, 2018
13,704
Your much better off with the pillow blocks instead of a part made of plastic. The plastic will not do anything to support the weight of your sculpture. The pillow blocks while working for rotation also have a good deal of thrust(the weight of your sculpture downward) handling capability. There is no thrust capability to a piece of plastic with a hole in it.
Certainly a UHMWPE sleeve bearing does not normally offer any axial support, while a correctly implemented pillow block bearing CAN provide a great deal of axial load support. But that will only happen if the rotating shaft is adequately tied to the bearing in the block. To adequately support this pipe shaft for both the axial load and the side load will take a correctly machined spacer or an correctly shaped wedge collar. Making ay of those parts will require a lathe, a tool, and a fair amount of skill. Or an additive printer able to print steel or a suitable alternative material, as well as the skill to create the build file. Neither of these are common among the general population.
 

shortbus

Joined Sep 30, 2009
9,754
Making ay of those parts will require a lathe, a tool, and a fair amount of skill.
So then your saying it's better to make a plastic plate type bearing, one that will float and not support the pipe shaft, instead of using pillow blocks? If making the shaft fit the pillow block correctly is too hard, how hard is it to make a hole of the correct size in the plastic? A hole that doesn't correspond to any, known by me, drill diameter. And that plastic will give no axial/thrust support what so ever to the shaft.
 

MisterBill2

Joined Jan 23, 2018
13,704
So then your saying it's better to make a plastic plate type bearing, one that will float and not support the pipe shaft, instead of using pillow blocks? If making the shaft fit the pillow block correctly is too hard, how hard is it to make a hole of the correct size in the plastic? A hole that doesn't correspond to any, known by me, drill diameter. And that plastic will give no axial/thrust support what so ever to the shaft.
NO!!! I am NOT saying it is better. I am describing the difference.. Neither scheme will be simple.
IF the connection to the motor was adequate and IF the motor shaft and the motor bearing could handle the end load of the sculpture weight THEN there would be a simple choice.
Unfortunately we don't have much of an idea as to any of those answers. A pair of pillow blocks, one above the surface and one below, using the same bolts, and adequately aligned, should hold that sculpture steady. If that arrangement could handle the total load, then the coupling could be much simpler.
So if the bore of the two blocks is 1.00 inches and the diameter of the pipe is 0.84 inches then the adapter sleeve to allow a snug fir will be 0.08 inches thick.
Do the pillow blocks have setscrews?
 

Thread Starter

mxabeles

Joined Apr 25, 2009
257
Great conversation. And very grateful. I was away in DC for the weekend, so I just was able to peruse the thread now. The pillow block does have set screws. That's the only way this works XD.
 

MisterBill2

Joined Jan 23, 2018
13,704
If the two set screws and the required shims are correctly adjusted then there would be very little off-center movement of the pipe. At that condition the coupling can be as simple as a cross-pin toward the end of the motor shaft and a pair of notches at the end of the pipe to sit on the pin.
Or, if the end of the pipe is threaded, use a simple pipe coupling to attach what is often called a cord grip, or even a "Greenfield" adapter, which can simply tighten onto the shaft. No machining or drilling required. That sort of connection is on lt suitable for low speeds and not much torque.
There is another question: How is that motor-gearbox assembly working out? How hot does the motor get with constant operation at the low speed?
 

Thread Starter

mxabeles

Joined Apr 25, 2009
257
If the two set screws and the required shims are correctly adjusted then there would be very little off-center movement of the pipe. At that condition the coupling can be as simple as a cross-pin toward the end of the motor shaft and a pair of notches at the end of the pipe to sit on the pin.
Or, if the end of the pipe is threaded, use a simple pipe coupling to attach what is often called a cord grip, or even a "Greenfield" adapter, which can simply tighten onto the shaft. No machining or drilling required. That sort of connection is on lt suitable for low speeds and not much torque.
There is another question: How is that motor-gearbox assembly working out? How hot does the motor get with constant operation at the low speed?
Thanks for the reply. I don't have the motor running constantly, I plan to have SSR relay + Arduino controlling the power to motor.
 

MisterBill2

Joined Jan 23, 2018
13,704
Consider the loading on this bearing relative to the bearing specifications. The axial load is about 35 pounds, and the radial load might be ten pounds. And the present bearing blocks are for one inch shafting. So the safety factor is about 100:1, probably better than that.
Next, consider the rotating speed, which is, I think, about 10 RPM.. The bearing max RPM for long life is 3000 RPM.
So for this application these bearings are far more than needed.
And finally consider that the TS is an artist, not a machinist.
So the heavy pillow blocks allow rugged mounting with reasonable bolts and if they are not tight enough it will not matter. AND those materials are already in hand. Tapered roller bearings are great for wheels in cars, that is certain. This application is not so demanding. Nor does it have an unlimited budget.
 

Thread Starter

mxabeles

Joined Apr 25, 2009
257
Top