🙁
Hi folks,
I need help from someone with experience of such issues.
My winding machine induction motor has been knocking annoyingly lately and the knock amplitude seems to increase with ambient temperature, as if some parts become loose with thermal expansion. The knock is a single loud tap feeling being transmitted from the entire motor body to the entire machine
The knock occurs only at a SPECIFIC point of the axle per each revolution which I marked with a pen. It also happens only when the belt is put on and under tension, which gives a hint that the side belt pulling force is needed on the axle. The more the belt is tensed, the more heavy is the knock.
Two engineers already gave me a hint that a possible reason could be some clearance between the pulley and the axle and proposed me to disassemble it, put some anaerobic bearing glue and put the parts back. Sadly I already did it and it didn't fix the problem at all.
Now disassembly of the motor will be quite hard. 🙁
It doesn't make sense for me to be a ball bearing, but what if it is the housing having a clearance. Aluminum has greater expansion coefficient than steel, so it makes sense to check the motor bearing housings. What do you think?
Hi folks,
I need help from someone with experience of such issues.
My winding machine induction motor has been knocking annoyingly lately and the knock amplitude seems to increase with ambient temperature, as if some parts become loose with thermal expansion. The knock is a single loud tap feeling being transmitted from the entire motor body to the entire machine
The knock occurs only at a SPECIFIC point of the axle per each revolution which I marked with a pen. It also happens only when the belt is put on and under tension, which gives a hint that the side belt pulling force is needed on the axle. The more the belt is tensed, the more heavy is the knock.
Two engineers already gave me a hint that a possible reason could be some clearance between the pulley and the axle and proposed me to disassemble it, put some anaerobic bearing glue and put the parts back. Sadly I already did it and it didn't fix the problem at all.
Now disassembly of the motor will be quite hard. 🙁
It doesn't make sense for me to be a ball bearing, but what if it is the housing having a clearance. Aluminum has greater expansion coefficient than steel, so it makes sense to check the motor bearing housings. What do you think?
>The more the belt is tensed, the more heavy is the knock.
Make it REALLY tense and run it, wait for the knock to wear itself out, then set back to normal tension? An embedded particle between rotor and stator? Or take it apart and look for a shiny mark as evidence of such? If it comes apart anymore...
Make it REALLY tense and run it, wait for the knock to wear itself out, then set back to normal tension? An embedded particle between rotor and stator? Or take it apart and look for a shiny mark as evidence of such? If it comes apart anymore...
Gathering thoughts and ideas here..
The knock also occurs at small RPM only, as if something has inertia and needs time to "load itself to knock". At increasing RPM knocking loudness reduces until it disappears.
The knock also occurs at small RPM only, as if something has inertia and needs time to "load itself to knock". At increasing RPM knocking loudness reduces until it disappears.
I would not rule out the bearings.
How old are they ?
What type: Ball bearing, conical,with a cage in good shape.
Rotating by hand, do you feel play axial or radial, a hard spot ?
How old are they ?
What type: Ball bearing, conical,with a cage in good shape.
Rotating by hand, do you feel play axial or radial, a hard spot ?
Hi,
No idea about the age of bearings, the motor was previously used. They're ball bearings.
Rotating by hand feels smooth like new. No hard spots, no clearances or knocking detected.
This reminds of me of stories with my old bicycle pedal-crank arm mechanism. An annoying knocking sound would occur when the left pedal would be pushed down from a specific top position. For the sound to occur the force of a foot was needed, it couldn't be done by hand. Changing the bottom bracket would fix the problem.
No idea about the age of bearings, the motor was previously used. They're ball bearings.
Rotating by hand feels smooth like new. No hard spots, no clearances or knocking detected.
This reminds of me of stories with my old bicycle pedal-crank arm mechanism. An annoying knocking sound would occur when the left pedal would be pushed down from a specific top position. For the sound to occur the force of a foot was needed, it couldn't be done by hand. Changing the bottom bracket would fix the problem.
The cage holding the balls in the front ball bearing has most likely failed. This allows things to move around until it is going fast enough the balls bounce apart and spread out.
The test is to see if you can wiggle the shaft when the belt is unattached. Any play at all means the bearing is bad.
The test is to see if you can wiggle the shaft when the belt is unattached. Any play at all means the bearing is bad.
No wiggle without the belt, in all directions, even when putting a lot of bodyweight. Turning is very smooth, as if the motor is new. No noise during turning.
A temporary solution would be to loose the belt a little. I don't need a lot of tension when winding fine wires, which is what I'm going to do during the following months until a solution is to be found.
A temporary solution would be to loose the belt a little. I don't need a lot of tension when winding fine wires, which is what I'm going to do during the following months until a solution is to be found.
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I would not think bearings only because the balls do not revolve at the same speed as the shaft rotates.
What kind of induction motor is it and what kind of circuit are you using to vary the speed?
Jn
Edit: is the motor rated for the side load you are putting on it? I always try to use a coupler directly off the shaft to zero all cyclic fatigue concerns.
What kind of induction motor is it and what kind of circuit are you using to vary the speed?
Jn
Edit: is the motor rated for the side load you are putting on it? I always try to use a coupler directly off the shaft to zero all cyclic fatigue concerns.
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The motor is described on the first page of this document:
https://elektromotor-online.nl/wp-c...t-TechTop-IE1-IE2-IE3-algemeen-01-05-2017.pdf
The model is: T1A 71-2. I'm varying the speed with a variable frequency 3-phase controller.
Good question. I have no idea if the motor is rated for side load. It would be probably a better idea to change the smooth surface pulley types with toothed surface for achieving the needed traction with less side loading.
Although I'm tensioning the pulley by hand and I'm not applying more than 60-70kg side tension. Should this be considered too much?
https://elektromotor-online.nl/wp-c...t-TechTop-IE1-IE2-IE3-algemeen-01-05-2017.pdf
The model is: T1A 71-2. I'm varying the speed with a variable frequency 3-phase controller.
Good question. I have no idea if the motor is rated for side load. It would be probably a better idea to change the smooth surface pulley types with toothed surface for achieving the needed traction with less side loading.
Although I'm tensioning the pulley by hand and I'm not applying more than 60-70kg side tension. Should this be considered too much?
First I was thinking the cage had a loose part, but that would make noise every time the vector max passed the part of the cage, not every rotation of the cage.
Then, perhaps one of the phases has a loose part such that every rotation the magnetic force pulls it to the cage but at high speed the mass is too high for the movement.
Is there an encoder feedback?
Then, perhaps one of the phases has a loose part such that every rotation the magnetic force pulls it to the cage but at high speed the mass is too high for the movement.
Is there an encoder feedback?
There is cooling fan at the rear side.
Anything loose ? Touching the fan housing ?
On a similar motor, I have seen a fan reinstalled reversed....
Anything loose ? Touching the fan housing ?
On a similar motor, I have seen a fan reinstalled reversed....
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The knocking sound exists even when I turn the motor by hand without power. So that should exclude magnetic force pulling.
I will check the rear fan tomorrow!
I will check the rear fan tomorrow!
So guys, I took the fan, then the rear lid off! What a surprise, the lid came quite easily. The rear bearing had some clearance in its lid bed and you can feel the knock from the bearing to bed. There are also traces of rotation in the bed of the bearing itself. Clear indication it was too loose.
This might be my knocking source!
P.S. Just took it apart, took out the rotor, the front bearing was loose as well, but not as much as the rear. I put anaerobic glue on both and put the motor back. Will give it a 24h of curing time and will test later.
This might be my knocking source!
P.S. Just took it apart, took out the rotor, the front bearing was loose as well, but not as much as the rear. I put anaerobic glue on both and put the motor back. Will give it a 24h of curing time and will test later.
I know you've pretty much got this figured out 50AE.
My bet is fan end bearing. Or the fan itself.
An induction motor rotor, in that size frames is usually a solid block of aluminium, so not loose squirrel cage to be concerned about, nor broken damper winding etc.
My bet is fan end bearing. Or the fan itself.
An induction motor rotor, in that size frames is usually a solid block of aluminium, so not loose squirrel cage to be concerned about, nor broken damper winding etc.
The increasing knocking rate with machine use made sense about the slippage wearing of the bed from the bearing. And the increasing of knocking with the room temperature is also logical due to the higher thermal expansion of aluminium.
Hope this did it!
Hope this did it!
Will look forward to your continued story.
I have a stand alone turntable motor with tha same "sickness".
I also suspected one end or both bearings seating to be the problem, but will wait to
hear, what you have to say when tested 🙂
I have a stand alone turntable motor with tha same "sickness".
I also suspected one end or both bearings seating to be the problem, but will wait to
hear, what you have to say when tested 🙂
I don't quite understand those bearings fit in aluminum bores. This is terrible mechanical design.
Normally a bearing is hard pressed in a steel housing.
Normally a bearing is hard pressed in a steel housing.
If I take a motor apart far enough that I have access to the bearings I just measure them up or read off any part number and then order some new ones.
I fixed a noisy tumble drier with a pair of real electric motor bearings bought new from a bearing specialist on line for the price of a couple of beers.
I would never put it back together again without new bearings if it is for more than occasional use.
I fixed a noisy tumble drier with a pair of real electric motor bearings bought new from a bearing specialist on line for the price of a couple of beers.
I would never put it back together again without new bearings if it is for more than occasional use.