Noisy electric motor

[Bryan]

The motor on my lathe has gotten noisier in the short time I've owned it. With no belt on it's a bit noisy; with a belt on, even loosely, it gets an intermittent death-rattle. It's quite loud and rather alarming. Since I know virtually nothing about electric motors, should I:

(a) Rip it to bits and have a look?
(b) Take it to a motor man?
(c) Source a replacement?

Would something like this (Ebay link) (http://cgi.ebay.com.au/BRAND-NEW-1HP-240v-Electric-1450rpm-Single-Phase-Motor-/380239163044?cmd=ViewItem&pt=AU_Power_Tools&hash=item5888052ea4#ht_1641wt_1061) be suitable? Does it have to be reversible? I'm happy to pull most things apart, but this sort of thing worries me. It looks... tricky. Here's a pic of the plate. Any guidance appreciated.

[Vernonv]

Would something like this (Ebay link) (http://cgi.ebay.com.au/BRAND-NEW-1HP-240v-Electric-1450rpm-Single-Phase-Motor-/380239163044?cmd=ViewItem&pt=AU_Power_Tools&hash=item5888052ea4#ht_1641wt_1061) be suitable? Electrically yes, mechanically maybe not - you will need to check shaft sizes and mounting arrangements.


Does it have to be reversible?It certainly is handy. Most single phase motors can be made reversible, but depending on the motor it might not be easy.

[.RC.]

First thing is check the bearings....Replace them if they are the source of the noise.

[steran50]

HI:),
I wouldn't buy that Motor. Have a look at the 'Please Note' it seems Warranty will be Void if the Wires are changed to Make the Motor run the Opposite Direction. I would say it is not Reversible. This would be better Crompton 1HP .75kw 1425rpm 240V Electric Motor - eBay, Electric Motors, Electrical, Industrial. (end time 24-Jun-10 09:35:59 AEST) (http://cgi.ebay.com.au/Crompton-1HP-75kw-1425rpm-240V-Electric-Motor-/370280876459?cmd=ViewItem&pt=AU_B_I_Electrical_Test_Equipment&hash=item563675c9ab) . Only 4 Pole Single Phase Motors are Reversible. I would as .RC. said check the Bearings - grab hold of the shaft and see if there is excessive movement and what does it feel like to turn is it rough.
All The Best:) steran50 Stewart

The shortest way to do many things is to do only one thing at once.

[Bryan]

Only 4 Pole Single Phase Motors are Reversible.

Does that mean I'm stuck with 1425 RPM? Cos 900 would be better for me, with no back gears.


I would as .RC. said check the Bearings - grab hold of the shaft and see if there is excessive movement and what does it feel like to turn is it rough.
All The Best:) steran50 Stewart

Ok, will report. Thanks

[tanii51]

have a snoop around in that link steran gave you there are 900rpm motors available there

[Vernonv]

Only 4 Pole Single Phase Motors are ReversibleI can't find anything to support this ... but would be happy to see information that does.
I just went and looked at an ABB single phase motor catalogue and while they mention how to wire their motors for different rotations, they make no mention or distinction between 2, 4 or 6 pole motors.

EDIT: even the seller in that ebay link you posted has 900, 1400 and 2800 rpm motors and it says that they are all reversible.

[eskimo]

I can't find anything to support this ... but would be happy to see information that does.
I just went and looked at an ABB single phase motor catalogue and while they mention how to wire their motors for different rotations, they make no mention or distinction between 2, 4 or 6 pole motors.

EDIT: even the seller in that ebay link you posted has 900, 1400 and 2800 rpm motors and it says that they are all reversible.

you just need to kick the "Start" windings in the opposite direction
I'm with you Vernonv

here is typical wiring diagram

[Bryan]

EDIT: even the seller in that ebay link you posted has 900, 1400 and 2800 rpm motors and it says that they are all reversible.

Great, thanks for clearing that up.

I may have found the death-rattle. There was no play in the shaft, and only a light ticking sound when turned. Like maybe brush noise? But what did find was a loose pulley. Tightened the grub screw. Still loose. Hmm. Remove grub screw. What's this, another grub screw! So there's a loose grub screw, then another one tightened on top of it. Go figure. :B

In the limited time I've had to play since then I haven't been able to reproduce the death-rattle. So hopefully that was it. Good to learn a bit about motors though. Thanks guys.

[Bryan]

EDIT: even the seller in that ebay link you posted has 900, 1400 and 2800 rpm motors and it says that they are all reversible.

Great, thanks for clearing that up.

I may have found the death-rattle. There was no play in the shaft, and only a light ticking sound when turned. Like maybe brush noise? But what I did find was a loose pulley. Tightened the grub screw. Still loose. Hmm. Remove grub screw. What's this, another grub screw! So there's a loose grub screw, then another one tightened on top of it. Go figure. :C

In the limited time I've had to play since then I haven't been able to reproduce the death-rattle. So hopefully that was it. Good to learn a bit about motors though. Thanks guys.

[eskimo]

What's this, another grub screw! So there's a loose grub screw, then another one tightened on top of it.

very common in some instance to find two grub screws...but I wouldnt have thought it would be needed in that situation...a lathe???

[steran50]

HI:),
Only 4 Pole Single Phase Motors are Reversible.

HI:),
The above is something I was told Years ago. Looking at the Weblink that 'eskimo' Posted the above does NOT appear to be Correct. I had a look on the Internet Myself and could find nothing to support the above. So I am going to put My Foot where My Mouth is and Say the Above is quite possible NOT Correct.

[Sterob]

Your right, it is NOT correct. What determines if a single pole motor is reversible or not, is whether both motor windings are accessible in the terminal box. This is because one has to reverse ONE of the windings of a single phase( split phase, cap start or cap run) motor to changes it direction of rotation.

Sorry, was going to pipe up earlier but got distracted.

Sterob

[Metalman]

I agree, the number of poles a motor has will not determine the direction it will start to rotate in. What does cause it to rotate in a particular direction is the starting system. With single phase motors the windings generate a stationary field which means the motor will only sit and hum and not rotate. As Eskimo said the motor must be 'kicked' in a direction to get it going. This is achieved a number of ways: using a capacitor; using a start winding or using a shading pole. The first two methods are usually capable of being reversed, the shaded pole motor can only be reversed by taking the motor apart and end for ending the field assembly (often not possible because of the wire routing or other mechanical issues). The shading pole system can be identified by looking inside the motor at the poles, there will be a single heavy loop of copper or brass around one corner of each pole. Shading pole motors have the poorest starting torque of the systems however they are the simplest, cheapest and most reliable and this is the reason they are used. Many appliances such as exhaust fans use these motors. Of the other systems, capacitors can fail and starting windings require a centrifugal switch system to take them out of the circuit when the motor is running, these switches can be noisy when the motor is turned over by hand.
Note that a single phase motor will continue in the same direction if it is switched into reverse when running, in a three phase motor the generated field rotates and when it is 'reversed' when running it will stop and go the other way.
To determine the approximate running speed of a 50 Hz motor divide 6000 by the number of poles and take away approximately 10%. For example: a six pole motor, 6000/6= 1000- 100= 900rpm.
Motors can have multilple pole systems for example some front loading washing machines have 2 pole/ 16 pole motors.
Hope this helps, I am pretty sure it is all right but am happy to be corrected.
Regards, Metalman.

[eskimo]

[QUOTE=in a three phase motor the generated field rotates and when it is 'reversed' when running it will stop and go the other way.
[/QUOTE]

I just hope your not trying to tell us that you can reverse a motor when running

?..it might stop and go the other way...but it can also have serious consequences for the motor..... and possibly the driven load....a standard 3 phase motor is not designed to to be reversed when running....I would'nt do it!!!...I would make sure the motor is stopped before reversing