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Motor heating

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Motor heating

Postby Phil » 22 Sep 2020, 09:14

This one is for Bob 8-)

My big Hegner has an induction motor (?)

It is a Bauknecht 0.18Kw

I did some cutting on Sunday and when I cleaned up found that the motor is extremely hot (burn hot)

What would cause this? Do I need to be worried?

What can I do to remedy?


HegnerMotor.jpg
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Re: Motor heating

Postby DaveL » 22 Sep 2020, 09:34

I know Bob will be along shortly, but I would see if the fan is still firmly attached to the end of the motor shaft.
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Re: Motor heating

Postby 9fingers » 22 Sep 2020, 09:41

DaveL wrote:I know Bob will be along shortly, but I would see if the fan is still firmly attached to the end of the motor shaft.


This is quite a low power motor and they don't always use a centrifugal switch to disconnect the starter winding but IF yours has a switch, it might have stuck shut and the starter winding is connected all the time. This will cause considerable extra heating.

hth

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Re: Motor heating

Postby Phil » 22 Sep 2020, 12:08

DaveL wrote:I know Bob will be along shortly, but I would see if the fan is still firmly attached to the end of the motor shaft.


Thanks Dave, I will check the fan.



9fingers wrote:
DaveL wrote:I know Bob will be along shortly, but I would see if the fan is still firmly attached to the end of the motor shaft.


This is quite a low power motor and they don't always use a centrifugal switch to disconnect the starter winding but IF yours has a switch, it might have stuck shut and the starter winding is connected all the time. This will cause considerable extra heating.

hth

Bob



Thanks Bob.
How do I check that? I will remove the motor and open up to check the fan.
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Re: Motor heating

Postby Woodster » 22 Sep 2020, 13:11

Surely everything runs hot in South Africa? ;)

Sorry, I’ll get my coat. :lol:
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Re: Motor heating

Postby Phil » 22 Sep 2020, 13:39

Woodster wrote:Surely everything runs hot in South Africa? ;)

Sorry, I’ll get my coat. :lol:


Ha, ha


The Brass Monkey weather will be visiting you soon! :lol:
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Re: Motor heating

Postby 9fingers » 22 Sep 2020, 19:01

Motors with centrifugal switches tend to make characterisitic noises.
When you switch off and as the motor slows there should be a click usually followed by a rubbing sound until the motor stops.
If there is a switch then there are more tests that you can do.
Do you have a multimeter capable of measuring resistance and ac voltage up to 250v ac?
A old fashioned filament light bulb fitted in a table lamp can be useful too.

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Re: Motor heating

Postby Phil » 23 Sep 2020, 08:43

9fingers wrote:Motors with centrifugal switches tend to make characterisitic noises.
When you switch off and as the motor slows there should be a click usually followed by a rubbing sound until the motor stops.
If there is a switch then there are more tests that you can do.
Do you have a multimeter capable of measuring resistance and ac voltage up to 250v ac?
A old fashioned filament light bulb fitted in a table lamp can be useful too.

Bob



I removed the motor from the saw, removed the fan cover - fan functions well, and then connected to power and ran it on the workbench.

It heats up on the inboard side (pulley side).

There is no play or movement on the shaft, everything solid.

The drive pulley and saw mechanism turns smoothly, nothing to cause a load on the motor.

Hegner_Drive pulley.jpg
(388.73 KiB)


When the motor is running a slight vibration can be felt on the mounting plate.

My neighbour is an electrical engineer (was working in his garage) and I asked him for an opinion.

"Can't see or feel anything wrong, there is the click when switching on so thats not the issue"
"Just run the motor on the saw and check if it keeps heating up"
"Maybe the sealed bearing is a problem?"

The saw was made in 1982 and this looks like the original motor, so maybe yes the bearing?
To look at the bearing means I would need to remove the drive pulley, which means the use of a tool which I do not have.

I don't particularly want to just run the saw with the motor heating up. Could end up a very expensive mistake.

Bob, I have a small multimeter and will look at what it can measure. Other alternative is to visit Son (he is more electronics)

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Re: Motor heating

Postby 9fingers » 23 Sep 2020, 09:56

Difficult to think that a bearing would heat up as much as you suggest and yet be free to turn and have little or no play.

Are there oil cups/nipples on the bearings - it possible on older motors. if nipples then unscrew and add a little oil - anything you have handy ever drips of the end of car dipstick will do. or just fill the cups and let it soak before run testing it.
If there are no oil points then up end the motor and make a reservoir from a ring of Blutak or similar (Plumbers Mait also good) and add oil inside the recess to let it soak into the bearing down the shaft. Not too much oil as you dont want excess in the rest of the motor.
Again let it soak before run testing it.

If that fixes the problem you can either leave well alone and be prepared to do this every year or so whenever it gets warm, or bite the bullet and fit a new bearing which will possibly see you out and the next user too.

If you think oil has got in and yet made no difference then we are possibly back to an electrical problem.

Bob
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Re: Motor heating

Postby Phil » 23 Sep 2020, 10:25

Bob, thank you very much.

Will try some oil first.

I need the saw back up and running ASAP as I need to start making Xmas goodies (If I get a good start now, I should be done by December 2021 :lol: :lol: )
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Re: Motor heating

Postby Phil » 26 Sep 2020, 12:13

9fingers wrote:Difficult to think that a bearing would heat up as much as you suggest and yet be free to turn and have little or no play.

Are there oil cups/nipples on the bearings - it possible on older motors. if nipples then unscrew and add a little oil - anything you have handy ever drips of the end of car dipstick will do. or just fill the cups and let it soak before run testing it.
If there are no oil points then up end the motor and make a reservoir from a ring of Blutak or similar (Plumbers Mait also good) and add oil inside the recess to let it soak into the bearing down the shaft. Not too much oil as you dont want excess in the rest of the motor.
Again let it soak before run testing it.

If that fixes the problem you can either leave well alone and be prepared to do this every year or so whenever it gets warm, or bite the bullet and fit a new bearing which will possibly see you out and the next user too.

If you think oil has got in and yet made no difference then we are possibly back to an electrical problem.

Bob



Ok, tried the oil bit.
Still heating up.

Will see if I can find a motor repair place close by.
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Re: Motor heating

Postby 9fingers » 26 Sep 2020, 14:10

Phil wrote:
9fingers wrote:Difficult to think that a bearing would heat up as much as you suggest and yet be free to turn and have little or no play.

Are there oil cups/nipples on the bearings - it possible on older motors. if nipples then unscrew and add a little oil - anything you have handy ever drips of the end of car dipstick will do. or just fill the cups and let it soak before run testing it.
If there are no oil points then up end the motor and make a reservoir from a ring of Blutak or similar (Plumbers Mait also good) and add oil inside the recess to let it soak into the bearing down the shaft. Not too much oil as you dont want excess in the rest of the motor.
Again let it soak before run testing it.

If that fixes the problem you can either leave well alone and be prepared to do this every year or so whenever it gets warm, or bite the bullet and fit a new bearing which will possibly see you out and the next user too.

If you think oil has got in and yet made no difference then we are possibly back to an electrical problem.

Bob



Ok, tried the oil bit.
Still heating up.

Will see if I can find a motor repair place close by.


A bit too far to send it to me Phil :lol:

Bob
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Re: Motor heating

Postby Woolf » 26 Sep 2020, 21:04

Phil these guys are excellent. Have rewound a number of motors for me.
Not quite in your neighborhood but not too far.
http://www.olgustavo.co.za/
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Re: Motor heating

Postby Phil » 28 Sep 2020, 12:33

9fingers wrote:
Phil wrote:
9fingers wrote:Difficult to think that a bearing would heat up as much as you suggest and yet be free to turn and have little or no play.

Are there oil cups/nipples on the bearings - it possible on older motors. if nipples then unscrew and add a little oil - anything you have handy ever drips of the end of car dipstick will do. or just fill the cups and let it soak before run testing it.
If there are no oil points then up end the motor and make a reservoir from a ring of Blutak or similar (Plumbers Mait also good) and add oil inside the recess to let it soak into the bearing down the shaft. Not too much oil as you dont want excess in the rest of the motor.
Again let it soak before run testing it.

If that fixes the problem you can either leave well alone and be prepared to do this every year or so whenever it gets warm, or bite the bullet and fit a new bearing which will possibly see you out and the next user too.

If you think oil has got in and yet made no difference then we are possibly back to an electrical problem.

Bob



Ok, tried the oil bit.
Still heating up.

Will see if I can find a motor repair place close by.


A bit too far to send it to me Phil :lol:

Bob



Thanks Bob.
I would have brought it myself, but then looked at the cost of travel, it would be cheaper to buy a new machine! :lol: :lol:
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Re: Motor heating

Postby Phil » 28 Sep 2020, 12:35

Woolf wrote:Phil these guys are excellent. Have rewound a number of motors for me.
Not quite in your neighborhood but not too far.
http://www.olgustavo.co.za/



Thanks Woolf.

I found a place in Hercules, about a 70km round trip.
Dropped it off this morning and will go back tomorrow to look at the damage.
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Re: Motor heating

Postby Phil » 29 Sep 2020, 11:08

I went back this morning to collect the motor.

However before I went I first had a look at young Minchin's guide to motors. 8-) So I at least had an idea of what the techy is talking about.

The thing-me-jigs that are around the shaft at an angle - they are worn away. They are unable to replace just that part.
I can carry on using it till the motor burns out. :shock:
Cool the motor with ice blocks and fans. :lol:

An identical new motor will set me back ZAR1500 aprrox (GBP75)

I will apply apply my mind to this situation while I carry on sawing away.
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Re: Motor heating

Postby 9fingers » 29 Sep 2020, 11:48

I should be able to dream up a scheme to stop the problem if you are happy to have an extra switch to operate once the motor has started.

What do you think?

Bob
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Re: Motor heating

Postby Phil » 29 Sep 2020, 12:51

Hello Bob,

Thanks very much, I am happy to try anything 'once'.
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Re: Motor heating

Postby 9fingers » 29 Sep 2020, 13:14

Phil wrote:Hello Bob,

Thanks very much, I am happy to try anything 'once'.


Can I have some photos of the motor under the connection plate and where the capacitor connects in please.

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Re: Motor heating

Postby Phil » 29 Sep 2020, 14:46

9fingers wrote:Can I have some photos of the motor under the connection plate and where the capacitor connects in please.
Bob


Bob, on their way on the 17:00 mail delivery.

Cheers
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Re: Motor heating

Postby 9fingers » 29 Sep 2020, 15:17

You will need a single pole push to make , let go to break switch capable of passing say 3 amps at 250v and to find room for it on the side of that box where your on off buttons are at the moment.

The action would be to push this switch first hold whilst the motor starts and then let go once it has got up to speed.

I've no idea what sort of electronic hobby type stockists you have in RSA but it wont be to sort of house wiring type switch but something much smaller. you might be limited for depth inside the box so that will be important in your choice.

Maybe have a look round and show me some examples of what you can get or instead give websites of likely suppliers and I can see what they have suitable.

Here is one suitable but RS known to be expensive so you might find the same elsewhere but cheaper
https://za.rs-online.com/web/p/push-but ... s/1035732/

push button.jpg
(25.58 KiB)


For scale the threaded part is 1/4" 6.35mm diameter

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Re: Motor heating

Postby Robert » 29 Sep 2020, 15:34

Assuming we are talking about a starting winding maybe a domestic light switch on a surface box? turn it on to start then off once it is running. Not as guaranteed to be off as a push to make but maybe more likely to have one laying around.

Not seen the pictures of course..
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Re: Motor heating

Postby 9fingers » 29 Sep 2020, 16:51

Robert wrote:Assuming we are talking about a starting winding maybe a domestic light switch on a surface box? turn it on to start then off once it is running. Not as guaranteed to be off as a push to make but maybe more likely to have one laying around.

Not seen the pictures of course..


That would work of course but I was trying for a more elegant solution with two buttons close together to be pushed with adjacent fingers.
Let's see which way Phil wants to take it re budget and ease of sourcing parts in RSA

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Re: Motor heating

Postby Phil » 30 Sep 2020, 13:08

Bob, thank you very much for the input.

I am parking this project for a couple of days as I have urgent work to finalise our audit report. :(
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Re: Motor heating

Postby Phil » 05 Oct 2020, 13:24

9fingers wrote:You will need a single pole push to make , let go to break switch capable of passing say 3 amps at 250v and to find room for it on the side of that box where your on off buttons are at the moment.

The action would be to push this switch first hold whilst the motor starts and then let go once it has got up to speed.

I've no idea what sort of electronic hobby type stockists you have in RSA but it wont be to sort of house wiring type switch but something much smaller. you might be limited for depth inside the box so that will be important in your choice.

Maybe have a look round and show me some examples of what you can get or instead give websites of likely suppliers and I can see what they have suitable.

Here is one suitable but RS known to be expensive so you might find the same elsewhere but cheaper
https://za.rs-online.com/web/p/push-but ... s/1035732/

The attachment push button.jpg is no longer available


For scale the threaded part is 1/4" 6.35mm diameter

Bob




Just to get my mind in the right direction............. :lol:

According to the chappie, the rotor is worn on the one side, see the CAD drawing, and that is causing the heating up of the motor.

Rotor_Worn.jpg
Rotor Worn one end - CAD
(33.96 KiB)


Bob, the switch - what will that bypass or assist in the starting up?

What wires would I cut and connect to the switch?
I like Robert's idea (cheap and easy as I have a switch) before I look for and invest in a switch.
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