[Bergeon 50 watchmaker lathe] Some help needed.

[Feynman]

Hi all,

my first post here, nice to meet you all, let me introduce myself: I'm a noob.

I recently scored a nice Bergeon 50 watchmaker lathe. The lathe was used very little and then it went in the cellar for decades but it still is in excellent conditions, I include some pictures here below. It required very little cleaning.

The motor has bronze bushings and the speed can be regulated with a handle on the side of the wooden case.

The problem is I've got white smoke coming from the engine (included a picture of the smoke...), I can run the engine with no load at slow speed for a few minutes with apparently no problems but if I attach the two belts (it has an intermediate shaft) and rev up the engine white smoke come out of the back and front air intake; mind you I'm not doing any cutting here just turning the lathe spindle with no loads.

 

I only started the motor a couple of times and it seems it does not like the high rpm,right before the smoke comes out I did hear some sort of electric crakling pretty much like in stick welding.

Can it be a problem with the bronze bearings? I mean a lack of lubrication that produce too much resistance torque? I never had bronze bearings, I tried to apply some lubricant (sewing machine oil) but I'm not sure if I'm doing it right. The two bearings have an oil port right over them (you can see the oiler in the picture with smoke), between the oil port and the bearing there is a felt like material that I guess tries to regulate the oil supply to the bearing.

 

What is the correct way to lubricate such construction? The way I did it is to put some oil in the outer cup then use a fine screwdriver to push the spring retained ball up and down so to "pump" the oil inside the felt. I don't know if it worked but it seems to me that the oil stays in the cup no matter how much pumping I do.

Do I need some sort of external oiler to keep the valve open and apply pressure to the oil?

I want to mention something else about the engine that might be significant: when I turn the rotor, by hand, clockwise it runs alright but when I turn it CCW it squeels like a mouse.

Any tip is greatly appreciated.

Thanks,

[RichardHarris123]

Hello and welcome from Leeds,England. 

It looks like an electric fault, whether or not it's fixable, I'll leave to members with more experience. 

[AndyGSi]

Yes, looks like electrical smoke so needs opening to investigate further

[Feynman]

Hi again,

thanks for the answers, I disassembled the motor.

I included some pictures if you want to have a look.

A couple of notes:

- There is some residual smell in the stator, there is no smell on the rotor.

- In the last picture you can see the bronze bearing with some oil dripping, the oil looks quite "dark", I lubricated the bearing last time. I don't know if it's important or not.

What do you think? It doesn't look burned to me but the smell is there....

[rjenkinsgb]

It looks a bit like there may have been a trace of oil on the brushes? That could cause smoke.

Also, is the insulation between the commutator segments flush with the copper? It should be slightly undercut so the brushes are not lifted from the segments, as that causes arcing and wear.

If it is flush, you can use a junior hacksaw blade to cut it in just a quarter millimetre or so. Deburr the comm with very fine abrasive sheet afterwards.

This info is about DC motors, but the principle is the same - just a shallower cut for a universal motor such as yours.

https://www.waiglobal.com/media/wysiwyg/1104-01-WAI-US-DC-Motor-Undercutting.pdf

[nevenbekriev]

See, what You describe seems like rotor short connection. If You assemble the motor and measure the current while it is rotated at full power, it should be much smaller (no load) than what is written on the motor plate. If no current is written on the plate, then the power should be written, divide it by voltage (220 or 110, which part of the world?). If the rotor is shorted, the current will be much bigger. In such case, just search for another suitable motor, it should be no problem to source one.

[SwissSeiko]

That is one nice lathe. As others have stated, these motors are very simple, and diagnosing the problem should be quite easy.

[Feynman]

Hi everybody again,

sorry for the late replies but I was waiting for some material to do some tests. Anyway:

@rjenkinsgb & nevenbekriev

thanks for the answer, the motor is basically new (I mean "old" new), there are no signs of wear on the commutator, I include a picture of the commutator section, again seems like there is no wear but the insulation is quite flush with the copper, is that weird for a "new" motor?

I run the motor with no lights in the room and cannot see any spark, I'm not sure about having oil on the brushes, it might as well be; the smoke that comes out at high rpm is quite persistent and keeps going even for a couple of minutes after everything has been shut down.

I did run the motor idle (no belts, no loads nothing) at a pretty low RPMs (few hundersds rpm) and I measure a power consumption of about 17 Watts (0.18 Amps at 230 V, power factor 0.4) at the plug. The motor is rated at 100 Watts, is that a reasonable power consumption at idle at such a low RPMs? I do not have any base for a comparison to be honest....

@SwissSeiko

I hope so :).

 

Thanks,

Dario.

 

[clockboy]

Welcome to the forum, enjoy.

[rjenkinsgb]

41 minutes ago, Feynman said:

I did run the motor idle (no belts, no loads nothing) at a pretty low RPMs (few hundersds rpm) and I measure a power consumption of about 17 Watts (0.18 Amps at 230 V, power factor 0.4) at the plug. The motor is rated at 100 Watts, is that a reasonable power consumption at idle at such a low RPMs?

The power rating of a conventional DC or universal motor is proportional to speed; 10% speed permits 10% power.

Are the bearings OK and the armature properly spaces or shimmed? Both the shaft around the bearing location and the flange against it look scuffed.

[nevenbekriev]

Hi Dario,

You supply the motor through regulator. This means although You apply 220 V to the input, the motor actually is supplied with small amount of it. To test the motor, You need to apply all the voltage, in other words You must turn the regulator to the Nmax, and then measure the power consumption. When no load, if the motor is OK, then the power should be significantly less than the one marked on the plate. You should try to identify where comes the smoke out. If it is not the rotor, then it is from one of the halfs of the stator

[Feynman]

19 hours ago, rjenkinsgb said:

The power rating of a conventional DC or universal motor is proportional to speed; 10% speed permits 10% power.

Are the bearings OK and the armature properly spaces or shimmed? Both the shaft around the bearing location and the flange against it look scuffed.

I don't know, the bearings look fine to me, there is a small axial play on the rotor, something like 0.5 - 1 mm. I'm not completely sure I'm lubricating them correctly though, they are just bronze bushing and not ball bearings...

18 hours ago, nevenbekriev said:

Hi Dario,

You supply the motor through regulator. This means although You apply 220 V to the input, the motor actually is supplied with small amount of it. To test the motor, You need to apply all the voltage, in other words You must turn the regulator to the Nmax, and then measure the power consumption. When no load, if the motor is OK, then the power should be significantly less than the one marked on the plate. You should try to identify where comes the smoke out. If it is not the rotor, then it is from one of the halfs of the stator

Good point about the regulator (please read below). I'm pretty sure the smoke comes out from the stator, when I take the rotor out there is no smell on it while the stator definetely smell.

Anyway I tried two additional runs of about 1 minute right now where I increased the regulator gradually to the max.

In the first run it reached 44 W at the max setting (again no load) with no problem, in the second run I tried to do the same gradual increase and somewhere near the max setting it cracked and smoked again, you can see the second run in the video here attached, the cracking at the end was quite loud. The max power absorption was 145 W, 3 times higher than the first.

 

First run to max rpms ---> 44 W, max setting reached no problem

Second run to max rpms ---> 145 W (motor rating 100 W), max setting almost reached before loud craking and again white smoke . Please see the video.

 

Thanks again for the help...

 

Edited February 4 by Feynman

[rjenkinsgb]

The noise at the end of the video could just possibly have been the armature picking up on the bearing and starting to roll around the inside, rather than running normally? That's the same effect as can happen with PC fans etc., causing them to suddenly start rattling or squealing. Bearing problems could also cause the excess power draw.

Motors with sintered bronze bearings usually have felt pads against one side of each, as oil reservoirs. 

Try using car engine oil on the bearings, and especially some on the felt pads, if it has any? That works well for both motors like that and PC fans!

It is possible that's nothing to do with the problem, but worth a try.

If the bearings are sintered and have run dry too long, the surface can get "smeared" and close the pores in surface, preventing oil reaching it from the bearing body.

The best cure is then replacement bushes, but putting eg. four spaced lengthwise shallow notches with a needle file may help with oil distribution, by breaking the surface and providing reservoirs.

 

Do you know anyone with a megger (insulation tester)? If so, it's worth checking both field coils and the armature for earth leakage, as that would indicate a definite winding fault.

An internal short with no earth leakage could happen within a field coil, but I cannot imagine how that could cause the noise?

[Feynman]

On 2/8/2025 at 12:18 PM, rjenkinsgb said:

The noise at the end of the video could just possibly have been the armature picking up on the bearing and starting to roll around the inside, rather than running normally? That's the same effect as can happen with PC fans etc., causing them to suddenly start rattling or squealing. Bearing problems could also cause the excess power draw.

Motors with sintered bronze bearings usually have felt pads against one side of each, as oil reservoirs. 

Try using car engine oil on the bearings, and especially some on the felt pads, if it has any? That works well for both motors like that and PC fans!

It is possible that's nothing to do with the problem, but worth a try.

If the bearings are sintered and have run dry too long, the surface can get "smeared" and close the pores in surface, preventing oil reaching it from the bearing body.

The best cure is then replacement bushes, but putting eg. four spaced lengthwise shallow notches with a needle file may help with oil distribution, by breaking the surface and providing reservoirs.

 

Do you know anyone with a megger (insulation tester)? If so, it's worth checking both field coils and the armature for earth leakage, as that would indicate a definite winding fault.

An internal short with no earth leakage could happen within a field coil, but I cannot imagine how that could cause the noise?

Hi,

I don't know. You're right about the felt, there is one, on each side, between the oiler and the bushing. I already tried to push some oil through the oiler but I'm not sure if the felt is getting "loaded" lubricating the bushing.

At the moment I bought one of those 150W sewing machines motors as  a temporary replacement, it seems to be working fine and is even quieter than the original.

I will disassemble the original motor and regulator and try to fix it later on, my neighbour has been complaining about the smoke.....

Dario.