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Old 27th Mar 2022, 1:21 pm   #1
paulsherwin
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Default Cleaning motor commutators

The motor in my 1934 Singer 201k sewing machine has just failed with a filthy commutator. I don't know how it's suddenly got in that state - it was acceptable a year ago when I last checked it. The failure was quite spectacular with lots of smelly smoke, and eventually the plug-in RCD tripped. Presumably the commutator had become contaminated with oil over the years which eventually burnt on.

I've now cleaned it with a combination of fine glasspaper and WD40 on a rag, and the motor is running normally again. However, does anybody have any advice about better ways to clean commutators? Is it worth investing in one of those thin truing stones? Is a fibre glass pen going to do a better job?

All suggestions gratefully received.
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Old 27th Mar 2022, 1:32 pm   #2
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Default Re: Cleaning motor commutators

Is the commutator 'true' and un-pitted? If not, then it will pick-up carbon off the brushes and arc + of course create 'brush dust'. In any event, it's important to effectively clean between the commutator segments for this reason. Hitherto I have re-turned commutators [on a troublesome washing machine motor] on a lathe - but they are so soft it could actually be done with a stone and power drill .... the final result however must be a 'cylindrical' rather than an 'ovaloid' commutator.

Best of luck Paul
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Old 27th Mar 2022, 1:52 pm   #3
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Default Re: Cleaning motor commutators

The motor is nearly 90 years old and has seen a fair bit of use (and abuse.) There is some sparking from the brushes, but it's not too bad. The brushes are wearing at a reasonable rate.
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Old 27th Mar 2022, 3:27 pm   #4
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Default Re: Cleaning motor commutators

I've skimmed commutators, using a really sharp lathe tool as the copper is soft, it needs to be very sharp otherwise the copper drags, then using a ground down hacksaw blade cleaned out between segments, then given it a final polish as you have done with very fine glass paper. On some a fibre glass stick has been enough. I drove the armature in the lathe to polish it, an electric drill might be enough just for polishing. We always bedded in the brushes using glass paper upside down, with a see sawing action. Ted
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Old 27th Mar 2022, 3:41 pm   #5
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Default Re: Cleaning motor commutators

I should explain that I don't have access to any sort of lathe. However, the design of the motor means the commutator can be accessed without completely dismantling it.
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Old 27th Mar 2022, 4:01 pm   #6
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Default Re: Cleaning motor commutators

It sounds like it may be worth truing it up.
Ideally you need a stone or fine flat file the width of the commutator or a bit wider if there is enough space.
Sticking a bit of fine sand paper to a lolly pop stick works well, and the stick can be trimmed to size.
Also worth reducing the level of the insulation between the segments first so it is a mm or so below the level of the segments.
If it has had oil on it clean it and brushes, holders etc with a bit of meths or petrol on a fine brush.
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Old 27th Mar 2022, 4:12 pm   #7
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Default Re: Cleaning motor commutators

I've used Autosol on a cotton swab for this followed up with a wipe down with IPA. I've done this with a few drills.
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Old 27th Mar 2022, 4:48 pm   #8
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Default Re: Cleaning motor commutators

I use a small hacksaw blade with all the "set" ground off so it's completely flat. Then a wash in WD40.
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Old 27th Mar 2022, 10:26 pm   #9
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Default Re: Cleaning motor commutators

Not all comutators have slots cut into them.!!

I would think what you have already done will work fine. Commutators dont like oil, so be very careful when oiling bushes/bearings. Its not often a sewing machine motor runs flat out for long periods so even if its slightly ovoid I dont think will effect you.

Just my thoughts.

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Old 27th Mar 2022, 10:36 pm   #10
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Default Re: Cleaning motor commutators

Thanks Joe, I'm not particularly concerned about this example, which just needs to work adequately as far as I'm concerned. The machine doesn't see very heavy use (mostly just minor alterations and repairs.) I was interested to hear the comments of more experienced members than me though.

Singer had a plant in Australia making 201s. I think they used CKD kits from the huge Kilbowie factory in Glasgow (now long gone.)

https://www.singersewinginfo.co.uk/kilbowie
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Old 27th Mar 2022, 10:53 pm   #11
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Default Re: Cleaning motor commutators

I did know that Paul. Mum actually had a beatiful french polished treadle machine made by Singer. My sister still owns it. It was purchased brand new about 1950.
I have a couple of brand new CKD motors in fact, but I think from the 1950,s not earlier. They have the large offset flat plug for connection to the "throttle".

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Old 27th Mar 2022, 11:00 pm   #12
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Default Re: Cleaning motor commutators

Singer used that 3 pin controller connector from the late 20s to the mid 60s. It's not a great design - it tends to fall off, and there's no provision for an earth connection.
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Old 28th Mar 2022, 12:07 am   #13
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Default Re: Cleaning motor commutators

From the Odhams "Radio Television and Electrical Repairs" book.

Many years ago, I used the brush bedding-in method with the abrasive paper reversed to clean a commutator that wasn't badly pitted, holding the paper still whilst rotating the rotor. I used "wet and dry" paper rather than emery cloth, as the latter tends to leave a deposit behind. The commutator was that of the dynamo for my car, and I rotated it using my electric drill and the rubber sucker from a sink plunger, which nicely fitted over the pulley.
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Old 28th Mar 2022, 8:43 am   #14
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Default Re: Cleaning motor commutators

In the white goods game we would bed in new brushes with a Comm Stick which was applied as the motor ran by touching on the comm, and within a few seconds the sparking would reduce and the revs increase dramatically as the brushes gained perfect contact. The stick released a fine abrasive powder in this process. I'd say, keep any contaminants off the comm, it wants to be squeaky clean and polished. I avoid using WD40 around anything electrical having seen too many items destroyed by well meaning husbands squirting it into switches and programmers, so wouldn't get it near a comm!
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Old 28th Mar 2022, 10:31 am   #15
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Default Re: Cleaning motor commutators

I agree with previous comments with regard to any contaminants being 'introduced' on to the commutator i.e. oil or silicon-based lubricants [WD-40 etc.] - these will ultimately pick up brush dust. The commutator should be squeaky clean and uniformly shiny after any truing or abrasive treatment i.e. by washing with IPA or similar. The graphite content of the carbon brushes provides adequate 'contact-lubrication'.
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Old 28th Mar 2022, 12:15 pm   #16
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Default Re: Cleaning motor commutators

Old commutators are likely to have aged - got hot and cold repeatedly and are prone to crack or lose their copper commutator sections.

They should be treated very carefully and aggressive cleaning (with chemicals or abrasion) will possibly damage them.

A fibre pen on the insulator sections should be enough to ensure no conductive residue is left between tracks - then a very light abrasion to the copper to get a shiny surface will normally return performance.

What is even more important are the carbon brushes and springs, which should be cleaned with anything that dissolves grease and oil. The springs applying tension the brush/commutator should be checked to ensure they both push evenly onto the commutator. Without enough tension, the brushes are prone to spark/arc more than they should, destroying the comm and the brush.

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Old 28th Mar 2022, 2:38 pm   #17
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Default Re: Cleaning motor commutators

I think I'll invest in a cheap fibreglass pen.
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Old 28th Mar 2022, 6:25 pm   #18
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Default Re: Cleaning motor commutators

A fibre glass pen will remove the crud, caused incidentaly by oil, it should then become useful again.
If you glance at any Singer service manual regarding servicing the motors, never use oil because build up as you have described will happen due to oil splashing and creeping onto the area where the brushes are.
Always use Singer Grease. A little like Vaseline, it warms up and lubricates the bearing by soaking through the cloth wick. When the lubrication is sufficient, it cools and solidifies again until needed to keep the bearings cool.
(If you had 'Oilite Bearings', never use grease).
Singer motors use bronze alloy bearings and must be greased.
Hope that helps with the many owners of these special and collectible machines.
I have a 99k that I refurbished, fitted a 'new old stock' electric motor and it uses a variable rheostat for the foot pedal. Crude but effective.
I will never forget trying to watch the news on our Bush 405 line tv, mother had to pause until the news was over because of the interference from the motor.
I recently bought a Singer 128, with the rotating shuttle, still in progress with that one. Looking for a treddle stand as the one I have has broken a cast iron leg but the leather belt is still OK after all these years.
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Old 28th Mar 2022, 6:31 pm   #19
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Thumbs down Re: Cleaning motor commutators

The mention of WD40 reminds me that when as a trainee maintenance electrician, I sprayed some onto the commutator of a large DC motor on a knitting machine whilst it was running. The results were quite spectacular & resembled a mini firework display ! Luckily I got away with it but a lesson was learned.

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Old 28th Mar 2022, 6:45 pm   #20
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Default Re: Cleaning motor commutators

Several external motor types were used with Singers of the black cast iron era, and they have different lubrication requirements. The motor in my 201k does need oil applied sparingly to the two bearings. Obviously I've no idea what's been applied to it in the past, and any liquid lubrication is going to take a toll eventually.

This is the first time I've needed to clean the commutator since I acquired the machine a decade ago, so it's probably been on borrowed time for a while.
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