Unimat Lathe Wrong Rotation

[Ken Weekes]

Hello All , I'm really new to all this but I saw several notes by Gerhadt
to Mick & I figure that Gerhadt can help me with this .

I have a Unimat Lathe ( small) that has started running in the wrong direction
to what it normally does . Anti clockwise compared to clockwise which is normal . When i stripped the motor it smelt normal . There is a small
Capacitor in the end housing that is connected across the Brush housings & a
3 rd . lead to earth . I noticed that there is wax like substance coming from
the Capacitor & leaking onto the housing .
My Question is this-------- Could this Capacitor be defective ? & could it be the cause of the Wrong Direction of the motor. ?
Also I can see the printing on the Cap & it reads------
F*F in a Diamond shape then under that is-------
N 1022 R1 & under that is--------
0.01 uf + 2 x 2500 pf then a circle with a 'B' in it .
under that is the rating of 240 Volts .
" " " " No. 66.2
" " " " " 560-2-7
Gerhadt , you seem to know these things so can you tell me if I'm on the right track ?
& Maybe where I can buy a Capacitor of that value , please
Also the Capacitor physical Size is 34 mm long X 11 mm in Dia.
Sure would be a BIG help to me it someone can help me with this one .
Best regards from Ken Weekes in Mackay , Qld.

[watson]

G'day Ken,
Looks like the Capacitor has gone to dog!
A Fault in that area could cause the motor to start in the wrong direction, and your best bet in Mackay is to suss out a motor rewinder or such, as they will know where to get the right Capacitor.

[Ken Weekes]

Thanks for your reply , Noel ,
My motor is small . Sewing machine size .
I'm not sure that the motor rewinders here would be interested in looking at it
but I'll try on Monday . Also there is a guy in the USA who has an untested
capacitor & wants US $ 25 for it ( untested ) Woo Hoo!
I didn't realiase that Mick had posted a similar question about a sewing machine motor but his is much larger than mine .
Well I'll take all the advise i can get to save my little lathe .
Here's hoping . Ken in Mackay

[watson]

There's another option.
Have a look at www.rockby.com.au under Capacitors they may have that one, and they'll be a damn sight cheaper.

[Ken Weekes]

Thanks a lot Noel , I'll look at them !
Regards from Ken in Mackay

[Ken Weekes]

G'day again Noel , Tried those people you suggrsted to no avail.
i'm really desperate to revive this lathe motor .
Can you suggest any other places to try ?
Thanks for trying .
Regards from Ken Weekes in Mackay .

p/s There was a person called ' Gerhard ' that wrote to this forum
& he seemed to know a lot about motors .
Do you know how to contact him ?
ken w .

[Quasimodo]

That sounds like another one of those pesky multi-pole noise suppressing capacitors that have been discussed on here lately in relation to power tools - I am not sure of a source in Australia and the manufacturers of such caps only want orders in the 1000 and up range

Have you seen this page:

http://www.lathes.co.uk/unimat/

the Maplin Electronics part number has changed but I think the part referred to is still in their catalogue.

Maybe some sewing machine motors used similar parts - could ask at a power tool repair workshop too. A US part may not be suitable as they used different motors I think.

And the usual precautionary warning, seek professional help when dealing with electrical matters. Make sure the electrical safety of the motor is checked as "One flash and you're ash".

[Ken Weekes]

Thanks for the quick reply . I forgot to look at Lathes UK .
(Tony's Site )
That part # you mentioned ? Is it an Australian Company ?
Can I google it ?
I didn't think it would be so hard to find one capacitor .

regards Ken in Mackay

[watson]

p/s There was a person called ' Gerhard ' that wrote to this forum
& he seemed to know a lot about motors .
Do you know how to contact him ?
ken w .

G'day Ken,
a pity Rockby couldn't help.
Now Gerhard........I reckon he lives in Europe, but you could contact him via PM.
Which is simple to use and goes directly to him....no one else.
Up on the top right there is a link to Private Messages.
Click that, and a new page will appear.
On the left side column, scroll down, and you'll see a link "Send New Message"
Click that, a new page will appear, and just put in "Gerhard" in the Recipient Username....add a title....type your message and you're directly in contact with Gerhard.
Have you tried Sewing Machine repairers in Mackay as well??

[Ken Weekes]

Thanks for the message Noel . I'll go back to your letter
& try to reach him in the morning .
I've been on the phone all day & the most common reply is
laughter when i say made in 1972 or 3 lead small capacitor .
Anyway , I am persistent . Most Watchmakers are used to
adversity . Me too !
regards Ken in Mackay

[malb]

Ken, I haven't been near a Unimat for some time but from the mention of brush holders and sewing machine motors, I figure that it is a small fractional horsepower univeral (Brushed) motor. In that case the capacitor connected between the brush holders and earth should only be for RFI and have no effect on the direction of rotation.

Direction of rotation would be set by the relationship between the magnetic fields produced by the field winding (stationary bit) and the armature (rotating bit). To reverse direction, all that is needed is to swap the leads at the brush holders.

If the motor was optimised to operate in one direction, the armature windings may be advanced relative to the commutator segments (rotating copper bits on the the armature that the brushes rub against). If this is the case the motor will be reversible but the reverse direction will have much lower power than the desisgned direction.

Did the problem appear 'overnight' or is there some chance that the motor might have been opened and reassembled incorrectly to create the problem?

[Ken Weekes]

Hi Malb. Thanks for your letter . I'll just say that the motor has never
been Disassembled & I've owned it since 1972 . I've recently used it
for some months as a Grinder & didn't notice any rotation change of direction
in it . Last week I had to do some turning which was too heavy for my
watchmakers lathes So the Unimat was fired up ! Hmmmm No Cut
wrong Direction of rotation . Panic . I called an Electrician mate &
began to disassemble the motor , taking note of the thrust washers etc
& asked him to A replace the power lead & B have a look at the windings
etc. Drew a blank there as I got it back undone . He said the windings
measured out ok . But when I cleaned the inner housing I noticed a waxy
substance at the Capacitor 2 lead end . The Cap is across the Brush Holders
& an extra lead goes to earth . I copied the lettering on the body & put it
into the letter you read . Now you know as much as I do .
A disassembled motor . a new lead & plug now fitted . Looking for a new Cap . Suggestions please .
Regards from Ken in Mackay .

[gerhard]

Hi Ken,

The Emco Unimat has a brush motor, not an induction motor. The product name incorporates "universal", and mains powered brush motors were called "universal motor" in the 50'd ans 60's, since they could run on both AC and DC. The larger Emcos (Compact, Emcomat and Maximat series) all have AC-only induction motors. These would need a capacitor for the necessary phase shift in their auxiliary field coils. The value of the capacitor you mention, is a typical noise suppression capacitor belonging to brush motors, applied to minimise the brush sparks and thereby dampen reception disturbances of radio and tv sets. You also mention "brush housings", so your machine is indeed fitted with a brush motor. In the case of a series connected brush type motor, the capacitor has nothing to do with sense of rotation or with starting up. The construction of such a motor enables it to start all by itself, and always in the same direction. Only when the brush wires are switched or the position of the brushes are changed, will the motor run in the other direction.

So the sudden change of rotation is a bit of a mystery. As for the capacitor, it is indeed defective if it has spilled parts of its contents, and it has to be replaced.

The capacitor needn't necessarily be of the same make or size, more vital is the exact value and even more so the rated voltage. A value of 0.01 microFarad (or 10 nanoFarad) is quite small. Coffee bean grinder motors an cheap juice extractor motors already have 0.047 microFarad (or 47 nanoFarad) or more. But never mind, though, if it reads "0.01", than 0.01 it is. This type of capacitor is called a "wide band suppressor capacitor". It is active over a wide frequency range and can suppress static brush spark crackling from the FM radio bands all the up to VHF and part of UHF tv channels. The larger 0.01 part does most of the work; if it shortcircuits or fails in any other way, there is no chance of transmitting mains voltage to any metals parts of the machine and to the user, touching those parts. This low-risk part within the wide band capacitor is called the X-part. The two components with the value of 2500 picoFarad, are both connected to the metal mass of the motor (used as a sort of common "ground") and if these fail, they may transmit mains voltage to the motor metal and the user. The small wide band capacitor parts are categorised as Y to remind of that risk. Nowadays, most radio and tv receptions proceed through cable and are is many cases even digital. There is no more real need to use a full XY-cap for noise suppression. If you open nowadays' coffee grinders, kitchen mixers, weed trimmers, vacuum cleaners and other brush motor driven appliances, you see small blockshaped capacitors containing the safe X-part only. So in your case an X-type suppressing cap (the modern and higher voltage rated variety is called "X2") will also do fine. A good electronics shop will be able to supply you with a 0.01 microFarad X2-cap, with must preferably be capable to withstand 275 AC Volts but at least 250 Volts AC. The "self healing" polyester foil types are the best quality on the market, in Europe they are called "MKT" types. A few dollars (as little as one or two) may get you such a part, whereas versions with readymade wires instead of soldering pins, may be slightly more expensive. Polypropylene film "MKP" types will also do fine, as long as the voltage rating is at least 250 volts AC.

Since the X2-types have no ground connection lead and therefore don't need a third "ground" wire, there is only the need to attach the two remaining wires parallel to the motor itself. There are also brush motors that have their suppressing capacitor connected over the two brush holders. In that case the field coils also have a suppressing function ("inductances"). You will soon what kind of connection your brush motor uses, most likely the first. The cap needn't necessarily be housed within the motor itself, it may be connected anywhere between the switch and the motor. The cap must never be connected before the switch, there must always be the motor as a parallel load.

The pics show examples of various suppressor caps. The second pic shows a vintage Unimat. The later models have brush motors too. There are copies of the original design made in China and Taiwan. Sometimes brush motors with permanent field magnets are used. These are probably fed through rectifier diodes to dress AC power into DC, since magnet motors run on DC only. They do however still need brush spark suppressing measures and will also be fitted with caps.

The sudden reversing of the motor is very puzzling. That is definitely no normal behaviour, i see no way in which its construction could allow it to do such a thing all by itself. Was any change in the wiring ever carried out at some point of time? I will look further into what may have been the cause, right now i can only speculate.

Greetings from Holland!

gerhard

[gerhard]

Oops, reread your post, i wrote and uploaded too quickly again. Happens to me more often, i must admit. You clearly mentioned that the capacitor was connected across the brushes. It the cap has wiring of the through-feed type, than some leads may have been switched during soldering or motor diasassembly. That could be a reason for the motor eversing, though that's only a guess, of course. You may not have soldered or disassembled the motor at all, in which case the mystery remains. But i couldn't imagine another reason, really.

Some months back i uploaded some other material about XY-caps, relating to a thread concerning a Metabo drill with a blown up cap. I used that drawing again underneath here. The second drawing concerns the different situation as you mentioned, when the cap is connected across the brushes instead of across the entire motor.

Regards

gerhard

[Ken Weekes]

Hello Gerhard , Ken here . Most of today I spent reading & re-reading your letter & couldn't believe how lucky I was that you wrote to me from Holland.
One of our Group members in the Forum had advised me on how to send you a private letter requesting that you advise me on this matter & the next thing I know your letter arrived.
Firstly, I want to thank you very, very much for your clear explanation & diagrams regarding my Unimat Motor, At the moment I am waiting for my Electrician friend to visit here so I can show him your letter. Even though I have read it several times today I might be missing something as I am reading it with a Watchmaker's eyes & not an Electrician's eyes.
I also noted that in one of your previous letters regarding a sewing machine motor you mentioned my Hero Nicola Tesla. I have always admired his work & I'm amazed by the volume of it. I'm sure the Americans would have benefited greatly had they given him a position of high importance & flooded him with money & then just let him pour out his knowledge.
In the last couple of days I have had some depressing news in that my best mate is now on a round the world trip with his wife (he's an Electrical Engineer) & I cannot contact him & the other Electrician that I'm waiting for at the moment is leaving in 2 days time for a 2 week 4 - wheel drive trip to the wilds of our State (Cape York) & so I'll show him your letter but I won't be able to act on it (re-assembling the motor) until he comes back to watch over my shoulder.
I am now going to look through some on-line catalogues for the Capacitors (4 lead type) that you described.
I am also going to undercut the insulators between the poles so that there is no chance of flash-over etc. It's a finicky job to do but I've done one of them before & the finished article is still running sweet.
Anyway, Gerhard, I'll sign off now & I don't really have enough words to thank you for what you have done.
Regards, Ken Weekes from Mackay, Queensland, Australia