Thread: Unimat Lathe Wrong Rotation

Hi Ken!

thank you very much indeed for the compliments and your very nice reply! I will have a look-out for suitable capacitors and i'll notify you when i found a source.

I've already started searching a little, and while doing so i stumbled across this interesting site:

http://unimat.homestead.com/techtip.html

You may already know it or else may find it worthwhile to read and also exchange information there.

Nikola Tesla is also my hero, Edison stole a lot from him, so did Marconi. This man was a true genius, but also a tormented soul. He was supersensitive and in time couldnt bear certain noises or smells or sights or types of food, that was probably the price he had to pay for having the brilliant visions he had, which came to him in flashes. This guy may have been able to see static and force fields and such, he designed and made things rather form his mind than from theoretic formulas. He is true science fiction book material, i wonder if there were ever movies made about him.

All the best from Holland!

gerhard

Hello again Gerhard , It's a small World . The link you told me about
was to an American Guy who I've been communicating with for a few
years . His name is Doug Feistamel . If you look on that site you will find a letter of support from me in front of the other letters in the list .

So I'd just like to say that we've got a new computer & I have not
downloaded the Digital Camera Disk yet . Soon as i do , I can send you
a pic of the original capacitor .
In your letter you had a pic of a 4 lead Capacitor . Gerhard , can you
tell me what the physical size of that one is , please .

On another note--------- We have 2 Geese ( old ones like us ) that
we use as guard dogs & lawn mowers . Every morning They call to the Wild Whistler Ducks that fly over . There are 8 that regularly come for breakfast but this morning there were 32 ! It's nice to know that the wild birds love a Feed of grain . Well that's my little bit of silly news from
Australia . My SKYPE I/D is queenie 354 .
Stay well , Gerhard & Best Regards from Ken in Oz.

Hi Ken, I have read you replies and note that the motor reversed before it was dismantled. I am at a loss as to how it could do this, but that is beside the point at this time. As an alternative suggestion, if you can reassemble the motor, try swapping the leads from the two outer (stationary) windings at the brush holders.

If that is not practical due to wire length, and you are game to reassemble the motor, you should be able to regain correct rotation at the lathe spindle by either running the belt in fig 8 mode temporarily, or by fabricating a motor mount to reverse the motor orientation so that the brush end is outboard of the headstock pulleys and run the belt normally. I make these suggestions as "make do" patches.

Have an old Sherline that I have had for 30 years, lousy lathe but I did manage to incorporate a reversing switch into the motor to reverse the armature field relative to the stator field for reversing. Could even loan you that motor if you could rig it somehow.

Mal

Hi Ken,

this PDF-document nicely sums up what suppressing caps are all about:

http://www.conis-bg.com/downloads_pd...capacitors.pdf

Look for the KP-series, these are the type and size ranges you want. Amongst the application examples mentioned, you will encounter "whitegood appliances containing induction motors". This may sound confusing, since we already established that induction motors do not need suppression capacitors, because they have no brushes. In whitegood machines like washing machines and dryers however, it is not so much the running of the motor but rather the motor being switched on and off lots of times during the program cycles. The capacitor in such cases is meant to suppress relay contact sparks which cause audible clicks on e.g. transistor radios.

Could you specify exactly what motor type or version your Unimat has? Than i will look for spare part lists and exploded drawing or maybe pictures from their interior. When i found these, i can advise you on what type and size of capacitor is best suited, and in what ways you can obtain it.

In several sites i saw, that the very first Unimat had an induction motor as well, like the larger Emco versions. This i didn't know yet. The early Dutch hammerite painted motor with built-in fan is probably an induction motor as well. The semicylindrical shape bolted on to it, may house a combined starting en running capacitor for its auxiliary windings. The later Dutch two tone painted brush motor is obviously derived from a sewing machine motor. The 90 Watts input sounds about right for such a motor, it's typical for electric household sewing machines. Some other Unimat motors are based on this motor design as well. Cranked up to 300 Watts with hardly any size increase and without an internal fan, i can imagine the overheating problems that i read about.

Surely this is not necessary anymore with nowadays motor technology. Have you ever though of changing the motor for a more powerful maintenance free alternative? Since the system uses belt drive, the motor needn't be fixed at the lathe's back, it may as well have its own fixed base and a longer belt. If adjustment of belt tension is the problem, than i would use a weight or sping loaded freerunning tension wheel, giving you even more belt length freedom.

Modern induction motors are much more compact than they used to be, they are easier on the ears and have a more stable rpm-behaviour between load and no-load. There are very nice industrial centrifugal fan motors around with their own sealed metal enclosure and their own external cooling fan and ball bearings. I will search for some examples and show them to you.

Geese are indeed very interesting animals. I was born in the east of Holland near the German border and that part of the country is a typical agricultural area. Many farmers there keep geese for watchdogs and i've also noticed that behaviour. They see their wild cousins making practice rounds to prepare for the big journey south and they react very strongly to them. You wonder what they might think or feel. I've seen a program of a guy in a microlight plane flying right amongst home raised geese and ducks, treating him in his artificial contraption as if he were one of them nonetheless. Amazing, what footage that was! I believe David Attenborough also had something to do with it, parts of it at least were also featured in a grand scale BBC nature series documentary.

Greetings

gerhard

Originally Posted by malb

Hi Ken, I have read you replies and note that the motor reversed before it was dismantled. I am at a loss as to how it could do this, but that is beside the point at this time. As an alternative suggestion, if you can reassemble the motor, try swapping the leads from the two outer (stationary) windings at the brush holders.

If that is not practical due to wire length, and you are game to reassemble the motor, you should be able to regain correct rotation at the lathe spindle by either running the belt in fig 8 mode temporarily, or by fabricating a motor mount to reverse the motor orientation so that the brush end is outboard of the headstock pulleys and run the belt normally. I make these suggestions as "make do" patches.

Have an old Sherline that I have had for 30 years, lousy lathe but I did manage to incorporate a reversing switch into the motor to reverse the armature field relative to the stator field for reversing. Could even loan you that motor if you could rig it somehow.

Mal

G'day again Mal ,
This Motor reversal couldn't have happened at a worse time for me because
both my Electrical Mates are away . That being said ----- Not to worry
because ( in truth ) there is no urgency to the situation . I'm retired & have
6 lathes . Greedy No , just happened to have all my close Family in the
trade & I have theirs ( deceased estate now ) & what i've gathered in the
time I've been in the Watch /Clock Trade . I'm pretty well tooled up , Mal .
So mate , don't worry about it too much . I want to cruise along &
gather the bits I need & the Info I need then put the motor back together
while one of my mates watches over my shoulder . Now you would think that
just changing over the Brush Clips would do the trick but not according to our USA friends. There are certain changes that must followed . I won't go over it now but the Info is in the Bag . Just waiting for Gerhard to find the
correct capacitor in Holland . Why ? Originality is what I'm aiming for.
When I pass it onto my kids , it will be as I bought it .
It works well and has always worked for me since 1972 .
This is just one little glitch in the time I've had it . Now it may take a couple of weeks but I'll let you know the final outcome when it's done .
Please just let me say that I'm amazed at the response from all of the Group
who've written in about this . Especially You , Mal .
Thank you from Ken in Mackay

G'day again Gerhard , I'm going to look at the pdf you listed in the morning .

I'll begin here with the Answer to your Question " what is the exact size of my lathe motor ? " Well friend , it is a ' Cella ' Dutch made motor & the output is 95 watts . The photo in your second letter of the Complete Kit Unimat Lathe IS the same as Mine & that includes the Motor shown .
I'll be back to you in the morning after I've looked at the pdf , ok .

& Yes Gerhard , I saw the Microlite that Mothered the Canada Geese .
My God , the photography was miraculous wasn't it .
Our old Goose is still Laying & my wife makes Pumpkin Scones with our Home grown Pumpkins & a goose egg . You'd be right at home here , Gerhard . back on the farm ! We are about 2 kilometers from the Pacific
Ocean & 14 kilometers from the Great Barrier Reef ( Google that )
Bye for the present from Ken in Australia

Hello again Grerhard , I've looked at the pdf file & I think that the Capacitor
KP_2A class X1 Y2 & value of 0.025 & 2x 2500 pf on page 4
Is this one suitable for my motor ?

I hope to hear from you soon , Best Regards from Ken in Australia

Now if you can build this its very cheap. Looking through my catalogue from WES in Sydney a .01uF 600V AC is $3.50 trade, 2500pF (2.5nF) or (.0025uF) is the same thing. Now that is not a preferred value its ether 2200 or 2700 and to be honest it really wont matter 2700 rated at 2KV cost is $1.35. None of that is polar so anyway in is fine. All you need to do is find out what lead is what.
Your suppliers would be WES (Wagner electronics) or theres a mob in Brisbane The Go company
Wes charges about $10 PP dont know about Go. You would have to solder this lot (Electronics solder, DO NOT USE plumbers solder) . I suspect its 4 leads, one is common 2 probably are supressors over the mains and the third the .01uF is the starter which will give you the phase to start. If there is room to hitch acroos that capacitor, all you probably need is to unhitch that lead and fit just the .01 across where that is. So your fix is $3.50 $10 pp.

Ok , can I have your phone No. please .
Regards Ken .

If that was for me Ken, I sent you my Email address in a private message, its not hard anyway Im @ hotmail.com

here is the pages from WES

Hi again,

yes, the cap model on page 4 of the PDF-file would be fine. But you could also use the components as ruggested by Rrobor. I've done that many times myself, making a sort of Frankenstein-circuit of loose components, soldered together to make a wide-band XY-alternative. Some machine i own have had them for years now and nothing failed or exploded. The ceramic capacitors suggested by Rrobor will do fine as the two Y-components, but for the X-part you needn't necessarily use the expensive polypropylene cap worth 3 Dollar 50. In the column right next to it, you see the perfectly fitting X2 MKP solution, which costs only 50 cents for 0.01 microFarad. Being a true X2 cap, specifically made for this task and able to withstand 275 V AC, that would be my choice.

As you mentioned the motor of your specific Unimat being of Dutch origin, i think the original cap was made by Philips or Van der Heem or Ero. Cella as such is an unknown name to me, i will try to find the original manufacturer. You said you aimed for preferably the original replacement part, but that will be very tricky to come by, some 30 years on. Besides, materials in these components deteriorate with age. These vintage caps contain foil with mere wax impregnated paper as insulation material (part of which you found molten and run out). Modern types contain quality plasticlike foils with better insulating and thermal reserves. And the motor is closed, so the replaced modern looking part is not in plain view anyway. Nobody need be the wiser.

To root out that creeping-in misunderstanding again: the 0.01 X-part is NOT used for starting or phase shifting through any auxiliary winding, brush motors do not need and feature such windings. The main duty for an X-cap is reverse voltage spike absorption , nothing more. These spikes are caused by the armature and field coils during commutating interruptions between the brushes and the commutator . The power consuming coils, operating in a magnetic field, also act as generating coils, and the reverse voltage is generated each time the fed power becomes zero for whatever reason. This effect is known as "counter-EMF" or "counter electric motor force". The high voltages and sudden current changes also cause the brush sparks. By absorbing the spikes and partly quenching the sparks, radio noise is suppressed by some deciBels. The active bandwidth in which the cap is active, has its center at approx. 1.3 MegaHertz, as is shown in the diagrams in the PDF-file. X-only caps have a much narrower bandwidth, but are deemed adequate nowadays because radio and tv receivers have either become more selective and disturbance-proof, or have gone digital.

Recently, i bought a Fein angle grinder on Ebay, which had seen very little use. The XY-cap had blown up on the user, but in such a spectacular way that the interior of the hind grip, where the switch and the cap were built in, was clad with bits of foil like wallpaper. Violent reverse voltage spikes are relatively normal in angle grinders, suppressor caps have a particularly hard life in these machines. Often dust particles, sucked in through the cooling air vents and blasting the commutator, are to blame. These particles often end up between the brushes and the commutator copper and are caught in the slots between the copper strips, scratching along underneath the carbon brushes until they are flung away again. Gritty dust is even known to slightly lift the brushes and severely hamper the current commutation. In a 2000 Watts motor, the sudden interruption of 10 Amps can cause violent sparking. The magnetic field in the motor is so strong at full power, that sudden power interruption can make all the motor coils generate nasty reverse spikes of 600 Volts or more. Caps can survive this hundreds of times, but after hours or years enough is enough. Like a leak in a central heating radiator, leaks in insulation can grow worse over times, especially with repeated peak stresses. Suppressor caps can also blow up when the switch is suddenly released on an overloaded motor, or when the mains power fuse blows during severe current intake. The reverse spikes can in such moments reacht values up to a 1000 Volts. The next time the tool is used, the shorting within the insulation layers makes itself known by a clear total failure of the cap.

The user may not have dared to touch the tool again. The user and the seller may not necessarily have been the same person, the seller he had tried the machine and found it to be in full working order. He may have been very lucky while doing so or he may have lied. Anyway, the price was right and i'm glad i always inspect used machines from the inside before i plug them in. The motor was fine but the gears ran less than perfect, so the machine probably seized and stalled very violently and the power was obviously cut during the occasion. The XY-value of 0.3 microFarad combined with 2x 4700 picoFarad was unobtainable trough every source i tried, so i made a Frankenstein alternative myself. Three 0.1 X2-caps soldered parallel and glued together in a little stack, with two 4700 pF ceramic high voltage caps for Y-parts. Worked fine, i rebuilt the gearbox and presto, as good as new Fein MSf 679c grinder worth 400 Euros. I recently took apart a Flex 2000 Watts angle grinder. Just an X-cap, no more Y-components. A mere grey blocklike MKP cap with black leads, worth 1 Dollar, that was all.

Success and greetings

gerhard

[FONT="Times New Roman"][FONT="Times New Roman"]

Hi Gerhard , Please send me your email address .

My email address is kweekes@ozemail,com.au

If you send me your email address via the above address then we can
talk regarding the Capacitors for the Unimat . & thank you for the
advise in your last letter .
Reghards Kew from Australia .

Gerhard , that should be [email protected]

regards Ken