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simonl
19th Sep 2019, 12:18 PM
Hi all,

My bridgeport clone came with an x axis power feed that does not work.

It's a Servo motors type 90 power feed made in the US. It has a cooked circuit board with some cooked rectifier and SCR's.

Some time ago I problem solved and sourced the replacement discrete components and had a go at a repair but I think someone prior to me has also done a similar thing. I've come to the conclusion that the entire board needs replacing TBH.

In short I can get a new replacement board from the US. The board seems to be almost a plug and play setup with the plugs etc.

Question is, at $US230 for the board, is it worth it?

I see that servo power feeds are very expensive, even S/H old ones like mine. Even sold for parts they are several hundy on occasions. They are also fully rebuildable Even though mine is over 40 years old.

I love rebuilding stuff and saving stuff from needlessly going into scrap or landfill and apparently these are a very nice power feed unit.

Should I take a chance or bin it and buy a Chinese POS and be done with it.

Also, from what I can tell, everything else is in good order. The field windings and armature are good.

It's totally stripped and cleaned up and been sitting in a box for about a year while I procrastinated over this decision

Simon




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simonl
19th Sep 2019, 01:11 PM
Some pics for anyone interested...https://uploads.tapatalk-cdn.com/20190919/b47e3e7742c3d11df2e69584114d84df.jpghttps://uploads.tapatalk-cdn.com/20190919/3d5dd46dc48766dbba86c5a200d3a7de.jpghttps://uploads.tapatalk-cdn.com/20190919/e90d4aeece63b1de0856a8c462142546.jpg

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BaronJ
19th Sep 2019, 07:02 PM
Hi Simon,

I would stick with it ! Its a simple thyristor motor speed control circuit. Even if you replaced every electronic component you would only be spending a few dollars. I've a circuit diagram kicking about somewhere for a speed control circuit that will provide you with a basic circuit to work with.

382254
Here you go !

simonl
19th Sep 2019, 09:06 PM
Thanks Baron.

Couple of things to take into consideration. The motor needs to be able to run in both directions and also the engagement handle has a cam on it which engages one of two micro switches that are mounted on the circuit board which in turn set the current path for the direction.

If I were to design and build a new circuit similar t o the one you posted then I would need to include these in the correct t place. Not impossible but a bit of mucking around.

As I mentioned above, a new circuit board is US$230 whic h is a fair amount. I could probably design and build on e for under $100 which would take e some mucking around.

Stuff it. Maybe I should.

One thing I forgot to mention,I actually have the schematic of the original circuit. A lovely gentleman from a repair company in the US who quoted me the price for the board also attached it for me in an email to help me repair the original. He was quite passionate about the build quality of these little power feeds.

Simon

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BaronJ
20th Sep 2019, 12:54 AM
Hi Simon,

It would help to have a look at the schematic of the original circuit.

Assuming that the board is in good shape it would be easy to just replace the bad components. The only other thing that I would advise is to check that you can either get or make new brushes for the motor. From the picture you posted the commutator on the armature looks to be OK. No loose segments or any suspicious burning, no nicks in the windings etc.



If I were to design and build a new circuit similar to the one you posted then I would need to include these in the correct place. Not impossible but a bit of mucking around.

There are basically only two connections to worry about, and those are the motor. It may look complicated because they might have brought the field and brush gear connections out separately.

malb
20th Sep 2019, 01:27 AM
Hi Simon,

There are basically only two connections to worry about, and those are the motor. It may look complicated because they might have brought the field and brush gear connections out separately.

I would anticipate that the field and brush gear connections would be separate at the motor as the only way to reverse it is to reverse relative magnetic polarities between the field windings and commutator/brush gear. Therefore, it needs to have a simple speed control followed by the direction switching associated with the engagement/direction switching mentioned by Simon, or the engagement/direction switching integrated into the control board (hence separate field and commutator outputs from the board).

Incidentally, if the thing is as simple as Baron suggests, I doubt that it would qualify as a servo system as Baron's circuit does not include anything for positional feedback, generally one of the criteria for a servo system, input tells it where to go, positional feedback tell it where it is, control system compares them and determines decides which way to go and how fast to go to get to the required position ASAP without overshooting.

Servo action should not be required for feed motor on a manual mill where only requirement is adjustable constant speed rotation is primary requirement, but is required for anything CNC where the control system needs to know the position at all times. Steppers are an exception in CNC as the controller counts steps and direction and keeps a running tally to determine position, which sort of works until something happens to cause a motor to miss one or more steps, and then the whole control system is out of whack until it is re zeroed. Servoes don't have this issue because they are constantly measuring shaft position and supplying that information to the amplifier/driver system.

QC Inspector
20th Sep 2019, 01:53 AM
I'm no sparky but I would get the new one. Reason being the resale of it will be more if it is original and not cobbled together with what might be perceived as junk parts.

Pete

simonl
20th Sep 2019, 09:57 AM
Hi Malb,

It's not an actual servo motor as such. Servo products is the brand name.

Pete, a new power feed from servo products is not an option for me as they are about $US800. If I bought new it would be a $300 "cheapie" from china via eBay. The point being that a new Chinese power feed would be inferior to the rebuilt power feed I have now. Hence the dilemma of repair or replace.

Simon

QC Inspector
20th Sep 2019, 11:12 AM
I meant to get the new Bridgeport circuit board not a new Bridgeport feed.

Pete

simonl
20th Sep 2019, 12:00 PM
I meant to get the new Bridgeport circuit board not a new Bridgeport feed.

Pete

Yea. It's tempting. There also a chance that I can do that and still end up with a power feed that does not work. I guess it's something I have to weigh up. I think I will do some more testing on the armature and the field windings to make sure they are still OK. If I find that they are suspect then it makes the decision a whole lot easier.

Simon

BaronJ
20th Sep 2019, 06:17 PM
Hi Simon,

Those motors will run quite happily on as little as 15 or 20 volts DC, or AC for that matter. Make a note of where the wires go, then simply connect the armature in series with the field coil and put a voltage across the whole lot. Beware of the back emf if you hold the wires with your fingers :U

The motor should run smoothly in either direction.

simonl
20th Sep 2019, 08:49 PM
Thanks Baron.

Btw, here is the schematic (in 2 parts) for the type 90 power feed.

SimonTapatalk Cloud - Downlaoad File Type%2090%20Schematic%20Left%20Side%281%29.pdf (http://cloud.tapatalk.com/s/5d84a054b52e2/Type%2090%20Schematic%20Left%20Side%281%29.pdf)Tapatalk Cloud - Downlaoad File Type%2090%20Schematic%20Right%20Side%281%29.pdf (http://cloud.tapatalk.com/s/5d84a061c1ea7/Type%2090%20Schematic%20Right%20Side%281%29.pdf)

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BaronJ
21st Sep 2019, 06:17 AM
Hi Simon,

Very interesting schematic ! Very clever the way that they have used a transformer to provide the phase switching to drive the thyristors and the way that they have split the motor field winding.

Whilst component replacement would be absolutely no problem, the motor would be an entirely different matter.
All the components are old style from looking at your pictures.

Do you have a multimeter ? Do you want to start to repair it ?

simonl
21st Sep 2019, 08:02 AM
Yes I have a multimeter and some basic electronic knowledge.

I won't have much of a chance over the weekend but yes I'm keen to at least explore the possibility of repair. Bare in mind that I suspect that the actual board ie tracks are damaged. I would imagine I will need to make a new board. I have made boards in the past using a freeware software package and using a laser printer and etching. The most critical part is ensuring the pc mounted micro switches are positioned accurately.

I suspect the first part is proper testing of the armature and field windings?

Simon

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BaronJ
21st Sep 2019, 05:29 PM
Hi Simon,

The first thing is to take a couple of good pictures of the drive looking straight down and towards the motor, then we can see exactly where everything goes.

From an earlier picture two things jump out, the thyristors should have a rubber tube over them. The metal tags are at mains potential, far to easy to touch and get a belt (shock). The other is that the motor is probably going to have to be assembled into the case in order to run it, so initially ohmmeter tests are needed to make sure that the windings have continuity and also the armature doesn't have any opens.

This probably means unsoldering the wires to the motor circuit board !

Old Croc
22nd Sep 2019, 09:16 AM
Simon, Mag-pro in Melbourne has them @ $290, good starting point. BTW, anything out of China/eBay, is now taking 2-4 weeks.
Rgds,
Crocy.

simonl
22nd Sep 2019, 08:59 PM
Thanks Crocy. That's a pretty good price if I go down that path.

Simon

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simonl
22nd Sep 2019, 09:10 PM
Hi Baron,

Here's another pic. Sorry it's best I can do for now. It's been a busy few days for me.

I'll remove the board tomorrow. No big deal to remove the board and cut the wires as the board is a throw away anyway but I will need it for a template for where to place the micro switches if I choose to make a new board from scratch. Btw I've also emailed servo products on the off chance they may still have a copy of the PCB artwork. Remote chance but worth an email.

Another option I have thought of is replacing the motor with a 250 watt DC motor from eBay. And buy a simple DC speed controller. Speed controllers are so small I think I could stuff it in the existing case and retrofit the DC motor as well. The power feed would look no different on the outside.

A new board holding the micro switches would control direction as original.

In the second pic you can see the brushes. They are brand new. I had already spent about $50 in parts for it from the US. Some parts are still available since they are used on later models.https://uploads.tapatalk-cdn.com/20190922/07aeb147788038d6fb95d7a1ec182729.jpghttps://uploads.tapatalk-cdn.com/20190922/02ef689ba9904952beba07c3e0383d12.jpg

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BaronJ
23rd Sep 2019, 12:33 AM
Hi Simon,

From those two pictures I can't see any reason to want to replace the board, obviously I cannot see underneath so my opinion might be different. The motor windings look to have been getting hot at some time in its life, so the first thing would be to confirm that the motor is sound.

Check the winding resistances, check for shorts to the frame. Put the armature back in and ohm between the brushes. You are looking for shorts and opens. You will get the values jumping up and down as you turn the armature, so look to make sure that the brushes are square on the commutator segment for each reading. Mark the shaft because you only need to rotate the armature 180 degrees in order to check every one.

Lets see where this takes us.

simonl
23rd Sep 2019, 08:22 AM
Thanks Baron. That makes sense. I'll give it a go and report back.

Simon

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simonl
24th Sep 2019, 02:40 PM
Hi Baron,

Ok. The armature windings returned a DC resistance of between 4.0 - 4.3 ohms in every position.

The field windings returned a DC resistance of 1.2K ohms.

I don't have a megger but with my multimeter set to the highest setting (Mega ohms) it returned open circuit for both armature and earth and field winding and earth.

I have cut the wires and freed the circuit board. You will notice a few of the wires are not original, I replaced those last time I had a crack at fixing it.

Also one of the limit switches (one on LHS) is cactus. Does not switch. Looks over heated.

Hope this helps..

Simonhttps://uploads.tapatalk-cdn.com/20190924/afdcf4ac46dfdd156e2ac92288668877.jpghttps://uploads.tapatalk-cdn.com/20190924/6340021e51115b8a97712a130cafabb5.jpghttps://uploads.tapatalk-cdn.com/20190924/f9f898505b5b328f34785833edf4b583.jpg

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simonl
24th Sep 2019, 06:12 PM
Hey Baron,

further to my last post, I'm a bit confused. looking at the circuit schematic it shows both a field winding and a shunt field yet physically looking at the motor and field windings, there are only 2 wires coming out. I can only assume that the motor has been changed over the years and it no longer has a shunt field?

I think I'm only just realising why I may have been confused when looking at the circuit schematic when attempting to repair the wiring.

Simon

BaronJ
24th Sep 2019, 07:03 PM
Hi Simon,

You beat me to that one :) I was about to ask where the other two motor wires were !

OK can you reassemble the motor so that you are able to apply a few volts to it. The field winding will be connected in series with the brushes. It doesn't matter at this point which way round they are connected. In the absence of a variable voltage PSU, I would start with 12 volts from a car battery or similar.

All we are doing at the moment is making sure that the motor is sound.

As far as the micro switches are concerned they are a fairly common one. You might actually find that the rollers will transfer from the old ones to the new ones. I tend to agree that the circuit board is in poor shape. If you want to go down the path of making a new one, I would carefully strip the components from the board and use it as a template for a new one.

Circuit wise modern components would easily replace a lot of what is in there, indeed a triac could be used to replace the thyristors, though their equivalents are available.

Anyway let's make sure that the motor is sound.

simonl
24th Sep 2019, 08:55 PM
Hi Baron,

Ok so I connected the motor up. In series with a 12vdc supply battery to one brush other brush connected to a field winding and the other field winding to battery.

Result: NOTHING!

I then connected a variable 0 - 60v supply. Once again nothing. It drew about 20mA.

I would expect the motor should be at least 150watts. But given the field windings are about 1.2K how would you get the required current draw if they were run in series?

Are you sure the windings don't need to be excited independent from the armature?

Simon

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BaronJ
25th Sep 2019, 01:50 AM
Hi Simon,

That's a little disappointing ! I would have expected the armature to at least try and turn. However you are right the field coils are separately excited from the armature as shown in the diagram. I suggested doing it the way that I did for the easiest. I used to test 220/250 volt washing machine motors using 12 volts. ***

382335
This is a drawing of the basic circuit taken from the diagram. The field coils are inside a diode bridge that is directly wired across the AC supply. The negative junction feeds a pair of diodes that in turn feed the armature via the direction switches. The other side of those switches is the variable voltage from the thyristors.

The transformer simply feeds a low voltage to the thyristor gates to turn them on. Because the transformer is centre tapped the thyristor gates are fed 180 degrees apart. This means that the thyristors are switched on, only on alternate half cycles of the incoming AC supply.

OK, connect the whole 60 volts across the field winding and try the 12 volts from the battery across the armature, and see if it runs at all. It should do.

That motor would only be 50 to 100 watts I would think. Does it say anywhere, on a rating plate ? I note that the one shown in your picture says 120 v 2Amp 60 Hz yet the indicator lamp has a 220 V label on it. The thought occurs to me that the motor might only be for 120 volts and not 220. In which case the field windings would be somewhat stressed at 220 volts even inside a rectifier bridge.


*** The Sinclair C5 used the Hoover washing machine motor on 12 Volts.

simonl
25th Sep 2019, 06:10 AM
Hi Baron,

Thanks for the explanation and circuit.

Wrt the lamp, yes the lamp and circuit breaker are non genuine parts that I sourced locally. They needed replacing and from memory they did not appear on the parts list in the US as available.

The unit runs on 110V via a step down transformer that is mounted in a case on the side of the mill. I figured even at 110V the lamp would still give some indication when switched on.


I'll try wiring up the motor with separate voltages to the armature and field winding.

Really appreciate your help.

Simon

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BaronJ
25th Sep 2019, 02:57 PM
Hi Simon,

That neon indicator lamp might not even light on 110 volts. The resistor value inside will be way too large in value. The 2 amp circuit breaker will be OK though.

Thankyou for the additional information about the transformer power supply. Is it an Isolated output, not an auto transformer. The reason that I ask is if the transformer has an Isolated output then you are not at risk of getting yourself between live mains and earth by using it to feed the motor field windings inside a bridge rectifier as I show in my picture.

We still need to confirm that the motor runs properly before we start to spend more time on it ! If the motor is indeed bad then a new strategy is needed.

simonl
25th Sep 2019, 09:19 PM
Hi Baron,

Connected the armature to one variable independent DC supply and the field coil on another supply. Nothing. It is evedent that the armature is energised because it becomes difficult to move or turn.

Then if I connect the field windings, still nothing happens. There is current flowing through both circuits but the motor has no interest in turning. Are you sure this thing does not need AC?

I ran out of time to test an AC supply but I hope to do that tomorrow.

Simon

BaronJ
26th Sep 2019, 12:35 AM
Hi Simon,

Its a universal motor, it couldn't care less about using AC or DC. In use it will have DC across the field and armature. The field will be a constant voltage because it is inside a diode bridge that is connected directly across the supply, the speed will be controlled by the varying DC voltage coming from the thyristors, the direction determined by the voltage polarity from the thyristors with respect to the polarity of the field coils.

I've just measured the field winding resistance of a similar size motor salvaged from a Kenwood food mixer. Its field winding is only just under 100 ohms !

I'm beginning to suspect that the field winding is basically open circuit. The fact that the armature is sticking to the laminations suggests that there is no magnetic field to push it away.

If you are absolutely sure that you have measured the field windings resistance correctly, you could look for the link wire between them and then measure each coil individually.

simonl
26th Sep 2019, 07:47 AM
Hi Baron,

I'll have another look. 1.3K seems high doesn't it.

I would have thought it would be the armature that burns out, not the field windings, but I only guessing about that. I must admitt to having very limited knowledge about such stuff!

I'm not sure what you mean about mesuring each coil individually. You mean in the field windings? I thought that would be one single piece of copper wire?

Simon

BaronJ
26th Sep 2019, 10:34 PM
Hi Simon,

In modern DC motors the field coils are replaced by powerful magnets. However your motor has two identically wound coils, somewhere there will be a link connecting the ends together. Probably hidden in an insulating sleeve somewhere.

382493

There is another configuration that is sometimes seen, where one end of each of the field windings is attached to one of the brushes and power is fed into the other ends. Your motor is not of this type of construction !

If one or both of the windings has gone high resistance, you could rewind them yourself ! Not a too difficult task but one that would easily be doable with care. But we can tackle that if we need to. For now we need to find out.

As far as the armature not burning up, it will never have had the full mains (110 volts) applied to it. On average maybe less than a third in normal use.

BaronJ
20th Oct 2019, 07:29 PM
Hi Simon,

Since you have not come back on this, I wondered if you have decided not to continue with a repair.

simonl
20th Oct 2019, 08:19 PM
Hi Baron,

No it's still sitting on the bench waiting. I have in fact found an d disconnected the wires that connect one side of the field windings to the other.

However, I have also recently been scraping the shaper ram, finishing the VFD installation on the mill and now just recently about to complete a quick adjust quill feed handle for the same mill.

In between working 60 hours a week....


It's been on my mind. I will tackle it again probably next week.

I really have appreciated your help with this. It probably would have been in the bin long ago if not for your help.

I'm slowly contemplating and preparing myself mentally to rewind the field by hand. It's got a lot of crud and glue which I need to remove in order to unwind and count the number of windings.

Give me a week! [emoji16][emoji106]

Simon

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BaronJ
21st Oct 2019, 05:10 AM
Hi Simon,

I've been watching your thread on scraping your shaper and quietly sympathising ! Having spent quite a lot of time myself learning to scrape little bits in comparison to what you have done.

Being retired there is no panic to do this and do that, so I do as much as I feel at any one time ! Some days its hard work, others fly by with not enough time to complete anything. I try and read the forum daily, though I don't always manage it. I'm here when ever you are ready to continue with this project.

As far as counting the windings is concerned, I would just cut across the bundle, slit the insulation to free the wires then count them and multiply by the length. The other is just to weigh them and measure the wire gauge. Either method will work, and its not that critical as long as both windings are the same.

Do both sides measure the same resistance ?

Anyway shout when ready :)

simonl
21st Oct 2019, 07:53 AM
Thanks Baron,

I am yet to measure both fields separately but I suspect they are not equal by a long shot. I'm confident that the motor does not turn because of the faulty field windings.

Wrt scraping. Yes it's bloody tiring that's for sure. Slow and steady is the go with frequent breaks.

Cheers.

Simon

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simonl
3rd Nov 2019, 08:17 PM
Bit the bullet today and removed half of the field winding. I really have nothing to loose since it was in pretty bad shape. To my surprise it contained two different wire sizes.

31 turns of approx. 0.7mm ECW and several hundred (yet to count them all) of approx. 0.12mm ECW.

I'm a little confused, this does suggest two different windings (as descibed in the circuit schematic) yet only two wires entered the field windings from the circuit board. I was not expecting this and as such I didn't really take notice of how the two types of copper were connected.

Luckily, I am yet to remove the other side of the field winding. I will do this in better light when I have plenty of time and will take better care to see how it all goes.

Here's a pic for anyone interested...

Simon
https://uploads.tapatalk-cdn.com/20191103/7ce478bd34ceb8c86887efa4ac2434d1.jpghttps://uploads.tapatalk-cdn.com/20191103/e20bccddf0789a0fac5d80ca0866e254.jpg

BaronJ
3rd Nov 2019, 08:35 PM
Hi Simon,

Its not uncommon to find that there are two different wire sizes used in a field winding. This is done to provide a heavier wire for making an external connection. You should find a joint somewhere in that lot where the two different wires have been joined. The only other possibility is a closed loop, a bit like a shading ring, a magnetic shunt, like in a small induction motor, but since it has an armature rather than a rotor, I doubt it.

simonl
3rd Nov 2019, 08:54 PM
Thanks Baron,

Guess I'll find out when I remove the other half.

Do you think I can form those windings on a suitable sized jig spun using the lathe and then slide in place or will I need to wind it straight onto the former?

Winding straight onto the former will be awkward and take forever!!!

Simon

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BaronJ
4th Nov 2019, 06:08 AM
Hi Simon,

Yes I'm sure that you can.

Rewind the coils in the same way as it was originally done ! Make a wood former, three pieces of plywood screwed together to form a bobbin. Stick it on a mandrel using the lathe and wind away. If you use the weight method you won't have to count the turns. Alternatively you will have to rig up a counter of some sort.

Wrap the coil in fabric tape in the same way as it was originally and hook it over one side and then form it to fit the other side, putting in the wedges to hold it in place. Make sure that you get the winding direction correct on each side or it will just buzz when powered up. Normally the winding would be shellacked after fitting, to provide insulation and hold the winding rigid.

The hard bit is getting the former the right diameter. If you can get the other coil out in one piece, you could use it as a guide.

NOTE:
If you haven't already removed the other coil, you can place the carcass in a vice and remove the wedges, then use a block of wood and a hammer to flatten the curved part on either side (top & bottom) so that the coil expands out of the slots, then it will just unhook. The new coil is put in place the same way, hook it in the slots and use a shaped piece of wood to form the curve just like the original ones.

familyguy
4th Nov 2019, 11:00 AM
Interesting thread here, motor winding is not that hard, you don't really have anything to lose - I rewound my mill motor from 1ph 240 to 3ph 240, check out the thread here https://metalworkforums.com/f65/t200978-arboga-mill-motor-rewind some of my pics show my hand cranked coil winder made from scrap timber, I watched some videos before I started - quite a few of them show guys in India rewinding motors and using an old piece of wood and a few nails as the coil former.

simonl
4th Nov 2019, 03:50 PM
Hi family guy,

Yes I remember that thread. I even commented that I would never have the ability to do a rewind. Go figure! Never say never I guess.

Mine should in a sense be easier, it only has 2 coils.

I'm just thinking of a way to rig up a counter and then attach it to the lathe.

Simon

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simonl
4th Nov 2019, 07:28 PM
Took the other side out this evening. I was a little more methodical this time. I used a heat gun to soften the glue and varnish. It was still not easy to remove.

This side will give me better info. I can make a former winder based on the sizing of this one.

Simonhttps://uploads.tapatalk-cdn.com/20191104/ede935626dd2aee8b0695e426c7a11ab.jpghttps://uploads.tapatalk-cdn.com/20191104/973d58df0d0b73e445a4cefde6b1ecbe.jpghttps://uploads.tapatalk-cdn.com/20191104/37a601660d288be0521c33528b66ef3c.jpg

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BaronJ
4th Nov 2019, 07:41 PM
Hi Simon,

A micro switch would give you an electrical pulse per revolution. But you would need a solenoid operated counter.

Stustoys
4th Nov 2019, 08:36 PM
I'm just thinking of a way to rig up a counter and then attach it to the lathe.

Do you have a count on turns yet?
How about you think about it as cutting a thread of X length at X pitch?

simonl
4th Nov 2019, 09:08 PM
Hi Baron,

Yea I'm thinking of using an induction sensor and an electronic counter.

Hi Stu,

You have lost me. I'm guessing using the saddle feed as a means of keeping count?

Also, No I don't have a count yet. I'll do that tomorrow when it's quiet and I don't get any distractions....

Simon

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simonl
5th Nov 2019, 04:01 PM
OK. I had another look at the feild winding coil. It's going to do my head in counting the no. turns. I suspect it's near 1000 or so. So I have decided to use Barons' idea and weigh the winding and go from there.

I have ordered a set of "precision" scales that should arrive end of the week:
https://www.ebay.com.au/itm/0-01G-500G-Electronic-Mini-Digital-Pocket-Jewelry-Gold-Weighing-Kitchen-Scales/372068828483?hash=item56a107c543:g:JAkAAOSw8a1ZsP6X

So Baron, or anyone for that matter. Whats the best way to do this?

Weigh the entire field winding, record the figure (call it m); then separate say 10 turns and weigh (call it m10). Divide m10 by 10 (for an average weight of 1 turn call it m1) and then divide the original winding weight m by that last figure m1 to get a rough estimate of the number of turns?

Sound like a plan?

To get a better estimate I could weigh 100 turns and divide by 100. But how accurate do I need to be?

Simon

Stustoys
5th Nov 2019, 07:19 PM
You have lost me. I'm guessing using the saddle feed as a means of keeping count?
Yes, say 500mm of 0.5mm pitch gives you 1000 turns.

But if you are going to use weight I'm not so sure you will need to work out number of turns anyway.

I'm sure BaronJ will be along shortly.

simonl
5th Nov 2019, 07:27 PM
Im constantly impressed by the way you think Stu. I get it now.

Wrt weight, are you suggesting that I can simply weight the windings and then wind some new ones based on weight without even worrying about turn count?

The reason why I suggested the above method is because it allows for deviations in weight from varnish residue/impurities and deviations in enamel copper weight from different manufacturers.

Simon

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Stustoys
5th Nov 2019, 08:03 PM
Well thank you

The reason why I suggested the above method is because it allows for deviations in weight from
As long as you picked windings of average length as there seems to be a fair difference between the inner and outer length.
But at least if you come up with a number making two the same will be easy.

How close they need to be to factory I have no idea and will leave to BaronJ, I'd count turns because I don't know enough to do anything else :D

BaronJ
5th Nov 2019, 09:20 PM
Hi Guys,

The actual number of turns is not critical, 5% variation wouldn't make a lot of difference at all.

I must admit I like Stuarts idea, However yes simply weighing the whole winding and doing the sums will do as well. The only important thing is that both windings should be as identical as possible.

Now the original windings used two different wire sizes ! This was done in order to make secure connections between the very fine wire and the outside world. At the time this motor was made it was probably the most easy way to do this. I would probably go with a modern high temperature plastic covered wire to do the joint. Kynar covered wire springs to mind, since this type is a solid core and a high temperature rated material and is cheaply available in several gauges.

But, there is always a but... Its very hard to strip the insulation without nicking the wire ! It would be my choice rather than PVC, enamelled or similar. Also get enamelled wire that will self strip when you solder it ! Often called "Solder through" or "Self fluxing" Saves a lot of frustration.

Michael G
6th Nov 2019, 07:05 AM
If the important thing is two identical coils, would it be more straight forward to make up two formers and wind both coils at once?

Michael

simonl
6th Nov 2019, 07:26 AM
Hmmm. Well with a bit of pre-planning and some extra thought it maybe a worthwhile to do that.

I'm still not 100% convinced I can pull this off either way. I'm not part singularly good with delicate or fiddly work. I'll wait for my $12 "precision" scales to arrive and make some further measurements.

For $300 I can purchase a new power feed. It's becoming increasingly obvious to me that it's no longer about the money but more the challenge...... as long as I don't spend $299 in a failed attempt! [emoji849]

Simon

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QC Inspector
6th Nov 2019, 07:34 AM
Was poking around and found this company that sells reconditioned units and repairs them too. Maybe it is possible to get windings or a motor from them. A long shot but you have nothing to loose at this point.

https://calmetrics.stores.yahoo.net/powfeedrepse.html

Pete

simonl
6th Nov 2019, 07:52 AM
Hi Pete,

In vast vast search for existing parts etc. I have visited their site and bought some parts from them such as new brushes, brush holders, bottom plastic cover, speed adjust knob and pot. All up about $60 worth of stuff. This was when I was expecting to repair the existing board and components. I replaced the SCR's and rectifying diodes. In the end I either missed something, did something wrong or didn't pick up another person's mistake in their attempt to fix.

I bought this mill from a machinist who wanted to rebuild it but either gave up or who's priorities in life had changed and no longer had the time or the will.

In that time he had it stored at his dad's house and it seems his dad had a "look" into fixing some things....

I saw it as an opportunity to own what seemed like a decent mill for cheap with repairs that were doable.

It came with a 200mm riser block and a universal dividing head so figured I'd get most of my money back i sold them if the mill was scrap.

For $1200 I'm still not sure if it was a bargain but it's probably worth a bit more now and it's nicer to use than my geared head mill!


Edit: they do reconditioning on servo power feeds. And can recondition my power feed even though they say parts are scarce. The cost is US$ 230 and I would have to ship to and from them. Unfortunately it's not an economical proposition.

Simon

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familyguy
6th Nov 2019, 09:57 AM
If it was me I'd be inclined to count the turns, if you feel the number of turns is around a 1000 and you are ok to count out 100 for weighing them then it's not that much more effort to do that 10 times.

I'm not sure if the following also applies to motor windings - I have wound many transformers and one of the steps is to calculate the total area taken by the windings and insulation - this means accurate measurements for the wire and insulation thicknesses are needed, if the total area taken by the windings and insulation is 75% or less of the available space then its good to go, at 80% it might be a bit tight to get everything to fit at 82% or more then the windings and insulation will almost certainly not fit.

BaronJ
6th Nov 2019, 07:35 PM
I'm still not 100% convinced I can pull this off either way. I'm not part singularly good with delicate or fiddly work. I'll wait for my $12 "precision" scales to arrive and make some further measurements.

It's becoming increasingly obvious to me that it's no longer about the money but more the challenge......

Simon


Of course you can do it :) I have complete faith in your abilities !

simonl
7th Nov 2019, 08:38 AM
Thanks for the input guys.

Baron, you have more faith in me than I do! I'm not very good with fiddly stuff. It's likely to end up thrown across the shed! BUT, I've got to at least have a crack before throwing it!

As familyguy says, anything more than 75 - 80% and it's going to be tight. Looking at the former (is that what you call it?) it was not easy removing the factory windings. There's not alot of room in there.

I think I'll do some more hand scraping on the shaper while I wait for my scales!

Simon

BaronJ
7th Nov 2019, 09:13 PM
Hi Simon,

No the former is the bit that you use to wind the coil on ! After winding you remove the former as its no longer needed.

The trick is that you put a layer of tape around the former that you then wind the coil onto, having first put strips of tape under that, bicycle spoke style, so that you can wrap the winding and prevent it coming apart when removing it.

I don't have any pictures that I can show you. I'll do a sketch !

familyguy
8th Nov 2019, 12:43 AM
I agree with BaronJ - it is not that hard - at the end of the day it is just a length of wire wound around a former - not really very technical at all probably there is more skill involved in your hand scraping - here's a couple of youtube links that will give you an idea of the process - each one uses a slightly different methods but end result is the same. Might help you to decide one way or the other.

https://www.youtube.com/watch?v=gJd5Ul3Kc4w
https://www.youtube.com/watch?v=maSxvrkfHNo

BaronJ
8th Nov 2019, 04:43 AM
Hi Guys,

That first video is a great introduction to rewinding Simon's motor stator, particularly since it is so similar !

However he winds two layers at once ! This is fine for a high voltage heavy current motor, Simon's motor isn't.

So only use one layer not two ! I found it interesting that he made no attempt to keep the wires in a bunch when removing it from the former. Also he showed how to size the former to suit the stator, which was nice.

The way that he used transformer paper and super glue was very informative, I've learnt something there !

383205
This is the sort of former that I had in mind. The space underneath the windings would give you space to wrap them and keep them together. However after seeing that first video a wrap of transformer paper would do the same job.

simonl
8th Nov 2019, 09:32 AM
Yea I have wated that video from that Babajan channel. Very interesting. I did notice that he two strands, called bifilar winding?

He certainly makes it look easy. Probably does a nice job and gets paid stuff all for making 50 a day!

Some takeaways for me on that are the former sizing method, the use of superglue and the use of that former paper. Is that a special type of paper or can I just use some heavy paper from office works?

Actually, I'm not sold on the use of paper. I think that some cotton warp, maybe 1/2" wide may do a better job and keeping in tight. However it's also going to make it bulkier too I guess.

Hope my scales come today.

Simon

waxen
8th Nov 2019, 01:51 PM
Transformer paper
https://new.abb.com/products/transformers/transformer-components/insulation-components-and-materials/transformer-insulation-paper

BaronJ
8th Nov 2019, 07:58 PM
Hi Guys,

I used to have several rolls of paper like that, not having any real use for them they got thrown away, along with hundreds of reels of enamelled and cotton covered Litz wire that went to the scrap yard ! I regret not keeping any. Though I do wonder what it would have been worth today.

One other point that I found interesting in the videos was the use of varnish that he just poured over the windings, I thought that it could become very messy even though he did use a drip tray.

simonl
12th Nov 2019, 08:05 PM
Ok. Scales arrived today.

I weighed the field windings after removing the 30 turns of the heavier wire.

I parted and cut a random amount of the windings, weighed it and proceeded to count.... all 331 turns. 331 turns weighed 6.10g.

The entire coil weighed 46.54g.

That means approx 2500 turns of 0.125mm ecw, not including the 30 turns of 0.75mm ecm at each end.

A $300 power feed is starting to look attractive....

Simon

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BaronJ
12th Nov 2019, 09:57 PM
Hi Simon,

That wire at 0.125 mm diameter, sounds like 16 AWG , take off a bit for the enamel and you get 18 AWG which is about 6.5 Ohms per 1000 feet, times 2.5 = 17 Ohms. that seems a little low to me !

I would have expected nearer to 50 or 60 Ohms. You could easily salvage that from an old wall wart !

simonl
13th Nov 2019, 09:23 AM
Hi Baron,

I'm confused. At 0.125mm I thought that would be 36 awg wire.

This has a mass of 0.076 lb/1000 ft.

That's 34.47g / 1000 ft (please excuse my mixed metric/imperial units)

At 46.54g that means 1350 ft of field winding.

36 awg wire is quoted at 445 ohm / 1000 ft.

That equates to a dc resistance of 600 ohms per winding.

Given I measured a resistance of 1.2k it seems about right?

Simon

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BaronJ
13th Nov 2019, 02:51 PM
Hi Simon,

I have me confused too ! I've obviously looked at the wrong value and got the resistance value wrong.

0.12 mm is 36 AWG, you are right it is around 415 Ohms per 1000 feet.

So your 600 Ohms figure is in the ball park.

The tables that I used were from the ARRL handbook, but I found this on line

https://www.rapidtables.com/calc/wire/wire-gauge-chart.html

Whilst not identical the calculator is OK.

I'll measure a couple of wall wart transformers later, because I'm sure that could be a cheap source of wire.

*****************************************
OK ! I've measured several. The highest reading I got was 650 Ohms primary and that was a 5 volt 1 amp DC output
and the lowest was 120 Ohms primary and 24 volt 1 amp DC output. There were various readings from several others between those two values, having output voltages between 5 and 24 volts all having output currents between 0.5 amps and 1.2 amps.

I also measured a shaded pole fan motor with a winding resistance of 160 Ohms.

Based on these measurements I'm not convinced that 600 Ohms is correct.

simonl
15th Nov 2019, 08:52 AM
Thing is, before I took the field windings apart, I measured the DC resistance as approx. 1.2K yet I couldn't get the motor working.

I'm still confident that my sample measurement and extrapolation of results has yielded a sensible result for the number of turns though. Not sure where I could have gone wrong with my calculations?

Simon

BaronJ
15th Nov 2019, 08:35 PM
Hi Simon,

Basic Ohms law says that 110 volts / 1200 Ohms = 0.090 ma. 110 volts x 0.090 = 10 watts.

I would have expected more than that, particularly since the armature resistance is so low !

BaronJ
16th Nov 2019, 09:03 PM
Hi Simon,

As you will know I've been measuring the winding resistance of a few transformers and the like recently. Well today I decided to have a look at an old microwave oven transformer. I measured the high voltage winding at several thousand ohms. Breaking off one end of the wire, I've discovered that it measures 12 thou diameter. Using the tables on

Wire gauge size chart | AWG table (http://www.rapidtables.com/calc/wire/wire-gauge-chart.html)

That tells me it is 36 SWG and 414 Ohms per 1000 ft. So 110v / 414 Ohms = 0.265 Amps. About 30 Watts.

These transformers are readily available and fairly easy to strip the windings off, so that would be a cheap source of suitable wire.

Let me know what you think !

simonl
17th Nov 2019, 10:02 AM
Hi Baron,

I really appreciate your continued help with this.

I found this on ebay, at $12 including free delivery I thought it was a reasonable gamble.

https://www.ebay.com.au/itm/Enamelled-Copper-Wire-SMALL-Dia-0-06-to-0-30-mm-Solderable-Wide-range/163600801163?var=463171662447&hash=item26175e1d8b:m:m40sCth1jrJOAy1vkbwr6DQ

I would have prefered the 900M roll but it's out of stock. In any case, the coil weighed 46g (including 40 years of crud and bit of varnish) so a 50g roll for each coil should do the trick.

Simon

BaronJ
17th Nov 2019, 10:34 PM
Hi Simon,

Yes that would do the job, nice that its solder through as well !

As you know am all for salvage and reuse ! The microwave transformer as a doner source of wire would be much cheaper and throw away if you make a mess of it.

OK you would have to mess about a bit to remove the winding, but there is enough on them to wind several coils.
I've already come up with a design for a winding jig that would let you wind both coils at one time based on the weight of the wire, rather than counting turns. You would however have to wind two spools of wire first from the transformer. A piece of cardboard postal tube will do.

Run enough wire to get say 40 - 45 grms on to half the tube, put a cardboard spacer on the tube to keep the wires separated and then wind another 40 grms on the other side. This will give you two known weights of wire. These will then wind two virtually identical windings. Simply wind on until the weight is about right, as I have said, its not critical.

HTH.

simonl
22nd Nov 2019, 08:39 AM
Hi Baron,

Yep Im with you. I really get a kick out of re-purposing stuff.

However, I have looked (mainly on eBay) for both new and S/H high voltage microwave transformer/power supplies and can't find any for cheaper than the copper wire I linked above.

OK if I happen to find one of the naturestrip as can happen from time to time but they are never around when you actually need one!

Got some other stuff on atm and my wife has started a new job in a completely different industry after 19 years in her old job. So things take time to get back into a "normal" routine.

I think I'll purchase that ecw anyway and having it waiting when I get a chance.

Simon

simonl
22nd Nov 2019, 03:52 PM
Was at school assembly today for school pickup. Talking to one of the mums that I know well, we got onto the conversation that included her telling me that she just bought a new microwave oven. Asked what she did with the old one.... she still has it. Looks like I have actually scored a free microwave oven for parts!

Less than 8 hours after my last post telling you that I can't find one for cheap! Funny hey?

Simon

BaronJ
22nd Nov 2019, 10:03 PM
Hi Simon,

Glad you managed to find one ! Those transformers can be very useful, not just for salvaging the wire from the transformer, but for other things ! Such as a spot welder ! Also there are some useful parts in there. But no way buy an old one ! I've had a couple just thrown over the back gate that I've stripped bits from and kept. Unfortunately the newer transformerless, inverter ones are not worth bothering with unless you want the micro switches. You can easily tell the difference because the good ones are very one side heavy, the transformer being behind the control panel.

If you see one dumped, pick it up ! I certainly wouldn't pass one up !

Once you have your transformer, very carefully cut the laminations away without damaging the wire, so that you can push the winding off the bottom of the core. At this point you can now find the end of the wire. Usually the spade connector is the place to start, as this is usually secured by tape holding it down.

Now use a cardboard postal tube or similar to wind on two piles of wire of about the same weight. Weigh the lot, so that you know how much weight you have. The actual weight doesn't matter as long as it is greater than the total weight of wire than you need. When you come to do the actual motor windings, you will be winding two coils at the same time so they will be identical. Now all you have to do is weigh the donor wire to work out the weight of wire you have wound onto the winding jig.

As far as a winding jig is concerned, four 3" inch nails and some plywood, a length of all thread.
Drill four holes in three suitable pieces of ply to suit the original winding corners, so that the nails will be a firm push fit. Make two spacers to fit over the all thread to separate the cheeks by the winding width. Clamp the lot together with nuts and washers so that you can spin it in the lathe.

Hope all this makes sense :)

familyguy
23rd Nov 2019, 12:18 PM
I've been away for 2 weeks and not sure where you are with this motor or even if you intend to try a rewind but you may find it easier to salvage the wire from the microwave oven fan motor if the wire size matches, I've found that the fan motor windings are usually not dipped in varnish which make it easy to get to the wire. The transformer is usually welded together which means taking a side grinder to it to get to the windings which are often - but not always - dipped in varnish.

Not sure what you have in your junk box but another good source of wire is old 3 phase contactor sets, the 24v coil ones will usually have wire that will be too thick but the 240v coils usually have wire around .12mm in diam.