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1A21 generator 24volt generator relay

Kohlerallen

Registered
I have a generator that appears to be about from 1940, received it in a non-running condition. Have cleaned it up internally and externally, and have it running. It starts by itself upon turning on a 110 volt load but does not produce power unless I manually close the points on the generator relay. Then I have all the power I want. Upon checking the coil leads I find that they show totally open with an ohm meter. Does anyone have a spare one of these relays, or even just the electromagnet coil that they might be willing to part with?
 

dkamp

eMail NOT Working
I don't have one, hopefully someone here has a parts set that would have a good one to put yours back in operation.

IF you cannot find one, the other possibility would be to carefully unwind the original, and wind in new wire to the old one... that is, if it really is open. You MIGHT find on disassembly that the break is somewhere close enough to one end or the other to repair and reassemble. I've done it with other relays of it's vintage and design, but not this one... but it shouldn't be a big deal.

Rewinding these isn't incredibly scientific- they were made using simple processes that a little ingenuity will replicate. Making a fixture from softwood to hold the coil as it is unwound and rewound, and putting it on some convenient drive, with a mechanical turns counter, will allow it to pay out efficiently. Having another fixture with a reel that can gather up the winding as you pay it out will give you an option to re-use the wire, or at least, keep your shop from becoming a huge mess.

Winding a new coil is simply a matter of loading the correct conductor onto your form, and keeping the winding organdized and tidy as it's wrapped onto the form. Once on the form, secure the ends, coat it thick with some flavor of varnish (polyeurethane works), let it set up, and then remove it from the coil form, put it back onto the relay armature and wire it up.
 

Kohlerallen

Registered
I don't have one, hopefully someone here has a parts set that would have a good one to put yours back in operation.

IF you cannot find one, the other possibility would be to carefully unwind the original, and wind in new wire to the old one... that is, if it really is open. You MIGHT find on disassembly that the break is somewhere close enough to one end or the other to repair and reassemble. I've done it with other relays of it's vintage and design, but not this one... but it shouldn't be a big deal.

Rewinding these isn't incredibly scientific- they were made using simple processes that a little ingenuity will replicate. Making a fixture from softwood to hold the coil as it is unwound and rewound, and putting it on some convenient drive, with a mechanical turns counter, will allow it to pay out efficiently. Having another fixture with a reel that can gather up the winding as you pay it out will give you an option to re-use the wire, or at least, keep your shop from becoming a huge mess.

Winding a new coil is simply a matter of loading the correct conductor onto your form, and keeping the winding organdized and tidy as it's wrapped onto the form. Once on the form, secure the ends, coat it thick with some flavor of varnish (polyeurethane works), let it set up, and then remove it from the coil form, put it back onto the relay armature and wire it up.
I'm thinking that might be the way I have to go, I realized today that the coil is not 24 volts. I measured voltage at the terminal feeding the coil and found it to be 60 volts. I had been thinking of wiring in a modern relay, but that is going to now be a problem.
 

dkamp

eMail NOT Working
When it's running, but has no load, it MIGHT be seeing 60v... but when it's active (meaning, the coil is carrying current), it may actually be CARRYING current at 24vdc. Two factors at play here- first is that the circuit may have both 120VAC and 24VDC on the same conductor... and your meter (particularly if it's a digital meter) may be seeing components of the AC atop the DC, and thus, not an accurate reading.

Realize that if you put 120vac on a coil, the coil's inductive nature will limit current flow, and if inductive reactance at 60hz is high enough, NO AC current will flow... just the DC current. Designs like this, are what make it such a hidden marvel.

Youngsters of the 'information age' usually don't understand things like this, but Old tech is remarkably cool. The technology lies not in an intricately-designed highly-integrated staff of LOTS of tiny silicon components and complex coding... but rather, a very simply-made, but very insightful, robust, and practical design.

When you see parts like these, realize that humans made them by hand. That means... you can REBUILD them by hand. Look at it, and imagine the circumstances faced by those who mass-produced them. Replicate their circumstances, and duplicate their work... success will be yours.
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
The exciter is 50 ~ 60 volts, but the relay coil is in series with a resistor.
 

Kohlerallen

Registered
When it's running, but has no load, it MIGHT be seeing 60v... but when it's active (meaning, the coil is carrying current), it may actually be CARRYING current at 24vdc. Two factors at play here- first is that the circuit may have both 120VAC and 24VDC on the same conductor... and your meter (particularly if it's a digital meter) may be seeing components of the AC atop the DC, and thus, not an accurate reading.

Realize that if you put 120vac on a coil, the coil's inductive nature will limit current flow, and if inductive reactance at 60hz is high enough, NO AC current will flow... just the DC current. Designs like this, are what make it such a hidden marvel.

Youngsters of the 'information age' usually don't understand things like this, but Old tech is remarkably cool. The technology lies not in an intricately-designed highly-integrated staff of LOTS of tiny silicon components and complex coding... but rather, a very simply-made, but very insightful, robust, and practical design.

When you see parts like these, realize that humans made them by hand. That means... you can REBUILD them by hand. Look at it, and imagine the circumstances faced by those who mass-produced them. Replicate their circumstances, and duplicate their work... success will be yours.
I'm not too confident in my ability (or patience) to do an intricate task like this. Would you be willing to try to unwind and rewind my coil? I of course would be willing to pay you for your time.
 

dkamp

eMail NOT Working
Hee hee... Hi Allen!

Got your coil today... or should I say... 'brick'... ;-D Yeah, this one won't unwind very well, SO... I'm gonna do some forensic engineering, make a winding form, and build up a replacement using educated estimation of length.

For everyone's benefit, I'll document the process here!

First, I'll calculate the cross-section, and estimate how many turns it'd require to make that stack. this won't get incredibly precise, but it'll get a ballpark for comparison.

Next, I'll estimate the resistance based on wire size and length, in comparison to the circuit voltage. Then I'll take an ohmmeter to my unit's coil, and HOPE that it's about-the-same-dude, which it probably is.

Then I'll put all these numbers on the table, and see where they fall. It'll be a 'love triangle' of three estimations, all I have to do then, is choose... do I do an average (falling dead-center of the triangle) or weight it more towards one direction than the other.

Making the new coil starts with woodworking- I make a thimble form that can be disassembled once the coil is wound, then I make a fixture to hold and turn the thimble. I'll affix a turns-counter to it, and a holder for the spool of wire you included, and a friction guide to keep the wire taut as it's passing onto the spinning thimble.


The wire Allen found and included, is Remington Industries Elektrisola P155. This is a 35awg Polyamideimide-insulation magnet wire. Polyamideimide a modern alternative to varnish-covered wire that I've not used before, but it looks very promising.

I have wound many inductors for my HAM radio gear, I've re-wound some relays and contactors, this will be my first opportunity to wind a replacement coil for a Kohler. It will be fun- stay tuned!!! Photos of the process to follow!
 

Kohlerallen

Registered
Hee hee... Hi Allen!

Got your coil today... or should I say... 'brick'... ;-D Yeah, this one won't unwind very well, SO... I'm gonna do some forensic engineering, make a winding form, and build up a replacement using educated estimation of length.

For everyone's benefit, I'll document the process here!

First, I'll calculate the cross-section, and estimate how many turns it'd require to make that stack. this won't get incredibly precise, but it'll get a ballpark for comparison.

Next, I'll estimate the resistance based on wire size and length, in comparison to the circuit voltage. Then I'll take an ohmmeter to my unit's coil, and HOPE that it's about-the-same-dude, which it probably is.

Then I'll put all these numbers on the table, and see where they fall. It'll be a 'love triangle' of three estimations, all I have to do then, is choose... do I do an average (falling dead-center of the triangle) or weight it more towards one direction than the other.

Making the new coil starts with woodworking- I make a thimble form that can be disassembled once the coil is wound, then I make a fixture to hold and turn the thimble. I'll affix a turns-counter to it, and a holder for the spool of wire you included, and a friction guide to keep the wire taut as it's passing onto the spinning thimble.


The wire Allen found and included, is Remington Industries Elektrisola P155. This is a 35awg Polyamideimide-insulation magnet wire. Polyamideimide a modern alternative to varnish-covered wire that I've not used before, but it looks very promising.

I have wound many inductors for my HAM radio gear, I've re-wound some relays and contactors, this will be my first opportunity to wind a replacement coil for a Kohler. It will be fun- stay tuned!!! Photos of the process to follow!
Now you understand why my confidence level for the project was so low. Good luck!
 

dkamp

eMail NOT Working
:ROFLMAO::ROFLMAO::ROFLMAO: No sweat, Allen- it's one of those things. Once I get done, I might send 'ya the jig to wind 'em, and you'll get sucked into the business of providing aftermarket replacement coils for old Kohler generators!!!
 

Kohlerallen

Registered
:ROFLMAO::ROFLMAO::ROFLMAO: No sweat, Allen- it's one of those things. Once I get done, I might send 'ya the jig to wind 'em, and you'll get sucked into the business of providing aftermarket replacement coils for old Kohler generators!!!
Just what I need. Another thing to keep my retirement life busy!
 

Zephyr7

Registered
Polyamide is good stuff, sometimes known as “kapton”. I have used it many times, and prefer it for magnet wire because it’s more durable. 155 wire is usually the “solderable” stuff that you can strip with a soldering iron and a molten blob of solder. I like the H200C stuff which can take a lot more heat, but has to be mechanically stripped.

Dkamp, if you can see the core size, just work out how many turns it would take to build up the same OD over the coil from that core, the. Multiply that by how many wire diameters it would take to fill the form in the other axis. You’ll want a good micrometer for this. Resistance measurements usually aren’t going to be accurate enough for turn counting, even with a 4 wire ohm meter.

On the plus side, this is an entirely doable project! I’ve rewound transformers before to get the voltages I wanted, it’s tedious but not difficult. If you want to do a really nice job, bake the coil in varnish under vacuum when you’re done winding it. This is known as “vacuum impregnating” the coil. You can do this in an old pressure cooker used backwards as a vacuum chamber, or have a motor rewind shop do it. It’s easier and probably also cheaper to have a rewind shop do the vacuum baking step for you since the varnish is REALLY expensive and usually has minimum orders of a gallon or more.

Bill
 

dkamp

eMail NOT Working
Thanks for the notes and the tip, Bill- I've wound others, did not put them under vacuum, but I actually have a painting pressure pot, and I believe it's structurally viable for pulling vacuum... I also have a pretty stout vacuum pump that came from a pointy-headed Appalachian-American... but as you noted, the varnish isn't ordinary stuff. Do you think vacuum-impregnating this coil is beneficial enough to warrant the circumstance?

I do plan on using the cross-section calcs to get in the right ballpark. I'll do resistance calcs and see if the numbers fall in same realm as the application's voltage suggests. When it's all sorted out, I'll probably aim a little high (add more turns than calculated), then have Allen test it... and if the turns count is too high, it shouldn't be difficult to pop it out, unwind some, and try again.

IF there's plenty of material left on this spool, I might wind a second. We shall see. First- build the form!
 

dkamp

eMail NOT Working
coil caliper.jpgSo I dimensioned the coil, and the paper 'liner' that protects the coil from the armature it encircles.
liner.jpg
 

dkamp

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I measured the core's overall dimensions:
Inside at 25.95mm x 20.37mm.
Outside 42.85mm x 35.75mm.

The winding CROSS SECTION came to 16.25 wide x 7.9mm high.

Then I verified the wire thickness:
original wire size.jpg
0.174 comes out to 34AWG... granted this has varnish on it, so the wire is a little smaller than 0.174 on account of the varnish, but that's where it is.

Time to do some math...
 

dkamp

eMail NOT Working
1A21coil.JPG

So at 16.25mm x 7.90mm, with 0.173mm wire, that's
16.25/0.173 = 94 diameters wide by
7.90/0.173 = 46 diameters high

94x46=4290 turns.

The coil average circumference is calculated by finding a midway between ID and OD on both vertical and horizontal. Outer windings will be longer, inner will be shorter, but the lengths cancel out IF you calculate the 'middle', so:

Average winding turn will be 123.8mm.

4290 turns at 123.8 will be 531m (161.8ft) long.

That all sounds about right so far...
 
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dkamp

eMail NOT Working
BTW... I DO have better mics than the subject in photo, but this one has a digital display that's easy to see in a photo, and the variation occurring in the coil makes it's accuracy irrelevant.
 

Zephyr7

Registered
Digital micrometers always feel like cheating to me, so I like to use my nice starrett vernier caliper. Smooth and no electronics! I’d never give up my digital caliper though, never! :)

I seem to remember thinking the same as you once that “calculating from the middle averages out”, and then finding out it doesn’t. It’s weighted a bit to the longer side in terms of overall length because it’s not a linear change the way you’d expect it to be. It’s been a while, but that’s what I remember so be careful.

Yes, I’d vacuum impregnate the coil. I’d always vacuum impregnate a coil that I want to last. You can probably get a motor rewind shop to do it cheap since it’s quick and easy for them with their always-running setup.

Bill
 
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