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generator my question: why have the movable brush on 31 gen. when we have regulator on unit to control output. what is max output, and min. output if no third brush? my generator is all apert ,the guy i got it from had case,end plates chromed,nice. i see from leading parts houses cat. drawing that exploded view shows how it goes together... new armature was in box too. rewrapped fields and going to put in service sometime on my 31.....thanks for input.....kev:cool:
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Re: generator Kevinmac,
What type of regulator do you have ? The normal can on the top is a cut-out, not a regulator. Marc |
Re: generator John Regan makes a regulator that looks like a cutout and you use the third brush to set the maximum output. I make an electronic voltage regulator that fits in place of the adjustable brush, and uses the stock cutout on top of the generator.
The cutout is simply an off/on switch that turns off when the generator output falls below battery voltage. This keeps the battery from feeding back into the generator and killing the battery or burning up the generator, or both. |
Re: generator Disconnected from the battery, a Model A generator will put up to (possibly) 32 volts depending if you hit that 'sweet spot' where the 3rd brush position maximizes output.
In real life if you paired the generator up to a 6V battery and generated 32 volts, you'd seriously overcharge the battery in short order. Thus, normal positioning of the 3rd brush is to make the generator generate about 8 volts (say) and maintain anywhere from 5 or 6 to possibly as much as 10 amps (or even a skosh more if you do a lot of starting at night when the engine doesn't get a chance to catch up on charge.) We're not so much interested in voltage because in these ranges, the battery holds it all back to about 6.5 or so (and so you don't blow light bulbs.) Not sure of what he has left you with his "all dressed up and nowhere to go" generator. He may have been headed for a totally regulated circuit? There are different ways to accomplish the thing most of them done by regulating the generator field and doing away with the adjustable brush altogether. I'm not sure how Tom does it, but he may keep the 3rd brush and use that output with his regulator. Take a look at the Ford wiring diagram, which if you zero in on the generator alone, gives you that "stock" wiring. Perhaps you can correlate to this and get your electrical bearings and figure out what you have. Tom (and I with less assurance) will give you clues later as to polarity, flashing the generator, and other details which can undo all your close examination and attempts to make something work. Wiring diagram at http://www.webjunk.com/modela/wp-con...amcolor2sm.jpg The Model A generator is seriously simple, as you can see. Joe K |
Re: generator Joe K,
Actually, the third brush regulates the amount of current only as the Model A generator is a constant current generator. Thus, for a constant current device, the voltage rises or falls to make the amount of current equal to what the third brush is set to. That's why the voltage rises to such a high level when the generator's output is disconnected...it's trying to push current into an open circuit and only knows to keep raising the amount. The battery keeps the voltage to the proper value and the ammeter shows how much current is going into the battery. Sorry, but I don't have a better explanation. Marc |
Re: generator Quote:
In practicality, the voltage changes are relatively small and the battery acts as "electrical flywheel" taking on and giving out electrical energy as required. I tink we both said the same thing but with a different focus. Joe K |
Re: generator so, Marc, is it correct to say that in a sense the battery is acting as a resistor the way you describe the circuit? What makes the gen a constant current device?
(of course all batteries do have internal resistance as we all know). Or are all gens constant current? The only parts gens have are 1) armature 2) field. Is this why some are able to adjust their gen to work on a 12V system and actually have that work? dave |
Re: generator When I worked at the farm, we converted a Ford 9N 6V to 12V service. The owner had been having problems with cold weather starting and felt that 12V would give it some additional energy for starting. (which it does certainly by putting 2x the amount of energy into the same battery envelope as it is twice the voltage.)
The tractor had a generator which was "two wire" as I recall. (no third brush and one wire coming out was the output and the other wire going in was for the field.) The only change to the tractor was to change the regulator to a 12V regulator and -voila the machine was instantly a 12V generator. I looked it up on the Internet (wot a tool this Internet) and confirmed my statement. http://www.mytractorforum.com/attach...1&d=1177096863 9N tractor circuit diagram above. The wiring coming off the right-hand side of the generator and connecting to the voltage regulator is the ground shown diagramatically. The other two wires are output and field supply. We made no other changes to the tractor and used the existing drum type bendix gear without issues. Well, it would "slam" pretty hard I thought compared to before, but the owner thought the drum bendix was equal to the task. We'll have to see what KevinMac can offer further for information on his spitshine generator but something like this may have been where his prior owner was headed. It is a more conventional setup - used post WWII until alternators became standard after the invention of diodes. Joe K |
Re: generator Joe K,
Yes, you can make an analogy with the battery as a "fly wheel". tbirdbird...For a generator that has the field connected to the armature, the device becomes a constant current device. The adjustment, third brush, decreases the amount of armature voltage, but the important thing is that the amount of energy to the field is directly related to the amount of energy from the armature. Voltage regulators vary the amount of field current to keep the voltage constant. Hard to describe the operation in detail as a lot of "electrical" stuff is needed , but the important thing is that the generator puts out a fixed amount of current set by the third brush and the battery takes in the "extra" that the car's electrical load doesn't need. Marc |
Re: generator http://en.wikipedia.org/wiki/Shunt_generator describes the differences between a series wound generator and a shunt wound generator.
The Model A generator is shunt wound, but of special kind in that the voltage impressed across the field is a function of the position of the 3rd brush. Thus at a constant rpm, the operator can adust the voltage of the field, and thereby adjust the current and voltage both of the output. Quoting the article above: Quote:
We can throw the additional variable of engine/generator speed at this as well, but it only serves to provide a different starting point for the movement of that third brush. I will be willing to simply call it a draw at this point. We cyberly shake hands and call our differences "interesting." This so we can better help the guy going forward. I think the ball is in his court now. Joe K |
Re: generator Quote:
Sorry to hear about the chromed parts. :rolleyes: |
Re: generator 1 Attachment(s)
James Peterson has a neat deal where he put a regulator on the back of the Model A Generator band. He has instructions how to hook it up and you disable the third brush. It's all inside and doesn't show. I will try to add a picture of it.
https://www.fordbarn.com/forum/attach...1&d=1424786450 |
Re: generator I was reading in a book "Direct-Current Machinery" first published in 1934 about the automobile generator. Quite interesting as the design of the generator had a number of deviations from a standard "generator" to make the output work correctly with a Storage battery.
Thus, if you get your information from sources of "shunt fed generator", you will not know about some of the clever design methods that are unique to the auto generator. This isn't the place to type in many pages from the textbook (junior year at College), but if you want to learn about it, make sure that you "goggle" for 1920's/30's auto technology, rather than just a random approach for a generator. Marc |
Re: generator Marc, care to post a link? I am not having much luck googling.....
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Re: generator I'm seeing on books.google "Direct Current Machinery" by Pender 1922 as a READ
Also "Direct Current Machinery" by McFarland 1938 as a Snippet View. Is it either of these you're seeing? There may be others in Hathi trust or any of the other archive sites. Joe K |
Re: generator Bird & Joe
The book I have is "Direct Current Machinery" by Royce G. Kloeffler, Jesse Brenneman, and Russel Kerchner. It was first published in 1934 and thus has lots of info on the "then current" technology for generators. The book had more printing and the one I have was printed in 1947 for an Electrical Engineering class at Cornell, taken by my father. I looked in my electric machinery text book for 1970 (UMass) and it didn't have lots of info about the auto generators in the 1920's\30's. Good reason to keep old books ! Marc |
Re: generator The book shows on Archive.org as a 1948 book.
If I can get it to download, I'll take a look at it tonight. "A day without learning is a day wasted." ~ Anon. Joe K Edit: The title sounds AWFULLY familiar - I think I may have it at home - from MY father's college experience. I do LOOOVE old books - even the smell. And the illustrations are SO much better than you find in our generation's texts. |
Re: generator Old books have "soul".....
With regard to the car info, it's on page 296 or section 177 in my book. Marc |
Re: generator That's a no-go on the book for me. Archive.com requires a membership and the book is actually found elsewhere. They carry it as reference only.
books.google has a "snippet" version and I can see the top of page 296 where it starts to address "acyclic dynamos" - but I don't think this is connected with the subject of our discussion (more on the lines of a "faraday" disk generator methinks.) So this will have to wait until I check the personal library this weekend. Fingers crossed. Joe K |
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