Edison dynamo

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deverett

deverett
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I've recently completed making an Edison dynamo from about 1890. This has been an on/off project for a couple of years filling in during other jobs.

Complete 1 (Medium).jpeg


Complete 2 (Medium).jpeg


Complete 3 (Medium).jpeg


It started off with me buying a set of castings from Poland. At the time, I had no idea what an Edison dynamo was or looked like, but it seemed like an interesting project and the price was cheap. The kit was quite complete including the rotor, which looks like it came from an old electric drill.

1 castings (Medium).jpeg


Looking at pics of Edison dynamos on the internet, I soon realised that the model as designed would not look anything like the real thing. I tried to modify the base casting to match the full size, but eventually gave up on that idea, so everything apart from the bearing housings and rotor were ditched and I set about carrying on with odds and sods lying around.

The numerous internet pics were of different sized machines and in different state of preservation/decay, but most of them showed a family likeness regardless of generating capacity. So I have no idea what size/generating capacity this represents. The motor armature was the dictating factor of model size.


Dave
The Emerald Isle
 

kuhncw

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Dave,

Nice work on an interesting project. Have you driven it to check voltage, etc?

Chuck
 

Rod Cole

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I was thinking the same as I hit post, how is the out-put?
 

k2steve

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Great looking model. Do you have plans to power it with a engine?
 

deverett

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Rod
I bought the kit off eBay, and as far as I know it was just a feeler for eBay sales because they have not advertised there since. The Polish company can be found here: https://www.danielasteam.com/e-generator-kit
If you look at their finished article and mine, you will understand why I changed it. I would not recommend buying the kit, everything is so simple to make up from stock materials. I should have taken the ball bearings off the rotor shaft, but was worried that I would score it in the process.
Ron M 4.JPG

These two were the main inspiration for my version, although they are a slightly later version.

Chuck et al
I haven't yet powered it up. Wondering what to use as a flat belt. My latest idea is a strip of denim from old jeans, dyed in tea and with some pva glue added to prevent fraying; trying to replicate a canvas belt. I tried a strip of leather, but that wasn't a success. I'll be using a fractional hp electric motor to power it (I don't have a suitable model engine).

Dave
The Emerald Isle
 

Jasonb

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bobden72

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Hi Dave nice dynamos but showing my ignorance what does the large leaver to the rear of the stator do please.
 

deverett

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JB.
I'll try my 'artificial canvas' first and if not successful, I might try you r suggestion.
Have you watched this video

Bob
The lever on the bridge piece is the on/off switch. The other (larger) one adjusts the phase (I think) but to be honest I don't have a clue!
Come up and see it at Doncaster in May.

Dave
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bobden72

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JB.
I'll try my 'artificial canvas' first and if not successful, I might try you r suggestion.
Have you watched this video

Bob
The lever on the bridge piece is the on/off switch. The other (larger) one adjusts the phase (I think) but to be honest I don't have a clue!
Come up and see it at Doncaster in May.

Dave
The Emerald Isle
Thanks for that Dave yes I can see now how it would change the phase of the output. Would love to come and see it in May but by then I will be half way through walking from Lands End to John O Groats. Will catch up with you some time.
 

deverett

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Thanks for that Dave yes I can see now how it would change the phase of the output. Would love to come and see it in May but by then I will be half way through walking from Lands End to John O Groats. Will catch up with you some time.
Only a small detour then?

Dave
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tjwal

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Very nice. The ephf museum is only a few hundred kms away. I’ll have to check it out someday.
The large lever is to adjust the angle of the brushes and hence the rotor magnetic field angle in relation to the armature field. Since this is a DC generator it really doesn’t change the phase. I don’t recall why this is done but I’m guessing that it has to do with the optimum rotor/armature angle changing with load.
 

Jasonb

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Thank's Dave, I think I did come across that one a while ago, bit bigger than what I'm thinking of which will be more along the lined of the Edison antique fan motors which could almost be made full size. The problem with all these videos and images is that I get distracted by other things that come up, this "electric engine" was something I saw while looking at the bi polar motors and had to make one.

 

bobcjohn

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We have museum in town that has one of Edison's type K dynamos in the basement, (poor condition). They allowed me to gather dimensions and pictures a few years ago. I built a dynamo based on those dimensions. It was scaled from an old armature (2" dia) I had in the junk drawer. Initially, I had to run it as a motor to put a small magnetic field into the poles. At first it would only produce 3 volt at no load, but the more I used the better it got, magnetic field I'd guess. Now it will run 12 volts no load and drop to 6 volts depending on the load. I found that the handle that moves the brushes changes the voltage. I was told that's because it picks the voltage off of the armature at different angles to the pole magnetic line of flux. 90° is the highest voltage.

Your dynamo is a much better representation of the Edison dynamo than mine. I'd be real interested in your test results.

Don't know how to insert a picture, sorry about that.
 

skyline1

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I used to work for a motor and generator manufacturer some years ago and that lever is indeed for altering the angle of the brushes with respect to the field slightly to maximize (or reduce) output.
as bobcjohn has explained
Large modern machines often have it too but it is preset by the manufacturer and doesn't need to be touched.

bobcjohn yes they do get more powerful as time goes on in fact self exciting machines have a small number of magnetic steel plates in the field poles along with the normal "soft" iron ones to maintain a little residual magnetism. this helps the machine "pick up"

As the machine starts it acts as a primitive permag machine which produces a small voltage energising the field which then produces more voltage further energising the field and so on until it reaches full power

But this only happens when there is a little residual magnetism in the first place. This is probably what was happening with your machine it was remagnetising itself. Running it as a motor for a little while was exactly what we did on full size machines for exactly the same reason. It also "beds in" the brushes.

jasonb I love your little solenoid motor I might build something like it myself. It makes some nice sparks from the switches. This is due to the back EMF from the solenoid coils as the magnetic field collapses. If you put your fingers across the coil while it is running you will probably actually feel them. They can be several hundred volts but with negligible energy unless it is a VERY large coil. (Attention Mr Tesla)

These back EMFs might zap your USB power supply eventually though. The best way to deal with it is to put a reverse biased diode across the coil ( CATHODE to coil +ve NOT ANODE) a 1N5408 or similar would be ideal
This will also prolong the life of your "switches" and they only cost pennies.

Best Regards Mark
 

TonyM

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deverett

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Following on from bobcjohn's suggestion, I thought I would test the dynamo by trying to use it as a motor.
First I checked the continuity from brush holder to brush holder. Power switch open, open circuit; power switch closed 0 ohms. All good so far.
I hooked up a 12v car battery charger and was very disappointed to see the amp. meter needle go off the clock (low power, 4 amps) and not a sign of movement of the rotor. I tried the power lever from full ahead to full astern, but it made no difference. Reversing the connections of the battery charger didn't help.
The circuit is such that from one brush holder, it goes through one column coil across the bridge then down through the other coil back to the second brush holder. The coils are wound such that if they were placed one above the other, the windings would be continuous, not a reversed winding. There are also some neodymium magnets in the bridge above the coils, again N down on one side and N up on the other.

Dave
The Emerald Isle
 

Jasonb

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Dave I have this image saved and will be winding mine as per the lefthand illustration, windings in opposite direction.
 

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deverett

deverett
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Ahh so, JB.
Seems like my coil windings are wrong. I got my (bum) info from the owner of the two full size ones shown.
I'm not going to do anything to it at least until after Doncaster. Will need to get some more cotton covered wire to do a rewind.

Dave
The Emerald Isle
 
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