Model generator build from scratch

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Tim Wescott

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Sorry to put a damper on your thinking, but if you had done Physics at school (Sorry, that is a very stupid old fashioned thing to suggest and probably "out-of-date") then you would know the magnetic field has to be perpendicular to the electric field. I.E. the magnetic field in-line with the AXIS of the windings of your toroid. I'll crawl back into my little hole and keep quite again...
K2.
So without a back-iron, the magnetic lines of force go through the coils and extend into the aluminum, where they are constantly changing because the dynamo magnets are turning.

With the back-iron, the magnetic lines of force from a magnet pole goes through a coil or two, hits the back-iron, turns (because they're following a path of less resistance), and come out of the back-iron again opposite a magnet pole of the opposite polarity. By and large, they're diverted from the aluminum frame, and they're even concentrated a bit in the coils.

The EMF induced by the magnetic field is along the direction of the wires, which is, indeed, at right angles to the magnetic field as it passes by the coils, even if it does change direction sharply when it gets to the back-iron.

It's the same principle of a transformer core -- the magnetic field lines follow the iron, because magnetic permeability is more or less the opposite of magnetic resistance.

I haven't done the experiment, but find a pair of nice strong magnets of a human scale -- something that can pick up a few nails. Dig up a steel plate, about 1/8" thick, not much bigger than the magnets side by side. Now put the two magnets on the plate, both with the same pole on the plate. You ought to be able to pick up some nails. Now put the two magnets on the plate, with opposite poles. You'll pick up far fewer nails, because the plate is shunting the magnetic field, in exactly the way that the iron wire I proposed would do.
 

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darwenguy

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Yes. But for the who missed that Physics class, I thought to explain what directions things needed to point. Glad you understood my ham-fisted explanation.
K2
You seam very keen to educate people, why dont you write your own thread on the subject. Do somthing helpfull like ;)
 

skyline1

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Fleming's left and right hand rules, Left Hand for Motors Right hand for Generators (GeneRIGHTors) indicate the directions of Current, Magnetic field and Motion respectivly.

If you hold the Thumb and first two fingers of the appropriate hand at 90 Degrees to each other the thuMb indicates direction of Motion, the Forefinger the direction of magnetic Field and the Index finger the direction of current (I)
 

Steamchick

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You seam very keen to educate people, why dont you write your own thread on the subject. Do somthing helpfull like ;)
Sorry, I know my limitations and do not know enough to teach people to design generators. But I know some basic stuff from O-level physics 50 years ago. That was all about simple experiments of counting nails you could pick up with a magnet when you had different materials masking the poles. Wood, aluminium, plastic, steel, etc. I learned that iron was 1000 times better than air at conducting magnetic flux. Hence I suggested you may find your generator much improved if you use iron in the poles and cores to the coils. I don't know enough to tell you how much better than air the aluminium will be.... as it works by eddy currents. E.g. alumium rotors on AC induction motors. Beyond that I don't know so much except to keep air gaps in magnetic circuits to a minimum.
End of lesson?
I do like your castings. Do you sell on a website or something? I am tempted to make my own generator.
K2
 

darwenguy

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if you follow my thread you will know this is a work in progress and im explaining the way im making this model. Repeatedly saying the same thing just comes across as ignorant and rude.
Ive agreed with everyones suggestions on iron. and understand there concerns about eddy currents. And ive given my findings. You need to remember these nedimium magnets are much more powerefull from what was available 50 years ago and maybe compare it to the generator/dynamo models currently available for steam models and not a alternator that spins at thousands of rpm's.
if i wanted an efficient generator i cant realy beat the 240v plugs on the wall, just a toy realy isnt it. Building steam toys is more about the making for me, i dont make much money but ive made hundreds of models that make people smile :)
 

Steamchick

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Sorry, I thought you were having a dig at me for not being a teacher, so I just tried to defend my situation.
I'll stop writing as you find it so offensive.
But I won't stop reading, as your casting work is interesting.
Please reply to my question.How can I purchase castings? Or have you blacked me for still writing?

K2
 

ajoeiam

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Fleming's left and right hand rules, Left Hand for Motors Right hand for Generators (GeneRIGHTors) indicate the directions of Current, Magnetic field and Motion respectivly.

If you hold the Thumb and first two fingers of the appropriate hand at 90 Degrees to each other the thuMb indicates direction of Motion, the Forefinger the direction of magnetic Field and the Index finger the direction of current (I)
Now I need to get you to explain to me how to get those 3 fingers to 90 degrees from each other. Trying and I would have to break a finger to get that position.
 

skyline1

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You need to remember these nedimium magnets are much more powerefull from what was available 50 years ago
Quite so, These modern Neo Magnets are so incredibly powerful that conserving and concentrating the magnetic field is much less important than it was years ago.

Try sticking a couple of them together and then pulling them apart it's near impossible. The only way to do it is to slide them apart and even then they grip like limpets. The really big ones, like those used for magnet "fishing" come with big warnings about trap hazards as one of these could badly crush a finger if it got caught between the magnet and something else magnetic.

It is even possible that an Iron core could actually REDUCE the field due to saturation

Now I need to get you to explain to me how to get those 3 fingers to 90 degrees from each other
Thumb up, point your forefinger, and index finger inwards.

Best Regards Mark
 

SailplaneDriver

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Anyone ever tried silicon steel?
That is what is used to make transformers and motors. It is laminated typically with shelac coating between the layers to minimize eddy current losses. It would be a lot of work to punch out the laminations for something like this unless you were going to go into production.
 

djswain1

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if you follow my thread you will know this is a work in progress and im explaining the way im making this model. Repeatedly saying the same thing just comes across as ignorant and rude.
Ive agreed with everyones suggestions on iron. and understand there concerns about eddy currents. And ive given my findings. You need to remember these nedimium magnets are much more powerefull from what was available 50 years ago and maybe compare it to the generator/dynamo models currently available for steam models and not a alternator that spins at thousands of rpm's.
if i wanted an efficient generator i cant realy beat the 240v plugs on the wall, just a toy realy isnt it. Building steam toys is more about the making for me, i dont make much money but ive made hundreds of models that make people smile :)
Well done, you've achieved exactly what you intended. It's a nice looking model that functions and adds interest to the engine that drives it. I totally understand your objectives and reasoning. :)
 

darwenguy

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Thank you.
Il update soon. Im just playing around with different coil and wire sizes now.
I reckon i can easily get this to produce a steady 6v at around 200RPM. And over 24v at 1000rpm.
If you compare this to the the two most comon available dynamos from PM and stuarts it performs quite well i think.
Stuarts is rated at 4v at 3500rpm.
Pm is rated at 10v at 5000rpm.
Obviousley this will require more torque, but even the stuarts dynamo is only rated to be used with there bigger steam models and gas engines. So still somthing relevent and usefull i think.
 

Steamchick

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Darwin guy. I can't resist writing to say "Well done" for your results of your endeavour.
I am keen to learn, so I can improve my generators. Can you tell us what you latest windings are?
Wire diameter and number of turns? - or is that a secret?
Will you be selling castings and plans?
K2
 

darwenguy

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Hi all,
Update on this project, ive done as many tests as i can bare to do, 6 or 7 now i think. with different wire and coil sizes.
And not realy a great difference between all of them.
Wire size, number of turns and volts with a load at 500 rpm are as follows.
0.25mm wire 100turns 6.5v
0.25mm wire 200turns 9.2v
0.28mm wire 150turns 8.5v
0.315mm wire 130turns 7.2v
0.355wire 120turns 5.8v

Im set on the 0.28mm wire now just for the fact its easier to handle than the smaller diameters.
So thats pretty much it now for the design and prototyping of this model, il probably do some more tests when i have finished my engine that i intend to run this.
This is my latest test peices, all working great just need painting and finding a good home. Oh still just waiting for some brass wing nuts and screws for the terminals.
20210524_175857.jpg

And just some of the prototype coils!
20210524_175931.jpg

Il add more pics of the finished model but that will probably be a thread in finished models section along with the engine and boiler.

Thanks for following along.
Best Regards.
Luke.
 

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