# Model generator build from scratch



## darwenguy (Feb 27, 2021)

Hi guys,
Ive been wanting to make a good model dynamo to run with a stationary steam engine.
I dont realy like the kits available from stuarts and pm, i just dont like the price of a modern motor guts in a fancy shell.
I have searched the internet for some plans but had no luck so im going to make my own from scratch.
Il make a full log of the design and build on here as it would be somthing i would want to see myself and i hope it helps somone or someone can help me along the way.
The more i searched the internet the more i become confused aboit generators, so im just starting from the basics i do know and see what works best along the way regarding wiring and magnet arangements.
Il try and keep it as simple as possible and add some cosmetc character to the final model with some nice castings.
The model will have a stator of 12 fixed windings and i think a rotor with 16 pole magnets.
The first prototype is just being printed in the 3d printer so picks to come soon.


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## darwenguy (Feb 27, 2021)

*

*
This is the basic look im going for, the rotor will be approx 75mm diameter and the whole model about 125mm across base.
It will make AC voltage so il probably hide a small rectifier in the base to make DC output.


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## BaronJ (Feb 27, 2021)

darwenguy said:


> The model will have a stator of 12 fixed windings and i think a rotor with 16 pole magnets.



Hi, I'm curious to know how you determined the stator and rotor configuration ?


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## darwenguy (Feb 27, 2021)

BaronJ said:


> Hi, I'm curious to know how you determined the stator and rotor configuration ?


I read a paper that suggested 3-4 ratio for stater to pole, ie 4 coils to every 3 poles to reduce cogging effect. But tis still may change yet.


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## Rustkolector (Feb 27, 2021)

Cogging can be an issue with PM generators so I am also curious about the stator-coil ratio you are considering. Can you share the source of that information?


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## djswain1 (Feb 28, 2021)

Good luck with it, as you say there do not seem to be many sources for kit dynamos/generators.
I am in the UK and came across this little unit on ebay:









						dynamo/generator, miniature, model engineering, live steam  | eBay
					

Find many great new & used options and get the best deals for dynamo/generator, miniature, model engineering, live steam at the best online prices at eBay! Free delivery for many products.



					www.ebay.co.uk


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## darwenguy (Feb 28, 2021)

Rustkolector said:


> Cogging can be an issue with PM generators so I am also curious about the stator-coil ratio you are considering. Can you share the source of that information?


I think it was a link in a feed on here, search generator and someone has made somthing simular. Like i seid its a work in progress and may change along the way.


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## darwenguy (Feb 28, 2021)

355407, member: 16767"]
I think it was a link in a feed on here, search generator and someone has made somthing simular. Like i seid its a work in progress and may change along the way.
[/QUOTE]
Also this keeps the 3 pbases at 120° (if i go that rout) so only 4 coils are in line with the magnets at one time so reducing drag.


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## darwenguy (Feb 28, 2021)

Today i made the simple test rig, first test will be with 12coils on the stator and 16 pole magnets on the rotor. With each pole oposing the next ie north, south ,n ,s, ,n ,s.
The stand has small bearings pressed in and a 6mm shaft.  The nedimium magnets are 25x8x2mm. The pully was slare from another project.
The enamald coil wire has arrived and its 0.25mm for the first test, il next make a simple former with a counter to wind the coils. Just waiting for a cheep counter in the post.
I do understand that generators work best with a iron rotor core and stator but im aimimg to make this from mostly aluminium alloy castings eventually to reduce drag maybe with just iron core centers.
This will be more like a typical diy style wind generator setup in principle.


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## mu38&Bg# (Feb 28, 2021)

It should be understood that cogging isn't a problem, except for motors requiring low starting torque or positional accuracy(servos). Once a motor is turning, cogging is no longer a factor. If building this with no back iron(core), there won't be any cogging anyhow as it's the interaction of the magnet and back iron. If aluminum is used in place of iron, you can expect a lot of "drag" due to magnets inducing eddy currents in the aluminum. The efficiency depends on proper magnetic design, though I understand efficiency is not the goal here. Back iron should be laminated to reduce losses. If coreless is the goal, just print the core? Youtube has several printed motor examples.

You can wind a single coil, test the output, and multiply by the number of coils in series to get an idea of how much voltage it will make. You don't' even have to wind a full coil, just a few turns, but voltage could be too low to measure.

This is approximately the size of a automotive alternator, which can easily make 2kW when wound and driven accordingly.


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## darwenguy (Feb 28, 2021)

dieselpilot said:


> It should be understood that cogging isn't a problem, except for motors requiring low starting torque or positional accuracy(servos). Once a motor is turning, cogging is no longer a factor. If building this with no back iron(core), there won't be any cogging anyhow as it's the interaction of the magnet and back iron. If aluminum is used in place of iron, you can expect a lot of "drag" due to magnets inducing eddy currents in the aluminum. The efficiency depends on proper magnetic design, though I understand efficiency is not the goal here. Back iron should be laminated to reduce losses. If coreless is the goal, just print the core? Youtube has several printed motor examples.
> 
> You can wind a single coil, test the output, and multiply by the number of coils in series to get an idea of how much voltage it will make. You don't' even have to wind a full coil, just a few turns, but voltage could be too low to measure.
> 
> This is approximately the size of a automotive alternator, which can easily make 2kW when wound and driven accordingly.


Im making a generator not motor.
I may use iron cores to increase power dont know yet im making this up as i go along.


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## kop (Feb 28, 2021)

Voltage Regulator for Permanent-Magnet Alternators
		






Now this is even less than an endorsement however I have heard good things about this company.
Several custom EV designers have reported great conversations with them.
As stated on the site small prototype are available.








						Catalog of Dies - Thomson Lamination Company, Inc.
					

TLC offers a very large number of catalog laminations available from Company owned production dies that customers can consider & evaluate before designing a new lamination.




					www.tlclam.net
				




The other option is a 3D router w/laser capable of burning through pig iron.

A somewhat caveman kludge is to wind the coils on a bobbin, insert a square headed bolt through the bobbin, drill a hoop with the desired number holes, thread the holes, and insert the bolts/bobbin from the inside.

As you may already know the wiring is connect the starts together and wind one, skip two, wash rinse repeat until you have three free ends that connect to the regulator/rectifier.

TMI? maybe but it's what I have


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## darwenguy (Feb 28, 2021)

kop said:


> Voltage Regulator for Permanent-Magnet Alternators
> 
> 
> 
> ...


Hi. I think the wiring diagram is over kill for my needs. I have a variety of bridge rectifier diodes to try and il probably just use a capacitor to stabalise the voltage a little. And simply regulate it with the speed, i only want to produce around 6v to run maybe a few lights for display.
I have capability to cast the parts in iron if i need too, i just prefer to use alloy casting.
Il wind the coils on a bobbin then make a former to shape them to the stator frame.
Im not sure yet how i will wire it, il first do some tests to see what works best.


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## BaronJ (Feb 28, 2021)

darwenguy said:


> I'm making a generator not motor.
> I may use iron cores to increase power don't know yet I'm making this up as i go along.



There isn't really any difference !  If you apply a few volts to the winding's the rotor should turn since you are using permanent magnets.


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## mu38&Bg# (Feb 28, 2021)

Generator and motor are the same, only the direction of energy transfer differs. I'll refrain from further comment unless asked.


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## darwenguy (Feb 28, 2021)

BaronJ said:


> There isn't really any difference !  If you apply a few volts to the winding's the rotor should turn since you are using permanent magnets.


Yes i know, motors and generators are very simular.


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## darwenguy (Feb 28, 2021)

dieselpilot said:


> Generator and motor are the same, only the direction of energy transfer differs. I'll refrain from further comment unless asked.


Yes i know that. I dont see your point? Im not worried about cogging it should not be a problem with this settup.


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## Geartooth (Feb 28, 2021)

With 12 coils and 16 magnetic poles, what frequency would result by spinning it at 1000 RPM?


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## Tim Wescott (Feb 28, 2021)

Next to copper, aluminum is about the worst stuff that you can use for efficiency.  Just consider that magnetic brakes are, essentially, magnets held up to a good conductor that's moving.  Back irons behind the magnets and the coils will significantly increase efficiency, and far more so if you use laminations that are electrically isolated from one another (the traditional thing to do is use varnish -- just about any paint-like material will work).

Personally, if I could find a sheet of magnet iron and I had a laser printer (or a friend with one) I'd cut out a stack of laminations from that, varnish them, and stack them.

Alternately, I've always wanted to try getting hunks of ferrite, and having them laser- or water-cut to shape.

If you don't want to mess with back iron, consider making the whole thing out of bakelite, or some other non-conductive material.


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## darwenguy (Feb 28, 2021)

Geartooth said:


> With 12 coils and 16 magnetic poles, what frequency would result by spinning it at 1000 RPM?


I have no idea, the 16 poles may change, it might be usless il have to wait and see how it performs.


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## darwenguy (Feb 28, 2021)

Tim Wescott said:


> Next to copper, aluminum is about the worst stuff that you can use for efficiency.  Just consider that magnetic brakes are, essentially, magnets held up to a good conductor that's moving.  Back irons behind the magnets and the coils will significantly increase efficiency, and far more so if you use laminations that are electrically isolated from one another (the traditional thing to do is use varnish -- just about any paint-like material will work).
> 
> Personally, if I could find a sheet of magnet iron and I had a laser printer (or a friend with one) I'd cut out a stack of laminations from that, varnish them, and stack them.
> 
> ...


Thanks i understand the need for iron cores and stator housing to make an efficient generator. Im not worried about efficency at all i just want it to look nice and make a few volts from a little steam engine. I mentiond it will be more like the diy wind generator type that use no iron at all if possible. If its usless then il add iron coil cores then iron rotor and and so on untill i get somthing working
Il have to find a link to a thread on here to explain what im aiming for. Again if the alloy housing causes that much loss il cast it in iron also.
First thing i need to do is make the coils and figure out the wiring setup that is the biggest task in my view the rest is all casting and maching the fun bit.


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## darwenguy (Feb 28, 2021)

This is the sort of thing im aiming for but a little smaller. see this thread by Manfred, i love the look of his model




__





						Dynamo build by castings
					

Hello to all of You,  in the last year I have learned howe a dynamo works and build my one CNC mill. The design work of the dynamo is done. Most of the pattern are finished. The foundry is next to my door, but still it takes time to get the parts on hand.  Manfred




					www.homemodelenginemachinist.com


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## Tim Wescott (Feb 28, 2021)

Geartooth said:


> With 12 coils and 16 magnetic poles, what frequency would result by spinning it at 1000 RPM?



You should get one cycle per pair of magnetic poles per revolution.  So, (16 / 2) * 1000 RPM * / (RPM / 60Hz) = 133Hz.  More faster is more better, though.


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## Tim Wescott (Feb 28, 2021)

Tim Wescott said:


> If you don't want to mess with back iron, consider making the whole thing out of bakelite, or some other non-conductive material.



I know you're probably not going to go there, but I had a thought.

I just realized that if you wrap some varnished iron wire around a form and bake it into shape somehow, you'll get the magnetic conductivity you need while breaking up the available path for eddy currents.

Assuming I could find really soft iron wire (physically soft usually means magnetically soft) I'd even try varnishing it myself, then wet it with epoxy and wind it up.

Alternatively, get the highest permeability iron-powder toroid cores you can find (amateur radio folks use them).  I know from experience that these will machine, although they're probably abrasive as all get out.  Use these for your back iron.

Or a ferrite core, if you can find a pair with pleasing shapes.  It looks like there's some sorta-OK ones from Fair-Rite (Amidon site shown, but they just resell Fair-Rite stuff.  This one's too small by a mile, but you could dredge through all that's available: FT-114A-67).


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## Chiptosser (Mar 1, 2021)

Tim
What is magnet Iron??    Bakelite,  don't know of anybody making that.
Are you talking abut phenolic material?


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## Tim Wescott (Mar 1, 2021)

I should have said phenolic.  You can get rods of bakelite, from artsy types if nothing else, but phenolic-linen would have better mechanical properties.  (It's actually a fun web search -- there's a _lot_ of interesting phenolic plastics out there.  If I had a project that needed artsy knobs & levers, I'd have a collection of Bakelite rods to make them from).

Magnet iron is steel that's alloyed with silicon instead of carbon.  

Steel that's hardened with carbon is both mechanically and magnetically hard.  Magnetic hardness means that the steel will become a permanent magnet.  It takes energy to coerce a hunk of steel into a magnet, so a magnetically hard steel causes loss each time the field reverses.  This causes drag (there's actually a kind of motor that uses this to good effect -- do a search on "hysteresis motor").

Steel that's hardened with silicon gets mechanically hardened but it's hardened magnetically to a much lower degree.  It's on the market as "magnet steel" or "transformer steel".  It's also hard to get in less than industrial quantities; you'd basically have to luck into it.  Unlike carbon steel, silicon actually lowers the ultimate strength of the steel, so it's not nearly as good a structural material as carbon steel -- but it's a worthwhile trade for a transformer or a motor.


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## jkimberln (Mar 1, 2021)

I have non-grain oriented electrical steel available.  This is good for generators not for transformers.  What I have is 0.014" thick and coated both sides for electrical insulation.  I had to get this stuff for a small turbogenerator I am still in the process of building.  This type of steel is hard to work with, machines like a pig and is better punched than processed any other way.  I'm using a 1" x 1" diametrically magnetized rare earth magnet.  The field coil is 4 pole and at 2600 rpm I'm getting 4.4 volts (I think) but have not measured the amps/watts.


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## darwenguy (Mar 1, 2021)

jkimberln said:


> I have non-grain oriented electrical steel available.  This is good for generators not for transformers.  What I have is 0.014" thick and coated both sides for electrical insulation.  I had to get this stuff for a small turbogenerator I am still in the process of building.  This type of steel is hard to work with, machines like a pig and is better punched than processed any other way.  I'm using a 1" x 1" diametrically magnetized rare earth magnet.  The field coil is 4 pole and at 2600 rpm I'm getting 4.4 volts (I think) but have not measured the amps/watts.


Im very interested to hear more about your turbo generator!
This is exactly somthing im also planning to make myself. I was just researching diametrical magnets last night and was looking at the same size magnets.
I have already made a small turbine running a small dc motor as dynamo and creates around 6v max. But i want to make a direct drive type to add onto my turbine and brushless is the way to go i think. Il add pic of my current little turbo gen set.
Regards luke.


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## darwenguy (Mar 1, 2021)

Today i made a simple winding bobbin that splits and mounted on a shaft to hold in the lathe. The other parts are formers to press the coils into the correct radius for the housing.
  The plan was to glue the coil a little while winding and then remove it from the bobbin. This didnt work out very well and without a counter i guess far too much wire was required to fill the coil.
Ive already designed and will print some permenant bobbins to wind the coils onto  tomorow. Im still waiting on a counter to come so will make a more permenant coil winding rig in the mean time.


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## Tim Wescott (Mar 1, 2021)

I'm trying to remember how I did this -- I think I put epoxy in the groove in my bobbin and then just wound the coil -- enough epoxy got squeezed out at each step that it glued the next layer down.

Obviously it was very messy, but it worked.

If you want to buy wire by the pound, you can get magnet wire that's coated with heat-sensitive glue.  Wind your coil, bake at the right temperature, and the glue melts.  Then you have a permanent coil that is, if you want, free-standing.

(Bobbins are easier).

Model airplane motors of the approximate size you're working with generate up to 20V at 10000 RPM with just ten or so turns of wire.  But -- 10000 RPM.


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## darwenguy (Mar 1, 2021)

Tim Wescott said:


> I'm trying to remember how I did this -- I think I put epoxy in the groove in my bobbin and then just wound the coil -- enough epoxy got squeezed out at each step that it glued the next layer down.
> 
> Obviously it was very messy, but it worked.
> 
> ...


Thanks yes i think permenant bobins in the coils is the way i will go now. I thought about epoxy but doing one at a time or making lots of formers isnt viable i would like to eventualy make more than one of these so il spend time making the coiling setup.


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## Richard Hed (Mar 2, 2021)

darwenguy said:


> Im very interested to hear more about your turbo generator!
> This is exactly somthing im also planning to make myself. I was just researching diametrical magnets last night and was looking at the same size magnets.
> I have already made a small turbine running a small dc motor as dynamo and creates around 6v max. But i want to make a direct drive type to add onto my turbine and brushless is the way to go i think. Il add pic of my current little turbo gen set.
> Regards luke.


That's totally beautiful.  Can we see it run?


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## darwenguy (Mar 2, 2021)

Richard Hed said:


> That's totally beautiful.  Can we see it run?


Thanks i cant find any videos of mine, but if you search youtube for 'cringle turbine' you will see some made by some customers.


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## SailplaneDriver (Mar 2, 2021)

Geartooth said:


> With 12 coils and 16 magnetic poles, what frequency would result by spinning it at 1000 RPM?



Output frequency will be Number of Magnetic poles times RPM divided by 120. For a 16 pole machine running at 1000 RPM you will get 133 Hertz output.


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## BaronJ (Mar 3, 2021)

SailplaneDriver said:


> Output frequency will be Number of Magnetic poles times RPM divided by 120. For a 16 pole machine running at 1000 RPM you will get 133 Hertz output.



I think you have a zero too many or you have missed a zero out !


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## Steamchick (Mar 3, 2021)

I understood Bakelite was the first "plastic" - actually a thermo-setting resin, that is plastic until set. It is derived from a waste from refining coal to make coke: Coke manufacturing By-products include fuel gas right through to all the bituminous products that cover roads and waterproof roofs, etc. (If we didn't dump it on the roads we would have huge festering mountains of "oil waste" for environmentalists to complain about). Nowadays, oil refining produces thousands of different resins and plastics - most better than Bakelite. Beware when machining "Tufnol" types of materials (fibre reinforced resin): The fluff from organic fibres, dust from glass fibres, resin dust, etc. are all TOXIC. They clog the lungs, can get into the blood stream and can (in quantity) cause anything from irritation, sore throat, coughing, to bleeding lungs and emphysema. You REALLY don't want to risk it!
Read the Safety material/data-sheet for the type of material you select. WEAR A GOOD DUST MASK! - Especially when cleaning the machine afterwards. USE A VACUUM CLEANER WITH DISPOSABLE BAG.


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## SailplaneDriver (Mar 3, 2021)

BaronJ said:


> I think you have a zero too many or you have missed a zero out !



My answer is correct. Here is the formula from Alternating Current Machines by Puchstein, Lloyd and Conrad first published in 1936. This is the 1954 edition.






The output frequency is inversly proportional to the number of poles in a generator or alternator. Same for the RPM.
Now think of it pragmatically by what actual motors or generators you can find. Here is a Baldor motor table showing number of poles versus RPM for a fixed frequency. As the poles go up, the RPM decreases. For 60 Hz, the RPM will be 3600 for 2 poles, 1800 for 4 poles, 1200 for 6 poles etc. Similarly for 50 Hz, 3000, 2000, 1000. For 16 poles at 50 Hz the base machine speed would be 375 RPM. We are running the machine 2.67 times as fast at 1000 rpm which means the frequency will be 375 times 2.67 or 1000 Hz.


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## BaronJ (Mar 3, 2021)

SailplaneDriver said:


> My answer is correct. Here is the formula from Alternating Current Machines by Puchstein, Lloyd and Conrad first published in 1936. This is the 1954 edition.
> 
> View attachment 123541
> 
> ...



Sorry !
Don't worry about it !  My error, I've got too many zeros, dammed fat fingers, I'll just blame the calculator...

Anyway interesting reading, thanks !


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## darwenguy (Mar 3, 2021)

Today i spent more time figuring out the coil manufacturing, i think ive got a good sytem now. The coil bobbin is clamped onto the former and clear epoxy was added during the winding, clear film was used to stop it sticking to the former. I then got a neat solid coil when the epoxy set. Although this method works its very messy and time consuming. So im makeing a set of 12 formers lined with teflon tape and use maybe clear nail polish lacker then at least i can do a set of 12 in a day.
I did a quick test with a single coil and a small led, and at 500 rpm it produces 0.7v  at 1000rpm it produces 1.7v.
I think il get what i need now with the voltage so im getting on with the pattern designs for the housing and will have somthing more interesting to show soon. 
Some pics of carious stage of the latest coil winding and test setup.


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## Rotormac (Mar 4, 2021)

SailplaneDriver said:


> My answer is correct. Here is the formula from Alternating Current Machines by Puchstein, Lloyd and Conrad first published in 1936. This is the 1954 edition.
> 
> View attachment 123541
> 
> ...


Surely if a 16 pole motor @ 375RPM = 50Hz then the same motor @ 1000RPM = 50*1000/375 = 133.5Hz ?


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## Steamchick (Mar 4, 2021)

Working in a cable manufacturing company back in the mid-1970s, I wound coils for a magnetic flux switch for a production device. The coils were wound on a simple wood former, with a paper inserted at every 4th or 5th layer, and the whole painted liberally with shellac before the next few layers were wound. This was based on the method used by an "old-timer" who did the similar job of making coils a few decades earlier. He said either paper (we used good newspaper) or cotton or linen (his wives old sheets!) were used as the fibre reinforcement. The finished coil was wrapped with strips of cotton (I used an old pillow-case for the fabric) and finally painted with more shellac. Shellac is basically a solid varnish that is dissolved in Meths to make the lacquer. As it has been used since Victorian times it has a good pedigree, and coils can be unwound if soaked in meths for a few days. I guess modern Epoxies (I guess 2pack?) are stronger, but the coil when mounted on a stator is going nowhere. Shellac seems to be good for 50 years or more - I don't know if epoxy will last as long? However you impregnate the coils I guess it will be a messy job. 
I have a Monkey Puzzle tree that "bleeds" large quantities of resin. I know that insects trapped in the resin become "Amber after about 50 million years or so, But I won't be around to see that. Also I know the Japanese used the Pine resin to make their Lacquer-wear - pre-plastic era moulded and decorated boxes, cups, bowls (usually black). When I was there in the late 1980s a guy told me they were replacing the lacquer with modern plastics, but on transformer and motor windings etc. it was still still the preferred option - cheap and proven for decades. Is it a simple case of dissolving the resin in hot water to make the lacquer? - Anyone know? 
Enjoy!
K2


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## Steamchick (Mar 4, 2021)

An observation on your test rig. The Orange stator looks like some Nylon or other non-magnetic material. "Of course" (an electrical engineer would say) you need an iron core to get to "practical" magnetic circuits so the magnetic field strength is much higher and the voltage and current will consequently rise.
Maxwell explained it all in the 1870s and wrote the text book still in use today. I'm not an Electrical engineer so won't try and explain. I'd have to read the book - but I suggest you do instead? Or the others on this thread?
Something to do with B=nI, dB/dT proportional to V? etc.
Cheers!
K2


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## darwenguy (Mar 4, 2021)

Steamchick said:


> An observation on your test rig. The Orange stator looks like some Nylon or other non-magnetic material. "Of course" (an electrical engineer would say) you need an iron core to get to "practical" magnetic circuits so the magnetic field strength is much higher and the voltage and current will consequently rise.
> Maxwell explained it all in the 1870s and wrote the text book still in use today. I'm not an Electrical engineer so won't try and explain. I'd have to read the book - but I suggest you do instead? Or the others on this thread?
> Something to do with B=nI, dB/dT proportional to V? etc.
> Cheers!
> K2


Il go with the setup i have at the minute, the epoxy works great its just the effort of mixing a new batch for every coil isnt practical. Like you seid they only need to hold there shape when instaled. Im making a set of 12 formers and then it wont matter if it takes a day to dry the lacher/varnish.
But they do need to be very acurate to creat as little gap between the magnets as possible.
The test rig is printed abs plastic.
Ive seid in my first post and many time now im not using iron if at all posible! Please see the link i posted to a previouse build by manfred


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## darwenguy (Mar 4, 2021)

I


djswain1 said:


> Good luck with it, as you say there do not seem to be many sources for kit dynamos/generators.
> I am in the UK and came across this little unit on ebay:
> 
> 
> ...


I make these lol, ive made 100's just finishing another batch of em. Im looking to make somthing a little more interesting and maybe produce as a kit.


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## Steamchick (Mar 4, 2021)

Hi Manfred. Sorry, I had just picked-up later in this thread. If you don't want to do metalwork, is there an 'iron-filled'polymer you can use to print your parts for the magnetic circuit? I'm an Engineer. Please forgive my prejudice, but to make an electromagnetic machine but not using simple materials to hugely improve the machine is like making the proverbial chocolate fire-guard. In my humble opinion. You are doing such a good job, why spoil it by using what is effectively a "magnetic non-conductor" where you need a "magnetic conductor"?
K2


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## Steamchick (Mar 4, 2021)

Sorry Darwen guy, I got my names muxed-ip. 
I thought I had opened a reply from someone called Manfred. Sorry to both of you.
K2


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## darwenguy (Mar 4, 2021)

Steamchick said:


> Sorry Darwen guy, I got my names muxed-ip.
> I thought I had opened a reply from someone called Manfred. Sorry to both of you.
> K2


Please see this thread by 'manfred'. It will explain the sort of thing im aiming for




__





						Dynamo build by castings
					

Hello to all of You,  in the last year I have learned howe a dynamo works and build my one CNC mill. The design work of the dynamo is done. Most of the pattern are finished. The foundry is next to my door, but still it takes time to get the parts on hand.  Manfred




					www.homemodelenginemachinist.com


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## TSutrina (Mar 4, 2021)

One time years ago when I worked for an aircraft generator manufacture, I am a mechanical engineer.  He said the relationship of peak voltage is a cubic relationship to speed.  Peak voltage occurs at zero output current.  Thus trip the generator breaker the wires see peak voltage.  Power relationship is a square of the speed term.  Thus double the speed doubles  results in four times the power.  The magnetic flux for a permanent magnet generator is fixed so I would keep the regulator if you want to do something with the power besides dump it into a heater.  I would add resistors in series with the inductor of the schematic above to represent the resistance of the wire coils.   Note generators driven by the jet engine directly are called wild frequency.  The peak voltage swing is quite large as it is in a vehicle because the generator is a axillary load and thus not determining the speed.  That is why a wound field is used for the rotor, to control the magnetic flux and thus the output voltage.   It is a lot simpler approach since the power needed is far less then that handled by the electronics of a PM wild frequency generator.


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## TSutrina (Mar 4, 2021)

Tim Wescott said:


> I should have said phenolic.  You can get rods of bakelite, from artsy types if nothing else, but phenolic-linen would have better mechanical properties.  (It's actually a fun web search -- there's a _lot_ of interesting phenolic plastics out there.  If I had a project that needed artsy knobs & levers, I'd have a collection of Bakelite rods to make them from).
> 
> Magnet iron is steel that's alloyed with silicon instead of carbon.
> 
> ...


The choice of the iron is greatly effected by the frequency of the changing magnetic flux and the the electrical frequency.  For 50 and 60 Hz carbon steel doesn't present a big increase in losses.  Aircraft magnetics at 400 Hz us silicon steels.  And for higher frequencies the choices of materials decrease until you get to powdered metal oxides.  The last choice is air.  I have not studied the design.  You always need a path for the magnetic flux.  At reasonable frequencies magnetic engineers always choose a magnetic conducting material.  The insulating materials are used where they do not want flux.   I have use the simple 2D magnetic FEA program  FEMM which has been around for decades for a windows program  I think it is not available for other platforms.  Finite Element Method Magnetics / Wiki / Magnetics Tutorial


----------



## darwenguy (Apr 14, 2021)

Hi, ive not had much time for this project recently but i have settled on the final design now. 
I have a satisfactory method of producing the coils and will add details of that soon.
i have done most of the pattern work now and hopefully soon will have somthing to show. But so far just patterns and hours and hours of sanding and painting.
The patterns are all 3d printed and will be made up as matchplate patterns on plywood boards.


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## darwenguy (May 2, 2021)

Hi all, managed to get some more done on this project.
I finished my little coil winding machine now and that turned into a little project of its own. But its a solid little machine that i hope does a lot of work.








The coil spools each have a scew that simply acts as a cam on the leaver to press a button on a cheep stock counter.




The spool winders have a layer of teflon tape on the inner faces.
The coil bobbins are clamped between the two parts and then mounted onto the winding machine.




I use two part liquid epoxy make the coils solid. The epoxy is added with a small brush as the coil is winding. The former can then be removed from the machine and left to cure.








The coils take about 1 minute each plus a little time setting up and gives me plenty of time to do a set of 12 before the epoxy starts setting after 30min.
Il see how they all turned out tomorrow and do some more tests. Ive now got some bigger magnets to try also these are 25x10x3 and much much more powerfull and also cheeper!
Not much more to show, but nearly finished all the paterns and have finished all the drawings now.
I should have this project wrapped up soon, im going to have a go at casting some bases tomorrow so will update on that.
Hers a pic of how the finished generator will actually look Like..




Best regards.
Luke.


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## Richard Hed (May 2, 2021)

darwenguy said:


> Hi all, managed to get some more done on this project.
> I finished my little coil winding machine now and that turned into a little project of its own. But its a solid little machine that i hope does a lot of work.
> View attachment 125026
> 
> ...


Too cool.  Too cool!


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## darwenguy (May 3, 2021)

Cast some bases this morning, they came out alright i think


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## Chiptosser (May 3, 2021)

Very nice job!


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## ShopShoe (May 4, 2021)

FYI - Shellac

You can still buy shellac. The traditional way is to buy shellac flakes and dissolve them in alcohol to the strength you need.

Google "Shellac Flakes" for sources and more information.

--ShopShoe


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## darwenguy (May 4, 2021)

Thanks shopshoe, i did look into shellac but when searching ebay it mostly showed stuff for furniture all different with added beeswax and the like. So wasnt in the mood for experimenting and wasting money. I also looked into baking the coils with ethonal but seams like more work. The epoxy was less then a fiver delivered and is enougth to make a hundred coils.
The coils turned out nice and solid and uniform..


----------



## darwenguy (May 4, 2021)

Hi all, a bit more done on this today.
I have plenty of coils to do more experiments with now, i made another test stator housing and did a nice neat job of wiring it up. But it was late in the day and ive gone and wired it all wrong so its usless and will start again tomorrow.








Also i need to make a 12 pole test rotor now as ive decided on making the unit single phase ac. I got these neat little single phase bridge rectifier units to convert to DC. they come as kits that just require soldering and fit nicely in the base cavety.












More work done on the patterns. All the patterns have holes for using pins to alighn the two sides of the matchplates. I nake them with the runners and gates included and just have to add the sprue holes when building the mold. Pics will explain. Still need a little filler on the holes then one more round of paint and sanding.
















I should have some more to show tomorrow.
Regards.
Luke.


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## Richard Hed (May 4, 2021)

darwenguy said:


> Hi all, a bit more done on this today.
> I have plenty of coils to do more experiments with now, i made another test stator housing and did a nice neat job of wiring it up. But it was late in the day and ive gone and wired it all wrong so its usless and will start again tomorrow.
> View attachment 125152
> 
> ...


Luv it!


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## darwenguy (May 5, 2021)

Hi all, today i made a full test rig with the full 12 coils and a new rotor with 12 poles.
The new magnets are much more powerfull and care must be taken as they can bite! When they snap together They are hard to seperate.
For this test it is setup as single phase AC, the 12 coils have 100 turns of .25mm wire each and are wired in series with each coil alternating in the winding direction. The two ends are wired into the bridge recfifier and a digital voltage display is wired to the DC output of the rectifier.
The generator is spun via the lathe with equal sized pullys and a drive band so that the lathe rpm display is rougthly the same as the generator rmp.
I had good results and this is the readings at the dc output...
At 500rmp =12v dc and 1.8amp
At 1000rpm=24vdc and 3.6amp
It will even produce 5v at 250 rpm.
As low as 12v a good spark can be seen across the terminals.
The voltage display isnt very acurate and draws some voltage but good for display for the photo.













Im quite pleased with these results and the final model should be a little better as the air gap between coils and magnets will be half the size.
Regards.
Luke.


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## Steamchick (May 6, 2021)

Hi Luke, looks good! It generates volts. But the real test is a plot of volts against amps - say at set speeds. 200rpm, 400rpm 600rpm, 800 rpm 1000rpm. For generator analysis you can not rely upon just volts. Really that is just a speed relationship as it is dB/dt. (B = Magnetic flux intensity)  but generators need to produce amps as well. You can but a combined voltmeter and a meter digital unit for just a couple of £. Then you have the tool to determine how powerful the generator really is. But be careful. As all the windings are effectively in series, the same current flows in them all, and too much current will simply burn-out coils. So check the current rating of the wire and DO NOT EXCEED THAT CURRENT when testing across a load. For varying loads, 12v car bulbs are pretty good resistors. The should also mean you can easily study current by connecting more bulbs in parallel.
This is the sort of size for a 12V. Generator for a motorcycle of 100 to 250 rating. But without iron cores you won't  expect to get anywhere near that. My guess is only 100dth.of that power. Not over 1A. But prove me wrong?


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## Steamchick (May 6, 2021)

Please can you post details of magnets - plus supplier?
I am sure I am not the only curious watcher here.
K2


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## darwenguy (May 6, 2021)

Hi im not sure if you read my post there? I have stated the amps at set voltages?
Is this wrong?
I used a multi meater to measure amps, i presume this puts the load on the generator as it certainly is noticable when testing.
I used the cheep digital display for demonstation as i just dont have enougth hands to use the multimeater and camera together.
Also yes using iron in the stator would increases performance up to about 25 percent but not much more at all.
At least ive proven all no nay sayers from earlier on saying irin must be used lol.
Best regards.
Luke.


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## darwenguy (May 6, 2021)

Magents are as stated in post and frome ebay, i think they label them as n52.


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## Steamchick (May 6, 2021)

On Magnets, All I have seen is "_Ive now got some bigger magnets to try also these are 25x10x3 and much much more powerfull and also cheeper!"_
Maybe you have an ebay reference number?  I have bought too many things and got the wrong ones because I wasn't so specific on E&@y. The supplier and a reference usually nails it.
On Voltage and current - sorry I missed that. - Somehow there are a load of posts I haven't read? a lot of pictures I had not seen? - I guess they were lost in the ether?
Now looking at the 12V x 1.8A I would have expected a similar sized motorcycle alternator to produce 10Amps at 3000rpm, but around 3 ~4 amps at 1000rpm. But with old "steel" magnets, not modern rare earth magnets. - This with a 0.004" air gap between rotor and stator poles. So maybe this difference is due to the number of windings, or the iron core in the motorcycle alternator? Remember Voltage proportional to rotor speed,  but Current proportional to field strength and number of windings. Current LIMIT is based on wire size.
Sorry about my missed stuff, but I am only trying to help you work out a good design. I do accept the command from the "Go away" button if you wish me to do so. (You won't be the first to say that).
Regards,
K2


----------



## Steamchick (May 6, 2021)

Crazy computer!
It has just changed your post #62 by adding a paragraph about Iron and added post #63!
I flippin give-up....
K2


----------



## darwenguy (May 6, 2021)

Yes the magnets are 25x10x3mm n52 rare earth il use whoever selling them cheepest on the internet.


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## darwenguy (May 6, 2021)

Hi all, managed to get some casting of the parts done this morning. The patterns all pulled realy nice, the molds are just cooling down and we can see how they turned out after dinner 
Also this melt was mostly recycled car alternator housing so very fitting i think.





Il update this evening.
Best regards.
Luke.


----------



## BaronJ (May 6, 2021)

Steamchick said:


> An observation on your test rig. The Orange stator looks like some Nylon or other non-magnetic material. "Of course" (an electrical engineer would say) you need an iron core to get to "practical" magnetic circuits so the magnetic field strength is much higher and the voltage and current will consequently rise.
> Maxwell explained it all in the 1870s and wrote the text book still in use today. I'm not an Electrical engineer so won't try and explain. I'd have to read the book - but I suggest you do instead? Or the others on this thread?
> Something to do with B=nI, dB/dT proportional to V? etc.
> Cheers!
> K2



Basically you need a conductor for the magnetic flux to link the coils !


----------



## Steamchick (May 6, 2021)

darwenguy said:


> Yes the magnets are 25x10x3mm n52 rare earth il use whoever selling them cheepest on the internet.


Thanks -the Na2 is the useful bit. I shall be ordering different dimensions anyway.
Cheers!
K2


----------



## Steamchick (May 6, 2021)

For spell-check's Na2 read N52   - which is what I typed.


----------



## darwenguy (May 6, 2021)

No problem steam chick,
Excuse my short replys but i only use this via my phone and it takes too long.
I think you can answer most of your questions if you read my posts.
Best regards.


----------



## darwenguy (May 6, 2021)

Just have a look for nedimium magnets they come in pretty much any size you want. This is still a work in progress so nothing set in stone yet


----------



## darwenguy (May 6, 2021)

BaronJ said:


> Basically you need a conductor for the magnetic flux to link the coils !


Why is this?


----------



## Richard Hed (May 6, 2021)

Steamchick said:


> On Magnets, All I have seen is "_Ive now got some bigger magnets to try also these are 25x10x3 and much much more powerfull and also cheeper!"_
> Maybe you have an ebay reference number?  I have bought too many things and got the wrong ones because I wasn't so specific on E&@y. The supplier and a reference usually nails it.
> On Voltage and current - sorry I missed that. - Somehow there are a load of posts I haven't read? a lot of pictures I had not seen? - I guess they were lost in the ether?
> Now looking at the 12V x 1.8A I would have expected a similar sized motorcycle alternator to produce 10Amps at 3000rpm, but around 3 ~4 amps at 1000rpm. But with old "steel" magnets, not modern rare earth magnets. - This with a 0.004" air gap between rotor and stator poles. So maybe this difference is due to the number of windings, or the iron core in the motorcycle alternator? Remember Voltage proportional to rotor speed,  but Current proportional to field strength and number of windings. Current LIMIT is based on wire size.
> ...


OK, GO AWAY!  But before you do, does you know if one can build a generator in which the coils are NOT in series?  Series just doesn't seem right to me but I have never workt with building generators.


----------



## darwenguy (May 6, 2021)

Richard Hed said:


> OK, GO AWAY!  But before you do, does you know if one can build a generator in which the coils are NOT in series?  Series just doesn't seem right to me but I have never workt with building generators.


This is wired in single phase, just two terminal ends to deal with. It could also be done in three phase with a different rotor config.


----------



## Steamchick (May 6, 2021)

Series coils are needed on "slow" generators to add the coil voltages to get the usable total voltage. But limited by wire size for current. 
Where a generator is driven "fast enough" to achieve output voltage at a useful engine speed, coils are connected in parallel to increase the current without getting too high a generator voltage at "over-speeds".
A bit of "mix-and-match"...
Cheers!
K2


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## darwenguy (May 6, 2021)

Hi all, so i got some decent castings all fettled and ready to machine in the morning now, actually already started on the rotor. I should have the first model finished by next week.
Il do another test when its finished now, il have to get some 12v car bulbs to show you as i only have 12v leds and it blows them in seconds as soon as it goes over 500rpm.


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## awake (May 6, 2021)

Looks like some really good castings! And a very interesting project.


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## BaronJ (May 6, 2021)

darwenguy said:


> Why is this?



If you consider your magnet passing the coil, one side is going to produce a unidirectional voltage which will get reversed as the magnet passes the other side of the coil.  This produces the alternating voltage that you see.  

By linking the coils with an iron frame the coils will see a second magnetic field from the produced voltage which will reinforce the one that the magnet produces.  Effectively using the the magnetic field created by the induced coil voltage plus the one from the rotating magnets.

Essentially the transformer effect.


----------



## darwenguy (May 6, 2021)

Yes but why do you say it 'needs' a iron stator? This is not true.
What you mean is an iron stator will 'increase' performance.
You need to think more homemade windmill generator type, they use mostly perspex and plywood stator housings and just rely on the magnetic flux to induce the coils.
Think as simple as holding a coil in one hand and a magnet in the other and waving them next to each other, a electric current is produced regardless of being near iron.
Ive already shown a working generator made just from plastic.
Best regards.
Luke


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## Steamchick (May 6, 2021)

You are correct: But the magnetic flux in the iron "focused" generator is 10 ~100 times bigger than the flux in air.  It's a thing called Magnetic permeability. A bit like carbon and clay in a pencil lead can conduct electricity ...,. but copper, aluminium and silver just do it so much better that people use those materials instead. Are the casings aluminium? That is so much better than air - but a long way off the "magnetic soft iron" used commercially.
Look up the numbers for permeability of materials on Wikipedia.
I'll catch-up with you tomorrow.
How much does a set of castings and drawing retail for? Methinks this may be my next project. (maybe with some mods....? I have some old motors and stuff that could donate some "magnetic iron").

K2


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## darwenguy (May 7, 2021)

Steamchick said:


> You are correct: But the magnetic flux in the iron "focused" generator is 10 ~100 times bigger than the flux in air.  It's a thing called Magnetic permeability. A bit like carbon and clay in a pencil lead can conduct electricity ...,. but copper, aluminium and silver just do it so much better that people use those materials instead. Are the casings aluminium? That is so much better than air - but a long way off the "magnetic soft iron" used commercially.
> Look up the numbers for permeability of materials on Wikipedia.
> I'll catch-up with you tomorrow.
> How much does a set of castings and drawing retail for? Methinks this may be my next project. (maybe with some mods....? I have some old motors and stuff that could donate some "magnetic iron").
> ...


You will just have to wait and see then wont you, your untrue statments just 
add confusion to the thread. The castings are basicaly just cosmetic and would still work if made from plastic. Iron will increase performance up to 25 percent thats all check for yourself.
Il have have this finished in a couple days and it will work as i intended it to.


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## Steamchick (May 7, 2021)

Hi Luke, Maybe you can post your calculations? I am without all the dimensions to do any myself.
I'm trying to resolve what I remember from Maxwell 40 years ago with what you are achieving. But I'll admit I haven't done the calculations since about 40 years ago, so may have got things mixed-up somewhere. I do remember working with various motorcycle alternators, and the difference between a 0.004in. And 0.006in air gap at the poles significantly reduced the output. Equally, reducing the air gap from 0.004in. To 0.002in clearance gave 30% to 50% more current. My instrumentation wasn't very accurate, but bulb sizes and flattening batteries gave me a good comparitor.
I like what you are doing, but I just don't understand the whys and wherefores.
Cheers,
K2


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## darwenguy (May 7, 2021)

Steamchick said:


> Hi Luke, Maybe you can post your calculations? I am without all the dimensions to do any myself.
> I'm trying to resolve what I remember from Maxwell 40 years ago with what you are achieving. But I'll admit I haven't done the calculations since about 40 years ago, so may have got things mixed-up somewhere. I do remember working with various motorcycle alternators, and the difference between a 0.004in. And 0.006in air gap at the poles significantly reduced the output. Equally, reducing the air gap from 0.004in. To 0.002in clearance gave 30% to 50% more current. My instrumentation wasn't very accurate, but bulb sizes and flattening batteries gave me a good comparitor.
> I like what you are doing, but I just don't understand the whys and wherefores.
> Cheers,
> K2


You seam to be looking for problems that dont exist.
Ive recorded all my method and finding from the start of this thread what more do you need. 
Did you even read the link to that thread of the beutifull model manfred designd and made himself? It works on the exact same method, Or did you just tell him he should use an old motorbike alternator instead!


----------



## Steamchick (May 7, 2021)

Sorry, I don't mean to upset you, but I picked up odd threads at different times. When I get time I'll study it all. 
K2


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## mu38&Bg# (May 7, 2021)

Nobody questions whether this generates _some_ power.

A few are trying to convey the importance of proper design.....
I said I wouldn't comment when it became clear after my initial response that the electromagnetic design of this generator was irrelevant. If the goal was to make a few watts regardless of efficiency, certainly that could be achieved. Fundamental electromagnetic design was well understood a century ago.

It doesn't "need" iron, but you have to understand what you're giving up without it. There is a tremendous loss in power density, they use far more magnet and copper than a standard design. Those DIY generators do "work", but are poor designs overall. When there is no constraint on size or efficiency, this can be acceptable. There are "ironless" designs, but even those use iron.

I understand giving up efficiency and the effort of a detailed design in exchange for something that "works" and looks the part is the goal here.  And that is fine. No need to get defensive about it, but understand that people are trying to help with a proper design.

You will find the torque required to drive the generator with the aluminum housing without stator back iron will be much greater than the plastic print.


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## darwenguy (May 7, 2021)

dieselpilot said:


> Nobody questions whether this generates _some_ power.
> 
> A few are trying to convey the importance of proper design.....
> I said I wouldn't comment when it became clear after my initial response that the electromagnetic design of this generator was irrelevant. If the goal was to make a few watts regardless of efficiency, certainly that could be achieved. Fundamental electromagnetic design was well understood a century ago.
> ...


----------



## TonySteamHobby (May 7, 2021)

The castings look great!  Any chance you have video of the process?
Great project, keep it up.


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## darwenguy (May 7, 2021)

Thanks tony, do you mean the casting process, i dont, i learnt most of what i know from watching 'myford boys' videos hes a great teacher!
Undate so far got to excited and already machined all the parts, forgot to take pics. I may record a detailed build log of this when the design is settled.


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## djswain1 (May 7, 2021)

darwenguy said:


> Hi all, so i got some decent castings all fettled and ready to machine in the morning now, actually already started on the rotor. I should have the first model finished by next week.
> Il do another test when its finished now, il have to get some 12v car bulbs to show you as i only have 12v leds and it blows them in seconds as soon as it goes over 500rpm.
> View attachment 125192
> 
> ...


Those castings look really good. Liking the mix of technologies as well, CAD 3D printed parts to make an alternator for a steam engine.


----------



## darwenguy (May 7, 2021)

Hi all, im very close to finishing this mk1 model now. Finished up all the machining and painted all the castings today, just needs assembling tomorrow 
The build process goes like this...
A 3d printed plastic ring holds all the coils in position, i only had red plastic for the printer so this one has been painted black for cosmetics.




And how it fits in the housing. You can see the size here! The pics dont realy show you the scale of this model. Although i do have big hands ha.




The coils are all wound the same, the start lead of each coil is marked with a loop....








The coils are then super glued into the ring. They must be alternating in the direction of winding! This is done by positioning them with the two loops next to each other than the next join is two straght wires then repeat all the way around(two loops, two straght)




The ends are then trimed and the wire coating is burnt off and sanded to bare copper. The pairs of wires are twisted together and soldered. Then small sections of shrink wrap is used to insulate the conections. And joins  are tucked away neatly between the coils.








And the finished stator ready for fitting..




Also had to glue the 25x10x3mm neodymium magnets into the rotor.




And thats about it all done ready to assemble tomorrow.
Heres the parts painted and drying


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## darwenguy (May 7, 2021)

djswain1 said:


> Those castings look really good. Liking the mix of technologies as well, CAD 3D printed parts to make an alternator for a steam engine.


Thanks, the cad and 3d printing have been a steep learning curve and ive just about got the hang of it after about 4 years haha.


----------



## mnay (May 7, 2021)

Great job, the castings look perfect.  
Mike


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## kuhncw (May 7, 2021)

Very nice work.  I like the vintage look.

Chuck


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## darwenguy (May 8, 2021)

Hello all, ive got this model finished now and il be honest im pretty pleased with myself.
It performs way above expectations and i hope you will agree it aint too ugly to look at. so ive more than met my goles on this first setup 
Heres a few pics of the assembly and the finished model.
the stator ring is fitted in the housing just a nice push fit holds it in place.




Fitted m3 studs to the base..




The little bridge rectifier is fitted into the base, a hole is drilled to fit the red led of the rectifier so it can be seen when running. Also fitted the two DC thumb terminals though they could be made smaller maybe.




And the finished model as it will look, the oil cups are just cosmetic but more shiny is always more better 




















And next to my other little generator..




Il set it up with some lights to display the output and post pics and video soon
Best regards.
Luke.


----------



## awake (May 8, 2021)

Very nicely done, and great job with the pictures to document it. I'm eager to see a video!


----------



## darwenguy (May 8, 2021)

Here is my quick and dirty setup as i imagined it would be setup before i started.
It has more than enougth power to light my little lamps.  My other model generator only lights one of these at normal speeds. Il find a bigger load to test it more. The LEDs i have here just start blowing at around 600rpm they are operate on 5v-12v dc.








And it running with the shop lights off.












Video coming in a min.
..


----------



## darwenguy (May 8, 2021)

Video here, the lathe sounds even more clunky in the audio haha. The speed is a little awkward to adjust on the lathe but gives a rougth measure of rpm.
I coild easily get more power from this model if i use more wire or even thicker wire an more of it, there is a lot of space to make bigger coils. But i just dont need that much electricity starts biting!


----------



## skyline1 (May 9, 2021)

Smashing job Luke it really looks the part and works well too

I agree about the terminal posts a couple of little brass studs with some tiny wingnuts would look more period. 

If you want to go the whole hog, braided fiberglass Hi temp wire painted black looks just like old cotton covered wire which would likely be used on something like this.

Best Regards Mark


----------



## darwenguy (May 9, 2021)

Cheers Mark.
Yes the terminals are a bit ugly they need changing. They were just what i had about, brass screws fiber washers and wing nuts sound like the plan.
Also did try getting some braided wire but its hard to find thin stuff. I did get some of the high temp stuff at 2mm but this turned out to be the actual copper wire size and the outer is nearer 4mm so way to chunky. Any thoughts on a supplyer?
Also the ugly screws nailing it to the wood was an after thought, so going to add some nicer looking lugs onto the outside of the base casting. Il prob do a full cast base eventually to display it with an engine i havent even made yet haha.
Best regards.
Luke.


----------



## skyline1 (May 9, 2021)

Hi Luke

Something like this might do the job High Temperature 0.3mm² to 6mm² Fibreglass Wire Appliance Cable HIGH TEMP 250℃  | eBay

You can get the stuff in pretty fine gauges down to 0.3mm sq which has a rating of about 3 amps and is available in black so you wont even have to paint it. It has an O.D. of just under 2mm so it should look somewhere near scale.

Unfortunately you may have to get it direct from China so it might take a little while to get to you. A quick search of EBay will often turn up a supplier with a U.K. warehouse though. Just search for High Temperature Wire.  You want the glass fiber stuff not silicone wire.

And these Solid Brass Wing Nut M3 M4 M5 M6 M8 M10 M12  | eBay should make some nice scale terminals with some M3 screws they are proper old school "Mickey Mouse" ones not the modern shape.

BTW if your figures are correct at 1000 R.P.M. 24 Volts x 3.6 A is 86.4 Watts which is quite an output power, this would light up an awful lot of LEDs

Best Regards Mark


----------



## darwenguy (May 9, 2021)

Thanks for the links Mark, il be ordering some bits soon.
I think my readings were pretty close, the higher reading at 1000 rpm i think was about the limit of the winding wire (its only 0.25mm) as it was flutuating and getting the smell of wire so i didnt push it too much.
I would like to drive this with a direct inline drive from a steam engine so idealy i need it to ooperate at low rpms.
I was thinking of adding more windings to get a slower rpm but i think the resistance will be too much with the .25 so im planning a test with .35 wire and maybe 130 winds on each coil. I think this would get decent voltage at around 150rpm. Does that make any sense,  Im not an electro magnectic engineer so my method is trial and error mostly.
Best regards.
Luke.


----------



## skyline1 (May 9, 2021)

Hi Luke

Are you talking about the wire diameter here or it's area. If it is 0.25 Dia then it's CSA is .049 mm² that is quite small for 3 amps and as your windings are in series that may well be why they are getting warm. Going up to .35 Dia will give you a CSA of .096 mm²  (almost double) if you have room on the bobbins. this may improve things. 

Adding more turns "should" have the effect of increasing the voltage and therefore the current at a given R.P.M. and load resistance allowing the generator to run more slowly for a given output but of course it will need more engine torque to do this. 

I am not an expert in rotating machine design and it is some time since I worked in the field. There are much more knowledgeable people on here who can give further advice and can probably  still actually remember the mathematics. However if I can help with any common problems I have come across during my own experiments I am happy to do so

As you said, your aim was not to produce a highly efficient machine but a practical model that is fairly easy to construct and produces a reasonably useful amount of power. In this you have succeeded admirably and at your usual remarkable high speed. Well done.

With small scale stuff like this experimentation is very much the way to go as all sorts of strange things can occur whose effects in larger scales are insignificant and can largely be ignored. These "little 'uns" rarely behave quite as the rule book says they should. So it will be interesting to see what effect your coil mods have.

I think your fluctuation problem at higher R.P.M.s may not be an Electrical one but plain belt slip. It is difficult to avoid entirely in small scale and even small amounts can have quite an effect.

Best Regards Mark


----------



## darwenguy (May 9, 2021)

Hi mark,
Yes the wire is .25 diameter, ive orderd .35 from the same supplier so the spool will fit my winding machine the same. 
I will i think need to make the bobins a little smaller to get the bigger wire and number of turns. There is a bit of space to make them wider and thicker also if needed.
Im actually happy with how its working right now.  Im just thinking mostly to make it a bit more robust. I dont realy want or need more than 12 volt and maybe an amp at the most. And the rectifier is only rated up to 24v out put so not sure if that would be damaged.
I do intend to produce this model as a kit, since my little dynamos have been so popular, ive made around 300 of them and had dozens of people asking for somthing bigger.
The only real alternative on offer is the prewound dc motor core with casing types from pm and stuarts.
Im thinking mine would be a kit of the castings with the preformed coils and printed part(maybe a fully formed stator), drawings and all magnets, elecrics and fittings. Im just a little worried about the electronics, maybe have to sell it with a warning 'do not exceed x rmp and amps' i can use a bigger rectifier but i think they add more loss so less good at lower voltage.
I think your right about the belt, it is just a soft over streched o ring, i just noticed it bouncing loads on the video.
Best regards.


----------



## skyline1 (May 9, 2021)

Hi Luke

I think a kit for this would be a real winner, as you say there doesn't seem to be anything like it on the market. I think they would go like hot cakes.

As for a warning, full size ones have rating plates with max R.P.M., Current and Voltage etc so why shouldn't these ?

Higher voltage rectifier diodes won't increase the loss they can simply withstand higher reverse voltages. the forward voltage drop is pretty much the same for any rectifier diode (about 700mV for silicon ones). There are some specialist ones like zener diodes that are by design, different, but for our purposes the only difference is that higher voltage ones are a bit tougher. For most of the common diodes high voltage ones don't even cost more.

I have a few ideas about the electronics and I might even be able to help you with  making the boards but I don't want to hijack the thread so I'll PM you and see what you think.

Best Regards Mark


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## darwenguy (May 9, 2021)

Cheers mark, i try to make things that arnt already available, i cant compete with the big names so im looking for a nich in a nich market realy,  mostly accesories for engines.
That makes sense, i could probably makeup some max rating plates, or even a sticker under the base. I know most people have a vague idea what there dealing with, its just the ebay market, only takes one or two wronguns to mess things up on there.
Ahh thats good to know, somehow i had it in my head they would have more loss.
Im interested to see any elecrtonic ideas, ifnot for this i have another generator idea for a direct drive turbine genset a bit smaller.
Best regards.
Luke.


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## skyline1 (May 9, 2021)

Hi Luke



darwenguy said:


> i could probably makeup some max rating plates, or even a sticker under the base. I know most people have a vague idea what there dealing with, its just the ebay market, only takes one or two wronguns to mess things up on there.



Very true, you might expect someone with the skills to make something like this from a casting kit to know what they were doing, but you never know with EBay.
A little etched brass rating plate would look great as well. I've made the odd one myself, it's not too difficult, it's the same process as making printed circuit boards.

The only way the POWER loss in a diode increases is due to the current flowing (Power = Voltage x Current)



darwenguy said:


> i have another generator idea for a direct drive turbine genset a bit smaller.



Oh yes, now you are talking, a sort of high speed mini version of this one for turbines. I would love something like that on mine, old school open frame and brushless so no more brush bounce, sounds like another winner to me. 

This might interest you, this is the baby sister to my big turbine set







Yes I've got two, I know, I'm greedy ! 

It's a classic symptom of turbinitus  I can't get enough of them, 

This was the first one, note no castings, this one was before I had set up the foundry, The casing is actually an old shoe polish tin. It is not quite as powerful as the big one  as it only has a single sheet rotor, but it goes pretty well.

You mentioned screwing things to bits of wood "just to test them" It appears we think alike in this, I just never bothered to make a "proper" base.

Best Regards Mark


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## Rustkolector (May 9, 2021)

Luke,
Good job on the alternator. I like slow running model engines that do things and alternators are my favorite engine load. 

If you want to provide a good steady alternator output voltage to smooth out engine input speed fluctuations and electrical load changes these little switch mode voltage controls work well. They are in-line installed controls and hold a 12v output steady until generator input voltage drops to about 12.5-13v. Just don't exceed their maximum input voltage limit...or come too close.








						DC-DC Converter Step-down Adjustable 4.5-60V 12v to 1.2-30V 5v 90W Power Supply  | eBay
					

Output Current: 3A. Can 30V 3A 90W at full load. Output ripple: Input 48V, Output 5V, 3A, ripple less than 10mV. Module Properties: non-isolated step-down module (buck). Full load temperature rise: 40°c.



					www.ebay.com
				




Have you noticed any physical effects of eddy currents between the plastic and aluminum versions of your alternator design, like when spinning the rotors by hand with no load?
Jeff


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## darwenguy (May 10, 2021)

Yes i respect most people have the comon sense. Its just the type that would buy one at 2am for somthing like a tiny wobbler engine, and then blame the wife and im left paying postage and packaging each way and ebay still take there chunk. Its happend more than once.
Nice prototype!, yes no need to get fancy when only testing ideas. Im thinking of maybe just a two coil stator and cylinder shape magnet. Maybe somthing like the peel tobo gensets used on locos. There have been some very nice models made already but very rare and pricey.
Il reply to you pm soon.
Best regards.
Luke.


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## darwenguy (May 10, 2021)

Rustkolector said:


> Luke,
> Good job on the alternator. I like slow running model engines that do things and alternators are my favorite engine load.
> 
> If you want to provide a good steady alternator output voltage to smooth out engine input speed fluctuations and electrical load changes these little switch mode voltage controls work well. They are in-line installed controls and hold a 12v output steady until generator input voltage drops to about 12.5-13v. Just don't exceed their maximum input voltage limit...or come too close.
> ...


Thanks Jeff, me too. 
I may look into this when i make a permenant display model, i actually quite like the fickering and having to adjust engine speed to the load. I think mark was right about the belt slipping.
Regarding eddy currents, its very hard to say, nothing realy noticable. There does feel to be more drag, but the bigger bearings have far more drag. 
Also i did notice that in the test with the plastic rotor i think ive wired the cappacitor the wrong way round or blew it. As the rectifier led would just flash with a flick of the finger and no load on the dc output.  were as the new one the capasitor now seams to hold a charge and the led lights and then fades off after a few seconds.
A curious feature, now is when flicked round with no load conected to the output, the rotor stops and then slightly starts to turn on its own untill the led goes off usually in the oposite direction, its only maybe quarter of a turn at the most, i suspect its the capacitor discharging to the stator and working like a motor.
Il do a test today for a good gour or so and see if the bearing loosen up or the aluminium gets warm, my concept of eddy currents is the old example of dropping a maget through a length of copper pipe and the drag slows its fall loads. But i wouldnt have a clue how to calculate this and dont intend to try.
Best regards.
Luke.


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## skyline1 (May 10, 2021)

Hi Luke



darwenguy said:


> Im thinking of maybe just a two coil stator and cylinder shape magnet. Maybe somthing like the peel tobo gensets used on locos. There have been some very nice models made already but very rare and pricey.



A 2 pole stator running at 30,000 R.P.M. a typical sort of speed for a turbine would give you a frequency of 500 Hz. (if I've got my maths right)  Frequencies in the 400 - 500 Hz range are fairly common in full size practice so I think the idea is perfectly feasible from an electrical point of view. The gas turbine APUs on passenger jets run at 400 Hz I believe. And they are used a lot in military applications.

We once built a large rotary power supply system for a Datacentre that ran at 440 Hz. Why this odd frequency (clue ask a musician) ?

I know the turbo generators you are talking about, they were very common on American locos. not seen quite so much over here but some locos were fitted with them. Models have been made but usually for larger locos 7 1/4" Gauge and up.



darwenguy said:


> i think ive wired the cappacitor the wrong way round or blew it.



Welcome to the club young man, you are not an electronics guy until you have blown up your first electrolytic it's a kind of rite of passage thing. You found out they are polarized the hard way like most of us, I have seen a few really big ones go in the past, they produce quite a  big bang !

The regulators Jeff mentions are the switching type I talked about in my PM they are another perfectly feasible option which would give you great control but might be a bit more than you need in this application.



darwenguy said:


> the capasitor now seams to hold a charge and the led lights and then fades off after a few seconds.



Great sign, it shows it's doing exactly what it's supposed to do.



darwenguy said:


> A curious feature, now is when flicked round with no load conected to the output, the rotor stops and then slightly starts to turn on its own untill the led goes off usually in the oposite direction, its only maybe quarter of a turn at the most, i suspect its the capacitor discharging to the stator and working like a motor.


 
Spot on, I think that is exactly what is happening, again it shows that everything is working as it should



darwenguy said:


> my concept of eddy currents is the old example of dropping a maget through a length of copper pipe and the drag slows its fall loads. But i wouldnt have a clue how to calculate this and dont intend to try.



Nor me, this sort of stuff is really deep electrical engineering, and the maths can get pretty eye watering. I studied it a little at College and don't intend to revisit it unless I absolutely have to.

Best regards Mark


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## darwenguy (May 10, 2021)

Just a little update, busey casting today but had a little play with shapes on my dinner. This is the sort of setup i eventually want to make, all my own designs i already made a dozen of these boilers, the engine i started years ago and needs finishing asap.


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## Rustkolector (May 10, 2021)

Luke,
The eddy currents I have encountered feel like a steady opposing force when you hand turn the alternator shaft without any load. When you spin the shaft on your plastic model the shaft likely accelerates exibiting only inertial opposing forces and then coasts to a stop with only the bearing seals as resistance. On the aluminum model the shaft may exhibit a stronger acceleration opposing force and stop turning more quickly when you let go of the shaft, and if powered for a longer time may build up heat when eddy currents are present. Unfortunately for DIY model alternator builders laminations using magnet steel are the only solution for efficiency and power. However, there are compromises that work quite nicely for those of us not chasing the best and most efficienct alternator design as you have shown here.  

You will get tired of flickering lights and adjusting the throttle. The SM in-line controller takes good care of the DC output and you will be very satisfied with the final more realistic performance. BTDT.
Jeff


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## Tim Wescott (May 10, 2021)

Rustkolector said:


> ... Unfortunately for DIY model alternator builders laminations using magnet steel are the only solution for efficiency and power. ...



I think that one could use enameled mild steel wire (probably by starting with mild steel picture-hanging wire, then enameling it with shellac or some modern equivalent).  Just wind it around a form into a toroid, in much the way the coils were wound, and use it to back up the magnets.  As long as the wire goes in the direction of the magnetic lines of force it ought to work.

The ferrite toroids that I proposed in earlier posts should also work, or a toroid wound from magnet-steel strip, if you can find any (probably from AC power transformer toroids, but AFAIK they don't make 'em that small).  There'll still be a loss of efficiency due to long magnetic paths if you can't figure out how to make pole pieces, but using a ferrous toroid should shield the aluminum housing from changing magnetic fields.

All of which is moot -- all suggestions of putting in a magnetic circuit have been resisted.  I even found some ferrite toroids that would work in between the coils and the aluminum housing, and that was rejected.  So -- let the work proceed.  It's not like it's going to be a paying project.


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## darwenguy (May 10, 2021)

Jeff


Rustkolector said:


> Luke,
> The eddy currents I have encountered feel like a steady opposing force when you hand turn the alternator shaft without any load. When you spin the shaft on your plastic model the shaft likely accelerates exibiting only inertial opposing forces and then coasts to a stop with only the bearing seals as resistance. On the aluminum model the shaft may exhibit a stronger acceleration opposing force and stop turning more quickly when you let go of the shaft, and if powered for a longer time may build up heat when eddy currents are present. Unfortunately for DIY model alternator builders laminations using magnet steel are the only solution for efficiency and power. However, there are compromises that work quite nicely for those of us not chasing the best and most efficienct alternator design as you have shown here.
> 
> You will get tired of flickering lights and adjusting the throttle. The SM in-line controller takes good care of the DC output and you will be very satisfied with the final more realistic performance. BTDT.
> ...


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## skyline1 (May 11, 2021)

Hi Luke 

It's coming along great ! I love your vertical engine, it looks similar in design to a Stuart 10. 

This setup is going to look great when it's finished. Very " Late Victorian, Early days of Electricity" styling. I think you have caught the period really well. 

How do you intend to fuel the boiler Gas ?

Best Regards Mark


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## darwenguy (May 11, 2021)

skyline1 said:


> Hi Luke
> 
> It's coming along great ! I love your vertical engine, it looks similar in design to a Stuart 10.
> 
> ...


Thanks Mark, yes i suspect it was sort of based on a stuart 10. I actually got the desighn from a drawing by 'julius de waal' his drawings are beutifull and freely available. Witch im sure he coppied the s10 design of. I then made it four times bigger and changed the stroke longer and nearly everything els to make this..... my first engine..




I then learnt cad and designd it again in half the scale and thats were its at now.
I think il run the boiler on gas, ive tried the solid fuel and its too messy and soon clogs up the fire tubes. Before i get shouted at by somone, i know the boiler isnt an efficient design the alloy is a great heat conductor! and no cladding! But it works for me and make more than enougth steem for my needs just want it to look nice. Heres what they look like finished..








And i also need to make a feed pump for this and a resovoir.
And a few more lamps with a classic volt meater display will finish it off nicley i think.
Best regards.
Luke.


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## Johan Maritz (May 12, 2021)

Beautiful boiler!


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## Steamchick (May 12, 2021)

Tim Wescott said:


> I think that one could use enameled mild steel wire (probably by starting with mild steel picture-hanging wire, then enameling it with shellac or some modern equivalent).  Just wind it around a form into a toroid, in much the way the coils were wound, and use it to back up the magnets.  As long as the wire goes in the direction of the magnetic lines of force it ought to work.


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.


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## skyline1 (May 12, 2021)

Fleming's rules IIRC


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## Steamchick (May 12, 2021)

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


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## Tim Wescott (May 12, 2021)

Steamchick said:


> 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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## ajoeiam (May 13, 2021)

skyline1 said:


> Fleming's rules IIRC


Sorry - - - what are 'Fleming's rules'?


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## darwenguy (May 13, 2021)

Steamchick said:


> 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


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## skyline1 (May 13, 2021)

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)


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## Steamchick (May 14, 2021)

darwenguy said:


> 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


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## darwenguy (May 14, 2021)

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


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## Steamchick (May 14, 2021)

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


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## ajoeiam (May 14, 2021)

skyline1 said:


> 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.


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## Chiptosser (May 14, 2021)

Use the other hand.


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## skyline1 (May 14, 2021)

darwenguy said:


> 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 



ajoeiam said:


> 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


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## SailplaneDriver (May 14, 2021)

Chiptosser said:


> Use the other hand.


There is a left hand and right hand rule. They are not interchangeable.


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## kf2qd (May 14, 2021)

Anyone ever tried silicon steel?


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## SailplaneDriver (May 15, 2021)

kf2qd said:


> 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.


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## djswain1 (May 16, 2021)

darwenguy said:


> 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.


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## darwenguy (May 16, 2021)

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.


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## Steamchick (May 16, 2021)

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


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## awake (May 18, 2021)

ajoeiam said:


> Sorry - - - what are 'Fleming's rules'?


The only two I remember are "Shaken, not stirred" and "Never say never again."

Wait - are we talking about the same Fleming? Ian, right?


----------



## darwenguy (May 24, 2021)

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.




And just some of the prototype coils!




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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## awake (May 24, 2021)

That's a lot of wire and a lot of winding - impressive results!


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## darwenguy (May 24, 2021)

Thanks. yes the winding machine has been essential, it must have made over 150 seperate coils now.
But i am pretty fed up with it to be honest, time to clear the bench and look at somthing els for a while.
Best regards.
Luke.


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## awake (May 24, 2021)

Sounds like it is time to "wind down" this project.


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## Steamchick (May 26, 2021)

Coil-up with a good book... And a glass of your favourite tipple.
An interesting development.
Thanks for the story, Luke.


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## darwenguy (May 27, 2021)

And just one more pic, also tried some green paint for a change  
Still waiting for the little brass wingnuts to finish these.


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## Madsciguy (May 31, 2021)

For simplicity divide by four, giving 3 coils ( at 120 degrees apart) and four poles (N,S,N,S). In one rotation, each coil would see two AC cycles, so 1000 rpm / 60 * 2 = 33.3 Hz (4 poles). So for a 16 pole design the frequency would be 133 Hz. For highest voltage connect the coils in three groups of 4 (series) in a "Y"  three phase configuration.


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## DKGrimm (Jun 1, 2021)

Madsciguy said:


> For simplicity divide by four, giving 3 coils ( at 120 degrees apart) and four poles (N,S,N,S). In one rotation, each coil would see two AC cycles, so 1000 rpm / 60 * 2 = 33.3 Hz (4 poles). So for a 16 pole design the frequency would be 133 Hz. For highest voltage connect the coils in three groups of 4 (series) in a "Y"  three phase configuration.


Your suggestion for wiring and your math are good, but I see only twelve poles on the rotor in the pictures.  That would also work, and would give 100 Hz.


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## darwenguy (Jun 2, 2021)

Madsciguy said:


> For simplicity divide by four, giving 3 coils ( at 120 degrees apart) and four poles (N,S,N,S). In one rotation, each coil would see two AC cycles, so 1000 rpm / 60 * 2 = 33.3 Hz (4 poles). So for a 16 pole design the frequency would be 133 Hz. For highest voltage connect the coils in three groups of 4 (series) in a "Y"  three phase configuration.


This makes no sense at all! And just seams a crazy ramdom statement to a question nobody asked. Dividing 12 by 4 would be 4 sets of 3 at 90 degree appart. And why would wiring it 3 phaze be sipmpler?


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## DKGrimm (Jun 2, 2021)

DKGrimm said:


> Your suggestion for wiring and your math are good, but I see only twelve poles on the rotor in the pictures. That would also work, and would give 100 Hz.


I just proved to myself how easy it is to put your foot in your mouth.  12 coils in the stator and 12 magnets on the rotor would put all coils in phase with each other, so no three phase output.  The output would still be 100 Hz at 1000 rpm, though.


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## MMER1116 (Jun 2, 2021)

Great job, thanks for sharing your project.


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## James Barker (Jun 2, 2021)

I am liking this post... it is different and I would love to get the STL. files for the casings.... Well done.


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## Madsciguy (Jun 15, 2021)

The question was asked back in Oct about a 12 coil 16 pole machine. Correct though, the pics seem to show a 12 coil and 12 poles,  a single phase machine with clogging reduced by embedding the magnets which reduces the flux seen by the coils. A three phase design provides much less ripple after rectification (assuming dc output is desired)


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## Steamchick (Jun 16, 2021)

Hi Madsciguy. ( I like the descriptive name!).
Perhaps you can explain the comment about "embedding magnets"? My physics background suggests that building magnets into metal will effectively short-circuit some of the field...or using metal clamps the bridge N to S, or metal bolts.... 
This then poses the big problem for most non-technical folk of how to fix magnets into the rotor?
Do you have any clever ideas?
Personally, I favour copying the car alternator arrangement for the armature, with the "field generator" clamped between 2 claw-pole pieces? Is mild-steel or cast-iron preferred for these poles, as "magnetic" alloy irons are not so readily available?  
Another question - I have a bicycle alternator, where the steel magnet rotor (10 poles) is on the outside of the stator. I propose to re-make the stator coil and pole pieces (rusted and broken) but thought to increase the field by adding neodymium magnets glued onto the pole pieces. Will this be a benefit, as the extra flux will saturate the steel, so will that prevent the extra flux being useful? Or will it simply use the permeability of the air for the "surplus flux"... I'm simply to old and addled to be clear in my head what will happen?
Finally, in a generator with alternating field poles, can aluminium be usefully used for the coil core? Or will the sinusoidal magnetic field simply lose all the power to internal circulating induced currents within the aluminium? (Back EMF.). I think those cores for coils should have high permeability and low remanence? But am I right thinking that mild steel has high permeability and high remanence? Aluminium, low permeability and low remanence, stainless steel low remanence and low permeability?
I.E. what metal must I buy to make iron cores for coils?
Thanks,
K2


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## Madsciguy (Jun 16, 2021)

Hi Steamchick,
First the magnet mounting question, yes, embedding cause flux lost and potential eddy current losses when running. I made finite element models to illustrate.  This is a 12 pole,  12 coil simulation with a 1.5mm gap, 10x10x3mm neo magnets on a 100mm dia rotor.




You can see the flux concentration at the magnet edges compared to surface mounting




The flux distribution in the gap is reduced and is not as even across the face




SURFACE MOUNT




.
EMBEDDED

This example shows that the gap flux (generated voltage) will only be reduced 15 to 20% by embedding the magnets 90% into the steel rotor. Flush mounting would likely cause a greater reduction. I typically use a pvc or wood jig to hold the magnets while bondingmagnets, using a 2-part epoxy with good shear strength. The magnets will always be strongly attracted to the rotor, so we only need to overcome shear and centrifugal forces.  When bonding magnets, keep the bond line thin and always clean all surfaces with acetone (not alcohol) before applying adhesive.

If the magnet flux is generally constant I use a mild steel, for a stator and pole pieces, I'd use ductile iron or lamination.
Aluminum for pole pieces would change your generator into an eddy current brake. So no.

Using Neo magnets could improve the bicycle generator if the air gap is not too small. You would likely get higher voltage at the expense of increased torque requirements. Friction drive? = abrasion of sidewall

For coil cores, use ductile iron or ferrite

Hope that helps


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## Willyb (Jun 16, 2021)

Hi Madsciguy 
Thank you for explaining this and adding the diagrams.  The topic can be a little hard to grasp especialy as one gets older.  I'm planning to design and build my own model generator in the near future.
Cheers
Willy


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## Steamchick (Jun 17, 2021)

darwenguy said:


> And just one more pic, also tried some green paint for a change
> Still waiting for the little brass wingnuts to finish these.
> View attachment 125911


Hi Luke,
I was loking for your website - but failed to find it (stupid me??) - and found this Utube clip. I guess you are NOT Myfordboy?

I suspect your generator is a whole lot more powerful than his...?
Where can I go with a view to purchasing a set of castings?
Thanks,
K2


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## Steamchick (Jun 17, 2021)

Hi madsciguy. Excellent explanation. The generators I fiddle with are for model steam engines. Old Sturmer Archer hub-dynasty are cheap when broken. Usually a broken wire or rust instead of laminations.
The 10 pole pm rotor is usually good, so just needs a new stator, so I'll have to find some ductile iron.
Thanks.
K2


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## DKGrimm (Jun 21, 2021)

Madsciguy said:


> I made finite element models to illustrate.


Your analysis is a valuable contribution to understanding the flux mapping in an alternator.  What analysis tool do you use?


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## Madsciguy (Jun 21, 2021)

I have been using FEMM (HomePage:Finite Element Method Magnetics) for about 20 years but only can consider myself a casual user. It is open source and will probably require some sort of prior magnetics/electrical knowledge to be a useful tool. I believe it was mentioned earlier in this thread. It is often used with lua scripting language to produce multi-step simulations of complex electrical machines. Many examples are available for those willing to tackle the learning curve.


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## DKGrimm (Jun 21, 2021)

Madsciguy said:


> It is open source and will probably require some sort of prior magnetics/electrical knowledge to be a useful tool.


Thanks for your input.  I have a (1962) masters degree in EE and some history in magnetic design, which means I have kind of a general feel for magnetic fields and recognize the vocabulary, but these methods are all new to me.  It sounds interesting enough to invest a little time studying.


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## Tim Wescott (Jun 21, 2021)

The big thing about any kind of simulation is that you have to either know what the simulator is doing under the hood, or have a good idea of what you _should_ see.  Because sometimes they go crazy.

Just trusting the simulator sometimes gets you garbage.

(And I've used FEMM -- it does its job well, but the learning curve _is_ steep).


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## Madsciguy (Jun 21, 2021)

Tim Wescott said:


> Just trusting the simulator sometimes gets you garbage.


I agree with Tim, it took 3 years of training before I had any confidence in my Solidworks stress simulations and nothing got presented until it was checked by a colleague.


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## DKGrimm (Jun 22, 2021)

Tim Wescott said:


> The big thing about any kind of simulation is that you have to either know what the simulator is doing under the hood, or have a good idea of what you _should_ see.  Because sometimes they go crazy.
> 
> Just trusting the simulator sometimes gets you garbage.
> 
> (And I've used FEMM -- it does its job well, but the learning curve _is_ steep).


Right you are, Tim.  I did a bunch of mathematical modeling during my career, both good and bad.  Modeling is a powerful tool for designing and understanding things, but the worst mistake you can ever make is to loose track of the fact that it is always only a model.


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## Tim Wescott (Jun 22, 2021)

Just like building a physical model of a generator (see how I'm trying to pull the thread back on track?)  You need to decide which parts you want to model accurately and which parts you don't care about, which parts will just naturally work and which parts you need to have to change because they're in a different environment...


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## skyline1 (Jun 22, 2021)

I agree with you on that one Tim, 

as as my late father put it "you can't scale nature". With so many square and cube laws at play here especially with Electro - Magnetics in these small scales some things need to be either overscale, underscale or done in a different way in order to get these things to work at all. 

At these small sizes phenomena which in full size are largely insignificant and can be ignored start to have much more pronounced effects. 

This tends to make Computer Modelling, as good as it is, less reliable. The best way is a physical model, and experimentation, just as the OP has done, (I'm trying to pull the thread back too !)

Such is his dedication, that he has wound several sets of tiny coils until he got the balance right and nearly went "round the bend" (ouch, bad pun) doing it. 

At the end of all this hard work and experimentation he has produced a working, practical and I think beautifully period looking alternator.

His design is not quite as unconventional as you might think "coreless" machines do exist and they are widely used especially in applications where weight is a concern. (like drone motors)

His seemingly "inside out" arrangement is also not unconventional at all, in fact it is the most commonly used arrangement today known as a rotating field alternator Advantages of Stationary Armature & Rotating Field Alternator 

Best Regards Mark


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