Model generator build from scratch

[skyline1]

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]

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]

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]

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]

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

 

[darwenguy]

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.

 

[skyline1]

Hi Luke

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)

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

 

[Rustkolector]

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.
https://www.ebay.com/itm/121425456284?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649
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

 

[darwenguy]

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.

 

[darwenguy]

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.
https://www.ebay.com/itm/121425456284?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649
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

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.

 

[skyline1]

Hi Luke

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.

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.

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.

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

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

 

[darwenguy]

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.

 

[Rustkolector]

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

 

[Tim Wescott]

... 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.

 

[darwenguy]

Jeff

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, i know what you mean im just saying i realy cant tell you as if it is its negligable. I ran it today for a good hour and half and nothing got hotter than room temp, the bearings were a little warm but thats it.
It does slow down quicker but i didnt have the capacitor on the first test.
Im realy not looking for a super efficient generator.
thanks jeff, im not ignorant and have listend to every recomendation and expained my method and reasons. Ive weighd up what knowlage i have and my abilitys and what materials are readily available to me times the man hours and this is my solution i know its not perfect but was never intended to be.
Thanks I did say i may look into voltage regulation when i set up somthing permenant.
Best regards.
Luke.

 

[skyline1]

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

 

[darwenguy]

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

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.

 

[Johan Maritz]

Beautiful boiler!

 

[Steamchick]

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.

 

[skyline1]

Fleming's rules IIRC