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Author Topic: DIY Dynamo/ Generator  (Read 8561 times)

gondolier88

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DIY Dynamo/ Generator
« on: July 14, 2009, 09:11:46 PM »

Hi,

Has anyone here made trhemselves a dynamo out of a motor?

I understand that you need something called a voltage regulator- but thats all I know!

Enlighten me please... ;)

Greg
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stallspeed

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Re: DIY Dynamo/ Generator
« Reply #1 on: July 14, 2009, 09:29:05 PM »

How to destroy a voltage regulator part 1 ..........
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boatmadman

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Re: DIY Dynamo/ Generator
« Reply #2 on: July 14, 2009, 09:32:25 PM »

and if you want 3 phase, you have to decide whether  it is to be self exciting or externally exciting :o :-))
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stallspeed

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Re: DIY Dynamo/ Generator
« Reply #3 on: July 14, 2009, 09:55:28 PM »

The replies will get better if the question is made easier. ;)
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Bee

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Re: DIY Dynamo/ Generator
« Reply #4 on: July 14, 2009, 10:17:08 PM »

Even with a regulator you really need a battery to stabilise things otherwise voltage just goes up the faster it spins and down as you put a load on it. The alternators in cars have a specialised regulator that provides a closed loop to help controll it all, but these regulators are not at all the same as 'voltage regulators' used to supply electronic circuits.

You might find a bit more explanation of this if you research wind generators and alternative energy.
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Proteus

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Re: DIY Dynamo/ Generator
« Reply #5 on: July 15, 2009, 12:26:33 AM »

is this for home or model?

Proteus
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gondolier88

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Re: DIY Dynamo/ Generator
« Reply #6 on: July 15, 2009, 11:09:53 AM »

Hi all,

I'm talking model size here- 6 or 12V- I would like to make a scale generating plant in a steam tug i'm designing and want to know the boundaries it would have to fall into to work reliably ie;

- Motor Size
- How to regulate voltage reliably
- How to calculate loads

It would be driven by it's own dedicated steam engine so would have a max rpm available of around 800- 1200 rpm.

Diagrams and INTELLIGENT answers <*< would be welcome please. :-))

Greg
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sheerline

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Re: DIY Dynamo/ Generator
« Reply #7 on: July 15, 2009, 11:39:10 AM »

Hi, so many variables here and very difficult to advise but I did a one off experiment using a Buhler motor with my steam engine,. This motor produced quite a good output. I did not clock the rpm but the maximum I could screw out of it was 9Volt dc @t 1/2 amp... thats just over half a watt. This was on my Vtwin oscillating engine, double acting, 15mm bore, 20mm stroke, running flat out at something like 20psi. For fun, I hooked it up to my transistor radio, using an electrolytic capacitor across the output and tweaked the speed of the engine for 9volt at the few milliamps drawn by the radio and carried on working in the workshop with this lot steaming and whizzing away in the background. After a couple of hours of this, I realised the thing had consumed huge quantities of gas (poor boiler arrangements) and was costing me a fortune but it proved that these motors were perfectly capable of producing a useable output. So, in answer to your question, yes it can be done, it is very wasteful but who cares, it's fun to watch.

Perhaps some of the other chaps have more detailed figures or may suggest a better motor/ generator than the one I happened to have sitting around.
Details of the Buhler motor come off the label on the casing and are as follows:     127k26960 ... 1.13 .043. 263 .00
Motor length... 3" (75mm)
Motor dia........1 5/8" (40mm approx)

Experimentation is very much the name of the game here... great fun even if the outputs and efficiency figures are totally lousy.
 Good Luck....Chris
Supplied by Model Motors Direct (don't know if he is still around)
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malcolmfrary

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Re: DIY Dynamo/ Generator
« Reply #8 on: July 15, 2009, 11:58:21 AM »

You could try a brushless motor.  A three terminal one will give three phase AC.  Voltage and current supplied will depend on the motor, speed of rotation and load.l

There is a nice explanation in here -

http://www.allaboutcircuits.com/vol_3/chpt_3/4.html

showing how to turn this into DC.  A nice big smoothing capacitor (electrolytic, about 1000uF per amp and a voltage regulator should do the job.
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gondolier88

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Re: DIY Dynamo/ Generator
« Reply #9 on: July 15, 2009, 12:28:04 PM »

Hi Chris, Malcolm,

I knew it must be possible!

How would you improve your design to make it more efficient Chris? Were the innefficiencies due to the steam plant or the motor or both?

Malcolm- thanks for the link, most helpful. When you say voltage and current are motor dependant do you mean that a motor that requires 12V and 4AHr to run @ 1500 rpm would produce 12v, 2AHr being driven @ 1500rpm?

Greg
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sheerline

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Re: DIY Dynamo/ Generator
« Reply #10 on: July 15, 2009, 01:01:15 PM »

The whole setup is simply just inefficient but you do the best you can. Msetup was just pure interest really but first off, you need a good engine /boiler arrangement . The engine should at least be double acting and not the oscillating type as these are notoriously wasteful on steam. If you were serious, you should really use a compound unit and one with a variable valve adjustment at that, so you can adjust the valve cut off and save energy. You also need a heavily lagged good design boiler.. there are many deigns for different applications here.r.
Using a motor as a dynamo is also not the best way. Dynamo's are wound a bit differently and you need a dedicated dynamo to get the best results. I don't have any info on these.. sorry, some of the others may be able to help here.
The dynamo drive also needs ot be considered and direct drive would be simplest and less frictional.
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dreadnought72

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Re: DIY Dynamo/ Generator
« Reply #11 on: July 15, 2009, 02:01:19 PM »

Sheerline's right - inefficient is the word.

A boiler/engine venting steam to the atmosphere might run around 5% efficient (in terms of the gas energy used to fire it). This sounds appalling, but you are generating rotary motion out of heat, so maybe that's fair enough.

A dynamo can run at ~90% efficiency to produce electricity from rotary motion, but if you're feeding that electricity into batteries and then into motors you'll be dealing with another ~90%. So the gas -> prop efficiency chain looks like:

0.05 * 0.9 * 0.9 = 0.0405

~4% efficient!

Not good - and while you might think that there's benefits in having ESC-type control over the motors, in reality you'd be placing sensitive electronics into a warmer, damper environment, compared to the (far simpler) battery-motor setup.

Andy
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sweeper

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Re: DIY Dynamo/ Generator
« Reply #12 on: July 15, 2009, 03:53:01 PM »

DC motor actiing as DC generator?
Yes, the types of generator are the same as those for motors ,electrically they are classified by the method of connection of the field system in relation to the armature.
To regulate the voltage adopt the same method as the "real" thing i.e. use a variable resistor to vary the field current - assuming of course that you have a machine with wound magnetic poles.

At the speeds you are considering it would be unlikely to be a raging success. If you think of the old stationary steam plants that were sold as toys (Mamod etc), using a single cylinder engine the output was barely sufficient to light a torch bulb.

In real terms a nice idea, in practice I think it would be a non-starter.
Sorry if this does your idea in, as an experiment great. In real terms, bury the idea! 
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malcolmfrary

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Re: DIY Dynamo/ Generator
« Reply #13 on: July 15, 2009, 04:03:57 PM »

Quote
When you say voltage and current are motor dependant do you mean that a motor that requires 12V and 4AHr to run @ 1500 rpm would produce 12v, 2AHr being driven @ 1500rpm?
I meant it literally.  Motor makers are sketchy at best when describing the performance of their products when used as intended.  Information about any motor performance as a generator will be non existent.  
Voltage is generated when the magnetic field links with the coils so is mostly dependent on the number of turns in the coil, current is somewhat dependent on the strength of the magnet and the reluctance in the magnetic path.  The faster the linkings are repeated, the more of both.  Probably.
When under load, anybody's guess.  It is an area at the moment for fairly informed guesswork backed up with patient testing, probably followed by the realisation as to why R&D is so horribly expensive.
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sheerline

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Re: DIY Dynamo/ Generator
« Reply #14 on: July 15, 2009, 08:14:58 PM »

Malcolm, in a nutshell, what we are all saying here is that you CAN produce energy using the ideas you have in mind but you need to get yourself some hardware together and experiment. If you really want to find out what kind of output can be gained from different types of motors you may have kicking around, try spinning them up from say... another motor and measuring the outputs from them. You will be able to load the motor/dynamo with some kind of variable resistor whilst measuring the current through it, whilst at the same time, measuring the voltage at the output terminals. As you load the thing up, the current will rise but the voltage will drop off... and so will the speed because the generator will begin to load the motor which is driving it. You could also do the same measurement figures for the driving motor. and draw up a graph or at least a column of figures for both. Only then will you be able to work out how inefficient your generator is.
One of the greatest learning curves comes from 'playing' with things and if you don't truly understand it all to begin with, you will eventually get a feel for what's going on and it will all begin to gel in your mind. Theory is great, but getting the hardware on the bench in front of you can't be beaten as the hands on method is much more absorbing.
   
Have a go mate, it's fun and interesting and even if it has the worst efficiency figures known to man, who cares, we're modellers and will happily spend hours watching the wheels go round just for the sake of it.  :-))
Chris
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gondolier88

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Re: DIY Dynamo/ Generator
« Reply #15 on: July 15, 2009, 08:28:41 PM »

Hi,

As far as the steam plant is concerned- it will be a gas or oil fired Yarrow watertube running at 100psi, Stuart D10 as main engine- I want to make a proper working steamboat however- so I want a generator set to complete the look- hence the need for a dynamo. What do people think of using a bottle dynamo from a bike lighting set- usually 12V on the old ones- reliable as they come!? I would be using a double acting oscillator as the generator engine- I could always run it through a gearbox to get 1500-1800rpm.

Greg
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malcolmfrary

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Re: DIY Dynamo/ Generator
« Reply #16 on: July 15, 2009, 09:22:02 PM »

I always remember them being very notchy to turn by hand so a hefty flywheel might be in order, and they always made the bike harder work, but that might have been due to the side loading.  As Sheerline says, the only real way to find out is to try.  I still reckon that a brushless motor and a bunch of 1N4005 diodes will give reasonable results.
Some of the original users of electricity were the fairground showmen, one steam traction engine to power carousel and a generator to light it at night.  Of course they didn't have to worry about RFI, there being no radios at the time to interfere with.
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Martin [Admin]

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Re: DIY Dynamo/ Generator
« Reply #17 on: July 15, 2009, 09:36:01 PM »


How much power / amperage would you like from the dynamo setup Greg?

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sheerline

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Re: DIY Dynamo/ Generator
« Reply #18 on: July 15, 2009, 09:42:22 PM »

Sorry Greg, I referred to you as Malcolm in my last post.
These old units were indeed notchy and it took a fair amount of torque just to get over the first hump of the magnetic field.
Again, 1800 rpm doesn't sound a lot, these dynamos used to fairly scream round. Now I haven't done any calculations at this point, I will leave it up to you but as I remember them, you had to be travelling at a fair rate of knots to get the lights anywhere near bright enough so, find out the dia of the dynamo wheel and the cycle wheel, calculate the ratio and start at 10mph as a guess. If you can find out how many rpm the cycle wheel rotates at thatspeed and multiply it by the dynamo  ratio, you will have the dynamo rotational speed at 10mph. Without the calculation, I reckon it must be quite high..... and the lights weren't that bright at that speed either!!
If you just want something simple to keep your boat radio nicads charged or run some LED lamps, then a simple setup with a selected motor from experiments may just do that for you.
Give it a whirl on the test bench, I'm sure us chaps out here would be interested to see what you get from it.

BTW Malcolm, one thing I remember about the old fairgrounds... when the dodgems power switch was thrown , the blast of 60s music being played on the record deck used  to slow down and gradually pick up once the cars got rolling. The volt drop was horrendous and the cables used to heat up. I still hear the odd 60s record on the radio which reminds me of fairground days.......and it doesn't sound quite right because it doesn't slow down at some point!! I don't know how old you are but I know there are more than just a few on here who know what I'm on about.
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malcolmfrary

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Re: DIY Dynamo/ Generator
« Reply #19 on: July 15, 2009, 10:00:29 PM »

Quote
BTW Malcolm, one thing I remember about the old fairgrounds... when the dodgems power switch was thrown , the blast of 60s music being played on the record deck used  to slow down and gradually pick up once the cars got rolling. The volt drop was horrendous and the cables used to heat up. I still hear the odd 60s record on the radio which reminds me of fairground days.......and it doesn't sound quite right because it doesn't slow down at some point!! I don't know how old you are but I know there are more than just a few on here who know what I'm on about.
I was thinking of the ORIGINAL users, before the turn of the previous century.  Up to last year when the new management got its knees firmly under the table at the Pleasure Beach, there was a very nice Fairground Society show which we as a local club had a standing "other interest" invite to display at.  It was always very illuminating (in every way) to see the results of another modelling discipline.  Some of the displays were nothing short of astounding both from the point of view of effort and accuracy.  Like the three and a half foot across carousel that packed down into its truck in the same way that the original did.  And I only saw that at the end of the show when he packed up.
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bogstandard

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Re: DIY Dynamo/ Generator
« Reply #20 on: July 16, 2009, 01:40:29 AM »

The model railway lads use a very small turbine to produce electrickery for their locos. Powered by a steam bleed from the boiler thru an on/off valve.
This runs at a constant hi speed turning a home made generator, but that could easily be replace by say a 280 or 380 sized motor to generate enough power for a myriad of small lights.

The main downside is the high pitched, continuous whine.


Bogs
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sheerline

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Re: DIY Dynamo/ Generator
« Reply #21 on: July 16, 2009, 09:53:45 AM »

BS, I think the turbines are quite steam greedy aren't they?  He is allready using a Stuart D10 as a main drive motor and running his boiler at 100 psi . Coupled with the twin cylinder V twin intended to run the dynamo I would suggest the heating requirements would have to be quite generous and the boiler capacity fairly large in an effort to cope. If the generator was kept fairly small and the loading pretty light he would probably get away with it but I reckon the bike dynamo is a bit on the heavy side.
Having said all that, it would be nice to know the bore and stroke of the oscillator, that way we could maybe get a feel for what kind of power is available for a generator.
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bogstandard

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Re: DIY Dynamo/ Generator
« Reply #22 on: July 16, 2009, 02:30:43 PM »

Sheerline, you are quite right, they are very greedy little things, but it needed to be mentioned just to show that a piston engine was not the sole requirement.

Again, another way would be if the engine was a constant runner, and used a variable prop for speed control of the boat, then the easiest way would be to put a geared takeoff from the main engine to drive a dynamo. That would ensure a continuous supply from the dynamo.

As is suggested a wobbler engine, the smaller steam engine will require a continuous bleed from the boiler unless you want the lights to go dim or out when the engine slows down.

I have found that when playing about with motors to use as dynamos, then the 12 volt 280 or 380 size are more than man enough for the job of lighting up a dozen small 12 volt grain of wheat bulbs when wired in parallel, and if you get the small low voltage 1.5v LED's, then a small 12 volt motor will be more than ample to power 10 of them if wired in series.

Bogs

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sheerline

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Re: DIY Dynamo/ Generator
« Reply #23 on: July 16, 2009, 03:31:26 PM »

Yes Bogs, I concurr it's all down to consumption at the end of the day and if the load is light (no pun intended) then the whole thing could be pretty compact.
As a point of interest, I repaired a diesel electric loco for Bob Symes  (he of Tomorrows World fame) many years back.I believe it could have been 2 1/42 guage.  He was running an old motorcycle dynamo from a glow motor and it produced loads of energy, sufficient to supply all the drive motors on the bogies and propel this big heavy machine adequately. Admittedly, the glow motor was powerful and spun the dynamo at considerable rpm so he had bags of power and all controllable via the speed controller, so producing fully variable forward and backward power to the drive motors.
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Re: DIY Dynamo/ Generator
« Reply #24 on: July 16, 2009, 05:14:33 PM »

would running the set up off a strimmer engine be better?
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