stirling genrator

[johnny]

how can i make a small generator for my stirling engine? i have the solar 1 model now. just getting started help would be appreciated.

[Ian S C]

Hi Johnny, small DC electric motors (toy) if driven will generate electricity. A good place to get one is an old casset player. The idea is to find one that runs fairly slowly, as the motor needs to be turned at the same, or better speed to give the rated voltage, ie., a 12 volt motor that usually runs at 2000rpm, must be turned at 2000rpm or a little more to produce 12 volts, a lot of motors run at speeds like 10,000 rpm +. Have a look a my gallery, theres a little motor there (2.5 cc)with a casset tape motor, this will run a small transistor radio, or charge NiCads. Start small, and build up if you feel it will take it. Ian S C

[theropod2]

Hey Johnny,

Also look into the small stepper motors that can be found in inkjet printers. These stepper motors will have 4 or more wire leads and when spun will produce alternating current. Usually the inkjet driver will also have rectifiers or diodes to convert that AC into DC. The thing to watch for with these motors is the "cogging" or resistance to motion. Some can have a quite high holding power as the magnets interact with the coils. The reward, if you can get one to work, is a higher output than most brushed DC motors of comparable size.

R

[Ian S C]

Most stepper motors have too much resistance to rotation (cogging) to be a lot of use in small Stirling Engines, the whole system, motor and generator must have the minimum of friction. Ian S C

[Junkie]

Yes, nearly all steppers have too much resistance. I found one that works on one of my coke can engines,
but I think it's unusual to find a stepper that will work in this situation.

For the engine you describe, a DC motor or home made PMG is probably your best bet.

[johnny]

how many windings would i need to include in a pmg to get 9 volts out or is 9 volts aiming high? here is a youtube video of someone elses solar 1 running
http://www.youtube.com/watch?v=wmyDq-49yd0&feature=related

[Ian S C]

Are you running the motor by solar power or with meths, or gas, depending where you are the solar power is proberbly as good or even better than other fuels. If you look on google under small home made generators/ alternators, you should be able to find one powered by a Hamster, a little developement of that, and you'll be up and running, that alternator runs at the speed of the little wheel thing that the Hampster runs in, so yours will I hope run a good bit faster, it will need a diode to convert the AC current to DC if you want to charge batteries, or run a radio, or light LEDS. Ian S C
just put in to google hamster power

[johnny]

i am still expirimenting with fuel but in general i will use kerosene. the reference to solar is a brand name.

[Ian S C]

Have you used kero before? If you use it with a wick, you will find it burns with a dirty flame, and it will leave whats called lamp black on the displacer cylinder (lamp black is on of the blackest pigmints there is). The way to get a clean flame is to use a pressure burner, something like a plumbers blow lamp. Ian S C

[johnny]

tried kero and yes it get the motor dirty i wont be using kero in the future lighter fluid works as well as vodka thanks for the info

[Ian S C]

Johnny, use denatured alcohol/ metholated spirtits, or isopropyl alcohol90% or better. Ian S C

[johnny]

how many windings will it taketo get 9 volts from a pmg

[Ian S C]

Johnny, how longs a bit of string, it depends on a number of things, how many magnets, and how strong are they. How fast is the generator turning. If you make up a disc with the magnets on it, rigged up to rotate either mounted on the crank shaft or so it can be belt driven, you can wind a trial coil of say 40 turns of magnet wire (enamal covered copper), don't no how you would measure wire where you are, but 24/26 SWG would be as good as anything. Attach a volt meter to the coil, and bring it close to the rotating disc, and see what you get, maybe 1.5V/ 2V, you can then wind more coils to get a good voltage, you might want 6 or 8 coils, you should be able to get wire at electronics hobby stores, and also the magnets, rare earth magnets are the way to go, although ferrite ones wont be too bad, just not so strong. Ian S C

[johnny]

thank you for the info Ian S C