generators

[tew]

What would be the best generator for a heat engine that runs at about 300 rpms. It has a 2" power cylinder. I currently use an old 18 volt drill motor. The best I get is about 1.2 volts

[Ian S C]

tew, use a number of different motors as generators, one of the best is a motor I got out of an old HP printer, I drive that one from a 4" pulley on the Stirling Engine, to a 1" pulley on the generator. Another good one is the motor from a Braun stick mixer (kitchen thing), it's a DC motor rated at 500 Watts, 220 V, and my Ross Yoke motor will run it up to 18 V, or 12 V under load. One of my smaller engines runs a motor from a cassette tape recorder, with enough power to run a 3 V transistor radio.
At 300rpm you might need to gear up the drive, you'll have to experiment on that, it depends on the motor you choose, and the power you have to drive it with.
You could use a bicycle dynamo, this would of course produce AC current, but you can soon sort that out with a diode, or better 4 diodes if you want DC.
Ian S C

[tew]

thx. Ian. Are any of your generators brushless and do you get more output from a brushless?

[Ian S C]

A brushless generator is an alternator, and will produce AC volts. Yes I have a couple, one based on a Sturmey Archer hub dynamo, and the other a modified shaded pole electric motor. A new armature was made, it's a 6 pole claw type with the magnets from three speakers(you can see the edge of one). The shading coils were cut, but I don't know if that's needed, there is a front cover with a ball race, and the rear bearing is also a ball race. Had it running on a steam engine, through a transformer to light a 25 Watt, 230 volt light to about half it's light out put, On my Stirling Engines it only puts out a fraction of that, but you only get out what you put in minus a bit.
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[tew]

Ian that looks like it would do the job. Do you have any idea of the effeciency of it. Where would I get a brushless about 1/4 that size?

[Ian S C]

I think that motor came from an electric fan. As it was as a motor, 5 Watt, 240 Volt, 0.3 Amp, 875 rpm, 50 Hz. it was made by Crompton Parkinson. The case is 4 inch diameter by 3 inch long. I'm going to have to strip it and put some Loctite on the shaft, as the armature seems to be a little loose on the shaft, I can't remember how I fitted it, there might be a nut on the other end of the armature. I ran it on one of the engines a week or two ago, didn't notice it then, Oh well something else to do.
You would need a lathe to make a new armature to replace the old squirrel cage rotor of the induction motor, but as you get smaller the efficiency drops rapidly. I think one of the best for modifying wold be a Sanyo bicycle dynamo, this is the type that runs on the tread of the tire, versus the bottle shaped ones that ran on the side of the tire.
If you did want to make an armature, I would suggest using donut shaped rare earth magnets.
Ian S C

[burnit0017]

http://www.6pie.com/faradayslaw.php

making your own is another option

[Ian S C]

I take electric motors from old printers, VHS recorders, old tape recorders, these motors tend to be fairly low reving (probably 5000rpm. maybe less. I know that some times I have exceeded the rated revs when the voltage out goes to 18V (12v motor). With small motors/generators of any type I consider to be about 50% efficient. This is my version of JamesG. Rizzo's Dyna, driving a generator ex HP printer, that is driving the fan on the radiator. The wires by the ciggy lighter are normally connected to a radio. Ian S C

[tentstovenerd]

I take electric motors from old printers, VHS recorders, old tape recorders, these motors tend to be fairly low reving (probably 5000rpm. maybe less. I know that some times I have exceeded the rated revs when the voltage out goes to 18V (12v motor). With small motors/generators of any type I consider to be about 50% efficient. This is my version of JamesG. Rizzo's Dyna, driving a generator ex HP printer, that is driving the fan on the radiator. The wires by the ciggy lighter are normally connected to a radio. Ian S C

any idea of watt

[tentstovenerd]

instead of a cooling fan, how about a chimney, say 2 meters heigh or 6' feet

[Ian S C]

Not sure the available power out put of these motors run as generators, that motor is able to produce about 5 Watts at the crankshaft, so allowing for the inefficiency of small electric motors, 2W to 3W would be as much as it could produce.
The reason for the electric fan is as a demonstration of the available power, the original design by Mr Rizzo had a fan driven by a belt from a pulley on the crankshaft. The engine in the photo has done over 1000 hours of running.
Ian S C

[cbstirling2]

I grabbed a 12 volt electric motor from a surplus store for only $2, it runs fine on 9 volt battery. When I tested for voltage after with a drill spinning it it does something very weird. At lower RPM it will generate up to about 6 volts but then it rather high RPM its voltage drops and then down to like 1 volts and then climb up to about 2.2 volts. Does anyone have any idea why the electric motor used as a generator would do that? Obviously it's a cheap little DC motor, but it is more sophisticated than a really really cheap 1.5 volt Motors. this happen because I do not have a load on the motor?

Is there a possibility that this may happen because I do not have a load on the little electric motor when used as a generator?

[Trevor]

High CB - Try a small load or a resistor of 1000 Ohm's across the terminals. This will give you a more accurate reading. I have had the same thing happen to me when I over revved a small dc motor and found when putting on a load, its voltage remained stable and accurate.
Trev

[thanh-cuibap]

Hi Tew...this is may be you need !! it's not very good, I will complete later....my motor : dc 6v . led 3v
https://www.youtube.com/watch?v=BEhZG4d ... e=youtu.be

[Trevor]

Not this little ducky Thanh. It doesn't do anything for me. Trev