Relatively Compact Power Generation Using Fuel

[Joseph]

Hello, I have researched relatively compact methods to try to produce about 250 watts of continuous electrical power but haven't found anything worthwhile yet. I may try to design a generator, probably a new type. The output will most likely be AC, but DC would work too. I am seeking a power source for an electric bicycle.<p>Reciprocating piston engines are bulky and somewhat heavy. Every bit of weight matters. Fuel cells suffer low power density and are prohibitively expensive. Solar cells are overly bulky and far from cheap.<p>I am inclining toward the possibility of designing something like a detonation or pulse type of engine which ignites in time with the resonance of a special low resistance tweeter. This way, less parts are needed since rotational power does not have to be converted to electricity. This way should not need lubrication either. Thanks in advance.

[cato]

Not at all. Thank YOU!

[jwax]

You're welcome. "Detonation or pulse" type of engine? "Low resistance tweeters"? Any links to such machines?

[Joseph]

You're welcome and thanks for your thanks. <p>Here is about the best I could come up with in terms of links. I think I originally thought of the idea several years ago with the advent of sonic compressors. I figured then maybe a sonic engine could also be built.

[Engineer1138]

I made an off the cuff remark last week about hooking up a generator to a model airplane engine. Might be worth a try.<p>jwax: just Google for "gas turbine beer" and see the gas turbine a guy built to cool his beer while working in the shed

[jwax]

Cold beer and 125 dbA in the shed- what could be finer?
How about US Patent 5,413,879. I'd like to see that built!

[Joseph]

Indeed, I am still considering the possibility of connecting a DC motor to a Cox engine. I still have one from an old van which used to have various cams for performing set maneuvers, depending on which cam is inserted near the front wheels. I think that is how it worked anyway.<p>I think the motor would turn the engine until it fired up on its own. I guess a diesel engine can be started by turning it fast enough, but on second thought, I have my doubts. It would not be very convenient to have to manually start it with the glow plug each time, especially if the system is set up like a hybrid vehicle.<p>I looked at that patent. That method is one way to boost the output of fuel cells, I guess. I had considered a straight turbine engine coupled to a motor, but decided it is too complicated to do right.<p>[ June 01, 2005: Message edited by: Joseph ]</p>

[Engineer1138]

Must be getting old. You said pulse jets and I sent you to the turbine guy. I meant this site: http://www.aardvark.co.nz/pjet/<p>Wait till you get to the part where he puts a pulse jet on a barstool on wheels and gets onboard!

[Joseph]

I like his Web-site. I see that he has had problems with intake valves wearing out, to my knowledge. It could affect the lubrication-free design goal I seek. Yet, my goal is different--he is going after thrust while I hope to vibrate a type of voice coil.<p>Some of my original thoughts included trying out a woofer for converting the combustion pulses to electricity. The efficiency would probably be low then, and also the heat would probably destroy it.<p>I also considered a steam engine, but it would tend to be too big and inefficient. Once I obtained about a watt of power by heating one side of a Peltier junction with a torch while the heatsink on the other side was placed in water.

[dacflyer]

heres an easy idea.. electric start weedeatter engine (2-cycle vareity)coupled with a motor or alternator of your choice,,
If i rember right, i used a old blower motor out of some junk car,the blower motor for the heater, it made more DC than i wanted, so i had to use a regulator to control output..and it worked fine to power 3 100watt.12v
lamps.. and whole thing weighed about 10lbs..
1pt of fuel lasted about 45-50 min..

[jollyrgr]

How about a "Maggie Mug" RamJet? In the US we call them "Auto Mugs" or "travel mugs". Whatever you call them in your part of the world they are the stainless steel drink mugs for use while driving. You take a couple of them, a sink drain strainer, a spark plug, and a fuel valve from a hobby "cox" type motor and make a RamJet.<p>See this site (be patient, the main page takes a while to load sometimes):<p>http://www.cottrillcyclodyne.com/Maggie ... aggie.html<p>Don't be discuraged by having to weld this together. The author shows how to use "epoxy welds" to make this engine. Of course you would probably want to go larger than the 20 oz mug used in the prototype. Maybe something like a 44 oz mug would do it.

[jollyrgr]

A note on internal combustion engines and their weight and bulkyness. A six horsepower gasoline engine weighs about 25 pounds, more or less.
(Reference engine: http://www.briggsandstratton.com/displa ... ocID=98838)<p>This is a complete motor, with fuel tank, controller (throttle), and so on. The fuel weighs six pounds per gallon.<p>To get a five horsepower electric motor you are talking 128 pounds. (Reference motor:
http://shop.emotorstore.com/estore/prod ... %5Fid=6007)<p>This does NOT include controller, power source, or any other needed items to complete an electric setup.<p>What most people do not understand is the power density stored in gasoline. And most of the energy is wasted as heat in a IC engine. Yet you can get six horsepower out of a 25 pound package. As reference a portable 3500 Watt generator with a 6.5HP engine will run 12 hours on 4 gallons of gas. (Reference page 13 of PDF here: http://www.briggsandstratton.com/om/pdf ... ='Portable% 20Generator%20%20030208')<p>
Try doing that with a battery pack. Noting the above references you can see that the engine weighs roughly 25 pounds and the motor/generator set weighs 127 pounds. Meaning the generator itself weighs nearly 100 pounds (give or take for the tubing and other components needed to hold the portable generator together).<p>[ June 02, 2005: Message edited by: Jolly Roger ]</p>

[Joseph]

That "Maggie Mug" thing is interesting. It could be connected to a turbine generator.<p>Right now, I am leaning toward the cox type engine coupled to a permanent magnet electric motor. It may weigh about three pounds including fuel. When the system is in use, the motor can be set to fire up if the battery voltage drops below some value.

[jwax]

Nothing like chemical energy for density, true!
There is a potent DC motor that is rated 2 KW output (2.5 HP) weighing only 11 kgms (24 lbs).
http://www.lemcoltd.com/lem_200.htm
Anybody ever play with a Lynch Motor?

[peter-f]

[Not that I propose this as a solution but...]<p>Has anyone looked into the Wankel engine? Would that be competitive?