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Posted: Tue Feb 26, 2008 4:23 pm
by pat123
I may try a pnuematic I'm not sure.
I read a report about a guy developing a six cycle engine. After the normal combustion of a four stroke there was another cycle where water was sprayed onto the hot cylinder to flash off into steam. Kind of like a Stanly steamer. It was projected to increase mpg by 40 percent. I think it was in popular science...

yeah i saw that in popular science too.

Posted: Tue Feb 26, 2008 4:23 pm
by Jared Haehnel
The propane idea if feasible,but just building the engine would be complicated too. Look at a gas run nailer can bury a 16d nail in a stud. They take gas cartridges and run like a simple combustion engine... which is also like a combustion launcher.

This is completely unfounded but you might be able modify a gas nailer (if you've got one) to work as an engine.... I doubt it though.. the more I think about it the less likely it becomes.

Posted: Tue Feb 26, 2008 4:27 pm
by pat123
How big of an engine do you think I would need to move about 200 pounds? this is going to be a tough challenge

Posted: Tue Feb 26, 2008 4:29 pm
by Fnord
Too much weight, what the fork do you do with the steam generated (add a turbine/reciprocating engine into the mix and you get more weight), too dangerous (boilers are quite upkeep-intensive if you want to keep them safe) too complicated due to condensate/oil separation, feedwater pumps, makeup water supply, pop valve, feedwater regulation, the list goes on and on...
What, like 500 pounds at most? As long as it increases efficiency it's worth it.
Adding a small engine such as the one jack posted would not add much extra weight. If you had a hybrid you could use it to generate electricity instead of mechanical energy.

I'm sure you could find a way to make a boiler safe with minimal maintenance, though it would be more expensive to build.

And it doesn't have to be hooked up to the radiator, you could probably get enough power from the exhaust system alone.

I still don't see enough reasons not to try something like this if I ever got the chance.

Posted: Tue Feb 26, 2008 4:38 pm
by pat123
so basically for a pnuematic i would just build a normal piston valve attached to a crank shaft? I wonder how hard it would be to have the exhaust hooked up to a compressor so it goes back into the air tank. that way I would never have to refill it with air.

Posted: Tue Feb 26, 2008 4:40 pm
by Sticky_Tape
I think you should make it a pneumatic for the simple reason of free fuel because after a while wouldn't it pay for itself?

Posted: Tue Feb 26, 2008 4:57 pm
by Jared Haehnel
No and this is why...

You've got to put energy into compressing the air to use... whether that be an electric, gas or man powered compressor you still have to put quite a bit of energy into the thing to... some way you will always have to pay for that energy... higher fuel bills... higher electrical bill... sore muscles... take you pick.

No such thing as free energy.

Posted: Tue Feb 26, 2008 5:11 pm
by pat123
maybe we can have a competition. We can see who can make the strongest engine out of unconventional fuel (air, propane, etc.)

Posted: Tue Feb 26, 2008 5:30 pm
by ShowNoMercy
Sure there is, solar electric and heat, geothermal etc.

Posted: Tue Feb 26, 2008 6:30 pm
by Ragnarok
spudchucker wrote:I think you should make it a pneumatic for the simple reason of free fuel because after a while wouldn't it pay for itself?
No. Any pneumatic engine like this will require huge gas consumption.

I had designs for such a thing ages ago, but I had to give it up because even under it's most efficent arrangement it would have used up the air sources I can reasonably use incredibly fast.
It would have been capable of catapulting whatever vehicle it was on with impressive acceleration, but not that fast overall because the supply would have been gone before you got up to speed.

The high density (if not pressure) of stored propane or butane as well as the much lower amount of it needed for each stroke of the engine makes a huge difference to how far such a vehicle could go.
However, unlike a pure pneumatic engine, a propane powered engine couldn't do stationary starts, and will need both a clutch that can handle the torque - and some way to start it.

It's not that simple building an engine from scratch. I've got a nice set of plans for a moderately powered propane engine, but I've "stalled" on finding a way to make the clutch. (Sorry, very bad pun)

Posted: Tue Feb 26, 2008 6:35 pm
by Sticky_Tape
Ok convincing so I would like to know how the spark plug works could you give me a diagram?

Posted: Tue Feb 26, 2008 9:02 pm
by tomthebomb137
iv been thinking about this 2day and i came to the same conclusion, i would sugest using your butane to heat water into steam to then run either a turbine or use it instead of compressed air in that pnuematic design

Posted: Tue Feb 26, 2008 9:06 pm
by ShowNoMercy
It takes a lot of heat/energy to make steam, they are more inefficient that an Otto cycle engine.

Posted: Tue Feb 26, 2008 9:23 pm
by Jared Haehnel
so basically for a pnuematic i would just build a normal piston valve attached to a crank shaft? I wonder how hard it would be to have the exhaust hooked up to a compressor so it goes back into the air tank. that way I would never have to refill it with air.

Hard, that would require an additonal input of energy to recompress the air and further complicating the system. A pnuemic engine works becuase of the unbalance of pressure. If you create any kind of back pressure the engine will seriouly loose power.

Your best bet would be to modify an existing engine to run on propane.
Sure there is, solar electric and heat, geothermal etc

You still have to buy/biuld something to capture and use that energy...then theres maintance...
How big of an engine do you think I would need to move about 200 pounds? this is going to be a tough challenge

It depends on gear ratios, how fast you want to go, a small engine geared down very low with tow just about anything around...just not very fast... You also have to add the weitgh of the engine, and what ever frame chasis you attatch it to. Plus add extra if you want to go any where fast.

Posted: Tue Feb 26, 2008 9:26 pm
by ammosmoke
Well, its all fairly ineffecient designs unless you come up with something that is truly revolutionary.