World's Simplest Steam Engine

Brillint! I am totally making one of these!

I am sorry to be so cynical, but since I have seen way too many prank videos by these people, I doubt it will work. My main concern is how the water in the tube gets replenished as it boils away.

Besides, the link is dead.

Google put put boat.

take a look at this idea
http://il.youtube.com/watch?v=9Sv9d2sD2jE

@Edward:
I've made this one before. it works just fine. I think you were more looking for "skeptical" rather than "cynical."

I have everything needed to make this project so I bult one. The results: Most of construction process is pure bunk. The biggest flaw, however, is that the device does not float. In fact, the tea candles by themselves do not float as high as the one shown in the video, much less one that is burdened with metal tubing.

Yeah, how do you keep water out of the holes in the cup? I guess the tubing needs to be tight.

Isn't this a "smoke engine?" Where's the steam?

I had a better time with this design, and yes it worked.

sorry:

http://www.instructables.com/id/Simple-Steam-Engine/

it's surly not steam, the water in the pipe expands and pushes out of each end, or more likely just one, as there's no way for air to get in it just pulls more cold water through, which heats and the cycle continues

It's not really a steam engine, but a hot water engine. If you go to the Dutchtub site, which is totally awesome, it has the same principle for heating your portable hot tub with a fire in the coiled metal tube.

Who wants to buy one for me?

http://www.dutchtub.com/

Pop-pop boats! Several members of uk.rec.sheds got together some years ago to race these up and down a trough in a friend's garden. Happy days.
Some home-made, some bought - I've still got one of each somewhere.

If I'm stuck on an island with a giant candle, some pipes and a torch, I'll know what to do! ;-)
Seriously, it's a nice little project for kids! The "bigger" problem, as some pointed out, is to make that thing float, but I guess you could add something to help, like Styrofoam.

Hello all,

This "steam engine" seems to be based off an obscure device known as a fluidyne. Wikipedia it!

Well, it's not a Rankine Cycle engine that most of us today (or from the 19th-mid 20th centuries anyhow) associate with a "steam engine", but it's a neat little experiment.

It's actually rather evocative of the *original* steam engine. Google "Hero of Alexandria" to find a picture and description his "Aeolipile". The did have it's own water reservoir, so it's not spot on but similar.

As for plugging the holes in the tin... Melt some friggin' wax if that proves to be a problem. In the video, the pass-thru holes are made deliberately tight to seal against the tube. Not enough bouyancy even with a good seal? Use a bigger tin!

Some of you people evidently didn't take much basic science in high school (or perhaps even grade school). Can you build anything without a half-assembled kit to start from? Is your idea of woodworking purchased at IKEA as well? Art is probably a paint-by-numbers affair as well, huh?

I'll disagree on this being a fluidyne. That's a Stirling cycle device, which this is not.

I have to disagree with you Sid... Can you explain to me why you think it is not a stirling cycle?

Also, I said it is based on a fluidyne, but you are correct that is not *exactly* a fluidyne.

OK, I started writing this with the intent of explaining why it isn't a Stirling cycle. As I thought about it a little, it IS Stirling based, although not in the conventional way. Kelly is correct.

Typically, a Stirling engine has its working fluid in a closed cycle. This gizmo has vented heat exchanger tubes, which aren't typically part of the deal on a Stirling. Also, in a Stirling cycle, the working fluid (commonly Hydrogen or Helium, but air works also, just not as well) gets shuttled back and forth between a constant heat source and a cold source via a displacer piston or via the motion of the power piston arrangement itself. Because this doesn't have either of those and the tubes are vented, so I was overly quick to call it a non-Stirling. It does have the heat source and cold sink though, and as others have pointed out, although the tubs are vented, the working fluid (air) doesn't get discharged & lost, except at the beginning when the air is first warmed. Once the hot part of the heat exchanger is up to temperature, you shouldn't lose any tube air.

I'll have to make one to try it, but here's how I think it works: it's actually continually "breathing" a little water in and out of the tubes as it rotates. When the tube is heated, it causes the entrained air to expand, which spits out the little bit of water at the bent tube ends and causes the gizmo to rotate from the reaction to the escaping jets. The gizmo rotating, causes the tubes to sit in *slightly* cooler water, which causes the air in the tubes to contract a tiny bit which re-ingests a smidge of water. There's heat transfer from the very hot air to the water coming in as well. As the air is reheated it expands again, expelling the water and causing rotation which gets the tubes back in colder water so it can resuck some water in. Gradually, the cup water will get warmer and warmer (although the cup loses heat to the environment as well).

It is a Stirling Engine, just not a "conventional" or classical one. It won't be the most efficient Stirling (in terms of work out per heat in), but it IS a Stirling.

I stand corrected and my apologies/thanks to Kelly!

Straight Thermodynamics Talk from Sid

By the way... some of you siad you tried it and found it not to work well... you might want to try cold water instead of room temp water. A Stirling engine's efficiency is improved by making either the hot side hotter or the cold side colder or both.

And if yours works OK already, I think it should spin faster with cold water. Let me know if this proves true.

That's a really neat thing to make I wonder how cool it would be to make a couple of these with some paper lanterns on top and float them on a river or lake as they spin. It'd be a great addition to the festival of lights here in Toronto. Also, I think the best way to make them float would be to seal up the holes with say some wax or glue then apply some styrofoam around the edge to help it float.

Ali S:- They're very low powered - it'd be OK on a lake on a still evening, but no good on anything with a flow or a breeze.

@ Skipweasel

Ah, too true. Of course, pools and indoor bathtubs don't count! ;)

I see lots of fancy names for what this little device is - Stirling, Rankine, fluidyne - but, seriously, it really is just a simple pump that uses thermal syphoning. Heating the water makes it expand, drawing up cold water as the hot water pushes out. It isn't rocket surgery 8-), and overly complicating the explanation certainly wont help those not even smart enough to get one of these little devices to float...

Is this steam engine or boil engine?

It's not a thermosyphon - if you've made one you'd see that it isn't. The flow isn't unidirectional.

The water is raised to boiling at which point it flashes to steam and ejects a spurt of water down the pipe and out. This provides the impulse to drive the machine forwards. Because of inertia the water always overshoots a bit and is then sucked back into the heated area, rapidly cooling it so the steam condenses and we're back to the beginning of the cycle again.
At first sight it may appear that this will produce no net thrust but since the jet being expelled tends to go all in one direction wheras the water being sucked back in will tend to come from all around the inlet there's an imbalance leading to an overall thrust.
Provided you can arrange a way to fill then chamber these motors will run fine on just one tube.
Simple motors can have just a coil of tube as the heating chamber, posher examples have a diaphragm over the top which pops up (like a food jar lid) with each expansion and flexes down again after. This makes the motor run better and provides a satisfying pop-pop noise. The coiled tube sort are nearly silent.