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

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

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?

Here pussy-pussy, here pussy-pussy.

Kudos to Sorcerer Mickey- I would so be naming that feline Janus.

Hey, I haven't tried heroin or snorting glue either... heh heh.

Again, for the complete morons out there like the aptly named Byrd Brain ... I just found it interesting that it is becoming a common strategy for books änd TV shows for "young adults" to "grow with the readers/viewers" as the series develops. A perhaps unintended consequence is when a 12 year old "shows up late" and reads a bunch in a row (much faster than they took to write), the parents might not realize that the intended audience is getting older with every book. Read between my crotchety barbs and understand the main point I was trying to make.

So, no I am not out to burn books or ban them or any such nonsense. The authoress has identified a market and provided a product to fill it. Kudos to her. Parents ultimately are responsible for what influences their kids so they need to maintain vigilance in the goings on in their kids'lives, which includes reading. If the protagonist is a submissive emotionally dependent tramp, just be aware of it. Hah hah, I couldn't help that last line... Loosen the bone a little folks ... you're acting like I'm calling your *own* kids names. Bella is a FICTIONAL character.

My president is smaller than your president!

I found it amusing that they had to specify that although they get gobs of Federal grant money, the work on this was done on a Friday evening after the lab officially closed. Translation: "Please don't let this be used as an example of frivolous waste of taxpayer $". Hah hah

Hey, at least I issued the disclaimer that I hadn't read THESE. I had read & seen the Potter books & movies and watched the Buffy for years. The gist of my comments concerned how *those* gradually morphed into very adult material and how the authoress of this is adopting the same approach. No value judgement, just an observation. If she can sell a lot of books by having the main characters be a romantic teen vampire and his slut girlfriend, more power to her.

What's the big deal? If your 12 year old is ready for Willow being a lesbian, Dumbledore being gay, and whatever the vampire teen "passion" stormie alludes to in these books, go for it.

I had never heard of these books until last night when one of the TV network news shows had a feature on the hoopla sorrunding the upcoming film and the promotions for it. OK, so now I am caught up. Sounds like a Buffy the Vampire Slayer style thing which starts out pretty innocent campy fun and then gradually turns up the content with teenagers whoring about and experimenting with witchcraft and (with Buffy anyhow) homosexual relationships. Nice. At least the authoress has figured out a way to print money by the bucketload. Too bad the central character seems rather a harlot.

Then I read stormie's post. I'm glad she defined NSFK. To me that is a reference to the Nationalsozialistisches Fliegerkorps (National Socialist Fliers' Corps), a pre-WWII Nazi paramilitary group. While of historical interest, I would not like my kids involved in that, either.

I am getting old. Straight talk from Sid.

If the cat can be trained to clean a clogged roomba of cat hair I will be really impressed.

They did a nice job. Just the same, I question the inclusion of "Multimedia Studies" in the government school curriculum. Sounds like nice stuff to learn on your own or at trade school, but not on the taxpayers' dime. Keep it Math, Science, English, History (note that I did NOT say Social Studies), Geography, and Foreign Languages. The rest of it is fluff that detracts from the important.

But like I said, nice job on the end result. It sounds like a good thing to do at a neighborhood center or after school somehow.

@Peeves - Ever heard of blutwurst or black pudding, alternate names for pretty much the same idea? The stuff in varied form is found all over Europe.

I like botulism -- it's all-natural, so it must be good for you.

I agree. Sid is cool.

Just an aside... I am REALLY sick of thankless moochers whining about their "toxic trailers". The materials used in those are the SAME used in other commerically available trailers/motorhomes/RVs, &c. and in all sorts of furniture and residential construction. Try finding a house that has no MDF in it nowadays. They act like special "toxic" materials were specified just to make them sick. It was just normal commercially common stuff they should have been damned grateful to get.

This is all a manuafactured crisis aimed on extracting more cash out of all of us. Next time (and there will be a next time) let them live in the streets.
Lazy S.O.B.s.... The hurricane was 3 years ago. Get a job and your own place to live.

I can't imagine a dustbowl-era migrant (look on shorpy.com for some great pix) complaining about the quality of a free house they were given. We've become a pathetic nation of entitled whiners.

Straight talk from Sid.

I wonder if his prior injury-aborted runs stemmed from tosses over the handlebars.

Very cool. Very old school British adventurer too. Kudos.

hah hah... I said "rapid", when I meant "rabid". :-)

Yeah, recycling Alumin(i)um is a no brainer it saves a ton of energy. The other materials get more questionable. The PM article (I read the print version) is pretty good.