Introduction: Hero's Engine

When I want hard boiled eggs, I boil them in a pressure cooker. If you haven't tried cooking eggs this way, you're missing out. The other morning, to help cool the eggs faster and to speed up releasing the pressure from the cooker, I removed the little pressure regulator on top of the cooker so I could safely open it to remove the eggs. Watching the steam and hot air shoot toward the ceiling, it also reminded me of seeing a Hero's Engine design once when I was interested in Stirling Engines. For about 2 or 3 years now, I've wanted to build a Hero's Engine.

I also wanted to build one of these in order to show it off to my kids. So I decided to build my first Hero's Engine last weekend. (Hero's Engine is also known as an Aeolipile. It's a very cool piece of machinery...even if Hero never really built one!)

So last Sat morning, I got busy and started. Having just experienced an unpleasant week at work, it was also a perfect way to get my mind off my job and on something else. I built this in about 2.5 hours - now if I include the amount of time drove to and I stood around in Home Depot looking at all the plumbing parts, TOTAL build time is more like 4 hours.

Step 1: Parts

If you use my design, some of the odd parts you're going to need are:

  1. A bearing (see pic). I dug this out of an old roller blade wheel. You can buy a bearing just like this at Home Depot, but they are way overpriced. Look online, or get some old roller blades at Goodwill.
  2. A 3/4" x 1/2" brass fitting - female to female. (Home Depot sku number is 098268624892)
  3. 3/4" to 1/2" brass reducer fitting. (I don't have this part number)
  4. Toilet Bowl Bolt Kit and Nuts (I don't have part number.) This can be found at almost any hardware store.
  5. 3/32 x .014 brass tubing (or similar). I already had this laying around, but I remember I got a package at Dick Blick for a few bucks.
  6. Sterno chafing fuel (used for camping or for keeping food warm). I bought mine years ago at a camping store for about 3 bucks per "candle". Keep them sealed and they last forever.

Other than these parts, the rest of the build is done with 1/2 inch copper pipe and fittings. Total cost of parts, not including the copper pipe (that I already had laying around), about 10 bucks.

Step 2: Be Safe

First and foremost be safe. You need to use fire for this project. Very hot fire! If you don't know how to sweat pipes, you probably shouldn't use this project to learn. Start somewhere else. Get someone who knows how to sweat pipes and have them teach you. You don't need to be great at it (I'm certainly not!) but you need to be able to completely seal the engine. Any leaks, and the engine won't work.

(BTW Have you ever watched a plumber sweat pipe? You don't need to be THAT good for this project, but wow is it cool to watch! I'm always amazed and think to myself, "Why am I'm using so much solder when I sweat pipe?!")

Last but not least, have these (see pics) right by you when you sweat pipe - A fire extinguisher and a bucket of water (note: it doesn't need to be clean water!).

A general contractor I used to work for always, always, always made me keep a bucket of water and fire extinguisher whenever I'd sweat pipe on any of his jobs. I'm glad he did. It taught me to do the same every time I sweat pipes now on my own, I grab a fire extinguisher and a bucket of water!

I'm lazy, so I use mapp gas. You don't need to for this project, propane would work fine.

Use lead free solder. Use solder that would normally be used safely for drinking pipes.

Step 3: Build the Engine

You need to cut about a 5 inch piece of 1/2" copper pipe. You're going to cap this piece and essentially seal it. The caps have vents in them which allow the steam to come out at a high velocity, creating "thrust" and causing the engine to spin.

The order you should go in is 1. Cut a 5 inch piece of copper pipe, 2. Cut two pieces of brass tube - these will be your vents 3. THEN attach the vents to the caps, 4. Then attach the 2 caps to the pipe.

If you try out of this order, I think you might have trouble getting the vents perfectly set.

See pics and notes in pics.

Step 4: Attach the Hanger

Now you need to carefully attach the hanger. . You're going solder the toilet flange bolt to the center of the engine. This will become the hanger.

Keep it as centered and as perpendicular as possible. Be precise. The better you work here, the less wobble you'll have and the smoother then the engine will run.

Now it's starting to take shape. The hard part is over!

Step 5: Build the Stand

I won't spend a lot of time describing this. It's pretty self explanatory. Just remember to get the height correct for your heat source.

Make sure you build the stand so your engine spins freely and doesn't hit the stand!

Note: I used a Sterno Cooking Fuel Candle. You don't need these but they work great.

Before you move on, this would be a good time to clean the engine and the stand off really well. The flux is nasty, sticky, etc. You don't want to bring it in your house in this condition. I scrubbed mine with scouring powder. It came out nice and shiny.

Step 6: Assemble the Engine on to the Hanger

This part can be tricky. Look at the pics and notes in the pics.

Step 7: Fine Tuning

After I got it assembled and ran it, the only thing that happened was steam pouring out the vents! No movement.

I realized my vents were too big. So I had to solder them down. The key is to get the holes on these vents as small as possible. You want the steam to come out at a high velocity.

Do not seal the vents completely - you need to get water in the engine via the vents. Make sure you have a pinhole size at the end of the vents. Small is good here.

Step 8: Final

Before your first run, disassemble the engine from the stand, now find a small container of water and draw up some water into the engine. How to do this??? you ask! This is the fun part. Take the engine, and pretend it's a straw. Suck up some water through one end. Use about 1/2 ounce to 3/4 of an ounce of water.

Do NOT let this run dry while it's over the flame. If it stops spinning because it's out of fuel, blow out your flame, then let it cool. If you allow it to overheat, your solder joints could start failing.

My first successful attempt with about 3/4 of an ounce of water allowed it to run for about 2 to 3 minutes.

Note: It will spew a bit of water at first while it spins up, before the water inside starts boiling and producing steam.

I haven't tried yet, but I'm thinking of using two chaffing candles side by side to get it to really spinning fast.

If you build this I hope you enjoy it like I have! Please let me know if you have any ideas or suggestions for improvements.

Step 9: ADDENDUM - Making It "faster"

Well, one of the comments from my kids was "Dad, can't you make it faster?"

And basically the design with the tube in the horizontal position (as one of the commenters below noted) doesn't allow me to fill it with much water. (I liked the suggestion of using a t connector). And as another commenter posted, the water is getting flung to the ends of each pipe by virtue of centrifugal force. So...back to the drawing board.

Step 10: Vertical Engine Parts

Liking the idea of a larger reservoir, I decided to build another engine more with a vertical design instead of horizontal design. Holding the engine is no problem - I have the frame already built. As you'll see, the challenge now is how to mount the vents.

I used:

  • 2 inch pipe caps
  • 1 small piece of 1 inch pipe.
  • I used 1/16th inch copper tube for the smaller vents (got this at Dick Blick).

Step 11: Drilling the Vent Holes

I wanted to use 3 vents. So to make them uniform, and equally placed around the engine, they need to be placed 120 degrees apart. (You'll remember some basic geometry from grade school, a circle - or a round pipe cap in this case - has 360 degrees. Divide that by three and you get 120).

At first I tried eyeballing it. Bad idea. Then I decided to make a small "jig" if you will, out of a piece of paper. I measured a piece of paper EXACTLY the circumference of one of the caps. Then folded it in half 2ce to get perfect thirds. Then I wrapped that around my pipe cap and marked it off. This is as good as you need it I think - I got it pretty darn close.

Step 12: Soldering the Caps, the Bolt, and the Tubes

This was the hardest step and a real PITA. If you try this, just don't be in a hurry with prep.

Flux everything, get everything in position. Then solder it all at the same time.

Step 13: Engine Running - and It Is Faster!

Step 14: And Even Faster...supplementing With a Butane Torch!

Just for fun. I'm using a butane torch along with chafing fuel. This is right at start up, so there is water remaining in the tubes from I filled the reservoir. This causes water and steam to spew out. It's loudest at this point too and makes it a bit more exciting.

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