The first project in Stan Bray's excellent book Making Simple Model Steam Engines (Crowood Press, 2005) is a modern take on Hero's Engine (also known as an aeolipile), the ancient steam reaction turbine described by Hero of Alexandria nearly 2,000 years ago. It's an ideal starter project for anyone dipping into model engineering - simple, educational, and surprisingly satisfying when it spins under its own power.

This is how I built my version, closely following Bray's guidance but with a few personal tweaks for materials I had on hand. The result is a small, desktop demonstration model powered by a humble tealight candle.

Materials and Tools

• Base: Scrap hardwood (I used oak) for the wooden base, shaped on the edges with a router.
• Boiler ("cylindrical pot"): A small copper tube
• Nozzles/arms: Two short pieces of 1/8" copper tubing bent into L-shapes and soldered to opposite sides of the boiler, angled tangentially for reaction force.
• Pivot/axle: A length of steel or brass rod passing through the top of the boiler (with a nut or cap as a bearing point) and attached to the pivoting arm from the stand. I used coat hangar wire.
• Support frame: Brass or mild steel strip for the upright bracket and cross-arm.
• Heat source: Standard tealight candle.

Tools

Basic workshop setup -lathe, milling machine, drill press, files, blow torch for copper work, hacksaw, and sandpaper.

No fancy castings or complex machining required - Bray emphasizes keeping it accessible for beginners with limited equipment.

Step-by-Step Build

Prepare the Base

Cut and sand a sturdy wooden block for the base. I shaped the edges using a router for a better look & glued green felt to the underside. Drill holes for mounting the upright bracket.

Make the Upright Support

Fabricate a simple L-shaped or goalpost-style bracket from metal strip. Mine is brass for durability and appearance, bolted to the base. The top has a horizontal arm with a pivot hole for the swinging boiler support rod. Bray's design keeps this straightforward - no precision bearings needed; a plain hole and a shouldered rod suffice. I used coat hangar wire for the horizonal arms.

Construct the Boiler

This is the heart of the model. Form or turn a cylindrical copper vessel with a sealed top (screw cap or soldered lid). Drill two opposing holes near the "equator" for the nozzle tubes.

Bend short copper tubes into hooked or angled jets (pointing tangentially in opposite directions). Solder them securely into the holes—ensure the openings face the correct way for rotation.

Add a filling hole or removable cap on top for adding water (I used a small nut soldered in place with a bolt plug). Pressure is very low, so no safety valve is strictly needed, but keep water level modest.

Assemble the Pivoting Mechanism

Run a rod through the boiler's top center (soldered or capped nut inside for reinforcement). This rod hooks over the horizontal arm of the stand, allowing free rotation. A loose fit is fine—friction is minimal once spinning.

Finishing Touches

Polish the copper for that classic shine (it will patina beautifully over time). I left the wood natural with a light linseed oil finish. Test-fit everything dry before any heat.

Testing and Running

Fill the boiler about 1/3 with water (distilled is best to avoid scale). Seal it. Place a lit tealight directly under the boiler on the base platform.

Within a minute or two, steam builds. It escapes through the angled nozzles. The boiler begins to rotate—slowly at first, then picking up speed. Mine spins steadily for a few minutes per fill, often making several dozen revolutions before pressure drops.

Completed Engine