Double Your Pleasure, Double your… um… steam?

As a maker, I see faults in the things I made that nobody else will ever notice. Awhile back I posted about a steam engine I built. I learned a lot, and I was really pleased that it ran well. But as always, I saw the faults, and I wanted to make another, better attempt.

Some Shortcomings

I built the first engine’s cylinder with beveled edges for visual interest. They looked fantastic, but I shouldn’t have beveled the back corners. The back side of the cylinder serves as the valve surface, and the bevels broke the seal for part of the engine’s cycle. Steam (or compressed air, in my case) would leak straight out into the air. This wasted a lot of potential power.

The second problem stemmed from the engine’s design. Steam only acts on one side of the piston, just like a car’s gasoline engine. That’s called a single-acting engine. But most steam engines act on both sides of the piston. That’s called a double-acting engine. As you would expect, that gives double the power.

To the Drawing Board!

I did a little figuring, and realized that I could adapt the design for the first engine to be a double-acting engine with just a little math and a second set of intake and exhaust ports.

I redesigned the piston and connecting rod. While I was at it, I designed a plate to bolt to the bottom of the cylinder and seal the space between the bottom of the piston and the bottom of the cylinder. The second set of intake and exhaust ports led into that space, so now steam could act on the bottom of the piston.

Naturally, I deleted the beveled cylinder edges too.

All About the Bling

I wanted the second engine to look even better than the first. But I didn’t want to mess around with paint, and I didn’t want to do as much engine turning (jeweling) as I did on the first. So instead I decided to go with an interesting mix of materials.

I chose polished brass for the cylinder and flywheel. Those are the dominant, dynamic parts of the piece, and brass gives it that old-time steampunk flair.

For the engine upright I went with polished aluminum to set off the brass. I used 2000-grit sandpaper taped to a surface plate (a really flat stone) to get the final polish.

The base is engine-turned aluminum, to hearken back to the first design that inspired this one. Ironically, I did the engine turning four times to get it to turn out right. So much for my intention to do less of it this time!

Finally, I made the crankshaft, flywheel nut and cylinder pivot from blued steel. Since these parts had to be strong, steel made the most sense. I already knew how to blue steel, and I figured it would look nice against the brass and shiny aluminum.

It works!

Here’s a video of it running. Enjoy!