The Stuart Beam Engine

This engine enjoys an interesting history. It all started out as a guilt trip. A professor wanted someone to demonstrate a steam engine to her class. I don't know how it came about, but somehow I got tapped to make it all happen. It wasn't as simple as it might seem to the average lay person.

I'm well enough acquainted in the region's steam community to know that portable steam plants are scarce to non-existant. Nevertheless, I tried by exhausting every connection I knew and a whole lot more I didn't know. The biggest steam plant I could find belonged to my friend, Francis; but, his was a small affair with an electrically heated boiler. After all, the energy available at a 120 Volt, 15 Ampere wall outlet will not run a like-wow-big power plant. If in doubt, do the math.

When the prof suggested setting things up on the loading dock and moving the class down there, it became immediately obvious that her expectations were far larger than the ultimate reality, something that could be swallowed up in a laboratory sink.

The class came and went as best as could be expected. I don't think anyone went home that day feeling greatly enriched.

To make a long story short, I felt badly about the way things turned out. You might call it a guilt trip. So I offered to build a steam plant and donate it to the class for future use. But, after I was well along with the project health issues forced the prof to give up teaching. Not knowing what would become of the program, making such a huge donation became too risky. Rather than see my creation wind up at one of the university's surplus sales, I decided to keep the engine you see here. It was the wisest thing to do.

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Here is my rendition of a Stuart Beam Engine. It is small enough to be portable and large enough to move it out of the toy category. The flywheel is seven-inches in diameter.


This shot shows the steam throttle valve, the steam chest and the cylinder. The bore is one-inch and the stroke is two-inches.

The valve on the left and the two petcocks on the cylinder were purchased ready-made. Except for the nuts and bolts, I machined everything else.

The larger pieces started out as rough castings, just as they came out of the sand molds at the foundry in England. Getting them cosmetically presentable takes a great deal of elbow-grease and a variety of hand files. Generally, I smoothed all the painted surfaces by hand and the bare metal pieces are parts I machined on lathes and milling machines.


Moving away from the machine one can see the "Watt linkage" attached to one end of the beam. Its purpose is to ensure that no sideways forces act upon the piston rod. The ingenious mechanism ensures that the piston rod moves straight up and down, even though the end of the beam follows a curved path.

Perfectly vertical movement is necessary to prevent excessive drag (binding) which would lead to wear and leakage at the steam cylinder penetration.


This close-up shot shows two important mechanical elements:
1) The crank converts the reciprocating motion of the beam into the rotary motion of the shaft and drive pulley.
2) The eccentric alongside the flywheel hub converts rotary motion to the reciprocating motion needed to operate the valve mechanism.


Here is another view of the Watt linkage. Those fussy little links make a huge difference in the appearance of a Stuart Beam engine. Either the craftsman gives attention to detail and carefully gives them their gentle barrel shape and radiuses the ends; or, they take the easy way out and merely drill two holes in a flat piece of metal and leave things at that.


By now you are probably wondering about the choice of colors: "A white steam engine?" you ask. You've got it. White!

For years I've saved every picture I've found of steam engines. Very few have bling and not a one of them are red and white. That cinched it! This one would be the red-and-white ground-breaker.


When it all came together the choice of colors paid off; it was one of ten nominees selected for "Best of Show" at the 2009 Gas Engine and Reproduction Show (GEARS) at Portland, Oregon.

You can see some of Captain Carl's excellent GEARS photographs and commentary here.


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Revised -- 11/27/09