A Bremen Walking Hot Air Beam Engine

There is a long story behind the Bremen. What it boils down to is this: In order to help dispose of someone's estate items, I bought this engine along with several others on the strength of a few photographs.

A cursory inspection did not reveal the problems hidden within. It appeared to be reasonably well constructed; however, if it ever did run, it must have demanded a horrendous amount of heat. It also required a considerable amount of effort to turn the flywheel; something, somewhere, was seriously bound up.

I decided to start all over and build it from the ground, up.

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The oven has been wrapped with glass fiber insulation and jacketed with a tin can. That, along with the scorched paint and a twist of the flywheel tells the whole story. Things were in a bind and instead of fixing the problem, excessive heat was applied, instead.

Hint: If you ever get a hankering to build a hot air engine, make certain that nothing rubs or binds. If it does, don't even think of trying to get it to run. If you don't follow this simple rule, you're bound to be disappointed.


Here is the rebuilt engine. It ticks over like a Swiss watch.


Notice that the hot cap oven no longer needs any insulation. This cutie now ticks over faithfully on a modest propane flame.

This engine is a quarter-scale model of the only known Bremen walking beam engine known to exist. Many Bremen hot air pumping engines survive, today, but they do not have the walking beam.

Created by Brad Smith, this is an excellent model. It was featured in a Modeltec construction series, May 1996 through April 1997.

Because I was so pleased with this one, I immediately sent off an order for Brad's casting set for the other style Bremen.

If you are interested in building either of these engines, contact Brad Smith via e-mail at (corlissbs.@aol.com), or, via regular mail:

Brad E. Smith
7574 S. 74th St
Franklin, WI 53132


If you are a hot air engine person, you are probably wondering what was the cause of the binding in its first lifetime. It boils down to one simple thing: Failure to follow the blueprint.

The pump body was cast with a spigot to facilitate holding it in a lathe chuck. The blueprints called for it to be cut off when it was no longer needed. However, it was left on, making the pump much too high.

Being too high, the crank could not operate because the throw would hit it. Rather than fix things, the original builder moved the pump to one side.

Because the pump's sucker rod connects directly to the power piston, forcing the rod to one side caused the power piston to bind in the cylinder. Badly!

Cutting off the spigot exposed the pump cylinder bore; it had been bored too deep. So, the pump was re-bored oversize and fitted with a new cylinder liner that had a top on it.

Another serious potential source of friction is the pump packing. The original had no way of adjusting it. Now, a knurled packing nut can be "tweaked" for best performance.


Rather than being disappointed with the Bremen's condition when I got it, I welcomed the challenge of bringing it to life. It required far more corrective measures than those mentioned here, such as, a new displacer had to be fabricated. The original leaked air! Massively!

This has been a very satisfying project, a good job, done to the best of my humble ability.


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