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Two cylinder LEGO engine runs on vacuum

Here it is, a working two cylinder, double acting Lego Steam Engine. Of course, the "steam" is either you blowing into it or running off of a shop vac.

Here you can see the action! Running on a vacuum, this engine probably does about 400 rpm. I would have included a recording of the engine running in this way, but the vacuum noise overpowered the sound of the engine running. Hear an audio (120k) of me blowing with all my might to run this engine!

View from flywheel side

Another angle of the engine running on vacuum. For some reason the engine ran better with the shop vac sucking than it did blowing. Compressed air motored it well, however.

Engine at rest

Here's a shot of the air inlet. This inlet is configured so that the holes in the sides of the cylinders line up with it at just the right moments to provide the power strokes.

Close up of valving and timing

Now let's disassemble the engine and take a peek at the valving and timing mechanism. Very simple, the cylinder just rocks this way and that to open and close the top and bottom timing ports.

Both cylinders draw from center steam box

In this image you can see more detail of the air inlet and "manifold" that routes air to all four timing ports.

Flywheel side view

More views of the engine, simply to clarify the design.

Top view

Notice the rubber tire flywheel on the left side. This isn't absolutely necessary to make the engine run, but it does run smoother with it there. This tire is from the Expert Builder #9 Go-Kart set that I received for my 10th birthday. I'm in my 30's now and still love playing with Lego!

Engine animation

These images are quite large, but please be patient. They are over 400 kbytes apiece. They are animations of the two cylinder that demonstrate the valve timing and crank throw angle difference.

Valving animation

Because the power strokes of the two cylinders are 90 degrees apart, the engine has stalled torque at and will start from any position of the crank, without giving the flywheel a spin!

View my Single Cylinder, Single Acting steam engine!

View another great Lego Steam Engine Website!