Lego reversible steam engine simulator; a vacuum cleaner powered engine

May 18, 2007. This month, I finally finished a new demonstrator of a steam engine with a reverse bar. When I tried to figure out how a steam locomotive can be reversed, I found a nice explaination and and animated GIF's on R. Booty's Walshaert Valve gear animation pages Many other pages, like Wikipedia these pages. Of course, I wanted to build something similar with Lego. Because I feared to run in a lot of problems with the large forces in Lego pneumatics, I decided to try something with a vacuum cleaner powered engine. Since my last version of such an engine could not produce any output torque , a lot of improvements were needed.


Vacuum cleaner powered 2 cylinder engine Lego pneumatic engine , reversible LPE

The first improvement was the use of cylinders with a larger surface for the piston. The old piston was square, 2x2 studs. The new one is 2x4 studs.Then, the vlaves have been redisigned. Now a shift over 1 stud is enough to redirect the air stream, while the piston in the cylinder moves over 3 studs. A one-cylinder version of the new engine is shown in the following pictures.

With a proper fly wheel and gearing, this engine might work with one cylinder. However, I could not make this engine run over more than 180 degrees.


The engine can be reversed by lowering the upper yellow beam.It appeared to be difficult to make it run without flaws, because the black rods sometimes touch the grey crank wheel slightly.

Then, I decided to make a 2-cylinder version to find out, if this design could work and be improved. I simply copied this design and connected the two engines.

and after a large number of tests to get the right phases between all rotating parts, and some arguing with members of the family complaining about the noise of the vacuum cleaner, YES, it worked!

The following pictures show more inside details of the valves and the cylinders.

All pictures were taken when I decomposed the construction. So I cannot make new and better pictures :-(

Now , I want to build a bew cinstruction with pistons of 4x4 studs, and more space for the reverse bar mechanism to get a completely working steam engine simulator with reverse bar. Check this.