CSSoh's Lego Pneumatics Engines of Yesteryear 15 Nov 2002

Pneumatic Engines of Yesteryear

The desire to build pneumatic "steam"-engines had existed even in the early days when the single acting cylinders were introduced. Here is a page on the early day pneumatic engines to set the historical perspective. My grateful thanks to the pioneer Engine Builders who have graciously shared with me pictures and descriptions of their creations, which have not been published before.

Early 4-cylinder Engine by Reinhard Beneke



Ben wrote that he built his first pneumatic engine back in 1988. Unfortunately his early engines were destroyed soon after building. The one pictured is from around 1990 (just before his dark age began) and survived by chance. This 4-cylinder engine uses the old type pneumatic cylinders from the middle of the eighties which are much easier running than the newer ones today.
The main idea of his creation is a crank shaft with one time 180° crank angle and cylinders with an angle of mathematically exact 90° between them. That makes 4 strokes per round: every 90°. Two of the bigger back wheels from the Technic Backhoe Grader set #8862 serve as the flywheel which runs five times as fast as the cylinder.
Ben says he's a little away from Technic now, 10 years ago it was his favorite theme by Lego. Now he's collecting trains and models from the 70's.... Check out Ben's World of ABS.

My Pneumatic Engines - Then and Now by Paul Krieg
Paul wrote: Dear Fellow Engine Builder, I can not tell you how EXCITED I am to find your web site. I have been building pneumatic engines for approximately 11 years. Except for a good friend of mine, I thought I was the only one. Now that has ended. I have a few things I would like to share with you regarding the history of my engines and some ideas that your visitors may find useful.

The First Air Tank? It started when a friend of mine received set #8862 and he realized that with all the tubing on this model there was enough reserve to actuate the cylinders 2 or 3 times between pumping. It was not long before he and his father had a copper air tank that fit in the cab.
I decided I had to have one, so I came up with a small glass jar with a plastic lid with a hole just big enough for the plastic ink tube of a ball-point pen to pass through. On the inside was a balloon as an inner tube. On the outside the pneumatic tubing fit nicely over the ink tube. Today I use soda bottles.

Single Acting Pneumatic Engines My first engine was built using a single acting cylinder from set #8040. The cylinder pushed a weighted arm up which flipped the valve to exhaust, dropping the arm, flipping the valve to actuate the cylinder, and the cycle would repeat. It was crudely built on a 10x20 green base plate and had to be held down when it ran. It did not use the vacuum. I recently found a much nicer and better example of a pneumatic oscillator at Kevin's Lego Page.

Since about 1991, I figured out how to convert to rotary motion using a crank made with 24 tooth gears. The valve gear also ran off an eccentric created using 24 tooth gears and levers to get the amount of movement and geometry right. Since then my engines have evolved.

	This is an opposed 2 cylinder single acting engine. It must have a flywheel to carry the engine through dead center. Single acting engines run much faster than double acting where Legos are concerned, I think because the air above the piston moves freely in and out by the piston rod. I have not yet built any engine that uses a vacuum. The thought has crossed my mind, however, that I should build a model of an old beam pumping engine like those of Thomas Newcomen and James Watt that will operate strictly with a vacuum as was done in those days.

Radial Pneumatic Engine About 8 years ago I built a 6 cylinder radial pneumatic engine based on those used on airplanes. I have built these using both single and double acting cylinders, but the single acting cylinders are my favorite because they move faster. The engine is large, so of course, I had to build something large to put it on. I have a WWI style biplane with 2 cockpits with all working controls and control surfaces. It measures about 3'1" long. I consider the engine to be the pinnacle of my engine design. It has been updated mildly as I was able to find better ways to do things.



	Reversing Pneumatic Engine Just before the 6 cylinder radial, I also came up with a reversing gear which is very simple. It is based on that used on old steam traction engines. You can use 2 of the medium size pulleys or 2 of the large. The large work best for timings sake. Have 2 pins in each pulley set 180 degrees apart. Set the 2 pulleys facing each other so they rotate independently except for when the pins contact. I use the half stud, half pin. The stud takes less space. Put this gadget between your engine and valve gear and the only tricky part is timing.

90° Transmission There is another thingy (I do not know what it is called) that is fun to build. It is more fun than useful, but transmits rotary motion 90 degrees without the use of bevel gears. I copied it from one I saw at the thresherman's reunion in Kinzer, Lancaster County, PA.



Today... Today I use the cams for the crank as you do. I have built 1,2,4,and 6 cylinder engines in both single and double acting forms. My valve gear differs from yours in that I have a 40 tooth gear at the end of the crank shaft which is the driver. A second 40 tooth gear engages the driver. This gear has a pin in it and drives the valve gear. The 2 gears allow for some fine tuning, but are more difficult to find the correct positioning than in yours.
...Hybrid Air Power I installed your version on one side of an existing car I have built to see how it does. It works very well! The hybrid vehicle shows only a very very slight improvement using the 40 tooth gears.



Here is Paul's e-mail: pdkrieg@epix.net

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Updated: 22 Nov 02