CSSoh's Lego Pneumatics Hybrid FT-LEGO Engines 21 Dce 2003

Hybrid FT-LEGO Pneumatic Engines

The LEGO medium double-acting cylinders are stiff and engines built with them cannot run fast. The new studless cylinder with the rounded bottom is functionally the same. The old single-acting cylinders are better in this respect and engines built with them run much faster. However">

Hybrid FT-LEGO Pneumatic Engines
The LEGO medium double-acting cylinders are stiff and engines built with them cannot run fast. The new studless cylinder with the rounded bottom is functionally the same. The old single-acting cylinders are better in this respect and engines built with them run much faster. However, the old cylinders are hard to come by. Those that I have obtained through Bricklink are of varying quality. Getting good quality ones would mean buying MISB sets which can cost a bomb. So I have been eyeing the Fischer Technik (FT for short) cylinders as suitable substitutes for the LEGO cylinders.
As it happily turns out, FT cylinders can be integrated with LEGO pneumatics to build hybrid engines that run much faster than those using the standard LEGO cylinders. The FT cylinders are double-acting and come in large and small sizes. They can also be used as single acting cylinders. With the addition of a one-way valve they can also double up as pumps for motorised compressors (more of that later on).

Hybrid Single Large FT Cylinder Pneumatic Engine
The first attempt was to substitute a large FT cylinder for the medium LEGO one in a single cylinder engine. Here is the original engine using the LEGO cylinder.


And here is the hybrid equivalent using the large FT cylinder. The same valve gear is used.

Note that the piston is fixed at the pivot point and it is the cylinder that moves to-and-fro. Also a half-spacing is used to get the geometry correct. The hybrid engine runs much faster than the original using the LEGO cylinder.

	This is the large FT cylinder sub-assembly. The fitting at the base of the cylinder accepts a LEGO axle. The metal FT axle at the piston end fits the holes in a LEGO beam. All parts are used as is, no need for any modification whatsoever. Neat! Note: The parts are all from the FT Pneumatic Robots kit.

Hybrid Single Small FT Cylinder Pneumatic Engine

A similar hybrid engine using a single small FT cylinder has also been successfully built. Note that an old type 24-teeth gear is used as the crank to accommodate the shorter stroke of the small FT cylinder. A half-spacing using a 1x2 brick with 2 holes is also required. The valve gear is the same as that for the large cylinder engine.






Hybrid Large 2-cylinder Engine
I have also found that the large FT cylinders can be used as substitutes for the LEGO cylinders in my 2-cylinder pneumatic engine design. The hybrid runs better but is still somewhat jerky as it lacks a proper flywheel.




Here are the details of the valve gear. Note the use of the 1x2 brick with 2 holes.


Hybrid Small 2-cylinder Engine - Unsuccessfull :-(
A 2-cylinder engine using two of the small FT cylinders was also tried but it failed to run for some reason. The pictures are shown here in case someone else wants to have a go at making it to work.



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Updated: 21 Dec 20 03