small pneumatic cylinder

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Welcome to my pneumatics page (no implied affiliation with the Lego Group). This page contains pictures of my own designs as well as links to works of others.

There are currently two popular compressor designs: small single-pump compressor by Michael Powell and dual-pump compressor by Ralph Hempel. I like both designs, especially Ralph's one, but I thought that I can come up with something better. First, I wanted full-stroke dual-pump version. Second, I wanted to use new Lego 9V motor geared down compared to Ralph's version to yield higher pressure. My best result so far is the compressor shown on Fig.1 (see assembly instructions below).

compressor front view close-up compressor rear view close-up
Fig.1  Front and rear views of the compressor

When I finished the compressor I started thinking about pressure switches. Two switch designs I found (by Ralph Hempel and Larry Pieniazek) are nice but a little bit too large for the simple function they accomplish. My idea was to put the cylinder on top of the switch and use connection plates as functional elements. First, I measured forward-off-reverse-off angles of the rotary switch (in case you are interested, the angles in degrees are -18..18(off), 18..72(forward), 72..108(off), and 108..162(reverse)) and then calculated possible trajectories of the cylinder arm using lego blueprint and pair of compasses.

compressor and switch close-up pressure switch side view pressure switch rear view
Fig.2  Pressure switch attached to the compressor

The pressure switch assembly is straightforward; the only tricky part is to find the correct angle for the polarity switch axle. When the switch is assembled properly, it cuts off the power just before the end of the cylinder stroke.

The compressor assembly is more complicated; the figures below illustrate various stages of the assembly. Note that the bottom part is attached to the front part on a half-hole offset. The relatively hard to find two-hole 1x2 beam is not essential to the design; it may be replaced by the "small turntable" System piece or plain brick of the same size.

required compressor pieces close-up front part assembly
Fig.3  Compressor assembly: required pieces, front part

front and bottom parts close-up assembled front and bottom parts
Fig.4  Compressor assembly: bottom part

front and motor assemblies front and bottom assembly, motor and top part pieces
Fig.5  Compressor assembly: motor and top part

If you need more details, check the DAT file (no pumps and tubing).