Subject:
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Reversible pneumatic engine
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Newsgroups:
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lugnet.technic
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Date:
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Sun, 1 Jun 2003 01:25:31 GMT
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Besides bipeds, I also love LEGO pneumatics.
Doug Carlson and I have been trying to work on techniques for making single
piston pneumatic engine with little or no flywheel. Doug has been having better
luck than I but neither of us have acheived the goal.
In attempt to have a success at something, I decided to work on a project I
thought of on Thursday. A reversible pneumatic motor.
First I had to make a pneumatic motor that went forwards. Then I disconnected
the forward swtiches, and added switches that made it go in reverse.
Then I pulled out the magic. My design for a Two input, one output pneumatic
multiplexer. One of the multiplexers, selects between the forward and reverse
inputs for one of the two pistons in the engine. A second multiplexor selects
between the forward and reverse inputs for the second piston of the pneumatic
engine.
When the multiplexers are both flipped one way, they both select the forward
inputs and feed them to the pneumatic engine's pistons, and the engine goes
forward. When the multiplexers are both flipped the other way, they both select
the reverse inputs and feed them to the pistons.
The two input one output pneumatic multiplexer requires requires three switches
per port on a pneumatic piston, for a total of six switches. In this picture:
http://www.brickshelf.com/gallery/kclague/Computing/p5280148.jpg
You see three switches combined to multiplex the inputs to one of a pistons' two
ports. The swtiches marked input1 and input2, merely shut off the inputs when
their pressure (or release) is not being sent to the output. This prevents the
release of the output switch from releasing the system pressure to the
atmosphere.
The input switches can either be off or on, and are always opposite of each
other. The output switch takes the outputs of each of the input switches
through what we normally think of as "output" ports, and runs the selected one
to the output port (normally the input pressure port).
The back side of the multiplexer has the same configuration of switches and
hoses, to give you a multiplexer for the second port on a pneumatic piston.
Here is a simple example of a multiplexer being used to select between two
switches, and the output is used to drive a piston.
http://www.brickshelf.com/gallery/kclague/Computing/p5280146.jpg
Finally, I have two pictures. The pneumatic motor with two multiplexers that
select between the forward and reverse timings. Its a rats nest, but it is a
nice example of using multiplexers.
To my knowledge this is the first reversible pneumatic engine.
Forward:
http://www.brickshelf.com/gallery/kclague/Computing/p5280040.jpg
Reverse
http://www.brickshelf.com/gallery/kclague/Computing/p5280041.jpg
The difference between the two is the positioning of the switch handles on the
multiplexers.
PLMKWYT
Kevin
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Message has 2 Replies:
 | | Re: Reversible pneumatic engine
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| (...) Very cool Kevin! Have you thought of using a sliding linkage like steam train valves? It would make it less than 100% pneumatic, but might make it somewhat less complex. ROSCO (21 years ago, 1-Jun-03, to lugnet.technic)
| | | Re: Reversible pneumatic engine
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| (...) Kevin, This is truly great! At the moment I barely understand it at all. I must build one. Reversible valve gears have interested me for some time. This is not the first reversible engine. I will soon upload photos to Brickshelf. My version is (...) (21 years ago, 1-Jun-03, to lugnet.technic)
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