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"Kevin L. Clague" wrote:
>
> After reasonable feedback about the complexity of my first reversible pneumatic
> engine, I realized there was a very simple mechanical solution that would give
> reversability *and* variable speed.
>
> http://www.brickshelf.com/gallery/kclague/Computing/p6010044.jpg
>
> http://www.brickshelf.com/gallery/kclague/Computing/p6010045.jpg
>
> The difference between going forward vs. backwards is the phase relationship
> (difference in angles) between the pistons and the timing switches. In one
> direction the switches are 45 degrees clockwise relative to the pistons, and in
> the other direction the switches are 45 degrees counter clockwise relative to
> the pistons. So I needed a mechanism to be able to change the phase, to make a
> reversible engine.
>
> When trying to add two rotational rates, I always think of a differential.
> While the differential subtracts (takes the difference), this is easily turned
> into addition by reversing rotations where necessary.
>
> In this case, once the engine is running, the switch rotation rate is the same
> as the pistons rotation rate, so the differential is subtracting the piston
> rotation rate from 0 to get the switch rotation rate (I'm not sure this is
> exactly right, but you get the idea.)
>
> What the differential does allow us to do though is change the phase
> relationship between the pistons and the switches. The pistons come in one
> axle, the switch rotation comes out the other axle, and the rotational position
> of the differential case adjusts the phase between the pistons and the switches.
>
> The transparent 24T/worm gear box controls the rotational position of the
> differential case. The worm gear provides a locking mechanism so that once
> changed, the case cannot move. Turning the axle that goes through the worm gear
> turns the 24T gear, which meshes with the differential case. Turning the case
> changes the phase between the pistons and the switches.
>
> When the switches have a phase of 0 relative to the pistons, the engine cannot
> run. As you change the phase from 0 to either -45 degrees, or 45 degrees,
> eventually the engine is able to run, but not at peak efficiency until the phase
> gets to -45 or +45.
>
> This makes it reversible and variable speed.
>
> Please correct me if I've got anything wrong above.
Wow, that's a great design for a reversible and variable speed pneumatic
engine. An ingenious use of the differential gear, too.
And not to fret about correctness of the explanation. If it works, it
must be correct ;-)
--
C S Soh
http://www.ozbricks.net/cssoh1
....where air is power!
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