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In lugnet.technic, Jason J. Railton wrote:
> In lugnet.announce.moc, 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
>
> This looks amazing. It took me a long time to realise how the phase control
> works, but now I get it. For anyone else who's lost, here's how I understand
> it:
Hi Jason,
I'm glad you like the engine. I'm not really into engines. I was just trying
to satisfy Paul Kreig's desire to have a reversible engine, and it struck me
that a differential was an easy mechanical way to do it.
I love differentials. Too bad I don't make wheeled vehicles much.
>
> The casing of the differential is held still by the gear in the clear box. This
> means that the input shaft from the pistons comes in, turns the inner
> differential gears, and turns the output shaft in the opposite direction. This
> then drives the valve controls. The differential casing doesn't move at all.
>
> Now, if everything is still, and you wind the worm gear, this will rotate the
> differential casing a little bit. As it turns, and if the pistons and input
> shaft don't move, then this will force the output shaft to turn a little bit.
> When you start the mechanism going again, the pistons will drive the valve
> control gears again, but they'll be slightly further ahead or behind than they
> were before.
>
> Once you understand that, you can see how the adjustments can be made whilst
> it's all running too. You use the advance to control the speed and direction,
> like a car engine.
>
> If you advance the mechanism, you make the valves open slightly earlier on each
> rotation, so the push of the piston comes earlier, which speeds the engine up.
> If you retard the mechanism, the pistons start to push slightly later, so it all
> slows down.
Very nice explanation. Thanks for that.
>
> Jason Railton
Kevin
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