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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:
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.
Jason Railton
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