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In lugnet.technic, Brian H. Nielsen wrote:
> In lugnet.technic, Mark Tarrabain wrote:
> > What I do find interesting is that the pressure produced by the
> > expansion of one piston probably would not normally be sufficient to
> > compress another piston where the combined load of both pistons is too
> > great to have otherwise been driven by a single piston. Your idea of
> > connecting them while they are all retracted to create a slight bias to
> > that end is ingenious, IMO, and may go some lengths to overcoming that
> > limitation. I'd be curious to know by how much.
>
> The work load done by the expanding piston is independent of the work load
> done by the compressing piston. As long as the expanding piston expands fully
> the air pressure in the compression loop will exert its maximum force on the
> piston being compressed. If the expanding piston does not expand fully then
> there is insufficient air pressure driving the expansion.
As a follow-up, over time the air pressure in the closed compression loop
drops due to slow leakages, so it requires periodic recharging. One way is to
remove and reseat the tubing, but a beter way is to add another T and a hand
pump to the closed loop. Now the pressure can be increased at any time to any
amount. I have hooked this up and it now and the compressing piston easily
switches 4 switches, which is all my spares at the momement.
There is a balance that needs to be achieved between the pressure driving the
expanding piston and the pressure in the closed loop. First calibrate the
compressing piston by causing it to expand and then retract. If the piston
doesn't fully compress use the hand pump to add pressure to the closed loop
until it does. This should be done in small increments and will probably need
only partial strokes of the hand pump. Now that the closed loop is calibrated
it should work fine until leakages lower the pressure.
The increased pressure in the compression loop adds extra work for the
expanding piston since it has to overcome the compression loop pressure. This
means higher air pressure is needed in the expansion loop. Consequently, how
much work the compressing piston can perform is limited by how much air pressure
can be put into the expansion loop - at some point the tubing will pop off.
It might be feasible to automate recharging the compression loop by removing
the hand pump and running a small pump on a compressor when the pressure drops
below the level needed for full compression. The small pump allows much finer
control over the pressure level in the compression loop.
Brian
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Message is in Reply To:
 | | Re: A better full adder!
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| (...) No offense was taken. My appologies if I gave that impression. I just completed some load testing on the compressing piston. It easily switched 2 switches, was just barely able to switch 3 switches, and clearly couldn't do 4 switches. Since (...) (21 years ago, 1-Jul-03, to lugnet.technic, lugnet.robotics)
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