Subject:
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Re: Pneumatic tubes capabilities
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Newsgroups:
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lugnet.technic
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Date:
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Fri, 6 Sep 2002 23:45:02 GMT
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Viewed:
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506 times
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In lugnet.technic, Pedro Silva writes:
> In a way, that was what I meant: since the tubes are made of rubber, they
> are somewhat elastic (thus they can increase their volume significantly if
> they are long enough).
I don't thing tube stretch is a factor here. The pneumatic tubes do not
expand very much at the normal pressures of Lego pnuematics. The tubes are
relatively stiff.
The volume comes from just the long length of tubing. (Think of a volume
calculation: cross-sectional area of inner tube times tube length)
> > Basically, if you have a lot of long tubes, your system will behave as if it
> > has an airtank. However, if you keep your system charged, this shouldn't be
> > a problem. With your system fully pressurized, the operation of the cylinder
> > should be instantaneous with the switch.
> Ok, I guess I got it: it can work, but it must be always "on", either to one
> side or the other.
Well, the compressor doesn't have to be on all the time. Use a cut-off
switch that will kill the compressor when the pressure reaches maximum, and
that will kick back in when the pressure drops.
> Now a second question: one single compressor, equipped with one of the old
> 9V motors (high speed, low torque), can handle just how many cylinders *very
> far apart*?
> (just as an exercise, suppose 12 cyls, app 5 m apart each from the compressor)
I think it depends on the frequency of use. You could operate many cylinders
with only on compressor if you operated the cylinders infrequently (say, one
at a time, spaced 15 or 30 seconds apart).
After reading Mark's response, I think I understand the problem a little
better. Because the pneumatic switches release air in the opposite tubes
when operating (i.e. one tube "pushes" to operate the cylinder while the
other is released and unpressurized), the next cycle of operation will start
with an unpressurized line. It sounds like you'll have a lot of tube between
the switch and the cylinder, and that's a relatively large volume to
pressurize quickly.
You may want to use several air tanks between the compressor(s) and the
switches. This will allow quick operation of a cylinder when hitting an
unpressurized tube.
This solution isn't great, as it will take a long time to start up. I think
once you get your tanks pressurized it should work well, providing the
frequency of use is very low.
You may want to experiment before building your system. Set up a cylinder or
two with a long stretch of tube to your switches. Hook up a compressor and
try operating the cylinders. Experiment by placing airtank(s) in the system.
> That was my hope. I think my idea can work, I just need to know how many
> compressors to place.
I guess it all depends on frequency of use. Just try experimenting. It's
been my experience that the more compressors you have, the better ;-)
TJ
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Message is in Reply To:
 | | Re: Pneumatic tubes capabilities
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| (...) In a way, that was what I meant: since the tubes are made of rubber, they are somewhat elastic (thus they can increase their volume significantly if they are long enough). (...) Ok, I guess I got it: it can work, but it must be always "on", (...) (22 years ago, 6-Sep-02, to lugnet.technic)
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