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"c s soh" <cssoh@singnet.com.sg> wrote in message
news:3C8076A2.E27D98A@singnet.com.sg...
> Hi there, Rob
>
> That thread led to an extensive discussion into the depths of "vacuum
> storage". It would appear that storing compressed air is no problem but
> 'the whole concept of "storing vacuum" is a little disturbing.'
You most certainly can store vacuum. How would a TV set work, otherwise?
When the tube is finally smashed or broken at the end of it's life, the
vacuum promptly disappears.
> Well, you can certainly pump air into a blue air tank (using the
> recommended 30-35 strokes of the new hand pump) and power your pneumatic
> device from off the compressed air for say 5-6 cycles before you need to
> charge up the air tank again. As a matter of fact, Mario Ferrari has
> used the compressed air stored in 7 of the blue air tanks to drive
> "Eolo" his Sumo robot to victory.
>
> Now try to *store* vacuum in one or more of the blue air tanks. Stop
> your pump and try to work your pneumatic device from off the "stored
> vacuum". How many cycles do you think your old pneumatic based device
> would work before you have to regenerate the vacuum?
You are confusing the stored vacuum that someone has created with the
operation of the old-style pneumatic system. Old-style pneumatics wouldn't
benefit from air tanks simply because there is no practical use for air
tanks in them - you could pressurize a piston and force it out to it's
maximum travel and have to do it with the handpump forcibly several times,
and then flip the switch the other way and watch the entire pressure
contained in the piston release itself in about 2 seconds. This was
especially true with a relatively light load on it.
> It is in this context that Christophe and I said that the air tank would
> not work with the old style pneumatics.
Because it did not rely on the concept of storing either air pressure or
vacuum, it relied on the creation of air pressure and of vacuum to take that
air pressure away.
> I note that your window walker has an umbilical that leads to one of the
> old hand pump which I figure has to be worked continuously. So you are
> not really relying on stored vacuum but have to generate it
> continuously. In which case an air tank to *store vacuum* would not be
> needed. I wonder if the creature may work better without the air
> tanks...
In conventional models, one has a need to generate air pressure
continuously, too. A vacuum has a negative pressure effect, without it if
you sucked the air out of everything the pressure of the atmosphere outside
would simply crush the object having air sucked out of it. Again, if vacuum
didn't have negative pressure where it exists, the TV wouldn't work! A note
here, the TV set does rely somewhat on the construction of glass that
comprises it's shape, but if the container you have has no physical strength
of it's own, there would be nowhere for the vacuum to be held, therefore the
vacuum is exerting negative pressure.
A vacuum could be said to be not just a space devoid of air or other matter,
it could also be said to be a physical force exerted on something that holds
it to a particular location. I wonder why they invented vacuum cleaners in
the first place, otherwise? ;-)
This is getting technical, I wonder if there's a lugnet.science or similar
discussion group? :-)
--
Cheers ...
Geoffrey Hyde
(Remove spamblock to reply.)
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Message has 1 Reply:
 | | Re: Pneumatics: the old and the new
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| (...) Exactly! (...) That's right! (...) Oh oh! Methinks you have not had the simple pleasure of playing with a hand pump (the new type of course) and an air tank like in the 8250 Submarine or 8462 Tow Truck or such like. Try it! (...) No need, just (...) (22 years ago, 4-Mar-02, to lugnet.technic, lugnet.robotics)
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Message is in Reply To:
| | Re: Pneumatics: the old and the new
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| Hi there, Rob That thread led to an extensive discussion into the depths of "vacuum storage". It would appear that storing compressed air is no problem but 'the whole concept of "storing vacuum" is a little disturbing.' Well, you can certainly pump (...) (22 years ago, 2-Mar-02, to lugnet.technic, lugnet.robotics)
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