Subject:
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Re: pneumatic cylinder: why not hydraulic ??
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Newsgroups:
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lugnet.technic
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Date:
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Thu, 8 Apr 2004 14:26:13 GMT
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Viewed:
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2998 times
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In lugnet.technic, Mark Bellis wrote:
> In lugnet.technic, Ross Crawford wrote:
> > In lugnet.technic, Kevin L. Clague wrote:
> > > In lugnet.technic, Chris Masclet wrote:
> > > > Hi everybody,
> > > >
> > > > I' ve read a long time ago something like this: LEGO pneumatic cylinder cannot
> > > > be use as hydraulic cylinder.
> > > >
> > > > Is anybody can explain me why ?? May be we can' t use water with cylinder (may
> > > > be cause of corrosion) but what about silicone oil ?? or something like that....
> > >
> > >
> > > The simplest reason is that when the switch is flipped to one side, the other
> > > port is released to the atmosphere.
> > >
> > > This means that your hydraulic fluid would spill all over the floor.
> >
> > Well one solution to that problem is to position all the switches above a
> > "hydraulic fluid catchment area", however I still think it would be prone to
> > spillage ;)
> >
> > ROSCO
>
> One key thing about hydraulics has always been "avoid leaks". To switch the
> fluid, just invent something I've wished for for years - the reverser switch.
> This switch has four ports, used in opposing pairs. Clockwise in a circle they
> would be A, C, B, D. In the middle position all ports are blocked. Pushed one
> way and A-C and B-D are connected. Push the other way and A-D and B-C are
> connected. The equivalent is to use four switches, with ports A to D being the
> middle ports of each switch. Connect the outer ports of the switches so that
> you get a crossover of the pipes without any leakage to the atmosphere in any
> position, whilst moving all four switch levers together. With ports on a switch
> being L, M and R, connect 1L to 3L, 1R to 4R, 2L to 4L and 2R to 3R. Connect
> the inputs to 1M and 2M and a cylinder to 3M and 4M.
I have created a pneumatic polarity reversor using four pneumatic switches.
I did an analysis and my pneumatic multiplexor works as a hydraulic switch that
does not have a free release.
http://www.brickshelf.com/gallery/kclague/Computing/p5280146.jpg
The above picture contains two pneumatic multiplexers. One facing us, and the
other away from us. For example, the gray hoses work with one mux, the black
(on the opposite face) work with the other.
I use these to do the polarity reversing needed to make my pneumatic quadraped
and hexapods be able to modify their walking behavior.
The interesting thing to note is that no matter what way the switches are
flipped there is no release. Using one of these muxes gives you a hydraulic
switch with *no free release*.
>
> These reversers can be chained, to make a parity generator! It is theoretically
> possible to make a very slow home computer out of Lego pneumatics!
This has been known to be true for a long time, although my version will not
contain parity.
>
> Applications such as this are one reason I like the new switches in 8455 Backhoe
> Loader, since you can put them back to back with no offset between lever pivots.
> This means you don't have to put the four switches in a line but can do 2+2.
>
> For hydraulic systems you'll need a powerful compressor and accumulator as well
> as a fluid reservoir and some means of ensuring that the pressure stays safe.
> I'm sure these complications ruled out hydraulics long before TLC designed any
> components.
>
> I'd like to write a book on Lego pneumatics - I have a few ideas already sorted
> into chapters, such as basics, building blocks and example systems.
Mark, I'd be very interested in the books contents as I have pushed the envelope
of LEGO pneumatics quite a bit.
>
> Mark Bellis
Kevin
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Message has 1 Reply:
Message is in Reply To:
 | | Re: pneumatic cylinder: why not hydraulic ??
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| (...) One key thing about hydraulics has always been "avoid leaks". To switch the fluid, just invent something I've wished for for years - the reverser switch. This switch has four ports, used in opposing pairs. Clockwise in a circle they would be (...) (21 years ago, 7-Apr-04, to lugnet.technic)
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