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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Wed, 7 Apr 2004 22:43:02 GMT
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Viewed:
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2758 times
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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.
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!
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 Bellis
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Message has 4 Replies:
 | | Re: pneumatic cylinder: why not hydraulic ??
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| (...) 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. (URL) above picture contains two pneumatic multiplexers. (...) (20 years ago, 8-Apr-04, to lugnet.technic)
| | | Re: pneumatic cylinder: why not hydraulic ??
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| (...) Mark, I thought this one through, and I get it. I can see how it works. The solution works equally well as my solution. I don't think mine is any more or less complicated, just different. Less hoses, more T's and other technic parts than (...) (20 years ago, 9-Apr-04, to lugnet.technic)
| | | Re: pneumatic cylinder: why not hydraulic ??
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| (...) Hi Mark, Is the cheapo ASCII art diagram below what you are talking about? We are viewing the switches/circuit from above. What is not shown is that the handles are all linked together. +-----+ +-----+ +-----+ +-----+ | | \ / | | | \ / | | \ / (...) (20 years ago, 11-Jul-04, to lugnet.technic)
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