Subject:
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Re: What the? Hydraulics
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Newsgroups:
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lugnet.technic
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Date:
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Wed, 23 Nov 2005 20:12:41 GMT
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Viewed:
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6326 times
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In lugnet.technic, Nathan Bell wrote:
> In lugnet.technic, danny staple <orionrobots@gmail.com> wrote:
> >
> > Vineet, if I have been following the threads properly- the
> > breakthrough that may allow the use of hydraulics with Lego penumatic
> > components is the set up which takes out the implicit forth port so
> > you dont get squirting oil from your creations. It is bulky at
> > present- but a good start. It is at current being used for interesting
> > and sophisticated pneumatic circuits using vacuum as well as
> > compression.
> > --
> > Danny Staple MBCS
> > OrionRobots
> > http://orionrobots.co.uk
> > (Full contact details available through website)
> >
> >
> > On 23/11/05, Kevin L. Clague <kevin_clague@yahoo.com> wrote:
> > > In lugnet.technic, Vineet Honkan wrote:
> > > > Kevin Clague-
> > > >
> > > > How can a lego pneumatic do hydraulic work? If I'm not much mistaken,
> > > > hydraulics
> > > > and pneumatics use two diferent sources of power.
> > >
> > > Hydraulics and pneumatics are similar.
> > >
> > > Pneumatics uses air, which is a gas and can be compressed. Air pressure
> > > difference is what makes pneumatics work.
> > >
> > > Hydraulics uses fluids which compresses a little, but not much compared to
> > > gasses.
> > >
> > > Both use pistons/rams hoses, and valves.
> > >
> > > Hydraulics are typically stronger.
> > >
> > > Kevin
>
> One question I have is related to the construction of the first generation of
> the Lego pneumatic system that had 2 ports for each piston (circa-1989).
FYI: The first LEGO pneumatics system had single ported pistons. Also the only
difference between pump and piston was that the pump had return springs.
Here is the 60mm version of the original pneumatic single ported system.
http://www.bricklink.com/catalogItemPic.asp?P=4701b
Unfortunately, bricklink does not have a close up picture of the 45mm red single
ported pneumatic system.
This is a picture of the original format pneumatic pump.
The original pneumatics also contained a pneumatic distribution block:
http://www.bricklink.com/catalogItemPic.asp?P=4692
This has two one-way valves one between the left and center port, and the other
between the center port and the right port.
The pump was hooked to the center port. Expanding the pump pulls air in the left
port. Contracting the pump pushes the air out the right port.
Switches were used to choose between pressure or vacuum.
Peeron indicates that original style pneumatics were still available in 1985.
> I had a piston from a 1989 pneumatic universal set in which I tried to put
> water in them to make it a hydraulic system. The valve broke either from the
> pressure on it or because I'm a moron. The piston failed to work too, So I had
> to take it apart (which is basically like crossing the Rublicon). The stopper
> (what's that thing called again?) had come off the piston rod. I discovered
> that it was 100% rubber and could come off if it the hole for the piston rod is
> stretched open wide enough.
The second generation pneumatics provided dual ported pistons, and pumps with a
single one way valve at the base. The switches were unchanged, but used
differently.
Hmmm.... there are two seals on a modern piston:
1. The o-ring (?) that seals shaft with respect to the atmosphere.
2. The piston head that separates the two pressure chambers of the cylinder.
The O-ring at the top is very vulnerable when the piston is a maximum expansion.
You have to be careful about your mechanical environment and try to keep the
shaft axially aligned at near full expansion.
Looking in my transparent cylinders, the piston heads appear to be rubber, with
the shaft going through it. I've never disassembled them to find out if the
piston head is just a fancy O-ring.
Did you have any sort of pressure regulator in your water based system?
>
> Wouldn't adding hydraulic fluid/water to Lego pneumatics damage them? Or were
> the parts I had in 1989 very different than today's pneumatic pieces. I do not
> wish to take apart one of my new ones since they are a valuable asset to my
> construction fleet, and doing so would be like crossing the Rublicon.
It depends on the fluid used. I would not use water as it may cause corrosion
on the shaft.
Take care with other fluids as well, as they may corrode the rubber or the
plastic.
>
> Also, if the top of a large Lego piston pump was submerged in the fluid- would
> that make the system a closed one?
I would never try to use the LEGO pneumatic pumps as a hydraulic pump.
Instead I would try to make a switch based system like Billy recently created.
> I always thought the difference between
> pneumatics and hydraulics is that pneumatics is generally an open system (since
> there is always an abundance of air) and hydraulics is generally a closed system
> (since hydraulic fluid is not in as great an abundance and would definately not
> be as safe to breathe in.
Well, I think the open vs. closed system is inherint in the two systems, but is
not a defining characteristic.
The root word of the word pneumatics is pneumo or pneum meaning air or gas.
There are many medical words that have the root word pneumo, having to do with
breathing air.
The root word of the word hydraulics is hydro meaning water or fluid.
So open vs. closed is simply a characteristic difference, but not a defining
one.
Imagine a small subermsible that used a water based hyrdaulic system it could
either be a closed system that used purified water, or an open system that
filters water at the inlet to the pump.
It is a hydraulic system that could be either open or closed. Also it could
have a pneumatic system to control its arms. That system would be considered a
closed system in that the air does not come from outside the submersible, and
the exhaust could be brought back into the submersible.
Pneumatics can be an open system on land because it is simple.
>
> Nathan
Kev
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Message is in Reply To:
 | | Re: What the? Hydraulics
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| (...) One question I have is related to the construction of the first generation of the Lego pneumatic system that had 2 ports for each piston (circa-1989). I had a piston from a 1989 pneumatic universal set in which I tried to put water in them to (...) (19 years ago, 23-Nov-05, to lugnet.technic)
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