Subject:
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Re: Pictures of New technique: Cascaded Trinary Pneumatics (aka mid-stop)
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Newsgroups:
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lugnet.technic, lugnet.robotics
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Date:
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Sat, 15 Oct 2005 20:56:15 GMT
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Viewed:
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520 times
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In lugnet.technic, Kevin L. Clague wrote:
> In lugnet.technic, Mark Bellis wrote:
> > In lugnet.technic, Mark Bellis wrote:
> > (SNIP)
> > > I have succeeded in directly cascading trinary pneumatic stages (where cylinders
> > > stop in the middle).
> > >
> > > This is a direct development of my mid-stop pneumatic JCB steering mechanism,
> > > which I first described here two years ago:
> > > http://news.lugnet.com/org/us/lugola/?n=916 (second paragraph from the bottom).
> > >
> > > I've taken some photos and will post them as soon as they come back from the
> > > developers. They will include the trinary system in all positions, as well as
> > > the Octopus Arm logic that I mentioned earlier. There will also be my earliest
> > > use of my trinary actuation mechanism and a pressure limiter (I'm sure quite a
> > > few people have their own versions of the latter).
> > >
> > > I took the actuation stage and the steering stage from my earlier work and added
> > > a combination of the two in the middle to make two cascading stages.
> > >
> > > I hope this will be useful for your walkers Kev. It's different from the way
> > > you were doing it. I have used opposing pistons for more power, and also extra
> > > frame members in tension to improve strength.
> > >
> > > The mechanism works quite well but I will keep improving it, probably by beefing
> > > up the power to improve reliability (with apologies to vegetarians :-) ). This
> > > might involve adding more cylinders to ensure that the mechanism reliably
> > > reaches its maximum distance from the centre position in both directions. The
> > > switch connections and the actuation mechanism that keeps the switch levers
> > > exactly the right distance apart are my own unique designs, which work well.
> > >
> > > I remember how it took quite a while to work out exactly how far apart the
> > > switch levers needed to be and which parts to use to achieve that distance.
> > >
> > > I wish my digital camera would arrive so that I could speed up posting!
> > >
> > > Mark
> >
> > Here are the pictures (at last!)
> >
> > They show the control stage, cascade stage and steering stage of Trinary
> > Mid-Stop pneumatic logic.
> >
> > Start in the centre position:
> > http://www.brickshelf.com/gallery/mbellis/Technic/Pneumatics/Trinary-Logic-System/cascaded_trinary_logic_evo1_1.jpg
> >
> > Moving to the left:
> > http://www.brickshelf.com/gallery/mbellis/Technic/Pneumatics/Trinary-Logic-System/cascaded_trinary_logic_evo1_2.jpg
> >
> > Moving back to the centre:
> > http://www.brickshelf.com/gallery/mbellis/Technic/Pneumatics/Trinary-Logic-System/cascaded_trinary_logic_evo1_3.jpg
> >
> > Moving to the right:
> > http://www.brickshelf.com/gallery/mbellis/Technic/Pneumatics/Trinary-Logic-System/cascaded_trinary_logic_evo1_4.jpg
> >
> > Close-up from the side:
> > http://www.brickshelf.com/gallery/mbellis/Technic/Pneumatics/Trinary-Logic-System/cascaded_trinary_logic_evo1_zoom.jpg
> >
> > Original switch geometry (robbed of hoses!):
> > http://www.brickshelf.com/gallery/mbellis/Technic/Pneumatics/Trinary-Logic-System/first_mid_stop_steering_switch_layout_1999.jpg
> >
> > I have developed the system further to improve reliability, also eliminating the
> > centre switch in each stage - you see that the control stage already has its
> > centre switch unconnected in this evolution. Evo 2 will be photographed with my
> > next batch of MOCs.
> >
> > Using only studless beams requires more framework than using studded ones,
> > especially the tensile members that absorb the pressure of two cylinders pushing
> > against each other. Using single cylinders is possible if the auto-extension
> > can be countered with a belt or elastic band that causes the cylinder to
> > auto-centre instead when pressure is applied to both ends.
> >
> > Depending on belt tension and input pressure, my design could also be used to
> > make a 7-stop pneumatic system! This is getting closer to hydraulics, which are
> > much easier to control to any desired position, except in the LEGO system that
> > doesn't have them! I don't recommend using water with pneumatic parts - I tried
> > it once in order to make a fire engine but the non-return valve of the old
> > pneumatic system soon failed. The more I experiment with the complex and
> > expensive LEGO parts, the more I decide to understand what is their original
> > design intent and stick to that.
> >
> > Mark
>
> Hi Mark, cool stuff!
>
> I guess that the ganged switches on the far right are the switch stage, but I
> don't know what the other two large blocks are, or how they work. One thing I
> learned early with documenting MOCs, is to never use black when there is another
> option. Black is so hard to photograph so that you can see anything inside the
> borders.
>
> Is the cascade stage in the lower left, and the steering stage in the upperl
> left?
>
> I think I see five switches in the lower left module, three ganged together
> using bands, and one on each end. I also see three switches in the upper left
> module. Are the switch linkages in all three modules like the one in the lower
> right?
>
> Thanks for sharing,
> Kevin
Hi Kevin,
Yes, the bottom right stage is the control stage, with 2 active switches. I
left the third one in to keep the stability with the cams and 2L liftarms so
that the 1x4 brick with holes moves as a parallelogram.
I got into the habit of trying to make models in a single colour! It's usually
the case that black is the colour I have most of, especially in Technic. In
lieu of better visibility, I used a couple of 8L axles, which each have a
cylinder pushing on them. They're separated by 3L liftarms with +o+ holes, with
a 1x4 brick with holes just behind the switch levers. The middle switch has a
peg in the middle hole of the 1x4 brick, with the outer switches' pegs resting
on the ends of the brick, pulled in by the belts. The same mechanism is used in
all 3 stages. I found that the belts had more pulling power on the ends of #2
axle joints than when they were lower down.
The bottom left stage is the cascade stage, with the middle 3 (2 in Evo 2)
switches controlling itself and the outer 2 controlling the next stage. The
outer 2 switches are rigidly linked to the adjacent ones so that they have more
limited movement than the centre switch, though I'm changing this for Evo 2.
The top left stage is the steering stage, which is similar but without the
output switches. I developed the cascade stage from this, and this in turn was
developed from the original switch geometry, which had a control stage and 4
switches controlling itself! That development was when I used the cams and 2L
liftarms so that I could get rid of the 4th switch.
Mark
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