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In lugnet.technic, Kevin L. Clague wrote:
> In lugnet.technic, Mark Bellis wrote:
> > In lugnet.technic, Kevin L. Clague wrote:
> > > In lugnet.technic, Kevin L. Clague wrote:
> > > > In lugnet.technic, Mark Bellis wrote:
> > > >
> > > > <snip>
> > > > >
> > > > > Interesting stuff! Should make walkers move more smoothly, with the possibility
> > > > > of more groups of legs. The trick will then be reversing all the groups, since
> > > > > it was easier with just two, using two polarity reversers.
> > > > >
> > > > > I have a centre-stop mechanism for pneumatic steering for a JCB. It's not part
> > > > > of an automatic system though, since I don't yet have an application for that.
> > > >
> > > > Was this single or dual piston?
> > >
> > > Mark,
> > > Did I miss your answer on this?
> > > Kev
> >
> > No, I was so busy at work that I missed a couple of days online!
> >
> > I had a look at both, but a dual piston scheme works better for steering because
> > of equalising the piston area and pushing at least 3 switches. In fact I have
> > two cylinders in parallel at the moment. One problem I can foresee with that is
> > that there is a net force towards the middle due to the auto-expansion effect,
> > so the mechanism in the middle has to have good compressive strength.
>
> <snip>
>
> I used some axle joints to optimise cylinder position limiting in normal logic
> > systems (without offset switches) in my Octopus arm. The base of one axle hole
> > is on the end switch and the other end hits the top of the cylinder, limiting
> > its contraction to the right amount. This reduces air usage on the logic board,
> > speeding things up a bit.
>
> Do you have a website where I can peruse your work?
>
> >
> > Mark
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
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