Re: Best pneumatic hexapod yet!

In lugnet.technic, Andréas Rootzén wrote:
> In lugnet.technic, Kevin L. Clague wrote:
>> I don't know if any of you saw this fabulous pneumatic hexapod, but my friend
>> Sigurd van Starkenberg:
>>
>> http://www.brickshelf.com/cgi-bin/gallery.cgi?f=137658
>>
>> It walks forward, backward and turns right and left.
>>
>> The thing that makes this superior to prior work is an elbow mid arm, that
>> lengthens for walking, and shortens for turns!
>>
>> Great job Sigurd!
>>
>> Kevin
>
> If theres ever a blueprint of this one I´d like a copy...never tried to build
> something like it but might try some day...
> How many Pneumatic Cylinders (18+4?) and Switches (52?) were used?
>
> Andréas

Hi Andreas,

  Given my email exchanges with Sigurd, I believe that the circuit is a
variation of the circuit I designed for my Quad242:
http://www.kclague.net/Quad242

  If so, you can find out more about the circuit design here:
http://www.kclague.net/Sequencer

  It looks like each leg has three pistons.  Each piston has two switches,
giving us:

  18 large pistons
  36 switches

  There are two switches for timing only:

  4 small pistons
  2 switches

  It also looks like four polarity reversors at four switches each.

  16 switches

  So your estimate is very good.

  18 large pistons
   4 small pistons
  54 switches

Each leg piston has two switches.  One switch lets you know when the piston is
expanded, and the other switch lets you know when the piston is contracted.
These switches, hooked together in series, act as AND gates necessary to create
the pneumatic sequence for walking.

Basically the walker has two leg groups that are mirror images of each other.
The left leg group includes the front and back legs on the left side, and the
center leg on the right side.

Sigurd's walker starts with both leg groups down, then lifts one leg group,
swings both leg groups (down group back, up group forward), and then puts the
forward group down.  Once all six legs are on the ground, the ciruit lifts the
back legs, leaving the forward legs down, swings the legs (this is the part that
causes forward motion), and then puts them back down.  This sequence is
reapeated to cause continued walking motion.

Sigurd's walker can walk backwards, by reversing the swing of both leg groups.
Reversing the swing of the leg groups is implemented using a polarity reversor
to reverse the swap the pressures applied at the piston's ports.

Sigurd's walker can also turn.  This is done by reversing the swing direction
for the two center legs.  This causes Sigurd's walker to turn one direction.  By
combining turn.  By combining reverse and turn, Sigurd's walker can turn the
other direction.

Reversing the pistons accounts for two of the four polarity reversors seen
inside the body of his walker.  The other two polarity reversors are used to
compensate for the fact that reversing the swing, also reverses the outputs of
the legs (remember those two switches per leg or hip piston hooked together
serially?)

If my struggle to balance terseness with completeness makes this post
incomprehensible (as often is the case), please ask questions.

Kevin