First, the source of inspiration. I know most of you who are
looking at this page have seen the
introduction
video on the Lego Mindstorms CD. In this video, we get a couple glimpses of one
very cool looking robot that is climbing up a window! Boy was I inspired! It
took me quite a while to figure out how to do this... It was actually a school
project that led me to the discovery of creating a vacuum pump with Lego. I
first experimented with some check valves and suction cups from an aquarium
store. With the check valves connected to a Lego pneumatic cylinder, I could
create a piston pump. Then I realized that Lego actually made a block with check
valves in it for the old pneumatic system, which was all single acting. (meaning
the cylinders have only one inlet. To push the piston up, air was pumped into
the cylinder. To pull the piston down, air was sucked out) I had one of these
old pneumatic sets when I was younger, but the key parts had been misplaced :(
Fortunately I was able to borrow them from Calum
Tsang. And so, the workings of
the window walker were born. I just had to figure out the walking mechanism and
the timing....
This sequence shows how I used two counter-rotating cams to flip the
pneumatic valve back and forth. This is geared directly to the drive train, so
the timing of the switching is critical. Just as two feet come up to the glass,
the other two have to be released, without falling off. Getting this to work was
tricky, but once I got it, it was pretty reliable.
The suction mechanism is a bit tough to explain without a diagram, so I have put an explanation on a separate page.
I really would like to have motor drive the vacuum pump onboard. I have made several attempts, but none were satisfactory. It seemed that once the motor was geared down enough to power the pump, it was too slow to maintain the necessary vacuum in the tanks.
I just recently put together the window walker in ldraw, so if you have the special parts required, and would like to have a go at building one, you can download the instructions here. You will probably need the pneumatic parts for ldraw, so you can download them here. Just copy them into your ldraw parts directory.