Nuts & Volts - September 2004

Personal Robotics

encountered were a PEM nut that had damaged threads and a few missing pieces, like #2 washers. I decided to clear every PEM nut with a tap, just in case. I also decided to inventory everything and was able to rummage though my junk box and get what I was missing.

The core issues I have are also features in their own ways and they are the fairly limiting geometry that a 2 x 6 walker possesses, along with the simplicity of the processor — the BASIC Stamp II. In a way, this is sort of an equal match. The BASIC Stamp II isn’t capable of the intense processing that is required to do the inverse kinematics that a 3 x 6 walker could use to more accurately walk, but I believe that it is also not necessary (more on that later, though).

Overall, this kit embodies the essence of what I think most of us see as the core of walking robots — lots of intricate, moving parts. While the simple 2 x 6 design and its processor are ill-suited for complicated kinematics, they do provide a great, simple start. A beginner should be able to jump into this right away and, in a few evenings, have a very high level of satisfaction. Additional third axis leg extensions can be added, along with an additional servo controller, as well, but, at that point, I would consider a processor with more horsepower to fully utilize the advanced geometry available.

Straight out of the box, this kit lacks the real complexity that I somehow thrive on, but I have to keep reminding myself that — just because I have been programming for 30 years and design insanely expensive motion control systems — not everyone else has or even wants to deal with that much wholesale madness.

Overall, a small degree of skill is necessary and be prepared to use some basic hand tools, as well as a 1/8” drill. I give this kit a solid A.

Extreme Hex 3R.

While the EH3-R lacks the refined presentation of the HexCrawler, it is a beast of a kit and very satisfying. Made of laser cut Lexan^®(not just generic polycarbonate) and 18 Hitec HS475-HB servos, this kit is a formidable challenge. The resilience of the Lexan gives the EH3-R an almost meaty feel as you assemble it, as though it were going to lurch into life on its own. Replacing the clean gleam of the HexCrawler was the slightly acrid tinge of laser cut plastic, but that really adds to the feeling of elemental life that the EH3-R conveys as you build it.

In fact, the actual build was relatively easy. I only found myself wanting an easy way to secure the servo wires, but a trip to the electronics store solved that with a variety of fastened and adhesive-backed wire anchors. I would also like to get my hands on the metal standoffs that are now shipping with the kits, as I see myself accidentally breaking some of these eventually. I did take artistic license

The EH3-R makes its escape.

with the build geometry, making each leg identical, rather than mirrored images of each other, but more on that later.

The build of this kit is a lot more intensive than the HexCrawler, due to the additional six servos, but, in a way, it’s a bit less complex due to the molded plastic pieces used to make