First, a warning: This bot is basically a microcontroller-brain version of the classic BEAM 4-legged walker. The BEAM 4-legger may be easier for you to make if you aren't already set up for microcontroller programming and just want to build a walker.
On the other hand, if you're getting started with microprocessor programming and have a couple servos kicking around, this here's your ideal project! You get to play with walker mechanics without having to worry about the fussy analog BEAM microcore tweaking.
So although this isn't really a BEAM bot, the following two webpages are great resources for any 4-legged walker:
Bram van Zoelen's 4-legged walker tutorial has a good overview of the mechanics and theory.
I took my leg design off his website.
Chiu-Yuan Fang's walker site is also pretty good for BEAM stuff and some more-advanced walker designs.
Done reading? Ready to get building?
Step 1: Gather parts, measure, plan a bit
2x Tower Hobbies TS-53 Servos
20in heavy copper wire: 12in for front legs, 8in for rear. I had 10-gauge. 12-gauge should work, but I'm guessing.
Battery is a 3.6v NiMH that was selling for cheap online.
The microcontroller brain is an AVR ATMega 8.
The frame is Sintra, which is hella cool. It's a plastic foamboard that bends when you heat it up in boiling water. You can cut it, drill it, matte-knife it, and then bend it to shape. I got mine at Solarbotics.
Drilled project board for the circuit
Snap-off headers (male and female) for the servo and battery connections
A 28-pin socket for the ATMega
Soldering iron and solder, wire
Some tiny bolts to hold the motors on
Here, you see me measuring out the parts, making a sketch for the frame, and then grabbing a ruler to make a paper template. I used the template as a guide to mark with a pen where I'd drill holes in the Sintra.