Jeremy learned a lot building PegLeg, and he ended up with a pretty neat robot in the end, too!
Somewhere way back in the year 2000, a show called Battlebots was on television. As a young engineering student, this badly made me want to build a robot to compete. After some preliminary research, I realized I knew next to nothing about radio control. Aditionally, I didn't have the machine shop skills or money to pursue a 'bot capable of actual combat.
Around this time, I also saw how someone had built a hexapod using only three servos, and some linkages. Known as the BS2-6 bot, this little walker didn't have a ton of documentation, but it did have a partial bill of materials. It used a Basic Stamp II for control, with which I had just familiarized myself in school. This seemed like a reasonable substitute for what seemed like an unattainable goal of building a combat-ready vehicle.
The inspiration, created by Jonas Aronsson
Even a simple walking robot like this one is harder than it looks to build. The concept might be simple, but actually making everything work well is another story. My tools at the time consisted mostly of a Dremel tool and a soldering iron, which made assembly challenging.
Eventually PegLeg was assembled using wood for both the top part of the legs and for what could be described as "pillow block" bearings for the middle legs. Screws were used both as the ends of the legs and as what everything pivoted on. Linkages were paper clips. Somehow it was able to walk. Barely.
The initial prototype, complete with wooden spacers.
The original PegLeg wasn't much to behold, both in form and function, however this happened at a really opportune time for me. I got a job as an engineering co-op at a company that allowed, and even encouraged, me to learn how to work in its machine shop. I also became proficient with AutoCad and, as simple as it may be, using calipers.
My newfound drafting and measurement ability allowed me to draw my robot and tweak changes virtually. My limited machine shop skills allowed me to make these tweaks accurately. Before my co-op term, I'd thought 1/32" was incredibly accurate. Sometimes it is, but when dealing with fitting screws and the like, it's extremely sloppy.
With access to lathes and milling machines, my joints turned from screws that naturally loosened, to turned dowel pins. My wooden pillow blocks turned into polycarbonate, and my screws turned from flathead screws using nuts, to Allen-head screws fastened to threaded blocks.
The final Peg Leg.
Additionally, I figured out where to source better components. These included threaded rods and rod ends to replace the paper clips, reducing slack between the servo's motion and the leg motion. Additionally, a discrete servo controller was added, taking processing load off the BSII chip and allowing for faster, simultaneous leg motion.
This whole learning process took years, but I eventually ended up with one of the most refined "hacks" that I have come up with, even to this day. After originally barely being able to make it walk, I was later able to demonstrate this bot walking with a heavy textbook on top of it. I've since moved on with other projects, but in some ways that hexapod walker was the start of my hobby of making things just for the enjoyment of it. I've documented the build pretty thoroughly if you would like to see more details.
— Jeremy Cook is a manufacturing engineer with 10 years experience and has a BSME from Clemson University. In his spare time he enjoys writing for DIYtripods.com.