Servo - September 2007

I tend to start with sketches on Microsoft PowerPoint. If things look complex, I’ll model with cardboard or wood, then proceed to aluminum or sheet metal before cutting expensive titanium or composites. My beetleweight

Fir Darrig went through many iterations. It started as a BVD to Fabrication bot, with 1/8” aluminum free form bent in a vise. Later, I transferred the shell to paper, onto posterboard, then to sheet metal. To bend the titanium, I made a wood model which was also the “shoe” for a homemade brake.

Ultimately, this process failed me when I tried to cold bend the titanium rather than applying heat, resulting in a big crack. I wound up running the sheet metal prototype with titanium appliqué armor.

My next attempt at using wood for a design medium came when I attempted to rebuild my Lightweight, Chupacabra, after its shredding by Killerbotic’s 2EZ. I ripped fir boards down to 1/2” square to simulate aluminum tubing. With the help of drywall screws, I modeled the frame around the components such as motors and batteries. The model went to my sponsor’s welding shop, where I learned another lesson about modeling.

In an attempt to make a low clearance bot, I’d cut the pieces very closely to the maximum possible dimensions. Unfortunately, I failed to indicate the “critical dimensions” to the fabricator, so it came back unusable for my parts. Slight tolerance buildups, differences in material dimensions, and frankly, just some sloppy welding resulted in a $200 frame I couldn’t use. Lesson learned: Build it yourself, or at least be there when it’s built!

For the next two bots I built, I skipped the modeling effort. Our highly successful antweight, Babe The Blue Bot, moved from version III to version IV using a

(L-R) Fir Darrig, wood form, titanium blank partially bent.

Side view of wood form being used as a bending brake shoe.

direct BVD (actually a dinnertime conversation from the kids, after the spanking defeat of III) to a 3D PowerPoint visualization, to fabrication. To size the pieces, I laid all components out on the raw baseplate material, drew around them with a Sharpie, then cut. This version worked very well, and it went from concept to arena with no modifications.