Servo - July 2010

problems involved the wedge jamming in the downwards position and high-centering the robot. Following this experimentation, the design was applied to our successful beetle Cloud of Suspicion’s first two revisions, as well as the third version of Gilbert. It proved effective time and time again against weaponless bots and spinners alike, and I actually wrote an article for SERVO about the design over a year ago. Unfortunately, as we began to travel and compete with more effective bots such as the Fierce robot fleet and many east coast spinners, wedgectomies became a steadily increasing occurrence. After having Gilbert’s wedge torn off and the top carbon fiber subsequently destroyed along with an even more caustic but successful fight with Cloud of Suspicion against the under-cutter Itsa?, I finally decided that it was time for something new.

The first thought that came to mind was to replicate the similar hinged wedge system used on our featherweight, Pinball. Pinball’s wedge differed from most of ours at the time in that the steel wedge itself is welded directly to the shaft which sits loose in an oversized hole made in each of the 1” thick UHMW side pieces. An initial problem we encountered with Pinball’s wedge design was that the shaft could be torn through the UHMW if pulled hard enough by a vertical spinner. This was later fixed by welding together a .125” 4130 steel bracket that completely covered the extrusion, leaving a hole for the shaft to ride in.

I likely would have gone this route if not for a fight with a horizontal spinner that left Cloud of Suspicion’s aluminum wedge support extrusion lopped off. With all this in

FIGURE 4. MH Robotics’ fairyweight, FIGURE 2. The third revision of Cloud of Suspicion, sporting our most recent wedge design.

FIGURE 3. Featherweight

Pinball, showing its shock mounted steel flat plate.

mind, I chose to follow Mike Daniel’s advice and draw up an all new hinged wedge design mildly based off of his old 30 lber, Doom.

The initial problem I wanted to address was how most hinged wedges rely on one or several mounting points based on a flat axis. I chose to combat this (no pun intended) by designing a right angle clamp that holds the shaft down on two perpendicular axis. This makes the entire assembly much more solid and the clamps themselves are nearly impossible to tear off, even though they’re being held in through machine screws to the soft UHMW. Of course, to maintain the idea of riding the design of singular plane mounting areas, I chose to have the wedge welded to the shaft. Initially, I planned on an .09” titanium wedge for Cloud of Suspicion and .075” for Gilbert, but the deal fell through.

Fortunately, we were able to go through with the design by using 4130 chromoly steel for the wedges, shafts, and even the clamps which would eventually be hardened for an even stronger assembly. The live shaft sat loose in a slot cut into the top corner of the UHMW, and was kept from falling loose through the several clamps. The only downside to this durable and complex assembly is in how many pieces and separate cuts, bends, and welds it entails. However, in the many fights that it’s been through thus far on Gilbert and Cloud of Suspicion, it has proven much more durable by far than the previous design.