Servo - November 2008

• First place 30 lb class:

Overthruster, Dale’s Homemade Robots

• Second place 30 lb class: Scimitar, Blade Robotics

For 2009, the Robot Battles main tournament is moving to a larger ballroom to handle the increasingly large audience. With Dragon*Con hosting a Robotics program track specifically to introduce more people to robots and robot fighting, the competition is only going to grow larger and more intense. So, if you’re tired of the same old arena, consider coming to Atlanta over Labor Day weekend 2009 and checking out not only the Robot Battles competition, but Dragon*Con as a whole. If you are already attending

the Con, and have (somehow) missed us for the past 18 years, then you know what to do next year. Here’s some resource links to get you started:

• www.robotbattles. com is the event’s website. Look here for the rules, photo galleries, and online community. Make sure to join the email list!

• www.dragoncon.org is the website of the hosting convention, Dragon*Con, your one-stop shop for any sort of science fiction, comics, fantasy, role-playing, anime, subcultures, and much more.

Überclocker holds Scimitar perilously

close to the stage’s edge.

As a bit of interesting trivia: The oldest robot fighting competition — Critter Crunch — began in 1987 at the MileHiCon in Denver, CO. Robot Battles is a direct descendant of Critter Crunch, with almost identical rule sets. SV

PARTS IS PARTS:

Chain Length Calculat r

and Chain Path Visualizer

● by Kevin Berry

An endless source of information on bot building is the RFL forum on Delphi Forums ( www.chief delphi.com/media/papers/1598). A recent thread had a great discussion about a software tool — Dr. Joe’s Chain Length Calculator, and the accompanying Chain Path Visualizer. This handy tool lets a builder input sprocket and chain data (up to 12 sprockets!) and out pops the geometry to build the rig. The Excel front end drives a macro called Goal Seek, that does loops of “what if” analysis to optimize the design. The outputs and a graphic visualize the answer, while the raw outputs are on other tabs.

I haven’t built any chain driven mechanisms myself that would require this level of calculations,

but according to the folks on both forums (RFL/Delphi and Cheifdelphi), it’s both useful and accurate.

Dr. Joe Johnson, the creator, has a few comments worth noting:

2) I move my “idler” up and down (or left and right) the amount I plan to build in to my adjuster so that I can tell if I can actually tighten the chain.

“This is a tool I use to get my chain adjuster travels right and to give my “gut” a chance to “see” the chain path before I commit to it in metal. It is not a perfect tool. It does not have any way to enter a slider, for example.

Here is how I use it most often:

Alternatively, I use it to see if I can swap sprockets and still tighten my chain with the different ratio (this is a non-obvious calculation at times).” SV