years ago, I helped UCSB
Engineering robotics professor Brad
Paden start up a robotics
educational outreach program to teach kids in grade, jr.
high, and high school robotics through the use of LEGO
later, it came full circle & Luke
Laurie, head of the RoboChallenge
program for Santa Barbara County heard about my work through a
common friend, Dr.
Megavolt, and asked me to do a seminar to show his students
and LEGO creations. Just a couple
of months later, we found ourselves putting on an all-day robotics
workshop for about 130 kids in 3rd-12th grade.
went through the robot design process & explained what goes
into a BattleBot, demonstrated Dr.
Inferno Jr. and Hell
on Wheels against some remote control toys & what
was left (not much) of Bot
Will Eat Itself, and showed how to make wireless remote
control LEGO bots with Itchy
I was really dying to get in on the Robo-Challenge action, so
we decided to hold a tug-o-war contest between the different schools,
and I was allowed to enter, too! I built a special bot, Longneck
(which I figured would either do very well or very poorly), and
an ordinary one, The Infernal Brick of Despair (IBoD), which I
had built just as a test opponent for Longneck.
a disastrous 1st-round loss for Longneck, both bots continued
undefeated through the winners' and losers' brackets until they
met each other in the finals, with Longneck coming out on top.
Wow--I didn't expect to sweep!
Barabara Newspress ran a short
article about the day's events.
Because this was a pulling contest, not a race, I needed a big
gear reduction for serious torque. I built IBoD's drivetrain with
a pair of 5:1 reductions. It still was a little fast--it traveled
way more than 1 foot in 1 minute (the distance needed to pull
the opponent to win). So I built a 2nd version of the drivetrain
with an additional 3:1 reduction, which went about 15 inches in
1 minute--perfect. Because all bots were subject to strict rules
to keep their specs similar, the only big edge I could gain was
to build a bot with a very tall tow point so the string would
be pulling down on my bot, thereby increasing the downward force
on my wheels, resulting in greater friction & traction (and
robbing my opponent of some of his grip, equal to the amount that
I was gaining). To keep Longneck from toppling while tugging,
I built a loooong neck with lots of weight concentrated at the
end (the RCX & 6 metal hooks) to counterbalance its tipping
tendencies. It turned out to be a tricky balancing act that took
lots of trial & error to refine, but I pulled it off. In a
successful run, Longneck's vertical beams would bend noticeably
while the head would lift off the ground and then drop back down,
dragging the opponent slightly forward, repeatedly until victory.
IBoD was simply a 4-wheel-drive block--I used a battery pack as
ballast to bring him up to weight and just piled on bricks until
he was at the weight limit.
the tricks I used to pull off the victory and that I'd love to
see students incorporate into their future tug-o-war designs are:
all of the weight allowed
way down for lots of torque
a high tow bar to "steal" the other bot's traction
tipping tendencies with a counterweight
using bevel gears--the spur gears have a greater contact area
& won't bend or slip as easily
DETAILS : Every
bot needed to weigh under 850g (Longneck was 849.7, IBoD was 849.9),
use 2 of the Mindstorms gearhead 9V motors, 1 RCX, and up to 4
"racing slick" tires were recommended. The bot had 1
minute to pull the other bot 1 foot to win the match.
getting serious mileage out of the parts donated by Switzer
Communications and LEGO