Build Your Own Combat Robot

Finally, care must be taken when grabbing hammer-wielding robots with a
clamp bot, as a firm grasp can also give the hammer bot the leverage to repeatedly
hit the clamp bot in the same spot. When attacking a hammer bot with a clamp
bot, try to approach from the side so as not to be in the path of the hammer arm.
Thwack Bots
Spaz, Blade Runner, and T-Rex are thwack bots. Thwack bots feature a powerful,
two-wheeled base, with a long-tail boom having an axe, pick, or hammer head on
the end. They are capable of spinning in place at high speed.
Thwack Bot Design
Chapter 10: Weapons Systems for Your Robot 217
Another design that uses only its drive motors for attack power, the thwack bot
spins rapidly in place, whipping a weapon on a long tail about at high speed.
Thwack bots are invariably two wheeled, as four- or six-wheeled designs cannot
spin in place rapidly enough to make for a satisfying impact. Usually, this design—
with exposed wheels and a symmetrical profile—allows them to run well when inverted,
thus making them a difficult opponent for wedges or lifters.
Narrow wheels are key to a thwack bot because wide wheels will add scrub resistance
and slow down the turning rate. Care must be taken to balance the robot
so that as much of the weight as possible is resting on the main drive wheels; any
weight resting on the tail or on any idler wheels is potential traction going to
waste. The wheels should be soft rubber, high-traction types, and foam filled for
survivability. Placing the wheels close together increases the top speed but will increase
the time it takes to reach that top speed.
Figure 10-6 shows a thwack bot schematic.
Typically, ratio of wheel size to wheel spacing is between 2:1 and 4:1. Thwack
bots typically have high driving speeds so that the high wheel speed can be turned
into a high spin rate. The need for high wheel speed and spinning requirements can
make this kind of robot hard to control.
The main design challenge with thwack bots is finding a balance between top
speed and spin-up time. Ideally, a thwack bot should be able to reach top rotation
speed in less than a single revolution, yet still have a top speed fast enough to do
damage on impact. A thwack bot that takes too long to spin up will find itself helpless
once an opponent has come within range to attack. Of course, more power
makes for faster spinning (thus, less time to get up to full spinning speed) and
higher top speed, so a thwack bot should have as much power as possible.
The primary weakness of the thwack bot concept is that it cannot move while
spinning. This type of robot must either spin in place and hope its opponent
drives into it, or charge to within spin radius and then spin—getting less than a
full revolution before striking its opponent. Several attempts have been made to
build a navigation system that allows a thwack bot to translate while spinning, by