Pololu produces an interesting set of components that allow you to have caterpillar type tracks on your small 250 g to 1 lb combat bots. They make
standard 22T and 30T (Figure 1) sets of tracks (they
differ only in the length of the track) which have two
12T sprockets with D shaped holes to be used with 3 mm
drive shafts, and two 12T sprockets with clearance holes
to match the supplied shoulder screw axles. The
recommended wheelbase of the 22T set is 48 mm and
the wheelbase of the 30T set is 85 mm. Pololu also
produces the Zumo® kit (Figures 2 and 3) which
includes the 22T track set, plus a chassis that can mount
two small motors and has space for four AA cells.
I think someone has already used that kit
successfully in a 250 g Fairyweight combat bot (the
chassis, motors, and tracks only weigh 100 g), but the
motor is really small (in Figure 4, it is compared to a
motor similar to those I use in my Ants) and may lack the
performance required for some Fairyweight and most
Antweight fights — especially if it's in a wedge or brick.
However, if one was to build their own chassis, then
they can use any gearmotor that has a 3 mm output
shaft. Pololu does provide some motor mounts that let
you do that, but they do not provide the 3D models of the
parts that can make designing your own chassis easier.
38 SERVO 03.2014
FIGURE 2. Zumo kit of parts.
FIGURE 1. 30T track kit.
● by Pete Smith
A look at the Pololu tracks and
their possible use in combat bots.
FIGURE 4. Pololu small gearmotor.