prop its opposition on the wall, or flip
and shove them toward the arena
pushout. The first build of Reptar
went through two tournaments:
Dragon Con Robot Micro Battles
2012, where it placed first; and an
event at the 2012 Atlanta Mini Maker
Faire, where it placed second.
The thin steel flipper proved to be
a major weak spot in the design since
during the Mini Maker Faire event, it
met with a vertical spinner which tore
and bent the flipper plate until it no
longer was able to effectively get
under low opponents. The wedge was
hammered flat several times during
the event but it didn't take long to be
bent back again.
After the Maker Faire, it was
decided that a rebuild was in order.
The main goals of the rebuild were to
shrink the chassis to allow for thicker
and more durable materials to be
used; to fully design the machine in
CAD to allow the flipper geometry to
be tweaked to get the desired range
of motion; and to redesign the front
of the robot to minimize the risk of
the front warping during a match.
After a few concept sketches, the
general concept was decided upon
and CAD modeling began. As part of
these discussions, it was decided to
move from scrap materials to 0.045"
thick grade 5 titanium for the majority
of the chassis. The flipper plate was
going to have a fixed wedge in front
of it made of 0.063" titanium to
provide a more consistent lead in
which would result in a more
consistent front profile, and allow
more efficient use of the front in a
plow-like fashion when the flipper was
upright. The internal components
remained the same and the wheel
dimensions were unchanged.
The build for this version of
Reptar was less hands-on than the
first generation. The majority of the
chassis was done with a waterjet with
only a bit of finishing work done using
manually operated tools.
Fully designing the system in CAD
prior to cutting metal meant that the
SERVO 02.2014 29
chassis for Reptar.
The gutted chassis
of the first Reptar
showing the damage
to the flipper plate.
The smaller lower profile design for the second