SERVO 07.2015 31
sold. It was a nice little speed
controller and came in an aluminum
enclosure which kept debris out of the
sensitive electronics. I really like mine
and put it back into this robot.
The frame will be kept, but
modified. Also, the one thing that has
held up and I think deserves a
mention is the flexible coupler in this
robot. This was an ingenious money-saving coupler my dad built back in
2002. It is a rubber steering coupler
(a.k.a., a rag coupler) from a car.
The hubs are made of shaft
collars, two large washers, and two
bolts that were welded in place and
then cut shorter (see Figure 1).
Progress started slowly at first,
but picked up steam quickly once I
got the drive mounted.
The old bearings were removed
from their housings. Some were still in
good shape, some were a little gritty,
and the remaining were frozen solid. I
salvaged enough bearings for the
2WD version and reinstalled them in
their mounts. I revised the interior
bearing from the cheap flange
bearing to a larger roller bearing.
These bearings worked very well.
To make room for the
pneumatic ram, I cut the
wheelchair motor’s shaft
down about 1.5.” I also
cut about 0.5” off the
wheel shafts, so I could
slide each motor out
about 2”. This gave me
plenty of room for the
pneumatic cylinder to fit
between the drive motors.
Somewhere along the
moves and various
attempts to put the robot
back together, I lost the
gearbox covers. This
wasn’t a huge problem,
but the covers are
necessary to hold the gear
oil in the gearbox with the
way they are mounted.
I fabricated some new
covers out of polycarbonate. I like
them because you can see the
internals of the gearbox and watch
the gearbox turn, which is cool.
Perhaps not the best-suited material
for the job, but I like it. Plus, if (read
when) the plastic fails, the red brown
grease will leak out and it will look
like the robot is bleeding — which is
The event in Tampa featured four
heavyweights: Gruff, The Big Cheese,
Bear Tooth, and my bot, which I called
Old Iron. When we got to the event,
we had pretty much everything ready,
so we got through safety pretty
quickly and helped to finish the last of
the arena assembly.
We had the very first fight of the
day. We were fighting The Big Cheese
which is a 2WD wedge with large 14”
pneumatic tires driven by wheelchair
motors. The fight started off well for
Old Iron. We were able to get under
The Big Cheese, and we were able to
Old Iron vs. The Big Cheese.
Old Iron vs. Gruff.