the weapon first. Finding a
pneumatic system which weighs
only a few ounces is no easy task. I
had to incorporate the ram, valve,
pressure tanks, tubing, and a
control to fire the arm. Luckily, I
was able to locate an Inertia Labs
pneumatic system from a fellow
builder. This system was originally
made for purposes other than robotic
combat, but thanks to Inertia Labs
who realized the system’s potential,
I now had the perfect pneumatic
system for my robot. My particular
system is comprised of: two air
tanks, roughly the size of a soda
can if it were made to 1/4 scale, a
2” stroke single acting ram and a
high flow miniature valve.
Now that I had my pneumatic
system, I designed the four-bar
throwing arm. After much trial and
error, I was able to create a set of
linkages which was able to give
adequate motion. Again, because
of the tight weight budget I was
on, I had to use a light yet strong
material to fabricate the parts from.
Carbon fiber was my first choice.
However, it is on the expensive side
and I happened to have a sheet of
blue 1/8” garolite which I decided
would fit the bill nicely. Garolite is
commonly referred to as the poor
man’s carbon fiber because of its
many similarities, but with the
reduced price tag.
Once I had the material chosen
and the arm made, I then decided
on what I was going to use to
propel the robot around. I have long
been an advocate of four wheel
drive in all robots because of the
maneuverability advantages.
However, fitting such a setup
into this robot was again a real
challenge; not only because of
the weight, but also the space.
I considered using two gearmotors — one on each side —
then using a belt to connect
wheels mounted on an axle on
the opposite side. But, the
only gearmotors powerful
Drive motors and arm installed; ready
for installation of the electronic and
pneumatic components.
enough to do this were both
too big and too heavy.
Instead, I decided to use
four GM- 19 35: 1 mini gearmotors. They were able to
provide enough power to give
the robot decent speed, as
well as good maneuverability.
They even have enough power
to push rather well. They will
not win in a pushing fight, but
they work enough to position
the arm under its opponent.
One thing that should be
taken note of with these very
small units is the even smaller
gears which reside inside them.
Much caution should be taken when
mounting and using these as debris
can easily find its way into the
exposed gearbox and jam the entire
unit. I recommend implementing a
cover of some sort to save you
the headache of rebuilding the
micro-sized gearbox.
I decided to stick with the
Garolite for the base plate because
I had been happy with its
performance during testing of the
arm. Rather than CAD everything,
I decided to keep with the original
plan and keep things simple. I drew
out the desired outline on a sheet
of paper and then added in all the
components on top to make sure it
was all able to fit.
After some minor tweaking, I
had my base plate outline. I then
cut out the shape, taped it to the
sheet of Garolite, and proceeded to
cut out the brand new base plate.
From there, I mounted the arm which
I already had made. Then, I mounted
the drive motors. After thinking of
several different ways to secure them
to the base, I decided to simply glue
them in place with Shoe Goo. This
glue is an invaluable tool to a
small robot builder. It is extremely
versatile and is able to perform
many different functions; one of
which we will talk about later.
With both the weapon and
drive system in place, it was time
to place the remainder of the
components and wire everything
together. I chose a three cell 740
mAh Thunder Power battery which
has been able to easily handle the
power requirements of the four
gearmotors and valve. To control
the drive, I selected a pair of Bane
Get Flippen ready for action: wired
up, armor mounted, stickers applied,
and tanks charged.
The last bend on the titanium armor
being set into shape.
SERVO 09.2008 27
