the weapon, which being mild steel
was no serious problem. CNC is as
unknown a technology to our team as
is CAD. Thus, we milled it as close as
the human eye could get it and stuck
it in a hand drill. When — upon being
activated — the hand drill stops
leaping out of your hand, you know
the weapon is balanced.
Step 4 was cutting some
semblance of a body. The core is a
fairly familiar rectangle of soft plastic.
Step 5 was the ring. Cutting slots
for the weapon shaft was shaping up
to be a bear, until we realized that a
sharp woodworker’s chisel and steady
pressure is invaluable for working with
Step 6 was mounting the motors.
The advantage of working with thick
plastic is the possibility of embedding
said motors right in the chassis. Hot
glue was considered, but in the end
we chose to use a simple face plate to
ensure a solid connection.
Step 7 involved piling everything
on a postage scale and frowning.
A great deal of assembly and
disassembly ensued, with the goal of
making the unforgivably large number
on the postage scale go down. More
steel came off the weapon. Large
holes were added wherever it was
practical to add a large hole. The top
panel went from 1/4” polyethylene to
1/8” polyethylene to cardboard and
rubber bands. Even a 3” x 4” square
of cardboard proved too heavy for the
bottom panel. Another hole appeared
in the ring, and it was just enough for
not one, not two, but three strips of
duct tape. It wasn’t pretty or strong,
but it held the guts in.
We wired it up. For those
interested, the drive system involved a
Sabertooth 5 ESC (electronic speed
controller) coupled to a pair of
unknown eBay gearmotors, which
SERVO 07.2014 39
Lining up the weapon motor and the weapon was one of the
few times copious measuring was employed. Everything else
was "close enough."
Sometimes the event organizer says our activation
light isn't bright enough. It wasn't a problem this time.
Some designs look good on paper. This one, not so much.
This is what we were
planning to build before
McMaster had a sale on