The circular saw was a
somewhat more complex build.
Again, the base structural member
is a length of 2” x 1” rectangular
tubing. The saw itself is attached to
a 3/4” shoulder bolt with a smaller
5/8” shoulder turned on it to allow
any standard 5/8” arbor saw blade
to be used. A timing belt pulley was
bored out and pressed onto the
shoulder bolt, then secured with the
stock setscrews. Between the press
fit and setscrews, there should be
minimal slippage during normal use.
The next piece that was added
was a set of legs to keep the saw
from dragging on the ground. The
legs were made with a pair of 1”
square tubing lengths that were
welded to the main rectangular
tube. Then, a large chunk of
UHMW square stock was shaved
down, pressed, and glued into the
posts to provide long lasting skids
for the saw to ride on.
The power for the saw was
initially intended to be pulled
directly from a cheap Harbor Freight
circular saw. During early testing, it
seemed like an adequate mounting
option. However, during further
testing, the cast housing proved to
be a weak point, shattering when I
was checking out the overhead
thwack attack method.
The design of the upgraded
saw mount takes two approaches
to help improve the durability of the
weapon motor. First, the face of the
mount consists of three layers of
material: 1/8” aluminum, 1/4” rubber,
and another layer of 1/8” aluminum.
This should give the whole assembly a
good deal of flex when dealing with
impacts, protecting the assembly from
shock to a much greater extent than
the old cast mount.
The other element of the gearbox
mount is the tie-rod plate. The main
function of this plate is to pull the
whole gearbox assembly together in a
way that avoids the impact forces
when the bot thwacks from getting
transmitted into the plastic gearbox
The final piece to be
added to the circular saw
attachment was the
addition of a large motor
guard to reduce the
chances of an opponent
getting a clean shot on the
weapon motor. A 1” square
post was welded to the side
of the rectangular tubing
and a 3/32” thick
aluminum plate was bolted to it and
bent to shape.
The final weapon system to be
created for Spanky was the chainsaw.
Initially, a good deal of time was
spent searching for an off-the-shelf
product (that was at one point
available) that consisted of #40 roller
SERVO 05.2014 29
in the creation
The hammer with
welded in place.
layout of the
The initial saw
The fully assembled circular saw
weapon attachment mounted to
the main platform.