Now comes the most exciting time
of the entire build process. That first
time you flip on the power switch
and bring your machine to life. It’s a
great time to be alive, isn’t it?
Wouldn’t it be great to stay alive?
That first time you flip the
switch is exciting, but it’s also the
most dangerous time in the build.
Over the past several weeks, I’ve
watched builder after builder posting
videos on You Tube.com of their
robot’s first weapon test. A little robot,
six pounds or less with aluminum,
steel, or titanium spinning at 5,000,
10,000, even 30,000+ RPMs sitting on
the floor with little or no protection
between the bot and builder. I
cringe and grit my teeth waiting for
a loose screw or random nut (that
was dropped on the floor and
forgotten a mere two hours ago) to
ricochet around the room. I further
cringe as the video continues with
the inevitable test hits. I’m a nervous
wreck after 40 seconds of video.
Don’t get me wrong. I’ve done
FIGURE 1. A storage trunk, a.k.a., the basis
for a robot test box.
FIGURE 2. Create a rectangular opening
in the trunk.
34 SERVO 04.2010
the same thing, and I’ve lived to tell
about it. My whole perspective
changed the day my vertical spinner
“gyro’ed” over upside-down with
the blade at top speed and struck
the concrete driveway I was testing
on. Pieces of concrete shot at me. I
was fortunate I was not hit. That
single event was a huge wake-up call.
“HEY, 10,000 RPM IS REALLY FAST.
HOW ‘BOUT WE TRY NOT KILLING
OURSELVES NEXT TIME, HUH?”
I’ll give you a breakdown of how
to build a small, simple test box that
you can use to spin-up those nasty
weapons, hit stuff, practice driving
with the weapon on, and not DIE.
Here’s the best part: The whole thing
can be built for under $100 and in
less time than it takes me to find a
pair of matching socks in the dryer.
You will need the following
items/tools for this project: a storage
trunk (see Figure 1; they can usually
be found in department stores for $20
in late summer when college students
are going back to school); a 14”x
28” piece of polycarbonate sheet
1/4” thick or greater; one 8’ long
2”x 3” piece of lumber; a box of wood
screws; some string or lightweight
chain; a drill; a hole-saw or spade
bit; and a jigsaw. If you have a
particularly nasty robot, you can
pick up a sheet of Medium-Density
Fiberboard (MDF) for additional
reinforcement (described later).
The process for building this box
FIGURE 3. Polycarbonate sandwiched
between the lid and the 2” x 3” piece of lumber.
is so simple it practically builds itself.
(Okay, it’s not that easy, but you could
build a robot to build the box for you.)
Altering the Trunk
You have your trunk sitting in
front of you. In theory, you could
throw the bot in there, close and lock
the lid, and call it a day. But unless
you’re a dolphin, it’s hard to drive your
robot via sound. The first thing you
need to do is create an opening in the
top of the trunk so you can see in.
Driving a bot via looking at it is so easy,
a caveman can do it. Measure in about
2” from each corner of the trunk; the
dimension isn’t super critical, so don’t
stress over it to much. Break out your
trusty (or rusty) drill and spade bit/hole-saw and create a hole in each corner.
The holes are for the purpose of
starting the jigsaw. Next, break out the
jigsaw and run a straight line between
the holes forming a rectangular opening
in the lid (see Figure 2). Now you
could throw your robot in there and
test, but the test box offers about
as much protection as a tissue in a
hurricane. (From experience, that
isn’t much protection at all).
Installing the Poly
What was once a perfectly
good trunk is now a perfectly good
trunk with a large hole in the top.
It’s time to install that
FIGURE 4. Lightweight chain used to
prevent the lid from opening completely.