shown in Figure 7. Both Phillips and slot types, in at least
two sizes are recommended. A set of needle-nose pliers
and diagonal wire cutters like the ones shown in Figure 8
will come in handy. There are times when you won’t have a
socket or wrench to fit a nut and you will be very happy to
have the needle-nose pliers.
A set of small sockets and wrenches will make your life
a lot easier. Don’t get a large automotive set. Most home
centers and hardware centers will have small kits like those
shown in Figure 9.
shown in Figure 10. The best thing to do is to photocopy
the template and enlarge it so the length is 11-1/8” long.
(I’m referring to the white portion of the template.)
Cut out the template and place it over the piece of
hardboard that will become the lower base and mark the
cutout and holes to be drilled. Then, flip it over and mark
the other side of the robot.
The drill hole sizes are shown on the template. The four
holes with the diamond pattern are the most critical.
Firebot Base Construction
Let’s start with the Firebot construction since it is
The Firebot has a round base that is exactly 11-1/8” in
diameter. I made mine out of 1/8” thick hardboard that I
picked up at my local home center for a couple of dollars.
In the end, we will have a lower base and an upper base,
so cut out two circles. Once cut, you can paint the base for
a more refined look. I painted mine blue.
You can now slip the four mounting screws on the
completed RS- 28 wheel assembly that you built last time
into the four holes as shown in Figure 11. If you were a
little off on your holes, you can enlarge the holes slightly
by about 1/64 at a time until you can slip the wheel
assembly in place.
Once in place, put a #6 washer and nut on each
machine screw and tighten with a wrench.
Next, you need to make a couple of cutouts and drill
some holes. This is best done with a template like the one
50 SERVO 12.2008
For this next step, you will need a caster like the
one shown in Figure 12. The caster needs to be sized so
the Firebot is level when in place. If you followed my
design exactly, this will be 4-3/8”. A variance of 1/8”
or so won’t matter that much. I got lucky and found a
heavy duty rubber caster that was perfect at my local
Next, place the caster near the
front of the bot and on the underside as shown in Figure 13. Mark
four holes and drill them. I used
four #10 machine screws and
washers to mount mine. The size of
the mounting holes on the caster
may dictate different screws.
I actually used my tap set and
drilled the holes and then tapped
them for my #10 screws.
Next, flip the bot over and add
a washer and nut to each machine
screw as shown in Figure 14.