FIGURE 11. First chassis assembly
with motors, side view.
the bot wheels lost contact with the
ground and the bot was easily
The UHMW and 1/16” thick
7075 panels are joined together
using mini nutstrip and 6-32 screws,
plus a few #6 x 1/2” Plastite screws
are used between the bottom and
the UHMW walls.
The top and bottom are the
same panels that are on the front
and rear bulkheads.
The top and bottom extend out
past the wheels on either side so
that 1/8” UHMW side armor can
protect the wheels. This thickness
had proved effective in Weta, so it
should prove adequate for this
Two holes in the main UHMW
walls are used for locating a 1/4”
bar than will be used as the pivot for
the front movable wedge.
The thickness of the UHMW and
titanium bar should prevent this
hinge from being a weak point in
I kept track of the weight of
each part in an Excel spreadsheet.
This is important because it’s too
easy to get your bot almost
FIGURE 12. First chassis assembly with
motors, top front.
complete and find yourself
overweight. Better to get it right
from the start.
Solid Works will work out the
weight for you if you input the
material’s density, and it’s
worthwhile investing in an accurate
electronic scale to weigh the other
parts. If your budget does not allow
for buying a scale, you can usually
find one at your neighborhood post
office or UPS agent. Ask politely at a
quiet time and they are usually quite
happy to let you use theirs.
Once I was happy with the design,
I made dxf files of the aluminum
panel and UHMW parts, and had a
set of panels and templates water-cut
They arrived within a week, and
I set the templates up and routed
out several sets of UHMW parts
I had previously made all the
required sections of nutstrip, cutting
them to length on a chopsaw and
then trimming to size on my mill.
Putting all the chassis together for
a trial build took only a matter of
minutes (Figure 6). A cordless
screwdriver comes in very handy
here as there are a lot of screws!
FIGURE 13. Trilobite
complete for Schiele.
Once all the panels are together,
the holes for the Plastite screws can
be drilled using the holes in the
aluminum top and bottom panels as
guides (Figure 7). The result is a
remarkably strong and rigid chassis.
Stripping the chassis back down,
I could then fit the drivemotors
(Figure 8); each motor was secured
in place using my standard
“1000RPMMNT” mounting plates
(Figure 9). Standard 4 mm “Dave
Hubs” and 2. 25” inch Liteflite
wheels (Figure 10) — all from
were added and the side armor
refitted (Figures 11 and 12).
I originally intended to use one
ESC per motor but when two of
the four ESCs died shortly after
installation and with time running out
before the next event, I changed to
using one of Banebots BB- 12-45 per
side with the two motors running in
parallel. I had the ESCs prewired for
use in Surgical Strike, so there was a
lot of extra wire and weight over the
four smaller ESCs but I had enough
to spare for that. A standard BR6000
receiver (I mix for tank steering in
the DX6 transmitter) and a
Thunderpower 850 mAh 3S LiPo
completed the wiring, and the bot
was ready for its first drive.
Performance — even on 3S —
was excellent, certainly fast enough
for the smaller arenas, and the bot
was easy to drive.
I used a holesaw to cut a large
hole in the top panel to allow access
to the battery connection, so this
could be used to power the bot up
for a fight. A strip of duct tape is
used to keep the electronics in
28 SERVO 10.2011