20 SERVO 10.2014
Its added discharge capability
might allow it to survive when
previous batteries had simply died
under the strain. My next competition
was to be Clash of the Bots in July,
and the shorter two minute fights of
the event would help battery life,
I wanted to maximize the
performance of the standard beater,
so the first thing I did was sharpen
the teeth to get a better bite. I
machined the edges of the teeth
(Figure 3) using a carbide end mill
and then machined the top faces of
each of the teeth to give a nice sharp
edge. Next, I made a new weapon
In the past, I threaded the end of
the 5/16” Ti shafts and use Nylock
nuts to secure the axle. However,
The split pin is likely more reliable,
but just a little trickier to remove in a
hurry. The new method weighs less
and leaves less sticking out for
opponents to get a bite on.
The new motor has a larger 4
mm shaft which should help reduce
the number of broken motor shafts
that plagued the old motor. I used a
pulley from SDP-SI on the motor.
These come with small setscrews, so
unfortunately it’s hard to get a hex
key small enough to fit them for this
I just drill them out to take a
couple of larger 4-40 setscrews
(Figure 6). I use a Dremel type tool to
add a flat to the shaft as well, and
that takes care of both problems.
Remember to add a little Loctite to
the setscrews so they do not come
loose halfway through a fight.
The motor and beater were fitted
to the chassis (Figure 7). You can see
the motor and its wires take up most
of the space ahead of the drive
motors. With the old motor, there was
still space for the weapon ESC
(electronic speed controller).
In the new arrangement, this has
to move behind the drive motors
(Figure 8). The old batteries I had
been using fit snugly beside the ESC,
but it turned out that the new 70C
version was a little longer. I needed to
remove about 1/8” of the chassis side
wall on either side before everything
could fit comfortably (Figure 9). A
fresh coat of paint and a new Kitbots
sticker, and Weta was ready for Clash
of the Bots (Figure 10).
So, how did the modifications
Figure 8. Weapon ESC moved to the rear.
Figure 11. Damaged beater bar.
Figure 10. Weta ready for Clash of the Bots.
Figure 9. Everything fits.
Figure 13. Damage to the 3D printed bots. Figure 12. Bigger battery.