SERVO 06.2016 21
complete, the next
major cut is a
through the upper
tube for the
weapon axle tube
to be placed in.
Once again, this
with a hole saw in
hole saw was just
long enough for us
to complete the
cut entirely from
one side, which
allowed as straight a cut as possible. This cut in progress can
be seen in Figure 4.
An additional hole was cut on the underside of the upper
tube to allow wiring to pass between both tubes. With the
major cuts completed, final mounting holes for the drive pods
and a slot for wiring to access the weapon motor were
added. With the tubes completed, the weapon motor
attachment, hoop mounts, and weapon axle tube all have to
The weapon motor attachment is completed by milling a
square tube into a lopsided “U” shape that will align with the
upper tube. When making the hoop mounts, I actually
decided to alter the initial design. Originally, I had planned on
the angled bracket being directly welded on to the lower
tube. However, after reconsidering, I decided to just create a
mount that the angled bracket could be bolted to.
This decision has two main advantages: First, it allows for
different angle brackets to be tested out to ensure a proper
rollover can be achieved; and second, it allows
easy replacement of an angled bracket if it gets
With all the parts cut out, a jig is made to
allow the tubes to be welded to complete the
chassis. The jig was made from scrap pieces of
wood that are glued to a base board. The final
result can be seen in Figure 5.
With the jig completed, we sent the frame
to a local welder to finish it up. Unfortunately,
when the chassis returned, the upper tube was
rotated about five degrees from the proper
orientation. This was partially our fault because
(as we found out) the jig had a little bit too
much slop in it, so it’s possible that the tube
had been moved to that orientation when it
was dropped off at the welder.
In hindsight, we realized it would have
Figure 2. Lower tube
circular cut in progress.
Figure 3. Lower tube cut
Figure 5. Chassis
parts in jig.