SERVO 05.2016 17
is capable of approximately 53
impacts per second. While not
outright destructive, the expectation
for this system is that it will find and
damage any exposed or otherwise
poorly armored components while
making a fantastic amount of noise.
With the thresher, we chose to
shrink it down to a 6” diameter to
increase the chances of the bot
picking up the opposing bot and
being able to keep the weapon
turning when a bot is sitting on top
Once the design was wrapped
up, it was time to get parts ordered.
For the thresher, rear spike, and flail
teeth, the parts were laser cut from a
sheet of 3/16” AR400 steel plate by
Discount Steel (www.discountsteel
.com) who I’ve been using regularly
for steel part fabrication recently.
As has been typical of them, the
laser cut parts arrived before some of
the other raw materials showed up.
With the laser cutting done, the
next step was to get the 1/4” 7075
aluminum and 1/16” 4130 steel parts
waterjet cut. This wound up being a
two-stage effort with some waterjet
fishing to find a few parts that made
their way to the bottom of the tank,
but everything came out nicely and
(with a bit of sanding to clean up the
normal taper) fit together quite well.
The 4130 steel parts needed a
bit of extra work beyond
waterjetting. The chain guard was
designed to cover the top and
bottom of the chain primarily to
prevent its own flails from damaging
With an improvised bending
CAD model of Morrigan
showing the flail
CAD model of
Morrigan showing the
It may look crude, but it
worked well as a bending rig.
There are better ways to
do this, but without buying
new tools it was the
cleanest way to get the
bends I needed.