usable range of motion
within the weight limit; 100
tons over one inch is easily
possible, but that is of no
use in combat. In all weight
classes, it is the robot
chassis that sets the limits
Return of the
CAD of claw mechanism.
CAD of Dragons Claw.
The UK has a long love affair
with crushers. We have had many
heavyweight machines successfully
use crushing weapons. The featherweight class however, rarely saw
the type, as effective crushing
weapons are heavy. Circumstances
in the UK at the moment are such
that high kinetic energy spinners
have very few opportunities to
fight. Combined with the extra 1.6
kg now allowed in the featherweight
class, it has opened the floodgates
for robots that could never afford
weight for crushing weapons to
make their entrance. There are
several crushers being built right
now, and Dragons Claw is the first
opponent and bringing the weapon
down to pin or crush. (Catching the
opponent was initially a concern as
the actuator has a speed of just 5
mm per second.)
Dragons Claw is able to control
its opponent once it captures them.
A light squeeze holds the opponent
in place so it can be taken to arena
hazards or for other robots to attack.
Increasing the power to crush the
opponent puts a full 1,000 kg into
the Hardox claw, and onto the target
robot through an interchangeable
titanium tip. In testing this process,
Tony bent the 10 mm steel pivot
pins, so they are now 0.5 inch
So, the robot is ready then?
Tony Booth, a good friend of
mine, decided to build a high power
crusher after winning an eBay
auction for a Linak LA34 linear
actuator. This particular item can
deliver a reliable 10,000 newtons
of force at 24 volts, so it’s perfect
for featherweight combat robots.
Tony did the right thing
when designing an unfamiliar type
of robot. He asked
everyone he could for
advice, listened to the
advice, and used that
advice when designing
the robot. It’s amazing
how many people
refuse to do this.
Based on a welded
Tony never underestimated the forces
involved in crushing your opponent.
He conducted many tests with a
temporary chassis and claw,
before deciding on the current
Supplying the actuator with
the (quite modest) current it
needs are two packs of 12V NiMH
batteries (in series giving 24V),
through a simple servo-operated
DPDT switch and failsafe. These
batteries also supply the Robot
Power Scorpion XL speed controller
which, in turn, runs the 18V drill
motor based drive system.
This mix of components is
proving to be very effective. The
robot is fast, turns quickly, and
(more importantly) rotates around
its weapon due to having the drive
right at the front. The electronics are small, light, and over
specification for their current
use. Dragons Claw has been
tested and proven itself to be a
very effective combat robot. It
has successfully pierced 10
mm plastics, 2 mm titanium,
and 6 mm aluminium, to
name but a few examples.
In fun events, it has proven
itself capable of catching its
Dragons Claw’s frame.
equals drilling holes.
SERVO 01.2008 25