Build Your Own Combat Robot

Clamp Bots
Clamp Design
Chapter 10: Weapons Systems for Your Robot 215
The clamp was first used on Namreko 3000 (Robot Wars, 1996). Other bots using
the clamp include Complete Control, Tripulta Raptor, Spike IV, and Mantis.
A clamp bot features an actuated lifting arm, with an additional movable piece to
act as a grabbing clamp that’s capable of grasping the opposing robot and lifting it
completely off the ground.
The clamp bot takes the strategy of the lifter one step further, adding a second
movable piece to the lifting arm to act as a clamp to solidly grasp the opponent
robot. A well-balanced clamp bot can completely lift an opposing robot off
the ground. As few robots can do anything when lifted off the ground, this
places the match completely in the control of the clamp bot.
The clamping mechanism must open wide enough to grasp the largest opponent
you are likely to face, and it should be designed to close in a second or less. A
slower clamp risks the opponent getting free before the clamp is able to close. The
grabbing mechanism should have a holding force at the tip at least equal to the target
robot’s weight, to prevent the claw from being forced open when the arm lifts.
Pneumatics are a good choice for the closing mechanism, as they can provide both
high closing speed and strong clamping force. Electric linear actuators or hydraulics
will also work, providing superior closing force to pneumatics at the cost of
a slower closing speed. Attaching the closing arm directly to the output shaft of a
gearmotor is another possibility, although it’s not recommended because it will
not be as durable as driving the arm with a linear actuator. Figure 10-5 chows a
clamp bot configuration.
Leverage is the key to a successful clamp bot. In most cases, your bot will be attempting
to lift a target that weighs as much as it does. While a lifter usually has to
lift up only one side of its opponent, a clamp bot must bear the entire weight of its
opponent on the end of its arm. To avoid falling forward while lifting its opponent,
the clamp bot will need frame extensions on either side of its arm extending
forward as far as possible. Having a center of gravity as far back as possible will
also help avoid tipping forward.
A successful clamp bot must not only be able to grab and lift its opponent, but it
must be able to carry the opponent around the arena. This means having a drive
train strong enough to carry twice the clamp bot’s own weight, and the front end
of the clamp bot’s frame must be designed to ride smoothly on the ground. Ideally,
a clamp bot would have drive wheels forward straddling the lifting fork, so that
the opponent’s weight is directly borne by the driving wheels. A clamp bot must
also have the speed to catch fast opponents.
The need for a strong, well-balanced frame; a drive system having both great
carrying power and high speed; and separately driven mechanism for grabbing
and lifting make clamp bots one of the more challenging robot types to attempt.