Build Your Own Combat Robot

230 Build Your Own Combat Robot
FIGURE 10-13
Deadblow, a
114-pound
pneumatic hammer
bot. (courtesy of
Grant Imahara)
builders use high-pressure air or nitrogen, which do not have to change state from
liquid to gas. This gets around the problem of the tanks freezing up, but it doesn’t
store nearly as much energy in the same space and requires huge tanks to run a
hammer for an entire match.
Another option is to drive the hammer with an electric motor. This makes it
easy to give the weapon 180 degrees or more of travel, allowing it to reach full
speed before hitting the target. Gearing should be optimized for maximum speed
at impact, taking into account that with too low a gear ratio, the motor won’t have
enough torque to get up to speed, while too high a ratio will mean that your hammer
will reach its top speed too early and not do as much damage as it should.
Problems of both speed and torque can be solved by choosing the most powerful
drive motor you can for the mechanism.
Some hammer robots have used a crankshaft mechanism to produce reciprocating
hammer motion from a continuously turning drive motor. When considering
this kind of mechanism, you should keep in mind two things: First, you want
the hammer moving at maximum speed when it strikes the opponent; many simple
crankshaft mechanisms will have the hammer traveling at top speed only in the
middle of the stroke. Second, if the hammer’s motion is interrupted mid-stroke, it
should have some way of reversing and striking again without stalling or having
to lift the entire robot off the ground.
Hydraulic-powered hammers have also been built. Hydraulics can provide tremendous
force that can accelerate a hammer very quickly, but most hydraulic
systems respond rather slowly and are not ideal for the high speeds required for
rapid-fire striking a good hammer system needs. Building a hammer mechanism