Build Your Own Combat Robot

FIGURE 10-12
Schematic of hammer
mechanisms.
Chapter 10: Weapons Systems for Your Robot 229
behind. This limits the hammer’s travel to at most 90 degrees, and less if you are
striking a tall robot. This isn’t much room to get the hammer up to full speed and
will mean that your weapon will strike only flat robots with its full power. A better
option is to use a mechanism that allows the hammer to travel a full 180 degrees,
permitting it to get up to full speed before it impacts. This can be accomplished
with a pneumatically driven rack-and-pinion mechanism driving the hammer
arm, or by using a pneumatic cylinder to pull a chain wrapped around a sprocket
connected to the hammer arm. Figure 10-13 shows a photo of Deadblow, one of
the fastest rapid-firing hammer robots to compete in BattleBots.
Whichever mechanism is used, the limiting factor in a pneumatic hammer’s
speed will be the rate at which you can make the working gas flow from your storage
tank into your driving cylinder. As the pressure regulator is a major bottleneck,
some pneumatic hammer bots have huge low-pressure reservoirs downstream of
the regulator to provide the high flow rates that the hammer needs. Other bots use
massively large-bore tubing and valves to minimize flow resistance in the pneumatic
lines. High-pressure systems that run gas straight out of a carbon dioxide
tank with no pressure regulation can provide extremely high rates of force delivery,
but these systems are expensive, dangerous, and difficult to build.
Carbon dioxide absorbs a lot of heat from its environment as it expands from
liquid to gas, which means that a CO 2 tank called upon to provide gas for many
hammer shots in a short period of time can freeze up and become too cold to deliver
gas quickly enough to keep the weapon running. To get around this, some