Build Your Own Combat Robot

Launcher Design
Chapter 10: Weapons Systems for Your Robot 213
The launcher is a specialized form of lifter, with an arm capable of not just lifting
but hurling its opponent into the air. This attack will not only flip the opponent
over, but quite possibly damage it from the impact, as well as make for a great
show for the audience.
A launcher needs to release a tremendous amount of energy in a short period of
time to work. Electric motors, linear actuators, and hydraulics are too slow for
this kind of mechanism. Most launchers use specialized high-pressure pneumatics
to get the impulse of force they need to fling the opponents, using modified hydraulic
cylinders and high-pressure valves and hoses to run carbon dioxide or
compressed air at 900 PSI or more. This is not a system that can be built with
off-the-shelf parts—high-pressure pneumatic launchers take years of research and
engineering to develop.
Another option is to use lower-pressure pneumatics and to engineer for a very
high-volume flow, with large-bore tubing and valves, and either a high-rate pressure
regulator or a large buffer tank. While the engineering of the pneumatics is simpler,
large-bore, low-pressure pneumatics will take up a lot more room in your robot.
A third option is to use a spring mechanism. A powerful torsion spring or compression
springs pushing the arm up, a powerful geared motor for re-cocking, and
a latching mechanism to hold the arm down until remotely triggered should make a
good spring mechanism. This type of weapon is heavier than a pneumatic system,
and the cocking and latching mechanisms take some serious mechanical engineering
skill to make. The time it will take to slowly re-cock the spring is also a significant
disadvantage because until the arm is down, your robot will be helpless against an
opponent. A single-shot launcher design that cannot be re-cocked should not even
be considered.
Figure 10-4 shows how launcher robots work.
Whichever mechanism you use to power a launcher, your frame and drive system
is going to be subjected to a tremendous jolt every time it fires its weapon. Your
frame must provide a strong structural path between the launching mechanism
and the drive wheels, as the arm is going to impart a massive downward force on
the frame every time it fires. The entire robot should be built with major jolts in
mind; be careful that nothing can shake loose and that all electrical components
and connectors are solid.
Finally, this kind of robot can be dangerous to build and test. The forces involved
in flipping several hundred pounds of robot through the air can kill you if
the weapon misfires with part of your body in the path of the flipping mechanism.
Be careful. Most competitions will require that you have some way of locking the
mechanism when not in combat, usually with a pin or rod passing through a hole
in the frame, which prevents the arm from moving.
A launcher does the most damage to an opponent when the hurled opponent
strikes the ground after being flung into the air. The mass of the target bot and the