Build Your Own Combat Robot

206 Build Your Own Combat Robot
This type of robot lives or dies by its power, traction, and durability. Choose
the largest drive motors and batteries and motor controllers to handle them, and
base your frame around them. You should have as a minimum 1 HP of total drive
power per each 50 pounds of your robot’s weight. More is always better, as the
strongest ramming robots have as much as 1 HP per 10 pounds of total weight.
Choose a gear ratio and wheel size that gives your robot a top speed of no more
than 20 MPH—more than that will be uncontrollable. Low-end acceleration is
very important, and you should aim to have your robot reach its top speed in a distance
that’s no more than three times its body length. Your robot’s stall pushing
force should be at least twice its own weight, as it not only has to accelerate but
also overcome the opponent’s mass and drive power.
To get as much of that power to the ground as possible, you need large,
high-traction wheels. Soft rubber pneumatic go-kart or wheelbarrow wheels are
best, but be sure to get them foam-filled if you want your robot to survive.
Solid-foam power wheelchair wheels have slightly less traction but more durability.
Avoid plastic wheels, solid-rubber castor wheels, or metal wheels with thin rubber
treads—these wheels not only lack traction, but their lack of compliance will make
your robot bounce and skip when it hits bumps or debris.
Four or six wheels are better than two for a ramming robot. Four wheels give
much better stability than two, allowing you to line up a target and make dramatic
cross-arena charges right into your target. Four wheels also make it possible to get
all of your robot’s weight resting on its tire tread, where you want it, and this design
allows you to put wheels all the way at the front and rear of your robot. This
is important when fighting wedge or lifting robots. For a four-wheeled ramming
robot, you should make the side-to-side spacing of the wheels at least as much as
the front-to-back spacing, as having the wheels farther apart front to back than
side to side will make the robot turn awkwardly.
Your wheels should be large, with a diameter between a quarter and a third of
your robot’s length for a four-wheeled design. Large wheels are more durable than
smaller ones, with more material that needs to be damaged to make the wheel useless.
Large wheels, protruding through the top of your robot’s armor as much as
the bottom, make your robot able to drive upside down as well as rightside up.
You should also design in as much ground clearance as possible, both on top and
bottom, to make your robot difficult to hang up on wedges, lifting arms, or debris.
If possible, make sure your robot can be tilted or have its front or back raised off
the ground, and have at least two wheels still touching the ground.
Finally, a ramming robot needs to be able to take serious hits. Armor is important,
but more than that, your robot needs to have a strong frame and internal impact
resistance. Keep it clean and avoid unnecessary external details, and stick with a
simple box with ramming points front and rear. Try to design to survive frame deformation—build
your drive system so it is not dependant on your overall chassis
alignment, leave generous clearance around moving parts, and leave a little slack
in all your wires so that connectors don’t pull free if a component shifts position.
Heavy components like batteries and motors should be well secured.