Page 48 - Build Your Own Combat Robot

FIGURE 2-5 Chapter 2: Getting Started 29
AutoCad was
used to design
Live Wires
prior to
fabricating parts.

The Game of Compromise
There has probably never been a bot made that didn’t involve some level of com-
promise on the part of the builder. This is where your time-, money-, perfor-
mance-, and availability-related trade-offs occur. We builders rarely get the
chance to use the best parts available, and therefore must settle for what we can
get. This is where you need to let go of your idea for a dream bot and start looking
at your project more realistically.
For example, say you want your bot to move at 20 mph and you want to use
8-inch diameter go-kart wheels. To move at this speed, the wheels need to turn at
840 rpm. Now you have to find a motor that can deliver that speed. You search all
of the magazines and catalogs you can find, scour the Internet, and you still can’t
find a motor that will give you the speed you want. This means you’ll need to build
a gearbox that can change the motor speed to the desired 840 rpm wheel speed.
Here you will be faced with lots of options, such as spur gears, sprockets, belts,
worm drives, and so on. In your search for motors, say you also found some gear
motors—you pick a few motors, and then calculate what gear reductions you need
to get the right wheel speed. At this point, you have several motor and gear options
to choose from to get your robot to move at 20 mph. So, now you have to choose
which combination you want to use.