article on weapon shaft thicknesses.
PHOTO 2
Optimization
Combat robots are born
overweight, and seem to get
heavier after that. This may require
a complete redesign or applying
some optimization techniques to
lose weight, improve strength, or
(hopefully) both.
Optimizing the shape is one
approach. Taking a solid disk and
removing material without removing
strength is a good example. One
key factor in the Moment Of Inertia
(MOI) of a disk is the mass at any
given radius. This means that metal
removed near the hub doesn’t count
as much towards MOI as metal near
the edge. Thin spokes aren’t as
strong as thick ones, so a number
of smaller holes may be better
than a few big ones. Think of a
honeycomb, web design, or a truss.
Two good examples are shown in
Photos 1 and
2.
There is a lot more help on
this topic in the book (about 3-1/2
pages worth) and all of it is worth
reading.
PHOTO 1
Drive!” Drive a lot. Hundreds of
hours, not just a few. Good driving
wins matches.
Structures
There are three main types of
robot structure: trussed, integrated,
and unibody. Trussed robots are
built using bars, bolted or welded
together, resulting in a very rigid
and light structure. The armor is
usually made out of plates attached
to the bars. They are a fast type to
build, and are easy to work with
during events. The plates (and
possibly truss members) can be
removed and replaced with spares.
The greatest disadvantage is the
welded joints which can be weak
points. Armor plates can also be
ripped off during fights (Photo 3).
Integrated robots receive their
name because the structure and
armor are integrated into a single
structure using screws or welds.
The armor plates are also in the
structure. Building this type of bot
is harder, but they can be very
compact and strong (Photo 4).
Unibody robots have their
structure milled out of a solid block
of material. Through milling, the
sides, bottom, and pockets for
components are created. No welds
or screws are needed except for
installing the top. These are the
lightest robots, and can be the most
damage resistant. However, you can
lose more than 80% of the material
in the carving process, not to
mention the amount of time spent
to do this. Another downside is that
a damaged structure can’t be
replaced (Photo 5).
Another way to make unibody
robots is through molding materials
such as composites like carbon
fiber or Kevlar. These are not very
popular because of the expense,
difficulty, and expertise needed.
Armor
Building and Testing
Full scale models are another
very helpful building step.
Components can be mocked up
(before spending money) from PDF
or CAD drawings. Design can take
up to 60% of the total development
time, so make it count. Once you’ve
modeled the bot and are ready to
cut metal, “measure twice, cut once”
is the rule.
Testing is often short changed
or overlooked. According to Carlo
Bertocchini’s Law, “Finish your robot
before you come to the competition.” Often bots are finished just
before (or at!) a competition,
leaving no time for testing. Many
things can go wrong if the bot
doesn’t have sufficient drive time
before competing. This leads nicely
to Show Master Dave Calkin’s main
advice: LTFD or “Learn To Freakin’
Like structures, armor types
come in three flavors: traditional,
ablative, and reactive. Traditional
armor plates are usually made out
of tough, hard materials that try to
absorb and transmit impact energy.
Hardness causes damage to
the opponent’s weapons, while
toughness resists damage. This can
be achieved using a composite type
armor, as well as the typical metal
plates. Depending on the materials,
PHOTO 3
PHOTO 4
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