temporarily. Not only would they be
able to test what is finished, but
they could also compete next time
with a more battle proven design.
On the other hand, working
with a modular design requires
more thought and precision. When
you are building a bot from the
ground up, you can play with
measurements more readily than
with this format. In your design and
machining process, precision will be
key. You cannot build independent
assemblies and expect to put it
together if the sizes of the holes
and components don’t match up.
Therefore, you will need to be exact
when working out the design of your
bot. The downside, however, is the
potential of over complicating the
design — a common mistake for many
builders. As a result, your bot can be
too bulky or difficult to finish in time.
Get Ready
To better prepare yourself for a
modular design, there are a few
things to consider before starting.
Do yourself a favor and standardize
the sizes of any fastener being used.
This will standardize the hole size
over the entire bot, as opposed to
dealing with multiple bits and loose
pieces. Accordingly, it is also important that you know which holes will
need to be countersunk. Bolt heads
getting in the way is a common
30 SERVO 11.2009
cause of miss-fitting pieces. Another
machining technique to consider
(that will also make your life easier)
is to tap holes. By doing so, you will
reduce the number of nuts needed
since the fastening grooves will
already be in the frame itself.
Another angle to consider
before starting is how much of the
bot needs to be modular. Depending
on the bot type or concept that you
have, there may be very little of the
bot that will benefit from a modular
design. You might only want your
motors to be in a quick release position, or only your weapon mounts
to be interchangeable with different
weapon heads. There is nothing
wrong with being specific about
certain aspects of your bot you
want to be flexible and those you
want to remain in a simple set-up.
The last thing you will want
to flush out beforehand is the
simplicity of your chassis. If you are
using multiple modular assemblies,
a simple yet rugged chassis to
mount them in will be preferable,
should any problems arise.
The Drive Train
Now that the basics have been
covered, it’s time to look at specific
examples of modular assemblies,
such as a modular drive train.
A modular drive design is usually
comprised of one of two approaches.
The first is that of modular motor
mounts and gearbox assemblies. Both
of these components are important
to keep well protected and attached,
but the ability to move or change
their configurations can be useful.
Another nice aspect of a modular
motor mount is repair. Motors burn
out and gearboxes break. These
problems are not fatal, but if you
can’t get at the broken parts in a
reasonable amount of time, you
might be in trouble. Therefore, one
good way to make sure your gearboxes and motors are easily removable is to mount the assembly via
quick release bolts. By quick release
I mean wingnuts, or Allen heads
with easy access for an Allen wrench.
A builder can go about devising
this assembly and its mounts
through a variety of methods. The
more compact method is to take
the assemblies for the motor and
gearbox mounts and combine them
into one single modular unit. If
done properly, the builder would
have one modular segment containing
the gearbox and the variable
number of motors to go with it. It
would also have the mounting
pieces to place the assembly in a
variety of positions inside the bot’s
frame. Of course, the builder can
simplify this method if the motors
are allowed to simply dangle off the
gearboxes; then it’s only a matter of
having a modular design for the
