OEM Module Robotic Platform
by William Smith
I’m always looking at robotic bases and there isn’t a better source than SERVO
Magazine. I’ve also run across many just by surfing around on the Internet. One
of my favorite sites to visit is the Junun.org site developed for the Portland Area
Robotics Society. I’ve never gone to any of their competitions or been part of their
club, but I still like the parts offered at this site.
What caught my eye the first time I went there
was the Mark III Chassis Kit. For $10, I got all the
metal parts to build a mini-Sumo robot as shown
in Figure 1. All I needed to add were the servos, wheels,
and electronics which they also sell at this site.
I wanted to use my own electronics and I had some
servo motors already, so all I needed to purchase were the
wheels. I bought the injection molded wheels for $6/pair
that use a simple rubber band as a tire. These are common
and found in many robotic kits. The servos I had were already
reworked for continuous rotation so that made it easier.
Taking apart a servo to modify them for this type of
operation isn’t difficult but depending on how much time you
FIGURE 1. Junun.org
Mark III Chassis Kit.
58 SERVO 06.2008
want to invest, it may be worth buying pre-modified servos.
I wanted to make this a quick and easy to build robotic
platform, so if I didn’t have some already I would just buy it.
Assembly
The instructions for assembling the Mark III can be
found at the Junun.org site or directly through the link
www.junun.org/MarkIII/Manual/index.jsp. The manual
explains very well how to assemble the chassis and servos
with very crisp and clear pictures. They cover their own
electronics but I’ll cover my design in a few paragraphs. The
chassis design is so simple but so effective, I think this is
one of the greatest beginner robotic kits you can purchase.
The only issue I ran into is some of my servos are taller
than others. When you place them back-to-back on their
side as this design requires, the mounting may need shims
to reach the servo mounts. I had a couple of Parallax servos
that were too tall, but my GWS servos fit fine. You may
want to purchase your servos from GWS just for this reason
alone. They also have a lengthy list of sensors and other
robotic accessories, but surfing around for that stuff or
FIGURE 2. Basic Atom OEM board.
