Bottom of version 1
Power switch used
servos. Otherwise, the pulse widths would mean the
opposite from side to side if one motor isn’t reversed.
Preparing the Base and Mounting the Wheels
With standard height servos, I had to cut the center
spindle off the base in order to make room for mounting.
This allowed each of the servos to sit on their side with the
bottom of each one nestled up against the other. For the
wheels, I used a pair of 2” round rubber feet from an old
piece of computer equipment that was being scrapped.
Each wheel was glued and then screwed to a standard
servo horn. Just about any servo horn will work. The hole in
the center allowed me to screw the wheel and servo horn
to the servo. That way, it could be removed later if needed.
With the wheels attached, I could then mark the base
46 SERVO 04.2012
(if you can’t wait)
for the clearance holes to allow the main drive wheels to
protrude through the bottom of the base. Working with
plastic is relatively easy, and a sharp Exacto or other hobby
knife will do the job. There are many different techniques
for cutting plastic but I usually make a light cut on the
outline and then go over it several more times, cutting a
little deeper each time. The motors were then mounted to
the base with double-sided tape and a cable tie was placed
on each one to keep them secure. On the underside of the
base, a small slider was used at the front and rear to help
keep the robot level. It did double-duty since the screw
holding the slider on also secured the 2” standoffs to hold
the tray for the BASIC Stamp board. A power switch and
connector for a charger were also added on the bottom of
the base to wrap that portion up.
There was just enough room left to install four AA
NiMH batteries on the base to keep the center of gravity
low. Two were in front of the servos and the other two
were behind the servos. These were the tabbed versions
with the leads soldered directly to the wires. They connect
to the power switch and also to a charger jack through a
10 ohm resistor (poor man’s current limiting) which will be
used with a 7.5V 200 mA unregulated wall transformer. On
top of the two 2” standoffs, I used a plastic CD to create a
platform to hold the electronics. Often, CD spindles ship
with a completely clear plastic CD which is ideal for this.
However, any CD or DVD can be used.
With this tray in place, four short standoffs were used
to mount the brains. Running the wires was then a simple
task. At this point, it was like any other BASIC Stamp
powered robot with a servo drive system. It just had a
much more finished look. There is still some room left for
future expansion. This little SpindleBot looked okay but I
knew it could be improved. It was a good first attempt, but
I wanted to make better use of the available area.
Improving the Design – SpindleBot 2.0
The next version (robot #2) was completely redesigned
and improved. It is amazing to see the difference between
the original SpindleBot and the next version. There is a lot
more packed into the same space, and it has a much more
polished look and feel.
This new robot really came together. One of the main
variations from the first robot is that I wanted to ensure
that the center support for the spindle could be preserved.