Page 195 - Robots Androids and Animatrons : 12 Incredible Projects You Can Build

hammer. This force will cause the tubing to collapse onto the shaft
making a strong friction fit. Strike the 3-mm tubing in one or two
locations for insurance.
If one looks closely at the gearbox motor shaft, there is a keyway
(flattened cutaway on the shaft) cut into the shaft. If you properly
strike the tubing at that location to collapse the tubing into the
keyway, you will create a very secure fitting between the motor
shaft and tubing.
The drive wheel is mounted by pushing it onto the 3-mm tubing.
The friction fit of the wheel is strong enough to drive the robot
without any slippage. If you wish to mount the wheel permanently
(something I have not done) to the shaft, try mixing slow-setting
epoxy glue and coating the 3-mm shaft with it before mounting the
wheel onto it.

Counterbalance
When the gearbox motor is mounted on the U channel, the weight
of the gearbox motor on one side makes the assembly unbalanced.
To balance the U channel, I placed 3 to 4 oz of lead on the opposite
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side. I have 8″ thick lead sheets lying around that I use to store
174 radioactive isotopes. Cutting and drilling the lead is easy. You can
mount any heavy object onto the shaft as a counterweight (like
fender washers).

Shell
The original tortoise robot had a transparent plastic shell. The
shell was connected to a bump switch that caused the robot to go
into “avoid” mode when activated. I looked at, tried, and rejected
a number of different shells. Finally I was left with no choice other
than to fabricate my own shell.
Rather than fabricate an entire shell, I made a bumper that encom-
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passes the robot. The bumper is fabricated from 8″ 2″ 32″ alu-
minum bar (see Fig. 8.6). The aluminum bar is marked at the center.
Each bend required in the bumper is also marked in pencil. The ma-
terial is placed in a vise at each pencil mark and bent to the angle re-
quired. The two ends of the aluminum bar end up at the center back of
the bumper. These two ends are joined together using a 8″ 2″ 1″
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long piece of aluminum bar. A 8″ hole is drilled on each end of the
aluminum bar. Matching holes are drilled in the ends of the
bumper. The bar is secured to the bumper using two 5-40 machine
screws and nuts (see Fig. 8.7).

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Chapter eight