CHAPTER 24 ■ BODY BUILDING
- Grind out the motor shaft cap holes on each side of the robot body to the desired
size. Centering the grinding-stone accessory in the motor shaft cap target area is
made easier by the screw-size hole you drilled in its center, back in step 11.
The golden rule of drilling and grinding: If you’re at all unsure, drill the hole smaller than you think
you need. It’s easy to drill and grind out additional material, but impossible to restore material if you
removed too much.
Don’t select drill speeds that are so fast that the plastic melts. Just work the stone through the piece at
low to medium speeds, at a moderate pace.
- Insert the motor to test the alignment of the holes and to make sure the motor
presses completely against the plastic container’s wall. (There is a raised section
on the gearbox cap around the motor shaft. Upon inserting the motor into the
holes, the raised section of the cap should stick out of the container; otherwise,
the remainder of the motor cap won’t screw flat against the plastic.)
Mounting the Motors
There are a number of ways to attach motors to a robot. Some people use double-sided foam mounting tape.
Also not unheard of are hook-and-loop fasteners, cable ties, duct tape, and hot glue. Usually the best solution
is to mount the motors in the manner in which they were designed: using the mounting screw holes.
Obtaining Metric Screws
The Hsiang Neng motors have two screw holes for M2.6 ISO metric screws. It would almost seem that an
American standard, UNC (Unified National Course) #3-48 screw size would be acceptable. But, metric
threads and UNC threads are not interchangeable.
Metric screws are standard outside of the United States. Most American hardware stores have at least
one drawer with miniature metric screws (see Figure 24-10).
Figure 24-10. Hardware-store display case (#341) of Hillman Miniature Metric Machine Screws
Purchase four M2.6 x 6 mm screws. Unfortunately, all I could find in the Hillman case were M2.5 x 8 mm
screws, which are satisfactory when washers are added. Micro Fasteners sells M2.6 x 6 mm screws (see
Figure 24-11), part #MSPPS2606, $2.75 for 50 pieces. McMaster sells 100 for $5.26 (#90353A112).