3c. Use a file or grinding wheel to remove the head of the rivet
that connects the tension roller to its spring steel leg. This will
leave you with a free-turning wheel held by a small metal bracket;
this is the drive wheel, or track wheel.
File or grind down one edge of the track wheel to reduce its
diameter all around. The track wheel will be centered underneath
the gyro wheel, but you want only one of its circular edges to
touch the gyro wheel.
3d. Thread the existing hole in the wheel bracket with the 10-32
NF tap, and attach it with a #10-32 machine screw and nut to the
mounting bracket you made. The screw should be about
it mustn’t interfere with the free turning of the track wheel.
3e. Fit the motor into the plywood rings and route the wires back through as you did in Step 1f.
3f. The depth of the plastic cap from rim to inside bottom should
be about ¼" greater than the height of the motor assembly from
the top of the large disk to the bottom of the gyroscope wheel. If
the cap is too deep, mark and trim its rim down evenly.
3g. Turn the cap over and mark a
4" rectangle centered
on the cap, plus 2 points
7" from the long sides, matching the
bracket mount holes. Cut out the rectangle and drill the holes
3h. Secure the bracket and drive wheel to the bottom of the cap
using two 6-32×
2" machine screws, washers, and nuts.