In this model, the motors are not directly driving the wheels but
instead are turning gears that will connect with gears on the wheels.
Figure 2 
Figure 1 1. Set one motor mount along the top of one bottom piece of channel.
Determine where you want the motor to rest – be sure to allow space
for the wheel and the gears. Note that the motor mount holes align with
the smaller holes on the channel and that you can use any two parallel
holes in the circle (Figures 1 and 2).
Figure 3 2. Using the 1-1/2" screws that come with the mount, bolt down the
unclamping end. Bolt the other side, but do not tighten it all the way
(Figure 3).
Figure 4 3. Place a gear hub spacer on the center hole of a wheel and line up
their holes. Thread a 1-1/4" screw that comes with the hub through a
small hole on the other side of the wheel (Figure 4).
Figure 5 4. Drop an 80-tooth gear over the screw end, followed by a set screw
axle hub (Figure 5). Thread the screw through all four parts. Repeat
this with the other three screws.
Figure 6 5. Slide an axle about 1/4" in the hub and hold it while tightening
the screw using the 3/32" hex key (Figure 6). Be sure tighten to it
against the flat side of the axle. Do not overtighten.
Figure 7 6. Insert the bushings in the hole where you want to place the axle
– there will be one on each side (Figure 7). Push the end of the axle
into the axle hole.
Figure 8 7. To lock the axle in place, put an axle set collar over the end
and push it against the bushing (Figure 8). Turn the collar until the
screw is
facing the flat side of the axle. Use the 1/16" hex wrench to secure it
to the axle.
8. Repeat Steps 1-7 for the other side of the chassis.