Step 1. Thread the M3 x 20 screw through the top hole on the drive wheel holder.
Step 2. Pick up 2 MR84zz ball bearings. Insert 1 MR84zz ball bearings into both ends of the drive wheel.
Step 3. Place the drive wheel in to the drive wheel holder and fix it in place with an M4 x25 screw and M4 washer. Lock the other end with a M4 lock nut . You may need a wrench to tighten M4 locking nut. Note: Do not screw it too tightly as it may restrict the free movement of the drive wheel. It is important that you leave enough room for the wheel to turn freely.
Step 4. Mount the assembled bearing holder onto the front support plates. And screw it with a wing nut.