Procedure: 1. Insert the Threaded Shaft 4×31mm into 3 Plastic Rings. 2. Insert the Threaded Shaft 4×31mm with Plastic Rings into the Flange Bearing 4×8×3mm. 3. Install the Threaded Shaft 4×31mm with the Flange Bearing 4×8×3mm into the Timing Pulley 90T. 4. Turn over the Timing Pulley Slice 90T. 5. Insert the other Flange Bearing 4×8×3mm into the Timing Pulley 90T. 6. Put the Shaft Collar 4mm on the Threaded Shaft 4×31mm. 7. Insert a Headless Screw M3×5 into the Shaft Collar 4mm by a 1.5mm Hexagonal Screwdriver. 8. Install a Plastic Ring on the Threaded Shaft 4×31mm. 9. Build another 3 wheels as step 1 to step 8 discribe. 10. Install the 25mm Motor Bracket on the DC Motor 25mm. 11. Insert 2 Countersunk Screw M3×8 into the25mm Motor Bracket to install the DC Motor. 12. Insert the DC motor with Motor Bracket into the Beam 0824-160. 13. Insert a Screw M4×14 to install the DC motor on Beam 0824-160. 14. Install the Shaft Connector 4mm on the DC motor. 15. Insert a Headless Screw M3×5 into the Shaft Connector 4mm. 16. Bulid another DC motor holder as step 10 to step 15 discribe. 17. Install Beam 0824-144 on the DC motor holder by a Screw M4×14. 18. Install Beam 0824-144 on another DC motor by a Screw M4×14 to build the Chassis.