VI. Final Prototype - CZ
For the final prototype, I finished designing the remainder of chassis of the robot in Solidworks. Like the robot legs, I made the entire chassis out of 1/4" lasercut plywood for simplicity. The legs of the robot are attached to vertical mounts which also house the gears of the robot. Then the vertical mounts are attached to a base plate which supports the motors and electronics of the project.
Figure 13 - Partial Assembly of one Side of Robot
I installed the motor and ran a test to see if the final design would work. Unfortunately, I found that the D-shaped motor shaft immediately stripped the 3D printed shaft adapter (shown in red in figure 13) and the legs didn't move. The failure was a result of two issues:
1) The 3d printed shafts that I had originally designed were not strong enough to transfer the torque from the motor to the legs. During testing, they flexed and deformed easily.
2) The combination of the 4 legs and 3 gears had a large amount of resistance which increased the torque required to move the legs.
Figure 14 - Video of Partial Assembly
To address the issues with the partial assembly, I completely redesigned the shafts to be 8 mm in diameter and decided to 3D print them with carbon fiber-reinforced nylon to ensure that they would be strong enough to handle the loads. By updating the shaft size, I also had to update the crank arms, gears, and vertical supports to accommodate for the larger shaft diameter. Once I had all of those parts designed, I lasercut a new set of parts and disassembled the original assembly.
Figure 15 - Carbon Fiber-Reinforced Nylon Shafts
I reassembled the partial robot with the new components and found that it worked significantly better than the previous version. The legs had lower friction and the motor was able to power the partial robot assembly.
Figure 16 - Partial Robot Assembly Working
With one half of the robot working, I lasercut and assembled the remainder of the robot. I attached the arduino, motor driver, and battery to the assembly and powered on the full robot for the first time. The legs walked exactly as I hoped for and the robot working properly.
Figure 17 - Full Robot Assembly
Figure 18 - Full Robot Assembly First Run
Finally, I put the robot on the ground and had it walk around the room to show that it can move under its own power.
Figure 19 - Full Robot Assembly Walking