Content for this page:

• Video
• Technical details of prototype
• Explain differences from previous prototypes
• Evaluate prototype performance
• Explain shortcomings

Final Prototype Design

The video above shows the operation of the final prototype. Similarly to previous designs, the final version is primarily constructed with laser-cut acrylic links and base plates. However, there are some substantial differences.

The first major improvement is the addition of 3D-printed links on each drive shaft, which are visible as the purple components in each linkage. These links include recesses for fasteners at each joint, which allows for a much more compact assembly. The doubly-supported couplers were changed to singly-supported because previous prototypes found that extra support planes had a tendency to interfere with each other and lock up the joints when load forces were applied. Finally, with the exception of the drive shaft, all of the bearings within the linkage were replaced with loosely-fit nuts and bolts. This change dramatically increases the ease of assembly while also enhancing the strength of the mechanism, with the drawback of additional friction at the joints.

The linkages are all driven by a single DC motor powered by a 9-Volt battery. The motor is mounted near the front and drives the front shaft through a timer belt-and-pulley system. It also drives a second timer belt across the side of the robot, which finally drives the back shaft through a third timer belt. The intermediary belt is necessary because the distance between the front and back of the robot is adjustable, so the two shafts cannot be directly connected. There are various points to attach idlers to the intermediary belt to tighten it for any configuration.