Lessons learned from the Final Prototype

While building the last prototype several problems that weren't considered were found. The three main points of interest were:

• Link on Link Interference

While making the movement, there were several links that collided with each other. In our analysis, we were only considering the position of each joint and not about the interaction of that joint with the physical linkages around it. The cause of this was the assumption of a zero-width linkage connecting each joint. Therefore the shapes of interfering links, the claw and the link parallel to the claw, were modified. The final curved versions of each link can be seen below. It is important to notice that the dimensions between joints were unchanged by curving the link, only the shape was modified.

• Transmission Angle

It was found that there was a certain position of the mechanism where the ternary link was aligned with the input crank, forming a toggle point. This toggle position caused the mechanism to require more torque at this point than what we originally designed for. To resolve this issue two changes were made: the input link was shortened in order to reduce the torque needed to get past this point and a gear reduction of 3:1 was used to increase the torque output from the motor at the reduction of the climbing speed.

• Fragile Plastic

During testing, we had a few acrylic cranks break because of the torque applied to get past the toggle point. A solution to this would be to use lexan so the plastic doesn't shatter as easily. The reason we did not use lexan was that we did not have an easy way to get the precise lengths between joints on the link if using lexan. in the future, using lexan or metal and a higher strength motor would help over come this issue.