Walking Monster “Penelope”

Spring 2016, Team of Five

The Task:

Build a machine with no wheels, powered by a seated pedaling human. It must be 3′ x 4′ x 5′, and safe to joust on within five weeks. In the joust, points are awarded for speed, appearance, and whether the rider can successfully use a mounted lance to knock a magnetic ring from an attachment to the beast.

Meet Penelope.

With inspiration from artist Theo Jansen, I worked in a team of five students to create Penelope for Thayer School ENGS 146. The machine was designed in Solidworks, then fabricated using a ShopBot, CNC milling, and repurposed bicycle parts.

Results:

Design:

Penelope uses a re-purposed bicycle braking system with a differential to skid steer. Brakes can be operated with one hand, while the other hand directs the lance that rests in the mount between the pedals. It was the first monster able to walk, and the only vehicle able to move both backwards and turn in addition to walking forwards.

Penelope took a close second place in the jousting competition.

Challenges:

Simplifying Design: Due to the accelerated nature of the course, the team focused on design simplicity and incorporating known elements: the Jansen linkage was selected for the legs as a known, functional linkage. Strategic cuts in the plywood allowed the vehicle pieces to be puzzled together, reducing time and error in assembly. The machine was designed to take advantage of the precision and speed of the Thayer machine shop Shopbot, requiring only a few parts to be milled.

Leg Stability: Initial walking tests showed that the lowest leg triangle was prone to bending, particularly on uneven surfaces or while Penelope was turning. While there was insufficient time to increase the plywood thickness of these triangles, we created extra ones to bring with us to the competition. The legs fractured in competition, but we were able to replace them and stabilize them with parts of the broken triangles (visible on the legs in the first image).