For the first prototype, a six-bar mechanism was used. The mechanism was designed to have an adjustable rocker point that would be fixed by a second input to allow climbing in two orientations: right-side-up and up-side-down. This prototype was constructed out of cardboard and pins to allow easier experimenting with ground joints and link lengths. The design can be seen from the front and from an isometric view in the figures below.

Front View of the Mechanism

After experimenting with different positions and we found two positions with paths different enough to allow climbing in two directions. Videos of the animation of both joints can be found below.

Climbing Backwards:

Some of the important lessons obtained from building this prototype were:

TO have exact dimensions is really important, therefore a precise cutting process would need to be used for the links in future versions. This was a major deciding factor in using the laser cutter on the final project.
Fixing the rocker position to the desired place was complex and didn't produce a movement path that was desirable for climbing since the paths for both prongs would interfere with each other. The interference would prevent the robot from climbing effectively. Due to this, we decided to fix the rocker position and focus on only climbing in one direction.
There is a position of the input crank for the mechanism where we encountered a toggle position. This toggle position required higher torque than what we had expected and made us aware that we would probably need a gear reduction on the output shaft of the motor for the final project.

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