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Methodology
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Our third and final design combined the strengths and eliminated the problems of the first and second. We created a rotating cylinder with a sliding counterweight inside that combined the fully-constrained nature of the four-bar with the discontinuous nature of the see-saw. Our weight slides along an angled shaft that rotates synchronously with the walking mechanism's crankshaft, shifting the weight quickly from the lifting foot to the landing foot precisely during the short period of time while both feet are on the ground. Timing is also easily and precisely adjustable by simply loosening and moving the timing belt.
Purchased Parts
For our final machine, we purchased:
| Part | Source | Quantity |
|---|---|---|
| 3mm steel shaft | generic | ~50mm |
| 5mm steel shaft | generic | ~700mm |
| 5mm precision ground steel shaft | generic | 200mm |
| 3mm x 6mm x 2.5mm ball bearing | generic | 6 pieces |
| 5mm x 9mm x 3mm ball bearing | generic | ~50 pieces |
| M3 x 20mm cap screw | generic | 2 pieces |
| M3 x 30mm cap screw, fully threaded | generic | 1 piece |
| 2in OD cylindrical steel stock | generic | ~1in |
| 5mm x 7mm x 8mm slide bearing | McMaster | 2 pieces |
| 91MXL012 1/8in timing belt | McMaster | 2 pieces |
| 140MXL012 1/8in timing belt | McMaster | 1 piece |
| DC motor | Pololu | 1 piece |
| AA battery pack | Amazon | 1 piece |