Our world is mountainous with difficult terrain to traverse. The ‘Segmented Mountain Climber’ is able to deftly maneuver up and down the steep mountainsides, and over their sharp peaks. Its Whegs, half wheel half legs, are able to climb over both small rocks and large boulders. It can also quickly reverse, turn and is able to continue movement even if flipped upside down.
Our original idea was a mountainous world with difficult terrain to traverse. We started by brainstorming many different models that could help climb mountains. We decided on a segmented car which could work best in a mountainous situation by conforming to the landscape. It’s called ‘Segmented Mountain Climber’.
During the first few days, we thought of various shapes for the vehicle, drawing inspiration from existing creations including roller coasters, snakes and trains. Then we brainstormed various designs for the wheels, including tank treads, legs, many small wheels, and large powered wheels.
In order to better visualize the connections and turning of the segments, we made our first prototype of the large-wheeled model. In essence, it was just a trio of cardboard boxes tied together with string, with an axle and pair of wheels through each segment. However, some clear problems came up: the connection was not sturdy enough, and the wheels failed to rotate. We discussed at length how to incorporate the right wheels and connectors into our design. We started looking at other possible wheel choices, and then we settled on wegs. A weg is essentially a spoked wheel with the rim removed. Deriving its name from the words "wheel" and "leg," it could use circular motion, but with legs. Compared to traditional wheels, they could climb over obstructions and had superior grip. We also decided to replace the strings. At first, we had considered ball joints by virtue of their versatility, however we chose to nix the ball joints in favor of universal joints, because they could be better incorporated into the segments. Universal joints are basically two axles intersecting at a point, offering flexibility in two dimensions. Furthermore, the ability to transfer torque is exclusive to universal joints, so they could prevent any one segment from falling over.
Taking these considerations into account, we replaced the string and wheels on our prototype with universal joints and wegs. Upon finishing, we realized that the wegs in the prototype had the right structure but would not rotate because of the material (cardboard), the number of legs (4), and the structure of the foot. We decided that a 6-legged wooden weg would work better, and we redesigned the shape of the foot to include rubber that could provide traction. Another problem was the turning, we considered models such as rack-and-pinion, which was too delicate and complicated, and exploiting right-and-left rotation differences, which wouldn't work as well in a multi-car design such as ours. We decided on using a servo to rotate the first compartment relative to the others, turning the rest in due course. We didn't know, however, how we could incorporate the servo into the overall design. We decided that the joints would be included into the design of the car segments, and the servo would be attached to the foremost universal joint via a 3D-printed attachment. Unfortunately, a problem inherent to servos was the elimination of one of the two axes of rotation; as a result, the first and second compartments would always stay firm on uneven ground.
Finally, after considering all these issues, we crafted the final product, learning from our previous errors. We used wood, which is much sturdier than cardboard; we used wegs, capable of scaling obstacles, and we used a servo to turn and manipulate the vehicle. We connected the motors and servo to an Arduino controlled by a remote. Overall, we had many separate design challenges; in the end, however, all the components came together to form a polished final product.