The linear actuators that we were given as part of this studio pulled with a force of 30 Newtons. Since we had decided to build a hexabot, a six legged spider robot, we needed to build the legs so that they would have enough strength to lift the robot.
At any given time, at lease three of the robots six legs would be touching the ground, so we needed to design the legs so that three of them could lift the entire robot.
We designed the robot to weigh 4.5 kilograms total, so each of the legs needed to be able to lift 1.5kg. We used equations, such as torque = force * distance, and force = mass * acceleration, to calculate the exact diamentions that the leg needed to be.
We then started 2D modeling the parts of the leg in rhino and laser cut them out of plywood. In the initial designs there were many interference issues. The linear actuators got stuck on the pieces of laser cut wood. To solve this, we made the wooden linkages different shapes so that the linear actuators would not catch on them.
After redesigning to eliminate interference issues multiple times, we finally made a model that had no interference issues and did not break the linear actuators. While we were working on the legs, the linear actuators went some through evolutions. The motors were swapped out for motors that were five times stronger. This made it so that our robot was able to lift much more than its own weight.
We then made five more linear actuators and began attaching them to the base of the robot. After we attached all of them, we started making a linkage that would span from a servo to the body of the robot.
A few intereference issues later, we had a linkage system that allowed the legs to rotate about the body.
After assembling the entire robot, we tried to make it walk, however, we found that the hinges that we used bent in the wrong direction. We ordered a new set of hinges, which should be sturdier and allow the robot to walk.
All of the linkages used in this project were parallelograms, since the pieces that were attached stayed parallel. This made both programming and designing the robot easier.