2. Design Process - JP

The video below served as inspiration for the design process of the 6-bar window mechanism.

Video 1: YouTube Video of 6-Bar Window Mechanism

Using the video and Aldo's Planar Mechanism Kinematic Simulator (PMKS) settings for the 6-bar window mechanism, the first design process was to tune the link lengths to create the desired movement. The desired movement is to create a sweeping motion of the coupler that rotates 180 degrees. By adjusting Aldo's settings, the desired movement was created. Using geometry, the link lengths and positions were obtained. The link lengths and positions were scaled to an appropriate size based on the size I wanted. I ideally wanted the mechanism to be big enough to visualize the operation and movement of the links. Therefore, I made the shortest link, the input crank, approximately 6.5 inches, and scaled the other links based on the input crank and positions in the PMKS. The video below shows the position and desired movement of the design on PMKS.

Video 2: PMKS 6-Bar Window Mechanism of Desired Movement

The second design process was choosing the materials. Since I wanted to keep the project simple but also contain as many do-it-yourself (DIY) aspects as possible, I decided to use plywood, wood dowels, and cardboard. The materials were bought from the CO-OP. The plywood came in sheets of 24 x 1 x 1/8 in and the dowels have a diameter of 1/8 in. The reason I did not use Texas InventionWorks or did not buy pins or screws to create the joint is that, as mentioned earlier, I wanted to create the mechanism with as many DIY aspects as possible. That meant creating the pin joints and slots by hand.

With the materials chosen, the next design process was to create the links and joints. The thickness of the links was to be based on the thickness of the plywood. In order to create the pin and sliding joints, the thickness of the links had to be at least three plywood pieces. Therefore, the links with no sliding slot, the input crank and follower, and the sliding joints were to be made three plywood pieces thick. However, since the sliding joints were three plywood pieces thick, the links with sliding slots, the ground, and the coupler, had to be made at least five plywood pieces thick in order to fit the sliding joints.

One of the troubling designs was making the joints. The initial design of the joints consisted of gluing a piece of plywood above and below a piece of cardboard. The internal supports of the cardboard would provide a pivot point for the dowel to create the joint. However, after constructing the joint, the internal supports were too spread out and created a loose joint. The second design consisted of using plywood to create the joint. The sandwich method was used again, but this time, two smaller plywood pieces were inserted in the middle layer to create a spacing that would be utilized as the joint. The initial concept of the second design worked; however, the middle plywood pieces were glued to where the joint was also loose. The second concept of the second design was made by inserting the dowel in the middle layer to set the size of the joint and the middle plywood pieces were glued such that they were flush with the dowel. This created a tight space for the dowel and created a sound joint. This design was used for the ground and pin joints. The slider joint was tested, and another problem arose: there was no security measure keeping the slider joint from sliding out of the sliding slot. Therefore, the third and final design consists of a layer of plywood that creates a slot that guides the sliding joint in the slot.

Another troubling design aspect was the sliding slot. The initial design of the slots was made to the exact lengths measured from PMKS. However, the sliding joints experienced limited movement when the joint neared the glued ends of the slot. Therefore, the sliding slots had to be made longer than they were initially designed to resolve this problem.