Kinematic structures

This week focuses on kinematic structures. Our goal was to design and create one by using anything we have learned during this course so far. I wanted to create some design on my own but didn't have any ideas. One of the design that interesed me and what was kind of an inspiration for the work this week was this short. I thought of creating something like that, but with a little bit of addition on my own. The added value would be, that the spinning wheels on the edge would not spin simultaneously, but one after another, crating new interesting pattern. I was also interested in Geneva mechanism concept and wanted to implenment it into my design.

Design

First thing to do was to come up wuth the design. The first idea was to create one big gear with small gears around it. The gear ratio between big and small gear would be 1:2 (one spin of the big gear would spin the small gear twice), but with design choice of missing half of the teeth of the middle gear, it would spin small gear only once. After that, the small gear would not spin due to the missing contact of the teeth. Flaw of that, however, would be possibility of movement of the small gear without contact of the teeth. The solution would be to lock the small gear of course.

The first design idea looked something like this.

I couldn't figure out teeth design, that would be able to spin gears flawlessly.

After some thinking, I came up with an idea of double layer gears with bottom layer being small smooth circles with cutouts, that would lock the gears after missing teeth contact and wouldn't touch each other otherwise. I have decided to create my desing in Fusion 360. To create gears, I have used Spur Gear Add-in. With that, I was able to create gears with wanted parameters without any diffiulty. This video helped me with creating the gear mechanism. The design process was quite tedeous and boring but Insights worth taking away from this were to define objects as components, not bodies. That allows users to use joints for assembling the whole mechanism. I have used Rigid joints to join layers of every gear, Revolute joints to allow gears spinning and Motion link to simulate gears spinning. With the motion link, I was able to imulate spinning wheels upon contact of the teeth and design the bottom layer in a way that it wouln't jam while moving. End design end up like this.

The creation process

My plan was to spare some material and use playwood cutouts for gears. Tha base and joints on which gears stand would be 3D printed. For 3D printing, I have used Prusa printer and PET-G material. For the gears, I have used the laser cutter with frequency 500 Hz, Power 100 % and Speed 16 %. Here are final pieces and the whole mechanism put together.

I have created holes in small gears usable for inserting some design, that would be able to rotate and create some visual effects. It is designed for pieces cut from the 4 mm plywood. I didn't have time to design any and spent most of the time by adjusting parameters of the pieces in order for mechanism to work well. Even the time on the laser cutter was limited, so I end up only with the mechanism and possible upgrades in the future.