This project was completed with a team of 5 mechanical engineering students my freshman year at Tech. The goal of the project was to take some real world object, break it down into its respective parts, create a 3-D model of each part, and assemble all the pieces into a full representative model of the object. As opposed to going for something simple and straightforward like a bike or chair, out team thought it would be a bit more exciting and challenging to go for an artificial hand. We chose an artificial mechanical hand that one of our groupmates had found by browsing google patents. Here is the link to the patent itself, and below is one of the drawings from the patent to show you what we were working with:
This choice was particularly challenging since we had no physical specimen from which we could get real measurements. That meant it was up to us as a team to decide on a few specific overall dimensions and to coordinate the dimensions of every part in order to make sure that they could still all interface, connect, and assemble. It took some deliberation, but we were able to agree upon a list of parts that realistically represented the hand as a whole when together. Having limited drawings was a tricky aspect of this step since it was not always clear where one part ended and another began. Regardless, our part list in the end allowed each team member to be responsible for their own subassembly.
I myself am a huge fan of any kind of gear interaction, so I was responsible for the gears, belts, and how they interacted to move the fingers. This design is actually very clever in the way it uses a spur gear in the palm to drive a partial ring gear at the base of the finger. The shell-like pieces which make up the bottom half of the finger act as a linkage arrangement which allows the top half of the finger to curl in as the finger is driven inward. I actually designed the gears myself for this hand without the help of any gear generator tool. I drew a tooth outline with specific dimensions to allow it to pattern itself around a circle. The ring gear was a similar concept but with a slightly altered shape and spacing.
I was also in charge of the assembly of the hand once all the parts were designed. It was exciting to see the pieces come together and fit cleanly. Luckily very few pieces needed shape or size tweaks to fit into the assembly, but when a problem arose I was able to coordinate with the person responsible for that part to make that alteration. I was also able to mate several of the pieces and develop a relationship between the movement of one part and the movement of one it touches. This allowed the pieces of the assembly to be manipulated more easily. For instance it was set up so that the outer surface of the spur gears and inner surface of the planetary gears stayed in contact, meaning if you rotated the spur gear, the planetary gear and finger would move in response. Overall this project was very interesting to work on and helped develop the CAD skills of everyone involved. Going for a more challenging object to model was a tough decision to make in the beginning but made the work more valuable and rewarding in the end without a doubt.
Here is what the finished hand looked like!