W: We are making models of hands to appreciate the biomechanics of force in the hand where the force is generated far from where it is applied. H: We first used our own hands as a reference. We traced out our hand on a piece of paper and marked a line on the areas of our fingers where the joints were. We got into partnerships and chose which partner’s hand to reference from. I was partners with Kobe and we modeled our hand off of his drawing. We got five straws for the fingers, five pieces of string that were all approximately 1ft long, two foam plates that connected the straws together and formed the wrist and knuckle area of our hand, and five rings to tie our strings to. Using the outline of Kobe’s hand, we got a straw for each finger, lined it up with the drawing, and marked the areas where the joints were so we knew where to cut. We used x acto knives to cut diamond shaped slits to represent the joints, this is crucial for making the fingers curl and move. We didn’t cut all the way through, we just cut about .75 inches in. If you don’t cut in deep enough, it made it harder for the force from pulling the string to make the fingers curl. We then cut a small slit at the top of the straw, so when we thread through string we can tie a knot and have it put there. We got the two separate foam plates and pushed our straws through. We made sure to align the lengths to what a normal hand would look like, bringing the pinky and thumb down more to shorten them and making the rest of the fingers a bit taller. We taped all of it in place to prevent the straws from slipping through, we wrapped tape around all the fingers together. Using our string, we tied knots at the end of all of them and began to thread them through each of the straws. Once everything was in place, we tied the rings to the strings, making sure all of the strings were at the same length. We later changed this to tying all the strings to one ring because it was difficult to pull on all five rings and they kept slipping out from the strings. We then pulled over a glove onto it, it looked much more like a hand after that. O: I realized how crucial the joints were to be able to actually move the hand. The slits on the fingers were responsible of curling and picking up the ping pong balls. I also realized that the force does not come from the fingers themselves but from the strings being pulled on the bottom near the wrist, not exactly the place where it moves. The first difficulty I had was when I was cutting the straws for the fingers. I would accidentally cut them lopsided, making the diamonds not aligned straight on the straw. When we threaded yarn string through the straws and began to pull on the string, the fingers would curl to the side and not directly down like we wanted. I realized how important it was for joints to be aligned, everything had to be uniformed in order to move correctly. Another difficult part was inserting the straws into the foam plates that connected all the straws together and threading the strings through the straw. Even though we had slits to keep the string in place while we pulled down on them, the string would often fall through. It was also hard for us to put the string through the straws in general because they would get stuck on the diamond slits that we cut out of the straws.
A: We thought that our hand was pretty successful. We were able to pick up all the ping pong balls and we were able to put them into the cup. With the materials we had and the time we had, I thought that the activity was successful and the results were effective in displaying how our hands function. I don’t think there is much to change about this process, I thought the model accurately represented one basic function of a hand; curling the fingers down. But if we were to make a more complex model maybe we can have more joints or other parts of the straw hand to have it not only curl but move in other ways. The model is limited to just how a hand would look just straightened out but maybe there can be more ways to move like fingers that can elevate upwards instead of just curling. I also think that we can make the fingers thicker, like wrapping something over the straws before putting the gloves over to have stable, firm fingers with “flesh” or “skin” over the thumbs.
1) What makes the human hand unique? The human hand is unique because of our opposable thumbs that allow us to touch our other fingers, therefore allowing us to grasp and manipulate different objects. Compared to any other primates and species in general we have such an advantage. It allows us to develop our fine motor skills and that has led us to being the dominant species on earth. We have a lot of power over our hands and we are able to use our hands for things like building and writing and so much more. Our hands are unique because they are the reasons why we have such an advantage in our world and they just allow us to do so much. 2) What other parts of the body might use a system similar to the hand? The foot is definitely similar to the hand in the way that there are five fingers, they can grip in some way, there is a variation in size of the toes and the fingers. Toes can sort of grip similarly like the fingers can, but they are not very useful to us like the hands are. The difference is that the gripping function of hands is a lot more pronounced. Toes can definitely curl like hands do and they can sometimes grip things too, but there is not much freedom in being able to pick up things or manipulate things like we can with a hand. The big toe can’t exactly pull in to touch the other toes like the thumb can. 3) What machines that you know of might use a similar mechanic and describe how they are similar to the hand? The first thing I think of is crane or claws inside those arcade machines. The objective of that game is to pick up a plush toy or ball with the crane and it’s three claws. I think the claws are very similar to human fingers in the aspect that they are made to touch each other to grab things. When you press the button the claws close in together and try to grab the plush in between it. It is similar to our human hand touching one another with opposable thumbs in order to grip things. But of course the claws don’t have joints to bend or curl anymore, and there are only three fingers that are all the same size compared to our five fingers that are different sizes.
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