Whew, all caught up! Now we are back to modern times. Fun fact about today, exactly 50 years ago, Apollo 11 and the Eagle LM and Columbia CSM departed for the moon. Anyways, back to the arm. This week wasn't exactly riveting design work, but it was critical research.
I'm going to be trying to build a replacement for a human arm, so I should get to know the general anatomy of the arm a little bit better. So far, I've been reading through a myriad of anatomy textbooks and 3D models of the human skeleton. A interesting resource I didn't think to check (until my sister suggested it) which has in fact, been surprisingly helpful has been figure drawing books. My favorite so far of this collection has been Figure Drawing For All It's Worth by Andrew Loomis. While the process of modelling and drawing a hand are entirely different (mainly because you can rely on measurements to thousandths of inches, therefor you don't have to work from general to specific as you would when drawing, It has greatly aided in my preliminary sketches of the arm. Slowly I'm approaching a "final" pre-CAD design. I'll elaborate a bit... -The arm will use 5x 9 gram PWM servo motors to control bend of each individual finger with and additional 2x servo motors being used to control the 2D positioning of the thumb. -20lb fishing line and or kevlar thread will serve as the tendons of the hand. -Elastics will be stretched along the back of each finger through a series of braces to return each digit to an extended position when so controls are applied. -Rotation and flex of the wrist and will be provided 2x high torque servo motors mounted in a standard gimbal assembly. -XT-60 and 3 wire communications connectors will be used to transfer all relevant control information from the forearm to the hand. -The forearm will include a 2700 mAh 3S LiPo battery and integrated discharge protection circuit as well as the micro controller which will be interpreting and processing signals. -A standard "bayonet" type mount will secure the arm to the socket. below the elbow. Lots of boring words that don't mean much without some drawings to demonstrate them. I'll be working on those on my two 8-hour plane trips in the next week.
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AuthorMy name is James Falcon Doss. I'm a member of Severn School's class of 2020 and have a passion for all forms of engineering. Archives
May 2020
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