Overview
EN1: Applications in Engineering - Biomechanics
Tufts University, Fall 2021
This was a nine day group project for "Applications in Engineering: Biomechanics". We were tasked to create a mechanical hand that moves when cords are pulled.
Tufts University, Fall 2021
This was a nine day group project for "Applications in Engineering: Biomechanics". We were tasked to create a mechanical hand that moves when cords are pulled.
Initial Prototyping
After creating a cardboard proof of concept, we dove into the mechanics of modeling curling fingers.
Our main focus was to identify how pulling strings could be translated into curling fingers. We chose to model off human fingers, using three sections with two joints per finger. I experimented with how weaving the string different ways through the sections resulted in curling motions. Three of these iterations are shown to the right, with the final string configuration displayed in the last photo. We decided to create three identical fingers and one "thumb", arranged like a claw so that the mechanical hand had better grip on cylindrical objects. |
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Refining Details
- In order to assist with the curling motion of the fingers and prevent the strings from slipping, rubber bands were added around each joint.
- The tips of rubber gloves were added onto the top-most joint of each finger in order to provide extra grip.
- A braided section of string was used to secure the mechanical hand to the user to allow a tight fit and adjustability between users.
- In order to reduce concentrated stress on the user's fingers when pulling strings, each string was attached to a small "finger sleeve" which snugly fits on the user's fingers.
Final Prototype and Testing
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The final prototype was capable of picking up and carrying a (mostly empty) plastic water bottle.
A hand dynamometer was used to measure the grip strength produced by the mechanical hand. The first trial yielded 6N, and the second trial yielded 11N. |
Reflection
This project increased my confidence in rapid design, especially doing so in a team environment. Given more time to refine this prototype, I would experiment with using different types of string as well as different angles of the fingers to increase grip strength. Additionally, the prototype did not extend/release grip once the strings were pulled. I would implement a different rubber band system to prevent over extension of the fingers and allow the hand to return to a neutral position. From a usability perspective, I would iterate the design to be able to put on with one hand, rather than requiring another's assistance.
