Design Considerations & Research

Since sailing is the primary use of this device, we wanted to avoid electronic components completely and create a purely mechanical device that would be durable with a fast, accurate gripping mechanism. We also wanted to take advantage of the natural movements of gripping a rope to allow the mechanism to work with the user instead of forcing the user to adapt to the limitations of the mechanism. In order to meet these constraints, we decided the input to our mechanism should be wrist pronation, a simple motion that naturally occurs when reaching, gripping, and pulling rope. The force produced by the wrist pronation would then be mechanically translated into a gripping force. Because of the intense aspects of the scenarios in which this device will be used (environmentally and physically) we wanted to make this device out of parts that could quickly be disassembled and reassembled in case replacement parts were needed.

Constraints given to us by Paul, the person for which this device was created, include:

-    Be able to grip rope ranging from 3/16” to 3/8” diameter

-    Be able to be used in wet environments without malfunctioning

-    Be able to grab and hold weight up to 80 lbs

          These constraints gave us a perfect starting point in the design of our device. Knowing that we wanted to use wrist pronation to actuate the gripping motion, we needed to figure out how much weight an average human wrist could rotate to determine what the mechanical advantage of the device needed to be. Through our research, we found that the wrist alone is capable of rotating the amount of force needed to grip the rope^[1], meaning that our mechanical advantage simply needed to compensate for any friction or resistance in the device.