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In addition, the current helical guide configuration considerably limits the range of motion of the user's elbow. This is because the analysis we performed did not account for the considerable size of the slider. By the time the user's wrist has gone through a quarter rotation, the user's elbow only goes through a 90 degree bend. This may be desirable in some cases, but in others, the user may feel overly confined by the mechanism. It would be prudent to consider the needs of the specific patient when designing future iterations.

Lastly, we need some way to prevent the slider from sliding off the railing. We considered adding stoppers at the ends of the helix, but this was left out for now to provide the prototype with as large a range of motion as possible. However, for users who are not able to finely control their arm motion, the slider could easily slide off and become useless.

Upper Arm Connection

The connection for the upper arm does not provide a true “ground” for the mechanism. As the user flexes his/her arm, the bicep will expand and contract beneath the upper arm connection. The current version of the connection grips the arm too firmly and shifts up and down as the arm flexes. This is uncomfortable for the user and could potentially pinch veins on the side of the arm. The Using the current components, more foam padding could be added. Alternatively, the user’s arm should could be wrapped in foam and then fitted with a larger version of the connector. This would then be locked into place around the foam.