In this week we finalized building prototypes for measuring ring design block. We built a total of 5 my models namely: interior tab, exterior tab(8 mm and 12 mm), concentric rings and Teflon stripped ring. Ideally, all the models have similar operating principle and general geometry. In general, the device have two rotating blocks; one rotates relative to the wrist while the other block stays stationery relative to the elbow. Two tabs slides in opposite directions on the rings corresponds to supination and pronation of the forearm. The distance between the tabs gives the angle of rotation.

We conducted three tests to help us in scoring our design solutions. We tested each solution against our design criteria which were amount of torque required to rotate the device, precision of the measuring tabs and durability of the models. During torque test, we attached a spring scale to the rotating rod and abruptly pull the rod tangential to the ring and record a video of each of fives uses per model. We played the videos on slow motion to analyse the displacement of the scale at which the rod started moving. For precision test, we attached a measurement tape onto each ring and let one member uses each model five times. We recorded angle of rotation of rotation of each use and eventually calculate standard deviation of the results of all five trials to see how consistent each device was. Lastly, during durability test, as team we analysed each model for number of failure points and severity of failure

On Thursday we gave a 15-minute presentation on progress of our project and imminent future plans and we concluded the week with brainstorming ideas for the wrist and elbow attachments design blocks.