A measurement mechanism at last! That’s right, this week my team was finally able to test all of our rotation measurement mechanisms and pick one: the internal tab mechanism shown below.

We decided on our choice after a decent amount of testing. First, we defined three design objectives that we wanted to target: torque (as a measure of ease of use), precision, and durability. Of course, safety was a constraint. For each design objective, we conducted a specific test.

In order to measure torque, we hooked a spring scale to the edge of the rod platform and pulled until the tab moved. The test was recorded on slow motion camera and the very first force reading was recorded as a measurement of the minimum torque needed to move the tabs.

We also wanted our device to be accurate but without reliable wrist and elbow attachments, we decided to test precision instead. Each ring measurement mechanism was strapped onto Jeremy’s arm and tested five times, with the angle of rotation recorded. The standard deviation for each measurement mechanism was then calculated and compared.

Lastly, we evaluated the durability for each measurement design concept through a team discussion where we analyzed the severity and number of failure points. After using all of our testing data to back up our Pugh scoring matrix, we settled on the internal tab mechanism as our final design solution for the rotation measurement system.

We ended the week by starting on brainstorming and screening/scoring for the wrist and elbow attachments, our next two design blocks which we’re tackling at once.

In other news, Borgestein left for Malawi this weekend. Since he was on a shorter technician program, he’s returning a few weeks earlier than the other Malawi students but I will still miss him. I enjoyed figuring out the laser cutters and 3D printers with him.