Under Pressure: Week 3

During class this week, Isaac and Max worked on Solidworks files for the project. They concentrated on finishing the foot brace from the 3D scans of Isaac's foot, as well as creating the motor casing that would attach to the brace. Jake and I (Kim) went to the shop to create a mount that the force transducer could be mounted to. The mount was created out of a large block of steel scrap metal and holes were drilled/counter-bored into it so that screws could be inserted into the mount and attach to the force transducer (while sitting flush with the surface). This mount can be seen in the picture below.

Picture showing the force transducer mount with counter-bored holes (this side would be facing down once the force transducer was screwed on).

The next day we met as a team to continue working on Solidworks and also test the motor with the new mount for the force transducer. We anchored the force transducer to the plate and then used a nut to tighten the force transducer shaft onto the motor mount. However, the force transducer shaft sheared off while we were tightening the nut. This was extremely unfortunate, as this rendered the force transducer inoperable.

The nut with part of the sheared off screw stuck inside it.

The sheared-off shaft/post on the force transducer.

Since we could no longer use the force transducer (and we had already done testing and gathered data using the tachometer alone), we emailed the professor regarding next steps and continued working on the CAD files. The finalized assembly (which includes both the leg brace pieces and the motor casing) can be seen in the images below. The large cylinder shape is the motor casing, which serves multiple purposes. Not only will it help prevent the weight from hitting or injuring something if it were to break, but it will also prevent the astronaut from accidentally hitting the motor against things while moving around within the spacecraft and working. The two halves of the leg brace provide a sturdy surface to attach the motor to. Since the shape is customized to the user's leg, it will hopefully be more comfortable to wear while also limiting the amount of movement of the brace. The two parts of the brace will be cinched down with Velcro straps. The parts were all sent to Josh for 3D printing (the leg braces requested at 70% infill, and the casing at 30% infill).

This image and the one above show the leg brace/motor mount assembly.

Dr. Gordon was able to meet with the team on Thursday morning, where we discussed the broken force transducer and next steps for the project. Dr. Gordon suggesting emailing the company to see how expensive and how long it would take to repair the existing force transducer. This was done, with pictures of the broken shaft and the diagnostics screen sent to the company. The technician who answered hinted that the force transducer was not being used as intended. He did not specify how long the repair would take, but said that it was more complicated than it seemed and that he would need to wait for parts from the manufacturer. This repair would also require mailing the force transducer to Utah. We will discuss this in class with Dr. Gordon before sending it out.

On Friday, Max met with Dr. Kim about possibly using his force plate or force sensor for our testing while we do not have access to the force transducer. The rest of the team picked up the 3D printed parts from Josh and went to Wes' shop. We cut out small squares of sheet metal that will eventually be used as the inserts to help anchor the motors to the foot braces. Jake and I ground the squares down to the desired size (~40 mm^2), while Isaac sanded part of the leg brace, as there had been a misprint. We also drilled holes into the square inserts for the motor's screws.