Unfortunately, today’s visit to Conestoga did not go as anticipated. The compression arms were printed just this morning, so there was no time to test the compression mechanism before arriving at the lab. Upon attempting to run the ventilation software, a number of problems revealed themselves.
Firstly, the arms are connected to the Servo spool via a string (one for each arm). The string was not setup beforehand, and proved to be difficult to setup accurately in a quick fashion. Also, it was difficult to ensure the string from each arm started taut, which is important as the servo is non-continuous, so every bit of rotation should cause compression. Therefore, a new way of connecting the string to the motor is needed.
Secondly, the Servo twists significantly when pulling the arms shut. This is due to the fact that the support is lined up with the servo body, but not with the spool, which is where all the force of the compressions is handled. This force generates a moment that twists the servo mount out of position. A new servo mount will need to be designed and fabricated which minimizes this unwanted effect.
Thirdly, when the bag is compressed, it is pulled in along its longitudinal axis, causing the back to slip off its support. It then gets stuck on the support, and causes some unwanted sideways forces on the design. A few options exist to fix this problem, but the one that is most likely going to be selected is a sloped piece on the inside of the back bag support. If the bag compresses too far, instead of falling off the support, it will slide down this slope, and slide back up after decompression.
Even though this visit to Conestoga was far from ideal, it at least pointed out some significant areas of improvement early enough that we can fix them before demonstrations begin.
