Concept 9 "twister": Issue with completing stroke

Currently experiencing a problem with completing the stroke for the 'twisting' or 'wringing' design. Using 4 struts, the AMBU seems to become pinched before fully deflating. This seems to result in a high turning resistance which the motor cannot overcome.

Currently exploring two solutions:

• reduce the number of bars to 3, which would eliminate the pinching effect
• add extrusions to the bars at the midpoint to cause a detent in the surface of the AMBU, directing the energy to cause exactly three folds in the bag