Design

Above, you can see a cut away of the Cephalobot. The robot takes inspiration from the indirect jets used by squid (cephalopods) for propulsion. The silicone bladder is housed inside the silicone body. At its end, the right side in the picture above, is a channel for an airline. The bladder collapses when it is subjected to negative pressure through the airline, this creates negative pressure in the body and draws in water through the intake valve which is designed to open only inward. The bladder can then be inflated with positive pressure. This in turn pressurizes the body, sealing the intake valve, and forcing water through the outlet valve. This creates a suction/jet cycle. The robot can be operated via a hand pump or through pressure and vacuum pneumatics.

The Nose cone was designed to reduce turbulence and back pressure on the robot during the jet cycle of actuation. Due to size limitations we could not make the fins as wide as we wanted to (which would have increased stability and reduced roll). Additionally, the nose cone was where ballast was added, the cone could be un-screwed revealing a housing for washers.

The bladder was designed with a bi-stable element, (the slight V you can see in the center of the bladder), though ultimately it didn't work as intended. No additional impulse, that we could discern, resulted from the inclusion of the bistable design element. However, the "bi-stable" feature did help guide the bladder to regularly collapse under negative pressure to the same geometry each time, which may have improved performance consistency. Further experimentation with bladder design would help draw firmer conclusions on this point.

The valve designs, as shown above, permitted one way flow through the body of the robot. The left set of images show the valves on their own, the right set of images show the valves mounted such that they can only open in one direction: for the intake, the valve can only open inward, for the outlet, the valve can only open outward. The designs were constrained by the cephalobot geometry and the requirement that they could open only one way. This meant the body of the robot needed to prevent the valves from opening the wrong way. Struts were added in key locations and the valves  were cut such that the cuts bisected the struts, ensuring that the valve would be supported in resisting "wrong way" flow.