Eagle I: Mechanical

(Competition tasks)The mechanical system on Eagle I consisted of an aluminum 6061 t-slot frame, two waterproof pelikan case enclosures, a pneumatic claw, pneumatic torpedo system, a servo-controlled marker dropping mechanism, and foam for buoyancy control. These systems interact to perform tasks during the competition, such as lifting a lid off of a box or shooting torpedoes through holes. Since this was the team's first year competing, we explored different methods of creating these systems by prototyping everything several times.

Eagle I

The image to the left shows Eagle I's mechanical frame and pelikan case hull, along with 8 thrusters mounted to the frame for movement in the water. The red parts are 3D printed brackets. In addition to the thrusters and foam shown mounted to Eagle I's frame, not shown in the photo are the mechanical claw, torpedo system, and dropper. The claw system consists of a pneumatic piston actuator and a sliding mechanism for opening and closing the claw, all made of stainless steel. 

Claw stress analysisClawClaw slider mechanism​When air enters the actuator, the piston on the inside pushes down onto the aluminum slider mechanism. This slider allows the aluminum claws to open and close whenever necessary. On the right is a screenshot of Solidworks stress analysis run on the claw. We ran a simulated 10lb load on the claw, shown by the purple arrows. The analysis shows that the claws can easily hold 10lbs without signs of stress.

Dropper system

Dropper CAD

The marker dropper system is a payload release mechanism, consisting of a waterproof servo motor pulling a pin to release each object onto the target when actuated. This system completes the objective of hitting a target in the bin. Originally, it was to be integrated with the pneumatic system, but this approach allowed for dropping a payload in a more controlled manner. Machining the pins connected to the servo was more difficult then expected. Since the size of the pins is ¼” diameter 316 stainless steel, these parts are too small to mount on a jig, and too hard to cut by hand. 3D printed pins were substituted in the meantime and were sufficiently functional, so these were used permanently. 

Marker analysisMarker diagram

Markers, when released, should sink in the water to hit the targets, but due to the density of many prototypes, the markers would float instead. With limited manufacturing capabilities, the solution was to implement a cavity inside the marker for a ballast to adjust its buoyancy.

The torpedo system is a pneumatic air system, which consists of check valves and pressurized air ejecting a torpedo. It provides enough initial pressure to fire the torpedos at the required rate. Original design was for the torpedo to be electrically propelled, but the current system is more robust. We struggled to create torpedoes with the proper buoyancy, and we had some difficulty modulating the air pressure to the trajectory would be accurate. The torpedoes flow with little resistance and with minimal straying from the desired trajectory. 

Torpedo flow simulation   Torpedo CAD

 

 

Torpedo system