Feed System

The feed system allows for footballs to be loaded with precision without another person present. More description follows below!

The pusher mechanism consists of a contoured piece to cup the football and a contoured piece to guide and push the back of the football. This allows the football to be inserted into the launcher system with precision and consistency across launches. The pusher interfaces with a lead screw attached to a stepper motor (see Electrical System). With the lead screw, we translate rotational motion to linear motion. This allows the pusher to feed the footballs into the launcher without someone actively pushing them, making the system able to have a single operator. We chose to use a lead screw because it was more affordable and accessible than a linear actuator and we had experience working with stepper motors.

We decided to make this piece out of PLA using a 3D printer. This is for a couple of reasons. The contours of the pusher would be difficult or impossible to achieve with accuracy on many machines. 3D printers can easily and accurately recreate the geometry we need. We also chose PLA because this piece is experiencing minimal load. The primary load on the pusher is the weight of the football and any force from the lead screw. To make this part printable with minimal supports, we broke it into a few different pieces and assembled it after printing. Without breaking up the part, we would have a lower quality print and iteration would take longer due to the longer print time. 

The pusher's lead screw housing was made of laser-cut acrylic due to its ease of manufacturing. Finger joints between the pieces of acrylic allowed for quick assembly. 

During the design process of the pusher, we did analysis with a free body diagram and hand calculations to ensure that the pusher could withstand the weight of the football. The support on the middle contour reinforces the part if unexpected load beyond the football is put on it. We also considered the thickness of the pole holding up the back contour and the bending moment that the pole could take. As a result of this analysis, we determined that our pusher would withstand the loads present in our system and 3D printing would be a suitable manufacturing method.