Frame Design

      The frame design was an exciting part of the process because with all the other physical parts we were mainly assembling things that someone else had created. However with the frame we would be able to design it exactly how we wanted it to be and create it ourselves.

SolidWorks Model
      We decided that we would 3D print the frame because it would be the cheapest and most effective method to accomplish our goal. To do this I first built the model in solid works. The heavier components that went in the frame would be the battery, Arduino, breadboard, and the receiver in decreasing order of weight. It was going to be important to design the frame in a way that the weight would balance. My original idea was to build a frame that had separate compartments for each component. The battery, being the heaviest with nothing else to counter balance it, would be in the middle. The Arduino would be off to one side of the battery with the breadboard and receiver balancing it on the other side. This design would give us plenty of room to work with the components and wire them together. The problem with the design was that it weighed too much. In order to keep our drone fairly functional the mass needed to stay under 800 grams. The mass of this design was somewhere around 600 grams. With the added weight of all the components the drone most likely wouldn't be able to get off of the ground without the motors constantly running at max velocity which would make our potential flight time very short due to battery constraints.
      I started with a new design that would be much more efficient. In the new design everything would go in a single compartment with the breadboard on bottom, the Arduino on top flipped upside down, and the battery sandwiched between the two with the extra components wrapped around the sides. This cut the frame mass down to about 150 grams.

Motors Mounts
     The other problem we faced was figuring out how to attach the motors to the frame. The motors came with four mounting screws but they were very small and short so I didn't think a 3D printed frame would be able to print a hole precise and small enough to hold the motors in place. To counter act this I designed the arms of the drones with prongs and then bought a thin piece of sheet metal that I planned to drill holes into for the mounting screws and then I would bend it around the prongs and glue it in place. This would give us a solid mounting surface while still allowing us to take the motor off if necessary.

Assembly
      Once these design parameters were established I went ahead with the 3D printing. Due to size constraints of our printer the model had to be cut up into four pieces and then glued together. I was a little worried about weakness in the joined areas however the Gorilla Glue that I used was extremely solid and held everything together excellently.
      Bending the sheet metal strip around the prongs created some difficulties. It was hard to get good 90 degree bends in the metal at the right spot so that it would fit around the prongs correctly. This led to slight bending of the metal at the spot where the motors were mounted. The motors had to be adjusted so that all of them would be level.
      The compartment needed a removable top so I used Velcro to attach the top to the rest of the frame.

      Here is a picture of the final frame assembly.