Engineering Projects/Rubberband gun/Howard Community College/spring2012/p1550jbf

Problem Statement

Design and make a rubber band Gatling gun that can reload itself.

Team Members

Summary

The main problem past teams have had is that the rubber bands were getting stuck on each other and not firing off. We made a design that would simplify the firing process, but toward the end of the allotted time, it became evident that we would not be able to use our plan. The gun was built very closely to the design displayed below, which is very similar to the Disintegrator. design. The gun ultimately failed to work properly, however. The only reason for this is that we decided to make the Gatling gun out of cardboard, due to recourse and time constraints. The problem is that, when the trigger rotates around to the wedge, the frame is not strong enough to hold the wedge in place. This results in the trigger simply pushing the wedge out of the way and therefor not firing.

Poster

Top Left: 123D drawing of gun, Top Right: Finished gun in operation, Bottom Left: Firing Mechanism, Bottom Right: Cardboard Pieces

Story

The first step we took was to choose a design. as previously stated, we chose the Disintegrator design. After deciding on the design, we drew the rubber band gun, firing mechanism, and gear piece, in the 3D drafting software known as "123D". This process took an unexpected to two weeks to complete, mostly because nobody in the team had ever used 3D drafting software and had to learn it. When the drawings were complete, we bought everything on the materials list and began constructing the gun. The guns construction was completed during the fourth week of the project in time to present on that week's Thursday.

Decision List

[Design Decision]

This is the main decision we had to make. Every other move we made just followed the design we chose, except one. The only other decision was to use 6 total barrels as apposed to 12

Material List

- Two 45" x .25" x 40" sheets of shipping cardboard

- Box cutter

- Scissors

- Ruler

- Pencil

- Hot glue gun

- A large supply of hot glue sticks

- Rubber Bands (3.5 in/po. x .25 in/po.)

- Two Electric Screw Drivers

- "Magnum 12" 12 shot firing mechanism pieces

- 6ft of quarter inch wooden dowel

- 6ft of half inch wooden dowel

- 3' x 3' x .25" sheet of balsa wood

- Electric Drill

- Saw

Software List

Software that the team used during this project was "123D," which is a tree dimensional drafting program, and the Maker-Bot software. The 123D software war used to draw the Gatling Gun itself, along with the gear and firing mechanism box, and the Maker-Bot software was used to create the gears for the firing mechanism.

3D drawing of Gear in 123D

3D drawing of Firing Mechanism Box in 123D

Time

38hrs 45min

Tutorials

- Cut six 30cm x 10cm rectangles out of the cardboard (these will be the sides of the barrels)

- Cut one 30cm x 30cm square for the base

- Cut four 30cm x 6cm pieces for the vertical post

- Cut out 24 firing mechanism pieces, whose dimension can be fount in the software section link

- Hot glue the vertical post pieces into a rectangular prism, then to the base

- Cut four 10cm equal lateral triangles to be fitted to the ends of the barrels

- Glue barrels together like in the Gatling gun picture(triangular prism)

- Glue a 6cm by 6cm cardboard piece to the top of the vertical post

- Glue a 6cm section of the quarter inch dowel to the top of the post

- Glue the frame pieces together as depicted in the pictures

- Drill .25" hole into center of the frame and insert onto the post

- Cut two 40cm sections of quarter inch dowel rod

- Drill .25inch holes into the centers of both ends of both barrels and insert each dowel rod

- Drill the same holes into the ends of the frame and fit barrels like picture

- Cut six 14cm sections of half inch dowel rod, cut notches into one end of each section

- Glue one of these sections to each vertex of the barrels such as in the pictures

- Cut out 18, 4cm sections of .25" dowel rod

- Construct Firing Mechanism boxes by inserting one of the recently cut out dowel pieces into each of the three holes.

- Then put the gear on the isolated peg, and the trigger facing away from the gear on the middle peg. Then glue the other side on.

- Glue each firing box behind each .5" dowel on each barrel vertex

- Screw, and glue a screw into the end of each dowel from the barrels

- Attach created wedge pieces behind triggers

- Now you are done, all you have to do is screw the screw with the screwdriver after loading the rubber bands

Gatling Gun Pictures

Next Steps

The next steps in this project would be to finish the second barrels, and then to begin designing an automatic reloading system.