Engineering Projects/Rubberband gun/Howard Community College/fall2011/501 Rubberman2

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Problem Statement[edit | edit source]

Our goal here is to create a working gatling gun that fires rubber bands as ammunition. It needs to be fully automatic and very similar to its military counterpart.

Team Members[edit | edit source]


Summary[edit | edit source]

We received the project of creating this rubber band gun. The biggest issues that were evident in the previous teams were that the gun was getting stuck and not actually shooting the rubber bands. We created a design that will eliminate those problems and is a very simple yet effective plan to make this gun with as few issues as possible. We had initially gone with the same design as we did in the previous four week project session, but decided to change the design as we quickly realized that it was not a good design for us to work with even though we had seen examples of it working. We decided to go with the idea of a gun like the Disintegrator!

Poster[edit | edit source]

This is the poster for the second session of our project

Story[edit | edit source]

We started out thinking this will be a easy project looking at many designs and going with the one we thought was the best one. we started to construct the project and soon figured out that it is much harder than it looks as we faced many difficulties. We had initially assumed that the design we chose, a cardbord cylinder would be perfect for it. Thinking about its light weight and already round shape we decided to build the gun of the cardboard cylinder. Then later we fell into sea of troubles, From finding the right materials, getting the materials in time. The barrel not spinning smoothly. Not finding the right motor to spin the barrel. The barrel being to fragile to handle all the force of the rubberbands and all the cutting and constructions required. We decided to abandon the first idea and go with a different deisgn called the Disintegrator. We found many videos of it online and it seemed very promising. Taking the lead, one of our team members orderd the parts of his own money and got a protype of the gun working within one week. We are hoping to get atleast the barrel done. so we can have some sort of an idea for the next team and provide them with as much info as possible so they do not make the same mistakes as us.

Decision List[edit | edit source]

1. We decided to closely follow the design of the Disintegrator.
2. We are using a special firing mechanism made specifically for rubber band guns.
3. We are going to attach ten of those to a circular barrel and attach that assembly to a drill.
4. We will have to have some sort of wedge-like trigger to disengage the locking part of the firing mechanism.

Material List[edit | edit source]

1.: 8ft of 1/4" dowel
2. 8ft of 5/16" dowel
3. 4 1/4"x6x2 poplar plank
4. 6'x8' CDX yellow pine ply wood
5. Magnum Corp. 10-count trigger set with template
6. Rubber bands.
7. Wood glue
8. 3/8" x 16" all-threaded rod
9. 6 nuts
10. Black & Decker 18V hand drill

Software List[edit | edit source]

We have used no software for this project, and we see no practical application of software in the future of the project.

Time[edit | edit source]

In class time is the best use so far, because the whole team is already together and we are all in the lab with all the tools needed.In addition to this in class/lab work time, the group decided to do indiviual work as it seemed to best fit everyone's schedule. The various busy schedules prevent us from all meeting up at other times during the week. All of our team members spent at least four hours a week working on this project.

Tutorials[edit | edit source]

  • Firing Chambers

1.) Using a band saw, cut 1/4"x6x2 poplar planks into twelve 6"x2" sections. Set aside remaining wood.

2.) Use a drill press to drill three 1/4" holes into each 6"x2" poplar section in the following locations:

1 - 7/16" from the top and 3 5/16" from the right side
2 - 7/8" from the top and 1 29/32" from the right side
3 - 7/16" from the top and 1 1/4" from the right side.

3.) Use the leftover 1/4"x6x2 poplar plank wood to cut twenty-four 2"x1" pieces using a band saw. These are to be used as spacers between the poplar sections.

4.) Use band saw to cut 1/4" dowel into eighteen 1" long pieces.

5.) Insert three 1" long 1/4" dowel pieces into six of the 6"x2" poplar sections.

6.) Use wood glue to apply two spacers flush with the front and rear ends of each 6"x2" poplar sections with dowels inserted.

7.) Use wood glue to apply two spacers flush, stacked atop the previously applied spacers.

8.) Place sprocket on the front end dowel of each poplar section.

9.) Place a trigger on the center dowel of each poplar section. NOTE: The rear appendage of each trigger should be wrapped around and outside of the rear dowel. This dowel forces the trigger back into place once it has been actuated.

10.) Use wood glue to apply a second poplar section to each of the assembled firing chambers. Dowels should travels through both poplar sections effectively holding the trigger assembly in place. The spacers should provide 1/2" of space between poplar sections to allow enough room for trigger assembly to operate without restriction.

11.) Clamp poplar sections together and allow to dry overnight.

Firing Chamber Walls 6"x2"
A complete firing chamber
  • Firing Chamber Encasement

1.) Using a band saw, cut three 6" diameter circles from CDX pine plywood.

2.) Using a drill press, drill a 3/8" holes through the center of each plywood circle. NOTE: Be sure to measure correctly or the all-threaded rod will not fit correctly which, will create wobble.

3.) Lay one circle flat on work space then, using wood glue, apply the rear end of the firing chambers at even intervals around the outside edge of the circle. Be sure that the trigger assemblies are facing outward.

4.) Using wood glue, apply second circle on top of the front ends of the firing chambers. NOTE: Make sure the circle's center holes are evenly lined up so as not to create wobble.

5.) Add a weight to the top circle to press the firing chamber encasement structure together to allow the adhesive to dry properly.

6.) Allow the structure to dry overnight.

All 6 firing chambers
RBG Chambers
  • Barrel Assembly

1.) Using band saw, cut 5/16" dowel into six 11" sections.

2.) Notch one end of each dowel using a knife or file.

3.) Using wood glue, apply 1" of the non-notched end of each dowel to the center of each front spacer.

4.) Using wood glue, apply notched ends, straight across, to the third plywood circle. NOTE: Be sure line the plywood circle's center holes are lined up evenly to prevent wobble.

5.) Wrap a rubber band around the front and rear ends of the 5/16" dowels to allow adhesive to dry properly.

6.) Allow to dry overnight.

  • Completing Rotating Barrel

1.) Thread the 3/8" all-threaded rod through the center holes of each plywood circle, front side first. As the all-threaded rod passes through the first plywood circle, start screwing two nuts on the the threaded rod. One should fit flush against the rear side of the first plywood circle and the second should rest flush against the second plywood circle. The all-threaded rod should protrude 1 1/2" - 2" outside of the rear side of the third plywood circle.

2.) Screw a nut onto the backside of the all-threaded rod as well as the the front side.

3.) Using crescent wrenches, tighten both nuts together into the front plywood circle. The nuts should be tightened strong enough to hold the front circle firmly in place. NOTE: Do not over tighten and damage the wood.

4.) Using crescent wrenches, hold the nut on the front end of the second plywood circle still while you tighten the rear nut into it. This should hold the firing chambers firmly in place. NOTE: Do not over tighten.

5.) Insert the rear slack of the all-threaded rod into 18V drill.

RBG mounted to drill
  • Video demonstration


Next Steps[edit | edit source]

The next step in to complete in this project is to develop a mechanism that uses a wedge that moves forward to actuate the triggers as seen on Disintegrator. This mechanism will need to be attached to some sort of encasement around the rotating barrel assembly. This encasement should also have a handle installed on it for functional use. Once that is complete, one would need to develop a way to automatically reload the sprockets.