Engineering Projects/Rubberband gun/Howard Community College/fall2011/550 JHK

Electronic Sections Expected

Problem Statement

How can a rubberband gun be made using Legos that allows efficient firing and quick reloading?
How does each different models of trigger systems work and how can they be built?
How to build a gun with the trigger system that can fire sequentially?

Team Members

Summary

A final product was successfully completed throughout the past four weeks. We set out to create a rubberband gun out of legos that can fire one or more rubberbands at once. The trigger system of our major product was made out of gears and works extremely well. It can even be winded, thus allowing our rubberbands to travel longer. And, unlike the other materials such as glasses or woods, our materials are light and yet durable even in intense stretch and pulls from the rubber-bands. The final product did not meet our ultimate goal but, helped the team to be able to push further on the project to get to the ultimate goal of creating sequential and gatling guns.

Below is the link to our weekly reports:

Weekly Reports

Poster

[Video of Crossbow firing 5 rubberbands]

[Video of the prototype gun firing a rubberband]

Sketch up of sling shot

Sketch up- Part of the trigger

Story

At the beginning, we found videos and samples of rubber band guns online to get an idea of how it works and what kinds there are. We found many different models and trigger systems and decided to start off with designing a crossbow and a pistol gun. The parts used were Lego pieces because it is easier to assemble and disassemble and they are readily available. The base for the guns were sketched on the computer and the bases of the guns were made from this. The difficult part was making a way to release the rubber bands efficiently and having a trigger to control it. After going through many possible solutions, we found a way to release multiple rubber bands using the pistol model and launch a projectile using the crossbow. The trigger is basically a lock that prevents the gun from firing when loading a rubber band and the lock is pulled to release the rubber bands. But, our professor gave some criticism that the main goal of this project is not to shoot numbers of rubberbands at the same time but to shoot them sequentially. Thus we started to push toward making sequential firing guns. The guns we had however, had a trigger system that had very limited amount of possible improvements that can be done to it and we came up with whole new design using multiple gears. The single gear can be used to load multiple rubberbands on each slot it has and also to rotate/release them and even stop each other when the rubberbands are loaded. We constantly pushed to improve upon this new design and at the final week, we were albe to come up with another trigger system that can build/test for the continuing team.

Decision List

Week 1

The groups met for the first time and discussed what materials we are going to use and what are available. Also looked at the videos on the web to get motivated and also think of what kind guns we are going to make.
We focused on gathering resources and materials.
We started easy with building a pistol and a crossbow.
We were struggling with the trigger systems. This made us to start researching for the trigger system.
We were able to come up with our first trigger system. We applied it on the crossbow and the pistol thus the single shot was tested.

Week 2

Studied more on the trigger system and looked to design more different and effective trigger system
Built upon the first trigger system we strengthened and improved further on whole structures of our guns
Our guns were improved to the point where we can start loading multiple rubberbands and fire them at the same time
Presented our project to the class and got the feed back that we need to start pushing towards firing rubber bands sequentially
New ideas of different trigger system came up and the group started to improve more and build another deisgn that can overpower the previous trigger and gun models

Week 3

Tested the guns we built so far to understand each gun's strength and weakness so that all the members know what to improve on those guns
Came up with whole new design of a gun along with whole new trigger system. The new design was the prototype for the further improved guns that will fire sequentially.
Tested out the new gun and it proved outstanding among the guns we have.
The new gun is improved within its trigger system: It is improved where the rubber band can be adjusted to get further stretched for increasing the power of the gun.
Another presentation was made in class to not only show our current progress but also to show our new design which allows us to start pushing towards building gatling gun and/or sequential firing guns

Week 4

With the time running out, there was no new designs built along with scarce resources for the further construction as well. This will make the continuing team to bring in more pieces.
The guns were further examined and some unnecessary parts were removed and added new better features with the spare parts we took out from unnecessary parts.
Started to design and plan on what kind of designs will the continuing team will make.
Another software for the 3D designing was found and it will be used to design for the continuing team.

Material List

Legos
Rubber bands

Software List

Chrome Browser (to research models)
Google Sketchup (to draw model guns)
3DTin (From Google Chrome Apps)

Time

Week 1, 4 hours of work was done by each student researching different models of rubberband guns and constructing prototype Lego rubberband guns.

Week 2, 5 hours of work was done by each student researching tirgger systems, improving on prototypes, creating another prototype, and uploading videos and pictures online.

Week 3, 4 hours of work was done by each student designing different guns and trigger systems, improving on the prototypes and uploading sketches online.

Week 4, 4 hours of work was done by each members of the team. The last week was spent to improve the latest gun model we built rather than trying to build new guns. But, we came up with another model that we are going to build for next project. Another Software was found that can help with sketching the designs, 3DTin.

Total over 17 hours of work was done for this project

Tutorials

Below is a website that jump started our research for a successful trigger system. Maybe the next team that works on the gun can also start from here.

Trigger system animations

Below is video tutorials of google sketchup. Sketch up is crucial when creating the preferred design of the gun. It allows you to change the small details on a gun

Sketch-up tutorials

Next Steps

Since a pistol was successfully created, the next step would be to build a gattling gun out of legos.
We're not only going to push to make a gatling gun, but also pistols or rifles shoots rubber bands sequentially. The main focus is the trigger system which we have improved drastically.