Step 4: Build your paperclip pen hopper and add a timing bump switch...

Building the hopper...

The hopper is another disposable ball point pen with the ballpoint pen and ink well assembly taken out. I used the cap to prevent ammo from bouncing out.

Building and attaching bump switch timer to the barrel...

1. Take a large paperclip and bend the small "U" away from the large "U" into what looks like a number 8.

2. Bend the paperclip into an "L" shape as pictured. 

3. Tape the small "U" to the top of our barrel with your favorite tape of choice. Masking tape works well for this.

Building the hopper holder...

1. Take one large paperclip and and straighten.  

2. Than using needle nose pliers bend into a u shape.  Leave plenty of length on the uprights of your "U".  They will stick in to the corrugated cardboard and allow us to position the hopper right where it needs to be.  The extra length also allows it to be positioned far enough away so that the barrel will not swing into our hopper holder. 

3. Take another large paperclip and straighten.

4. Using the needle nose pliers wrap one end around the corner of the "U" we just made.  Wrap enough time so that the two paperclips will not shift relative to each other. 

5. Bend the paperclip we just wrapped around our "U" into an "L" shape. 

6. Take another large paperclip and straighten.

7. Wrap around the "L" we just made to extend the length of the "L" and give you enough to wrap around the hopper enough times to secure it tightly.

cool project :). can you make more airsoft traps?
Made something similar once using the little broadcaster out if a seed spreader and a motor from a rc car it used a funnel for a hopper with the trigger being at the base of the hopper so when the trip wire was pulled it both turned on the motor and dumped the bbs onto the spinning seed spreader it would cut through a cardboard box if you loaded it with pop corn kernels
I have a birthday card with a spinning candle it will work good for this purpose
You are brilyent
I just finished building one from an old rechargeable air mattress pump, and reusing some of the shell it came out looking nice. I loaded it up in a box and tapped the wires together, and in that split second, it emptied the hopper. I used a 3rd pen cartage to hold the center wire up and model glue to fuse the hopper to the barrel, and the guard to the shell. Now to make a dead-man switch muh wah ha ha ha
I like it! I hope it defends you well.
I apparently set something on top of mine, making the hopper jiggle, so I put a little more model glue to hold it into place, and being the inpatient person that I am, I started it up, and ended up with "cobwebs" shooting from it. something that I am going to have to try for halloween affects :D
I'm going to tinker with it, i I remember correctly, mythbusters made something like this, and had it so that it would shoot out of one spot... now to just drink aa 2l of soda to harvest it's bottle<br>
Hey, could you a few more pics on this step?
I made a hole just behind where the balls were to feed in, and it works just fine for me.
hey its good but you need more clear pics and more details because i cant figure out how it launches the balls....
Sorry, i might sound a bit snotty here, but it seems my physics lessons have finally come in handy. Centrifugal force is not real, you may be referring to centripetal force, is the force that's causing the pellets to shoot out of the pen. The pellets want to move in a constant speed straight line, but the barrel of your pen is pushing against the pellet while it stays in place when the pen rotates, causing the pellet to fly out of the pen. Just like those amusement park rides where the ride spins around really fast, no force is pushing you out, its just the force of the wall behind you that is constantly pushing you in a circular direction, your actually accelerating toward the center of the circle. This is referred to from newtons first law, objects in motion or rest want to stay in motion or stay at rest unless acted upon by an outside force. Yay physics!
Umm... Not to be snooty either. Yes you are right, technically speaking centrifugal force is a fictitious force. However it is very common to use the term centrifugal force when describing forces applied on an object from it's frame of reference.<br> <br> Or in other words theoretically speaking the air soft projectile from it's frame of reference is experiencing a centrifugal force, or a force causing it to move away from the axis of rotation of the machine gun motor. Centripetal forces are used to describe forces pulling an object towards the center of rotation.<br> <br> I appreciate the physics theory here. But it has become quite standard to reference centrifugal force in different mechanical systems that utilize rotational forces to fling an object outwards. For example a centrifuge is a device that references centrifugal force in the name, or describing how the system works.<br> <br> <a href="http://strangengines.wordpress.com/2008/05/01/benjamin-reynolds-centrifugal-gun-1830s/" rel="nofollow">Here's an example</a> of another machine gun invented quite some time ago that references centrifugal force.<br> <br> Regardless of how fictitious centrifugal force is in physics theory, according to laymen's terms it exists enough to be a common way to reference mechanical systems that utilize rotational forces to fling object outwards. The centrifugal machine gun is intended to fling projectiles outwards, not pull them inwards. Otherwise I would name it a centripetal machine gun. But thanks for being thorough.
relly coll but need beter pictures when you add the moter becouse i cant figure out how it lunches the pellets
SWEET!!! Cant wait to build it!!

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Bio: I'm a product designer, who believes in working backwards. Instead of taking technology and seeing what problems I can solve with it, I take ... More »
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