Pneumatic Pen Gun is Fit for James Bond

The James Bond franchise is well-known for many things, but perhaps most important to us hackers are the gadgets. Bond always had an awesome gadget that somehow was exactly the thing he needed to get out of a jam. [hw97karbine’s] latest project would fit right into an old Bond flick. He’s managed to build a single-shot pellet gun that looks like a pen.

[hw97karbine] started out by cutting the body from a tube of carbon fiber. He used a hacksaw to do the cutting, and then cleaned up the edges on a lathe. A barrel was cut from a piece of brass tubing with a smaller diameter. These two tubes will eventually sit one inside of the other. A custom front end cap was machined from brass. One end is ribbed and glued into the carbon fiber tube. The barrel is also glued to this end of the front cap, though it’s glued to the inside of the cap. The other end of the cap has 1/8″ BSP threads cut into it in order to allow for attachments.

A rear end cap is machined from Delrin. This piece also has a Delrin piston placed inside. The piston has a small piece of rubber used as a gasket. This piston valve is what allows the gun to operate. The rear cap gets glued into place and attached to a Schrader valve, removed from an automotive tire valve stem.

To pressurize the system, a bicycle pump is attached to the Schrader valve. This pushes the piston up against the barrel, preventing any of the air from escaping. The piston doesn’t make a perfect seal, so air leaks around it and pressurizes the carbon fiber tube. The Schrader valve prevents the air from leaking out of the pen body. A special machined button was threaded onto the Schrader valve. When the button is pressed, the air escapes; the sudden pressure imbalance causes the piston to shoot backwards, opening up a path for the air to escape through the barrel. This escaping air launches the projectile. The whole process is explained better with an animation.

Now, the question left in our mind: is this the same pressure imbalance concept that was used in that vacuum pressure bazooka we saw a couple years back?

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Fail of the Week: [Chris] vs. The Gorn

This week, [Chris] tips the scales but ultimately fails. He’s on the road, hacking through the Great White North and improvising from a poorly-lit echo chamber that happens to have a vise.

Knowing nothing about firearms (do you believe that?), he decided to build a BB cannon out of pure scrap. Several kinds of sparks fly, starting with a Hitachi drill-as-lathe and ending with a tiny cupcake sparkler. [Chris] proceeds to bore out some redi-rod by eyeballing it and offers helpful tips for course correction should you attempt same. Having centered the cavity, he drills out a tiny hole for a fuse.

His first fuse is of the crushed up match head paste variety. It burns kind of slowly and does not launch the BB. Naturally, Plan B is to make napalm glue to adhere Pyrodex pistol powder to paper. As you might imagine, it worked quite well. The wadding was singed, but still no joy. After packing her full of propellant, it still didn’t explode and merely burned out the blowhole. So, what gives? Insufficient barrel length? Should have used bamboo instead of redi-rod? Didn’t want it badly enough? Give us your fodder below.

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Airsoft turret has turn, tilt, and auto-feed to keep those BBs flying

airsoft-turret-with-laser-cut-parts

Yet another project that proves you need to acquire a laser cutter. This Airsoft turret rotates, tilts, and includes a hopper for ammo.

All of the pieces were cut from acrylic. The base includes a bracket which keeps the large rotating gear level by sandwiching it between the layers. That and the tilt mechanism are pretty straight forward. The module responsible for loading the BBs is pretty neat though. It uses a gear with round teeth the same diameter as the ammo. Once a BB is picked up it is forced upward into the tubing that feeds the gun. Get the full picture from the demo video after the break.

The one thing [The Liquider] is wondering about is how to provide feedback for the tilt and rotate functions. We can’t think of an easier way than to use simple rotary encoders. The Arduino Mega he wishes to use as a driver will have no problem interfacing with reflectance sensors and the acrylic makes it simple to mount this type of black and white encoder wheel.

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Easy to build parts tumbler you can add to your shop

This parts tumbler was easy to build but it still does a great job of rounding rough edges and polishing the surfaces of parts cut with a CNC machine. You can see that it mounts in a bench vise, and the cooling fans have a magnet which holds the tray in place on the anvil portion of that tool. Since you’re not constantly tumbling parts this makes it very easy to store the unit between uses.

[Neo7CNC] mounted the wooden tumbler plate directly to the motor shaft. This is done with the help of some aluminum stock which bolts to the round wooden plate, and has a hole and set screw for the motor’s keyed shaft. There are four wooden dowels which cradle the plastic coffee jug where the parts go. As a first test he used zinc BB’s that he already had lying around, but has put some steel ball medium on order for future projects.

It’s certainly more robust and powerful than the LEGO ball mill we saw a while ago. Just be careful with motor. Even at a lowly 60 RPM it ended up getting really hot and that’s the reason there’s a heat sink and fan unit included in the build. See it in action after the break.

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Airsoft minigun packs quite a punch

[Kuba_T1000] built a multi-barrell Airsoft minigun with an unbelievable firing rate and an almost inexhaustible ammo pack. The gun is made entirely from aluminum which meant some time on the CNC machine. The six barrels don’t rotate but they are all used, resulting in the carnage shown in the video after the break. That large box you see is the ammo pack, which can hold 16,000 BBs and uses an electric feed system to reach the necessary delivery speeds. It is certainly not something you’d want to run into as part of an automated turret.

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