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?
Continue reading “Pneumatic Pen Gun is Fit for James Bond”
Every electronics project of sufficient complexity needs standoffs – little plastic or metal cylinders – to mount boards to one another. Keeping hundreds of little plastic trinkets around doesn’t really fit with the hacker mentality, though: it would be far simpler to keep some Delrin rod stock around to drill and cut standoffs as needed. [HomeCSP] created a device to do just that, allowing him to turn 1/4″ Delrin rod stock into any size standoff he needs.
Before building this device, [HomeCSP] was taking plastic rods to the drill press fitted with a very tiny drill bit for a #2 screw. The problems with that technique should be evident to anyone. The new solution uses an old cordless drill and a 6 inch piece of linear rail, effectively turning some bits of scrap into a horizontal drill press with a stationary bit.
The end result is a machine that can bore a hole straight down a 1/4″ rod. With a box of screws these homebrew plastic rods are much cheaper than off-the-shelf parts and can be made in any length desired.
[taulman] over on Instructables has been working on his own version of a 3D printer. Unlike the usual PLA or ABS filament all the RepRaps and Makerbots use, this printer uses nylon to make parts with very interesting properties.
Most extrusion printers are designed to print with ABS (a very hard plastic that melts around 220-230° C) or PLA (a somewhat softer plastic that melts at about 180° C). [taulman] is using Nylon 6, a very slippery and bendable plastic that melts around 320° C (about 600 degrees Fahrenheit). He’s doing this with a hot end of his own design and a ‘spiky’ extruder bolt that allows high-temperature thermoplastics to be extruded into any shape imaginable.
For the longest time, the 3D printer community has been using low-temperature thermoplastics such as PLA and ABS. There are obvious benefits to these materials: it’s pretty easy to source a spool of filament, and the low melting point of these plastics makes building a printer easier and safer. Now that [taulman] has the high-temperature plastic nut cracked, he’s moving on to easily-machiniable Delrin and transparent Polycarbonate. Very cool, and hopefully in a year’s time we’ll have a choice of what material to run in our printers.
After the break, there are a few videos [taulman] put up showing his printer at work and the properties of his 3D printed objects. It looks like [taulman] can print objects that are impossible on any other 3D printer we’ve seen; the flexible iPhone case probably couldn’t be made on any other DIY machine.
Continue reading “3D printing with Nylon for a more useful objects”
[Dennis] recently invested some money in the Tormach Tooling System for his CNC’d Sieg SX3 mill in order to make his tool changes easier. While the kit allows him to easily account for height offsets while changing tools, he has no quick, reliable means of locating the spindle in relation to his workpiece. Tired of manually finding the edges of his workpiece for each axis, he built himself a DIY touch probe to automate the process.
The theory behind the probe’s operation is pretty simple. In the probe’s housing, three conductive rods are mounted perpendicular to the probe tip. Each rod rests between two metal balls forming a complete circuit. When the probe touches the edge of his milling material, the circuit is broken, sending a signal to his CNC control box.
The probe is comprised of several different parts, milled from either aluminum or black delrin. [Dennis] says that after everything was assembled, the runout on the probe was unacceptable, so he made a few tweaks, and now the runout has been reduced to about 0.00025” – well within acceptable tolerance limits for any work he will be doing.
Be sure to check out his site, as there are plenty more pictures of the probe’s construction, as well as additional video.
In the meantime, continue reading to see a quick video of the finished probe in action.
Continue reading “DIY CNC touch probe”
[Philysteak527] modified a Nerf rifle, making it semi-automatic thanks to the powers of compressed air. This is not a simple change to make, and rests on his ability to design and manufacture a bolt-action that fits in the gun, works with the Nerf ammo, and uses a CO2 canister and solenoid valve for the firing action. Knowing that, it’s not surprising to find that he’s an engineering student at Stony Brook University. He started with some POM, or polyoxymethylene plastic sold under the brand name Delrin, and used a CNC lathe to machine the parts for the bolt. Add in some brass fittings, a solenoid, tubing, and the electronics and you’re in business.
We’ve embedded the test footage after the break. Looks like the new internals allow a rather fast firing rate (maybe 2-3 shots per second?) and achieve a distance between seventy and one hundred feet.
Continue reading “Nerf gun converted to CO2 powered semi-automatic”