DO NOT build a fully automatic battery-launching air gun

There’s nothing quite like [Elliot]’s cherubic sense of wonder and maniacal laughter after he tests his fully automatic AA battery-launching air gun. That fires 600 rounds a minute. At 200 feet per second.

We need to take a minute and say [Elliot]’s gun is stupidly unsafe. He used PVC pipe to hold air pressure, so that may… explode one of these days. Also, the AA batteries coming out of the end of the barrel have the same kinetic energy as a .22 rifle bullet.

The mechanics of the gun is a simple blow forward bolt. When he pulls the trigger, the bolt – and battery – are forced forward due to air pressure. After the bolt has cleared a plug, air is allowed to flow through the bolt pushing the battery along with it. Once the pressure in the barrel is back down to normal, a spring forces the bolt back into place and the 23 round magazine loads another battery. Simple, really. [Elliot] posted some pics of his gun on the spudfiles.com forum.

The gun is accurate to about 100 yards. It’s a very impressive piece of engineering for a bit of PVC pipe, but we don’t feel the need to copy this one. Check out the videos after the break to see this thing in action.

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Automatic dog dish filler never goes dry

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[Avatar-X] has a Siberian Husky that gets a lot of exercise throughout the day, and as you would imagine, drinks a ton of water as well. We all suffer from memory lapses at one time or another, and while he is normally good about keeping the bowl filled, he occasionally forgets. He has tried a handful of various auto-filling dog dishes, but none of them seemed to work all that well, and they often rapidly built up healthy bacterial colonies.

With the help of some friends, he rigged up an automatic water dish filler, that ensures his pup always has a sufficient supply of water. He tapped into his kitchen water supply with a standard refrigerator hookup kit, and ran some tubing up into his cabinets, where he placed a garden irrigation valve. The valve is controlled using an Arduino which senses the bowl’s water level using a pair of wires.

The system looks like it works pretty well if the video embedded below is any indicator. [Avatar-X] provides code and schematics for the water control circuit on his site, free to anyone looking to build a similar system for their pets.

If you are interested in learning more about automating some of your pet’s care, be sure to check out these hacks we featured in the past.

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Automatic ball launcher is for the dogs

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A while back, [Dino] built an automatic ball launcher for his dogs, but he wanted to revise it to make it smaller and a bit more user-friendly. While watching an episode of “Prototype This”, he came across a great idea to improve his launcher, so off to the workshop he went.

He repurposed a power window motor from a car, and mounted it to some wood-reinforced aluminum sheeting in his garage. He added a piece of aluminum tubing to serve as a spring-loaded launch arm, which is drawn back by a small lever attached to the window motor.

When a ball is dropped onto a switch at the bottom of the launcher, the window motor starts turning, which pulls the launch arm back into place. Once the arm reaches the tipping point, the spring snaps it forward, launching the ball across the yard. The lever attached to the window motor eventually makes its way back under the launch arm, and is stopped by a switch that is also attached to the motor.

After the prototype was finished, he added some more wood to protect the mechanism from his dogs and vice versa. A hopper was added to the top of the structure to allow the dogs to load the launcher themselves, after a bit of training.

Now, some of you might wonder what is wrong with [Dino’s] arm. Truth be told, it works just fine. If you are a frequent Hack-a-Day visitor, you know that he spends plenty of time in the workshop, so this is an easy way to let the dogs entertain themselves until their owner is ready to play.

Check out the video embedded below for a demonstration of the launcher, as well as a detailed walkthrough of how the mechanism works.

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Home Built Revolving Shotgun

Sometimes, you just need more ammo available. In this weapon mod, the chamber of a 12 gauge shotgun, a hammer from an 1857 Remington Perc Revolver, and other parts from an Italian auto shotgun were all combined to make this happen. The gun is of questionable legality depending on what state or country it resides in. Don’t quote us on it, but the members of the forum seem to think it should be fine anywhere in the US but California. Slightly more practical than other shotgun mods we have seen, the inventor has been kind enough to share some stills of the inner mechanisms to see how this gun ticks.

[via Neatorama]

Home Brew Coffee Machine

There are already a lot of different ways to brew up a decent coffee at home, from the humble saucepan to the elegant vacuum flask. In an office environment the choice of coffee-making technique can have a major impact on workplace harmony—how can people be expected to work happily when the kitchen is filthy with grounds and the coffee is always stale? “Someone have mercy,” [Christian Finger] lamented, “and boil a pot of fresh.”

In the end he took extreme measures, building a machine that grinds whole beans, measures out a dose, brews a cup and self-cleans. He used all sorts of odds and ends to put the thing together, detailed in his long and hilarious build log (english translation—and check out the dude’s sweet ride). Refer to his shockwave animation for a summary of the intended operation.

The end result is an extremely impressive Goldbergian contraption—download the video from the build log. It is pretty noisy and probably energy- and water-hungry, but that wouldn’t stop us from using it every day, if given the chance. Hell, this here could form a major part of your next breakfast machine.

We’re sure that there is further potential in this, because to get the really freshest possible cup of coffee you’d want to roast the coffee beans just before grinding them. Then you’d be well on your way towards something else entirely: a delicious breakfast machine.

LEGO automatic transmissions

[AviatorBJP] is building some impressive automatic transmissions using LEGO parts. Your best bet is to check out his YouTube channel as he’s got a slew of videos related to topic. We’ve embedded test footage of first and second generation vehicles as well as the most recent flywheel design after the break. But we’re getting ahead of ourselves, let’s look at how the system works.

Each transmission centers on a mechanism that includes hinged arms attached to a central axle. The arms are held together with a rubber band but as the axle spins faster, they overcome the elastic force of the band and begin to pivot outward. This pulls the shaft in one direction, moving its gear up to the next position in the transmission box. To test the system [AviatorBJP] uses a treadmill. A string is attached to the front of the vehicle to keep it in place and the treadmill is switched on to simulate engine power.

This design is quite brilliant, and he’s not keeping it to himself. If you’ve grown tired of the manual LEGO transmission you built, you can follow his multi-video build process to make one of these for yourself.

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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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