Trebuchet Sends Eggs Flying

Without any sort of restrictions on designs for trebuchets, these medieval siege weapons are known to send 90 kilogram projectiles over 300 meters. The egg-launching trebuchet contest that [AndysMachines] is entering, on the other hand, has a few limitations that dramatically decreased the size of the machines involved. The weight of the entire device is limited to no more than 3 kg, with any physical dimension no more than 300 mm, but that’s more than enough to send an egg flying across a yard with the proper design and tuning for maximum distance.

Trebuchets distinguish themselves amongst other siege weapons by using a falling weight to launch the projectile. The rules of this contest allow for the use of springs, so [AndysMachines] is adding a spring in between the trebuchet arm and the weight in order to more efficiently deliver the energy from the falling weight. More fine tuning of the trebuchet was needed before the competition, though, specifically regarding the stall point for the trebuchet. This is the point where the forces acting on the arm from the projectile and the weight are balanced, and moving this point to allow the projectile to release at a 45-degree angle was needed for maximum distance.

The video goes into a lot of detail about other fine-tuning of a trebuchet like this, aided by some slow-motion video analysis. In the end, [AndysMachines] was able to launch the egg over ten meters with this design. Of course, if you want to throw out the rule book and replace the eggs with ball bearings and the aluminum and steel with titanium, it’s possible to build a trebuchet that breaks the sound barrier.

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Catapult Your Best Wishes With This 3D-Printable Card

It’s the season to be surrounded by greeting cards of all shapes and sizes from friends old and new. News of their families and achievements, reminders that they exist, and a pile of cards to deal with sometime in January. Wouldn’t it be great if you could send something with a little more substance, something your friends would remember, maybe even hang on to?

[Brian Brocken]’s 3D-printed Da Vinci catapult kit may not fill that niche for everyone, but we can guarantee it will be a talking point. The Da Vinci catapult design uses a pair of springs similar to an archer’s bow, to unwind a pair of ropes and thus turn the shaft upon which the catapult shaft itself is fitted. All these components are mounted in a single piece with sprues similar to an injection moulded model kit, allowing the whole to easily be posted in an envelope.

The parts are all available to print separately among the files on the Thingiverse page for those with no need to mail them. For the casual spectator he’s made a YouTube video that we’ve placed below the break, detailing the design and build process as well as showing the device in use.

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Reinforce Happy Faces With Marshmallows And Computer Vision

Bing Crosby famously sang “Just let a smile be your umbrella.” George Carlin, though, said, “Let a smile be your umbrella, and you’ll end up with a face full of rain.” [BebBrabyn] probably agrees more with the former and used a Raspberry Pi with Open CV to detect a smile, a feature some digital cameras have had for a long time. This project however doesn’t take a snapshot. It launches a marshmallow using a motor-driven catapult. We wondered if he originally tried lemon drops until too many people failed to catch them properly.

This wouldn’t be a bad project for a young person — as seen in the video below — although you might have to work a bit to duplicate it. The catapult was upcycled from a broken kid’s toy. You might have to run to the toy store or rig something up yourself. Perhaps you could 3D print it or replace it with a trebuchet or compressed air.

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Hackaday Prize Entry: Room-Tracking Red Vines Flinger

[Vije Miller]’s Arduino Licorice Launcher is based on the simple and logical premise that one must always have a voice-activated Red Vines catapult in the workshop. When he calls out to the robot, it turns to aim at him and flings a piece of licorice at his head.

The chassis is CNCed out of quarter-inch MDF and the spring-loaded catapult arm is managed by two servos, one to tension the arm and one to secure it until it’s triggered.  Third and fourth servos aim the catapult and dispense another piece of licorice from the magazine. His robot adapts a radio homing technique [Vije] learned about from RoboWarner, which allows a robot to track a moving RF signal.

[Vije]’s first prototype uses an Arduino Uno connected to a serial port on a PC, but he hopes to acquire an MKR1000 WiFi module, which combines a Arduino Zero with WiFi. Already, this Red Vines launcher is a complete success; the marketing team at Red Vines sent him a huge pile of swag and free licorice for his efforts. You can check out [Vije]’s promo video of the project below.

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Electronic Table Top Catapult

[Unusualtravis] came up with this fairly slick electronic catapult. This easy to construct and moderately cheap rig has an arduino as the brains and controls for 3 servos. One is the release, another controls tension, and the third controls the angle. Both the circuit and the construction are very simple making this a perfect weekend project. He would have preferred it to be a bit smaller, so shoot him your design if you manage to shrink it.

We’ve always been rather fond of catapults of whatever complexity, so feel free to send in any variations you’ve worked on.

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Beer Catapulting Fridge

We’re not sure where the fascination to have your libations flung at you came from, but we can’t say we’re entirely against it. This beer catapult robot (dead link try Internet Archive) will pull a cold one from its gullet and fling it to you, or in your general direction. While he doesn’t have the source code available for the Arduino bit, we’re OK with that. We’re more interested in the mechanisms at work here and there are plenty of pictures of his set up.  It seems very similar in design to this one we covered back in 2007, which also appeared on” The Late Show with David Letterman”.  Join us after the break to see the thing in action.

[thanks Springuin]

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The Backyard Ogre Catapult


Today we’ll be setting aside the circuits and solder for a little while in favor of good old fashioned wood and bungee chords to make this backyard catapult. Items needed include nine sections of 2×3 wooden beams of varying lengths, some screws and eye hooks, a bungee chord, a broom handle, and a few other things which are all detailed in the read link below.

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