When we picture the Medieval world, it conjures up images of darkness, privations, and sickness the likes of which are hard to imagine from our sanitized point of view. The 1400s, and indeed the entirety of history prior to the introduction of antibiotics in the 1940s, was a time when the merest scratch acquired in the business of everyday life could lead to an infection ending in a slow, painful death. Add in the challenges of war, where violent men wielding sharp things on a filthy field of combat, and it’s a wonder people survived at all.
But then as now, some people are luckier than others, and surviving what even today would likely be a fatal injury was not unknown, as one sixteen-year-old boy in 1403 would discover. It didn’t hurt that he was the son of the king of England, and when he earned an arrow in his face in combat, every effort would be made to save the prince and heir to the throne. It also helped that he had the good fortune to have a surgeon with the imagination to solve the problem, and the skill to build a tool to help.
When shooting archery, if you want to be accurate, you need arrows of uniform specification and quality. One important part of this is making sure each arrow has a spine of similar stiffness. Traditionally, this is checked in a very analog way by using weights and measuring deflection of the arrow spine, but it can be done electronically too with this tester from [dvd8n].
The principle of operation is simple. The arrow is held up by two supports, 28 inches apart. The user then presses down in the center of the arrow, deflecting it by a 1/2 inch where itreaches a stop , and load cells at either end of the tester measure the force required to deflect the arrow by the set amount.
It allows arrows to be electronically measured in a fashion that is compatible with existing standards for measurement. The Arduino hardware which measures the load cells can also easily run conversion maths to display the arrow’s measured stiffness in whatever common spine measurement standard is desired. The system can also weigh the arrows, a useful thing to know for the home fletcher.
That said, [Kamal Carter]’s build is pretty darn cool. He wisely chose to use just about the weakest bows you can get, the kind with strings that are basically big, floppy elastic bands that shoot arrows with suction-cup tips and are so harmless that they’re intended for children to play with and you just know they’re going to shoot each other the minute you turn your back no matter what you told them. Target acquisition is the job of an Intel RealSense depth camera, which was used to find targets and calculate the distance to them. An aluminum extrusion frame holds the bow and adjusts its elevation, while a long leadscrew and a servo draw and release the string.
With the running gear sorted, [Kamal] turned to high school physics for calculations such as the spring constant of the bow to determine the arrow’s initial velocity, and the ballistics formula to determine the angle needed to hit the target. And hit it he does — mostly. We’re actually surprised how many on-target shots he got. And yes, he did eventually get it to pull a [William Tell] apple trick — although we couldn’t help but notice from his, ahem, hand posture that he wasn’t exactly filled with self-confidence about where the arrow would end up.
Compound bows (unlike recurve bows, their more mechanically-simple relatives) use a levering system with pulleys and spring tension to grant the user a mechanical advantage. We’re not exactly sure what to call [Zünder’s] bow design. He shared his unconventional take on a DIY bow that uses coiled springs as well as some other unique features.
What we really dig about [Zünder]’s design is how easy it is to grasp how it all works. As he demonstrates using the bow, the way the levers, pulleys, and spring tension all work together is very clear. The 3D-printed quiver and arrow rest are nice added touches, and we especially love the use of three toothbrush heads to provide contained support for a nocked arrow. The ring of bristles are sturdy enough to easily support the shaft, and don’t interfere with the arrow’s fletching.
Many Hackaday readers may also be familiar with the Discworld series of fantasy novels from [Terry Pratchett], and thus might recognise a weapon referred to as the Piecemaker. A siege crossbow modified to launch a hail of supersonic arrows, it was the favoured sidearm of a troll police officer, and would frequently appear disintegrating large parts of the miscreants’ Evil Lairs to comedic effect.
Just as a non-police-officer walking the streets of Ank-Morpork with a Piecemaker might find swiftly themselves in the Patrician’s scorpion pit, we’re guessing ownership of such a fearsome weapon might earn you a free ride in a police car here on Roundworld. But those of you wishing for just a taste of the arrow-hail action needn’t give up hope, because [Turnah81] has made something close to it on a smaller scale. His array of twelve mousetrap-triggered catapults fires a volley of darts made from wooden kebab skewers in an entertaining fashion, and has enough force to penetrate a sheet of cardboard.
He refers to a previous project with a single dart, and this one is in many respects twelve of that project in an array. But in building it he solves some surprisingly tricky engineering problems, such as matching the power of multiple rubber bands, or creating a linkage capable of triggering twelve mousetraps (almost) in unison. His solution, a system of bent coat-hanger wires actuated by the falling bar of each trap, triggers each successive trap in a near-simultaneous crescendo of arrow firepower.
On one hand this is a project with more than a touch of frivolity about it. But the seriousness with which he approaches it and sorts out its teething troubles makes it an interesting watch, and his testing it as a labour-saving device for common household tasks made us laugh. Take a look, we’ve put the video below the break.
We like cheap FPGA boards. It isn’t just that we’re cheap — although that’s probably true, too — but cheap boards are a good way to get people started on FPGAs and we think more people should be using FPGAs more often. One inexpensive board is the Max-1000 from Trenz and Arrow. At $29, it is practically an impulse buy. [ZipCPU] did a great write up on his experience using the board. He found that some of it was good, some was bad, and some was just plain ugly. Still, for $30, it seems like this might be a nice board for some applications or for getting started.
Billed an IoT Maker Board, the tiny board sports a Intel (formerly Altera) MAX10 device with 8,000 logic elements, a USB programming interface onboard, 8 MB of SDRAM, and both PMOD and Arduino MKR headers. The MAX10 has an analog to digital conversion block (with an analog mux for up to nine channels) and the ability to host a 32-bit soft controller onboard, too.
As it turns out, it’s not feasible to print an entire crossbow yet. But [Dan]’s crossbow build does a good job of leveraging what a 3D printer is good at. Most of the printed parts reside in the crossbow’s trigger group, and the diagrams in the write-up clearly show how the trigger, sear and safety all interact. Particularly nice is the automatic nature of the safety, which is engaged by drawing back the string. We also like the printed spring that keeps the quarrel in place on the bridle, and the Picatinny rail for mounting a scope. Non-printed parts include the aluminum tubes used in the stocks, and the bow itself, a composite design with fiberglass rods inside PVC pipe. The video below shows the crossbow in action, and it looks pretty powerful.
Actually, we’ll partially retract our earlier dismissal of entirely 3D-printed crossbows, but [Dan]’s version is a lot more practical and useful than this model. And for a more traditional crossbow design, check out this entirely hand-made crossbow.