Powerful Crossbow is Almost Entirely 3D Printed

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.

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3D Printed Tourbillon Clock

3D printed clocks have been done before, but never something like this. It’s a 3D printed clock with a tourbillon, a creative way to drive an escapement developed around the year 1800. Instead of a pendulum, this type of clock uses a rotating cage powered by a spring. It’s commonly found in some very expensive modern watches, but never before has something like this been 3D printed.

3D Printed Clock[Christoph Lamier] designed this tourbillon clock in Autodesk Fusion 360, with 50 printable parts, and a handful of pins, screws, and washers. The most delicate parts – the hairspring, anchor, escapement wheel, and a few gears were printed at 0.06 layer height. Everything else was printed at a much more normal resolution with 0.1mm layer height.

Because nearly the entire clock is 3D printed, this means the spring is 3D printed as well. This enormous 2 meter-long spiral of printed plastic could not have been printed without altering a few settings on the printer. The setting in question is Cura’s ‘combing’ or the ‘avoid crossing perimeters’ setting. If you don’t disable this setting, the print time increases by 30%, and moving the print head causes the plastic to ooze out over the spring.

There’s a 26-minute long video of the 3D printed tourbillon clock in action that is horrendously boring. It does demonstrate this clock works, though. You can check out the more interesting videos below.

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The Hovalin: Open Source 3D Printed Violin Sounds Great

[Matt and Kaitlin Hova] have created The Hovalin, an open source 3D-printed violin. Yes, there have been 3D-printed instruments before, but [The Hovas] have created something revolutionary – a 3D printed acoustic instrument that sounds surprisingly good. The Hovalin is a full size violin created to be printed on a desktop-sized 3D printer. The Hovas mention the Ultimaker 2, Makerbot Replicator 2 (or one of the many clones) as examples. The neck is one piece, while the body is printed in 3 sections. The Hovalin is also open source, released under the Creative Commons Attribution Non-Commercial Share Alike license.

A pure PLA neck would not be stiff enough counter the tension in the strings, so [The Hovas] added two carbon fiber truss rods. A handful of other components such as tuners, and of course strings, also need to be purchased. The total price is slightly higher than a $60 USD starter violin from Amazon, but we’re betting the Hovalin is a better quality instrument than anything that cheap.

The Hovalin was released back in October. There are already some build logs in the wild, such as this one from [Emulsifide]. Like any good engineering project, the Hovalin is a work in progress. [Matt and Kaitlin] have already released version 1.0.1, and version 2.0 is on the horizon. Hearing is believing though, so click past the break to hear [Kaitlin] play her instrument.

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3D Printed Quadcopter Props

Here’s something that isn’t quite a hack; he’s just using a 3D printer as a 3D printer. It is extremely interesting, though. Over on Hackaday.io [Anton] is creating 3D printable propellers for quadcopters and RC planes. Conventional wisdom says that propellers require exceedingly exacting tolerances, but [Anton] is making it work with the right 3D file and some creative post-processing treatment of his prints.

These 3D printed props are a remix of an earlier project on Thingiverse. In [Anton]’s testing, he didn’t get the expected lift from these original props, so a few small modifications were required. The props fit on his 3D printer bed along their long edge allowing for ease of slicing and removal of support material. For post-processing, [Anton] is using acetone vapor smoothing on his ABS printed design. They come out with a nice glossy sheen, and should be reasonably more aerodynamic than a prop with visible layer lines.

Although [Anton]’s prop is basically a replica of a normal, off-the-shelf quadcopter prop, 3D printing unique, custom props does open up a lot of room for innovation. The most efficient propeller you’ll ever find is actually a single-bladed propeller, and with a lot of experimentation, it’s possible anyone with a well-designed 3D printer could make turn out their own single-blade prop.

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Raspberry Pi Opens Doors

The Raspberry Pi is a cheap credit card sized computer that has opened the doors of embedded Linux to millions of people. But in this case, it’s literally opening a door. The Computer Club at Western Michigan University had to move to a different room which brought with it a new challenge. The door handle was more difficult to turn than the old one. Nothing that a NEMA 17 stepper couldn’t handle, however.

After printing a few gears and wiring up an Easy Driver board between the Raspi and stepper motor, they had the basics of a door opener in place. A 5v relay is used to keep the power off the stepper when not in use, and a limit switch is used to monitor the position of the door handle while a Hall Effect sensor tells when the door is open and shut.

Be sure to check out the project as all source, parts list and schematics are available in case you have a simliar door that needs amending.

Full Size Custom Claw Machine Built with Parts on Hand

You know how it goes – sometimes you look at your social calendar and realize that you need to throw together a quick claw machine. Such was the dilemma that [Bob Johnson] found himself in during the run-up to the Nashville Mini Maker Faire, and he came up with a nice design that looks like fun for the faire-goers.

Seeking to both entertain and enlighten the crowd while providing them with sweet, sweet candy, [Bob] was able to quickly knock together a claw machine using mainly parts he had on hand in the shop. The cabinet is nicely designed for game play and to show off the gantry mechanism, which uses aluminum angle profiles and skate bearings as custom linear slides. Plenty of 3D printed parts found their way into the build, from pillow blocks and brackets for the stepper motors to the servo-driven claw mechanism. A nice control panel and some color-coded LED lighting adds some zip to the look, and a Teensy LC runs the whole thing.

Like [Bob]’s game, claw machines that make it to Hackaday seem to be special occasion builds, like this claw machine built for a kid’s birthday party. Occasion or not, though, we think that fun builds like these bring the party with them.

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