Interfacing a shaft to a 3D printed gear doesn’t have to be tricky. [Tlalexander] demonstrated a solution that uses one half of a spider coupling (or jaw coupling) to create an effective modular attachment. The picture above (and this older link) shows everything you need to know: the bottom of the coupling is mounted to the shaft, and a corresponding opening is modeled into the the 3D printed part. Slide the two together, and the result is a far sturdier solution than trying to mate a 3D printed gear directly to a motor shaft with a friction fit or a screw. This solution isn’t necessarily limited to attaching gears either, any suitable 3D printed part could be interfaced to a shaft in this way.
These couplings are readily available, and fortunately for hobbyists, come in sizes specifically designed for common stepper motors like NEMA 17 and NEMA 23. Ironically, these couplings are often used when building custom 3D printers for those same reasons. With this method interfacing anything at all to a motor shaft becomes mostly a matter of modeling a matching hole out of the part to be 3D printed. One coupling even provides two such attachments, since only one of the two sides is used.
The image up top is from [Tlalexander]’s Rover image gallery, which contains a ton of fantastic pictures of the work that went into the gearboxes, a major part of the Rover’s design that we’ve seen in the past.
Making waves in the music world is getting harder. Almost anyone who has access to the internet also has access to a few guitars and maybe knows a drummer or can program a drum machine. With all that competition it can be difficult to stand out. Rather than go with a typical band setup or self-producing mediocre rap tracks, though, you could build your own unique musical instrument from scratch and use it to make your music, and your live performances, one-of-a-kind.
[Pete O’Connell]’s instrument is known as the Rhysonic Wheel, which he created over the course of a year in his garage. The device consists of several wheels, all driven at the same speed and with a common shaft. At different locations on each of the wheels, there are pieces of either metal or rubber attached to strings. The metal and rubber bits fling around and can strike various other instruments at specified intervals. [Pete O’Connell] uses them to hit a series of percussion instruments, a set of bells, and even to play a guitar later on in the performance.
While it looks somewhat dangerous, we think that it adds a level of excitement to an already talented musical performance. After all, in skilled hands, any number of things can be used to create an engaging and unparalleled musical performance with all kinds of sounds most of us have never heard before.
Continue reading “The Rhysonic Wheel Automates Live Music”
On the face of it, keeping fluids contained seems like a simple job. Your fridge alone probably has a dozen or more trivial examples of liquids being successfully kept where they belong, whether it’s the plastic lid on last night’s leftovers or the top on the jug of milk. But deeper down in the bowels of the fridge, like inside the compressor or where the water line for the icemaker is attached, are more complex and interesting mechanisms for keeping fluids contained. That’s the job of seals, the next topic in our series on mechanisms.
Continue reading “Mechanisms: Mechanical Seals”
It’s the latest in instrumentation for the well-appointed shop — an acoustically coupled fast Fourier transform tachometer. Sounds expensive, but it’s really just using a smartphone spectrum analyzer app to indirectly measure tool speeds. And it looks like it could be incredibly handy.
Normally, non-contact tachometers are optically coupled, using photoreceptors to measure light flashing off of a shaft or a tool. But that requires a clear view of the machine, often putting hands far too close to the danger zone. [Matthias Wandel]’s method doesn’t require line of sight because it relies on a cheap spectrum analyzer app to listen to a machine’s sound. The software displays peaks at various frequencies, and with a little analysis and some simple math, the shaft speed of the machine can be determined. [Matthias] explains how to exclude harmonics, where to find power line hum, isolating commutator artifacts, and how to do all the calculations. You’ll need to know a little about your tooling to get the right RPM, and obviously you’ll be limited by the audio frequency response of your phone or tablet. But we think this is a great tip.
[Matthias] is no stranger to shop innovations and putting technology to work in simple but elegant ways. We wonder if spectrum analysis could be used to find harmonics and help with his vibration damping solution for a contractor table saw.
Continue reading “The Tachometer Inside Your Smartphone”
Here is a two-part Navy training film from 1953 that describes the inner workings of mechanical fire control computers. It covers seven mechanisms: shafts, gears, cams, differentials, component solvers, integrators, and multipliers, and does so in the well-executed fashion typical of the era.
Fire control systems depend on many factors that occur simultaneously, not the least of which are own ship’s speed and course, distance to a target, bearing, the target’s speed and course if not stationary, initial shell velocity, and wind speed and direction.
The mechanisms are introduced with a rack and pinion demonstration in two dimensions. Principally speaking, a shaft carries a value based on revolutions. From this, a system can be geared at different ratios.
Cams take this idea further, transferring a regular motion such as rotation to an irregular motion. They do so using a working surface as input and a follower as output. We are shown how cams change rotary motion to linear motion. While the simplest example is limited to a single revolution, additional revolutions can be obtained by extending the working surface. This is usually done with a ball in a groove.
Continue reading “Retrotechtacular: Fire Control Computers In Navy Ships”
[Tommy Gober] built this Yagi-Uda antenna that has some handy design features. The boom is a piece of conduit with holes drilled in the appropriate places. The elements are aluminum arrow shafts; a good choice because they’re straight, relatively inexpensive, and they have #8-32 screw threads in one end. He used some threaded rod to connect both sides of the reflector and director elements. The driven elements are mounted offset so that a different machine screw for each can be connected to the appropriate conductor of the coaxial cable. The standing wave ratio comes in right where it should meaning he’ll have no trouble picking up those passing satellites as well as the International Space Station.
If you’ve ever been caught in the situation of needing to drill a clean straight hole down the center of a bolt or rod, you’ve probably tried and ended up with a broken bit or tilted hole, and a ton of cursing to boot.
[Vik] let us know about this nifty trick for drilling ‘down the middle’ using a simple hobby drill press and vice. He claims it’s ‘physics guiding the bit’ but in reality its just crafty use of a chuck. Either way the quick trick works, and will hopefully save a lot of hackers some headaches in the future.
Let us know in the comments if you have any simple quick tips that you use when you’re out in the shop.