A Saturday afternoon. The work week was done, the household chores were wrapped up, and with almost a week left until Christmas, there was just enough wiggle room to deny that there was still a ton of work left to prepare for that event. It seemed like the perfect time to escape into the shop and knock out a quick project, one that has been on the back burner since at least March. I’m nothing if not skilled in the ways of procrastination.
This was to be a simple project — adding an aluminum plate to a plastic enclosure that would serve as an antenna entry point into my shack. Easy as pie — cut out an rectangle of aluminum, cut and drill a few holes, call it a day. Almost all of my projects start out that way, and almost every time I forget that pretty much every one of those builds goes off the rails at exactly the same point: when I realize that I don’t have the fasteners needed. That’s what happened with this build, which had been going swimmingly up to that point — no major screw-ups, no blood drawn. And so it was off to the hardware store I trundled, looking for the right fasteners to finish the job.
Finding hardware has long been where my productivity goes to die. Even though I live a stone’s throw from at least half a dozen stores, each with a vast selection of hardware and most open weekends and nights, the loss of momentum that results from changing from build-mode to procure-mode has historically been deadly to my projects. I’m sure I’m not the only one who has run into this issue, so the question is: what can a hacker do to prevent having to run out for just the right fasteners?
So you’ve built a fine kite, taken it to the beach, and let it ride the wind aloft on a spool of line. Eventually it has to come down, and the process of reeling all that line that was so easily paid out is likely a bigger chore than you care to face. What to do?
If you’re like [Matt Bilsky], the answer is simple: build a motorized kite reel to bring it back in painlessly. Of course what’s simple in conception is often difficult to execute, and as the second video below shows, [Matt] went through an extensive design and prototype phase before starting to create parts. Basic questions had to be answered, such as how much torque would be needed to reel in the kite, and what were the dimensions of a standard kite string reel. With that information and a cardboard prototype in hand, the guts of a cordless drill joined a bunch of 3D-printed parts to form the running gear. We really liked the research that went into the self-reversing screw used to evenly wind the string across the spool; who knew that someone could do a doctoral dissertation on yarn-winding? Check out the “Reeler-Inner” in action in the first, much shorter video below.
With some extra power left from the original drill battery, [Matt] feature-crept a bit with the USB charger port and voltmeter, but who can blame him? Personally, we’d have included a counter to keep track of how much line is fed out; something like this printer filament counter might work, as long as you can keep the sand out of it.
Ground plastic bits go in one end, finished 3D-prints come out the other. That’s the idea behind [HomoFaciens]’ latest build: a direct-extrusion 3D-printer. And like all of his builds, it’s made from scraps and bits most of us would throw out.
Take the extrusion screw. Like the homemade rotary encoders [HomoFaciens] is known for, it appears at first glance that there’s no way it could work. An early version was just copper wire wrapped around a threaded rod inside a Teflon tube; turned by a stepper motor, the screw did a decent job of forcing finely ground PLA from a hopper into the hot end, itself just a simple aluminum block with holes drilled into it. That worked, albeit only with basically powdered PLA. Later versions of the extruder used a plain galvanized woodscrew soldered to the end of a threaded rod, which worked with chunkier plastic bits. Paddles stir up the granules in the hopper for an even flow into the extruder, and the video below shows impressive results. We also picked up a few tips, like using engine gasket paper and exhaust sealant to insulate a hot end. And the slip coupling, intended to retract the extruder screw slightly to reduce stringing, seems brilliant but needs more work to make it practical.
There are usually two broad user interfaces for clocks. On the one hand you’ve got the dial clock, the default display for centuries, with its numbered face and spinning hands. The other mode is some form of digital clock, where the current time is displayed directly as alphanumeric characters. They’re both useful representations of time, but they both have their limits.
Here’s a third model — the linear clock. [Jan Derogee] came up with it thanks to the inspiration of somewhat dubious run-ins with other kinds of clocks; we feel like this introductory video was made with tongue firmly planted in cheek. Whatever the inspiration, we find this idea clever and well executed. The running gear of the clock is just a long piece of M6 threaded rod and a stepper motor. A pointer connected to a nut rides on the rod, moving as the stepper rotates it. There are scales flanking the vertical rod, with the morning hours going up the left side and afternoon hours coming down the right. The threaded rod rotates one way for twelve hours before switching to the other direction; when the rotation changes, the pointer automatically swivels to the right scale. For alarms, [Jan] has brass rods running along each scale that make contact with the pointer; when they encounter a sliding plastic insulator to break the contact, it triggers an alarm. An ESP8266 controls everything and plays the audio files for the alarm.
We recently posted about a spectacular 3D-printer fire that was thankfully caught and extinguished before spreading to the hacker’s house or injuring his family. Analyzing the remains of the printer, the hacker determined that the fire was caused when a loose grub screw let the extruder’s heater cartridge fall out and touch the ABS fan shroud. It ran full-on and set things on fire.
A number of us have similar 3D printers, so the comments for this article were understandably lively, but one comment stood out by listing a number of best practices for wiring, including the use of ferrules. In particular, many 3D printers connect the heated bed, which draws a lot of current, with screw terminals to the motherboard. While not the cause of the fire in the original post, melted terminal blocks are a common complaint with many DIY 3D printer kits, and one reason is that simply jamming thick stranded wire into a screw terminal and hoping for the best can result in increased resistance, and heat, at the joint. In such situations, the absolutely right thing to do is to crimp on a ferrule. So let’s talk about that.
This is something that’s been in the works for a long time. It’s a primarily 3D-printed build, showing just how easy it is to build complex machines from scratch in this day and age of rapid prototyping. Over time, [Ivan] has experimented with different screw shapes and taken feedback from his audience on how to improve the craft. With some changes to the gearing and drive layout, the tank returned to the beach, with great success. Powered by twin brushless motors and controlled by off-the-shelf RC gear, the tank has no trouble scooting about the sand.
The project shows the value in iterative design, with [Ivan] taking time to lay out all the parts which have changed since the last revision. It’s a project that is now a five-part series, and we can’t wait to see where it goes next. There’s every chance an amphibious version could be in the works. For something on the larger scale, check out this screw drive tractor set to conquer Canada.
They hold together everything from the most delicate watch to the largest bridge. The world is literally kept from coming apart by screws and bolts, and yet we don’t often give a thought to these mechanisms. Part of that is probably because we’ve gotten so good at making them that they’re seen as cheap commodities, but the physics and engineering behind the screw thread is interesting stuff.
We all likely remember an early science lesson wherein the basic building blocks of all mechanisms laid out. The simple machines are mechanisms that use an applied force to do work, such as the inclined plane, the lever, and the pulley. For instance, an inclined plane, in the form of a splitting wedge, directs the force of blows against its flat face into a chunk of wood, forcing the wood apart.
Screw threads are another simple machine, and can be thought of as a long, gently sloped inclined plane wrapped around a cylinder. Cut a long right triangle out of paper, wrap it around a pencil starting at the big end, and the hypotenuse forms a helical ramp that looks just like a thread. Of course, for a screw thread to do any work, it has to project out more than the thickness of a piece of paper, and the shape of the projection determines the mechanical properties of the screw.