The round bottom of a proper wok is the key to a decent stir fry, but it also makes it hard to use on traditional Western stoves. That’s why many woks end up in a dark kitchen cabinet, unused and unloved. But wait; it turns out that the round bottom of a wok is the perfect shape for gathering something else — radio waves, specifically the 21-cm neutral hydrogen emissions coming from the heart of our galaxy.
Turning a wok into an entry-level radio telescope doesn’t appear to be all that hard, at least judging by what [Leo W.H. Fung] et al detail in their paper (PDF) on “WTH” or “Wok the Hydrogen.” Aside from the wok, which serves as the main reflector, you’ll need a bit of coaxial cable and some stiff copper wire to fashion a small dipole antenna and balun, plus some plastic tubing to support it at the focal point of the reflector. Measuring the wok’s shape and size, which in turn determines its focal point, is probably the hardest part of the build; luckily, the paper includes tips on doing just that. The authors address the controversy of parabolic versus spherical reflectors and arrive at the conclusion that for a radio telescope fashioned from a wok, it just doesn’t matter.
As for the signal processing chain, WTH holds few surprises. A Nooelec Sawbird+ H1 acts as preamp and filter for the 1420-MHz hydrogen line signal, which feeds into an RTL-SDR dongle. Careful attention is paid to proper grounding and shielding to keep the noise floor as low as possible. Mounting the antenna is a decidedly ad hoc affair, and aiming is as simple as eyeballing various stars near the center of the galactic plane — no need to complicate things.
Performance is pretty good: WTH measured the recession velocity of neutral hydrogen to within 20 km/s, which isn’t bad for something cobbled together from scrap. We’ve seen plenty of DIY hydrogen line observatories before, but WTH probably wins the “get on the air tonight” award.
Thanks to [Heinz-Bernd Eggenstein] for the tip.
[JSK-koubou] has quite the talent for creative woodwork, particularly building interesting tools or improving existing ones. This recent project (multiple build videos below: part 1, part 2, and part 3) is a very flexible type of guided pull saw, whereby a fine-toothed saw blade is fixed in the bed, and the workpiece is pulled over it it. By fixing it at a shallow angle, and enabling the blade to be raised up through the bed, the workpiece can be progressively cut by simply pulling it over the blade, then winding it up a little until the final cut length is achieved.
From a construction perspective, the tool is all-metal, built from a collection of the off-the-shelf parts, and thick, hand-cut aluminium alloy plate, nary a CNC tool in sight. The only unusual component is the saw blade itself, which might be a bit tricky to track down if you were so inclined to reproduce the build. It appears (well if you believe the auto-translation by Google Lens, anyway) to be a spare blade for a commercial guide saw available in Japan at least.
We found it particularly pleasing to see the use of a home-built anodizing setup to give it a bit of a jazzy color scheme for some of the plates, just because. Like with many of the build videos from this YouTuber, it is well worth watching all of them, if only just to gather a few ideas for one’s own workspace, if you can stop yourself getting distracted looking at all the other neat tools he uses on the way.
DIY tool builds are not uncommon in these parts, here’s a neat DIY combo table-based project, and here’s a homebrew auto-lowering metal bandsaw which could be a real timesaver.
Continue reading “A Beautiful DIY Guided Saw”
TL;DR — when [Colin Furze] is your “safety inspector,” you really should be reconsidering your project goals.
Most of us have probably by now seen the SawStop brand of self-stopping table saw, which detects when something meatier than wood has the bad taste to touch the spinning blade, more or less instantly stopping it and preventing sudden traumatic amputations. It’s an outstanding idea, and we’d love to see the technology built into all table saws. But alas, SawStop saws are priced out of reach for many woodworkers, which left [Ruth Amos] to roll her own DIY version of the system.
It should be stated right off the bat that none of what [Ruth] does here is a good idea, and that everything shown is really just a proof of concept. The basis for her build was a somewhat flimsy-looking contractor-style saw, to which [Ruth] attached an Arduino set up to detect when something conductive touches the blade. She shares no particulars on the sensing method, but our guess is capacitive coupling. She then sets about experimenting with a series of above-table gizmos to arrest the blade, with limited success, plus all the attachments would make the saw essentially useless. But working above the table does make sense in the prototyping phase, and allowed her to figure out what wouldn’t work.
In the end, it was an electromagnetic clutch from an electric lawnmower that seemed to do the trick, albeit at the expense of heavy mods to the saw and a considerable increase in the system’s angular momentum. Nonetheless, the blade stops pretty close to instantly in the old hot dog test. It doesn’t drop the blade below the table, of course, and the hot dog is a little worse for the wear, but it’s still pretty impressive.
We’ve discussed SawStop’s technology before and why it isn’t perhaps as widely available as it should be, if you’re curious.
Continue reading “Homemade SawStop Attachment Is Just About As Sketchy As It Sounds”
We often take electricity for granted, to the point of walking into a room during a power outage and still habitually flipping the light switch. On the other hand, there are plenty of places where electricity isn’t a given, either due to poor infrastructure or an otherwise remote location. To get common electric power tools to work in areas like these requires some ingenuity like that seen in this build which converts a chainsaw to a gas-driven grinder that can be used for cutting steel or concrete. (Video, embedded below.)
All of the parts needed for the conversion were built in the machine shop of [Workshop from scratch]. A non-cutting chain was fitted to it first to drive the cutting wheel rather than cut directly, so a new bar had to be fabricated. After that, the build shows the methods for attaching bearings and securing the entire assembly back to the gas-powered motor. Of course there is also a custom shield for the grinding wheel and also a protective housing for the chain to somewhat limit the danger of operating a device like this.
Even though some consideration was paid to safety in this build, we would like to reiterate that all the required safety gear should be worn. That being said, it’s not the first time we’ve seen a chainsaw modified to be more useful than its default timber-cutting configuration, like this build which turns a chainsaw into a metal cutting chop saw.
Continue reading “Chainsaw Cuts More Than Timber”
Typically, someone’s first venture into coding doesn’t get a lot of attention. Then again, most people don’t program a CNC table saw right out of the gate. [Jeremy Fielding] wasn’t enticed with “Blink” or “Hello, world,” and took the path less traveled. He tackled I/O, UX, and motion in a single project, which we would equate to climbing K2 as a way to get into hiking. The Python code was over 500 lines, so we feel comfortable calling him an over-achiever.
The project started after he replaced the fence on his saw and wondered if he could automate it, and that was his jumping-on point, but he didn’t stop there. He automated the blade height and angle with stepper motors, so the only feedback is limit switches to keep it from running into itself. The brains are a Raspberry Pi that uses the GPIO for everything. There is a manual mode so he can use the hand cranks to make adjustments like an ordinary saw, but he loses tracking there. His engineering background shines through in his spartan touchscreen application and robust 3D model. The built-in calculator is a nice touch, and pulling the calculations directly to a motion axis field is clever.
We’ve covered [Jeremy]’s DIY dynamometer and look forward to whatever he builds next. Until then, check out a light-duty approach to CNC that cuts foam in two-and-a-half dimensions.
Continue reading “Measure 1024 Times, Cut Once”
Table saws are highly useful tools, but tend to take up a lot of space. They’re usually designed to handle the bigger jobs in a workshop. It doesn’t have to be that way, however, as [KJDOT] demonstrates with a miniature table saw.
It’s a saw that relies on a simple build. The frame is made of plywood, and can be built with just a drill and a hand saw. A brushed motor is used to run the saw, using an off-the-shelf PWM controller and a 24V power supply. A handful of bearings and standard brackets are then used to put it all together, and there’s even a handy adjustable fence to boot. With a 60mm blade fitted, the saw is ready to go.
It’s a build that would be great for anyone regularly working with wood or plastics on the smaller scale. If you like building dollhouses, this could be the tool for you. You might also find the table nibbler to be an enticing proposition. Video after the break.
Continue reading “Minature Table Saw Gets The Teeny Jobs Done”
Among the most dangerous jobs in the United States are timberjack and aircraft pilot. Combining the two wouldn’t sound like a recipe for success, but in fact it makes the job of trimming trees near pipelines and power lines much safer. That’s what this helicopter-suspended chainsaw does. And it definitely doesn’t look safe, either, but here we are.
The saw is equipped with ten two-foot diameter saws and is powered by a 28 horsepower engine which is separate from the helicopter itself. The pilot suspends the saw under the helicopter and travels along the trees in order to make quick work of tree branches that might be growing into rights-of-way. It’s a much safer (and faster) alternative that sending out bucket trucks or climbers to take care of the trees one-by-one.
Tree trimming is an important part of the maintenance of power lines especially which might get overlooked by the more “glamarous” engineering aspects of the power grid. In fact, poor maintentance of vegitation led to one of the largest blackouts in recent history and is a contributing factor in a large number of smaller power outages. We can’t argue with the sentiment around the saw, either.