Some equipment comes with a backstory so impressive, you can’t help but treat it with reverence. For instance, this Hantek scope’s front panel and knobs have melted when a battery pack went up in flames right next to it. Then, it got donated to the CADR hackerspace, who have in turn given us a scope front panel refurbishing master class (translated, original), demonstrating just how well a typical hackerspace is prepared for performing plastic surgery like this.
All of the tools they used are commonplace hackerspace stuff, and if you ever wanted to learn about a workflow for repairs like these, their wiki post is a model example, described from start to end. They show how they could use a lasercutter to iterate through figuring out mechanical dimensions of the labels, cutting the silhouette out of cardboard as they tweaked the offsets. Then, they designed and printed out the new front panel stickers, putting them through a generic laminator to make them last. An FDM printer helped with encoder and button knob test fits, with the final version knobs made using a resin printer.
Everything is open-source – FreeCAD knob designs, SVG stickers, and their CorelDraw sources are linked in the post. With the open-source nature, there’s plenty of room to improvement – for instance, you can easily put these SVGs through KiCad and then adorn your scope with panels made out of PCBs! With this visual overhaul, the Hantek DSO5102P in question has gained a whole lot more character. It’s a comprehensive build, and it’s just one of the many ways you can compensate for a damaged or missing shell – check out our comprehensive DIY shell guide to learn more, and when you get to designing the front panel, we’ve highlighted a fewlessons on that too.
The device can’t do much more than blow each limb outward with a varying amount of force, but that’s enough to be able to steer and move the little unit. It has enough power to make some very impressive jumps. The ability to navigate even with such limited actuators is reminiscent of hopped-up bristebots.
Electronic control of combustions in the joints allows for up to 100 explosions per second, which is enough force to do useful work. The prototype is only 29 millimeters long and weighs only 1.6 grams, but it can jump up to 56 centimeters and move at almost 17 centimeters per second.
The prototype is tethered, so those numbers don’t include having to carry its own power or fuel supply, but as a proof of concept it’s pretty interesting. Reportedly a downside is that the process is rather noisy, which we suppose isn’t surprising.
Want to see it in action? Watch the video (embedded below) to get an idea of what it’s capable of. More details are available from the research paper, as well.
Welding is often a hot and noisy process. It generally involves some fancy chemistry and proper knowledge to achieve good results. Whether you’re talking about arc, TIG, or MIG, these statements all apply.
The same is true for explosion welding, though it’s entirely unlike any traditional hand welding methods you’ve ever seen before. Today, we’ll explore how this technique works and the applications it’s useful for. Fire in the hole!
Don’t Blow Them Apart, Blow Them Together!
Explosion welding occurs near-instantaneously, but is done in a progressive fashion. The angle of collision, as well as the speed of the explosive front, is key to getting a quality weld. Image credit: NASA, public domain
The technique of explosion welding is relatively new compared to other metal-joining techniques. In the two World Wars of the 20th century, pieces of shrapnel were often found stuck to armor plating. Close observation showed that shrapnel was in fact welding on to metal armor, rather than simply being embedded in such. Given that collisions between shrapnel and armor often occur without the extreme heat of typical welding operations, it indicated that it was instead great velocity of the impact between shrapnel and armor that was melding the metals together.
The same results were later recreated in the lab, and explosoin welding was developed into a refined technique after World War II. 1962 saw DuPont patent a process for explosion welding later to be known under the “Detaclad” trademark.
Madison, WI hackerspace Sector67 is in a period of transition as they move from their current rented location to a new property that will be their permanent home a half mile away. Last Wednesday (September 20, 2017) an unfortunate propane explosion in the new building led to the injury of Chris Meyer, the founder and director of the hackerspace.
The structure has been stabilized and renovation is continuing, but Chris was seriously burned and will be in the hospital for at least a month with a much longer road to complete recovery. It is fortunate that nobody else was injured.
This accident comes at a time when Sector67 essentially has two spaces to maintain; the existing space is still running, but many of the members are focused on the construction of the new space. The building needs significant work before the move can take place. Currently the roof is being raised so that the building can go from one awkward-height story to two normal stories, doubling the size. An expiring lease and imminent demolition of the current location by developers means the clock is still ticking on the move, and this explosion means Sector67 will have to work even harder, and without the presence and constant effort of the person who has been leading the project.
[Matthias Wandel] is a woodworker par excellence. He’s the guy behind all those wooden gear contraptions, he made cove molding on a table saw, and if the phrase, ‘don’t do this unless you know what you’re doing’ applies to anyone, it applies to [Matthias]. Now he’s getting into the fidget spinner craze, but there’s a problem in the workshop: [Matthias] couldn’t find the right sized drill bit, so he modified a Forstner bit to contain the heart of a spinner.
[Matthias] has a few roller skate bearings, which are 22mm in diameter. However, the closest drill to this size was 7/8″, or 22.23mm. A drill can be ground down, so the bit was chucked into a hand drill and taken over to the bench grinder. As with most things [Matthias] demonstrates, you shouldn’t do this unless you know what you’re doing. [Matthias] does.
With the bit ground down to 22mm, [Matthias] drilled a hole in a piece of wood, inserted the bearing, and completed an epic quest that was his destiny. There is no use for fidget spinners, so [Matthias] decided to make this one explode. After cutting several notches in this wooden spinner, [Matthias] applied shop air liberally and spun the spinner up until it fell apart.
You can check out the video of the fidget spinner carnage below, or check out [Matthias]’ write-up here.
Normally, when something explodes it tends to be a bad day for all involved. But not every explosion is intended to maim or kill. Plenty of explosions are designed to save lives every day, from the highway to the cockpit to the power grid. Let’s look at some of these pyrotechnic wonders and how they keep us safe.
Explosive Bolts
The first I can recall hearing the term explosive bolts was in relation to the saturation TV coverage of the Apollo launches in the late 60s and early 70s. Explosive bolts seemed to be everywhere, releasing umbilicals and restraining the Saturn V launch stack on the pad. Young me pictured literal bolts machined from solid blocks of explosive and secretly hoped there was a section for them in the hardware store so I could have a little fun.
Pyrotechnic fasteners are mechanical fasteners (bolts, studs, nuts, etc.) that are designed to fail in a predictable fashion due to the detonation of an associated pyrotechnic device. Not only must they fail predictably, but they also have to be strong enough to resist the forces they will experience before failure is initiated. Failure is also typically rapid and clean, meaning that no debris is left to interfere with the parts that were previously held together by the fastener. And finally, the explosive failure can’t cause any collateral damage to the fastened parts or nearby structures.
Pyrotechnic fasteners fall into two broad categories. Explosive bolts look much like regular bolts, and are machined out of the same materials you’d expect to find any bolt made of. The explosive charge is usually internal to the shank of the bolt with an initiating device of some sort in the head. To ensure clean, predictable separation, there’s a groove machined into the bolt to create a shear plane.
Frangible nuts are another type of pyrotechnic fastener. These tend to be used for larger load applications, like holding down rockets. Frangible nuts usually have two smaller threaded holes adjacent to the main fastener thread; pyrotechnic booster charges split the nut across the plane formed by the threaded holes to release the fastener cleanly.
“Eject! Eject! Eject!”
Holding back missiles is one thing, but where pyrotechnic fasteners save the most lives might be in the cockpits of fighter jets around the world. When things go wrong in a fighter, pilots need to get out in a hurry. Strapping into a fighter cockpit is literally sitting on top of a rocket and being surrounded by explosives. Most current seats are zero-zero designs — usable at zero airspeed and zero altitude — that propel the seat and pilot out of the aircraft on a small rocket high enough that the parachute can deploy before the pilot hits the surface. Dozens of explosive charges take care of ripping the aircraft canopy apart, deploying the chute, and cutting the seat free from the parachuting pilot, typically unconscious and a couple of inches shorter from spinal disc compression after his one second rocket ride.
There’s little doubt that airbags have saved countless lives since they’ve become standard equipment in cars and trucks. When you get into a modern vehicle, you are literally surrounded by airbags — steering wheel, dashboard, knee bolsters, side curtains, seatbelt bags, and even the rear seat passenger bags. And each one of these devices is a small bomb waiting to explode to save your life.
When we think of explosives we tend to think of substances that can undergo rapid oxidation with subsequent expansion of hot gasses. By this definition, airbag inflators aren’t really explosives, since they are powered by the rapid chemical decomposition of nitrogenous compounds, commonly sodium azide in the presence of potassium nitrate and silicon dioxide. But the difference is purely academic; anyone who has ever had an airbag deploy in front of them or watched any of the “hold my beer and watch this” airbag prank video compilations will attest to the explosive power held in that disc of chemicals.
When a collision is detected by sensors connected to the airbag control unit (ACU), current is applied to an electric match, similar to the engine igniters used in model rocketry, buried within the inflator module. The match reaches 300°C within a few milliseconds, causing the sodium azide to rapidly decompose into nitrogen gas and sodium. Subsequent reactions mop up the reactive byproducts to produce inert silicate glasses and add a little more nitrogen to the mix. The entire reaction is complete in about 40 milliseconds, and the airbags inflate fully within 80 milliseconds, only to deflate again almost instantly through vent holes in the back of the bag. By the time you perceive that you were in an accident, the bag hangs limply from the steering wheel and with any luck, you get to walk away from the accident.
Grid Down
We’ve covered a little about utility poles and all the fascinating bits of gear that hang off them. One of the pieces of safety gear that lives in the “supply space” at the top of the poles is the fuse cutout, or explosive disconnector. This too is a place where a small explosion can save lives — not only by protecting line workers but also by preventing a short circuit from causing a fire.
Cutouts are more than just fuses, though. Given the nature of the AC transmission and distribution grid, the lines that cutouts protect are at pretty high voltages of 11 kV or more. That much voltage means the potential for sustained arcing if contacts aren’t rapidly separated; the resulting plasma can do just as much if not more damage than the short circuit. So a small explosive cartridge is used to rapidly kick the fuse body of a cutout out of the frame and break the circuit as quickly as possible. Arc suppression features are also built into the cutout to interrupt the arc before it gets a chance to form.
[Big Clive] recently did a teardown of another piece of line safety gear, an 11 kV lightning arrestor with an explosive disconnector. With a Dremel tool and a good dose of liquid courage, he liberated a carbon slug from within the disconnector, which when heated by a line fault ignites a .22 caliber charge similar to those used with powder actuated fastener tools. The rapid expansion of gasses ruptures the cases of the disconnector and rapidly breaks the circuit.
Conclusion
We’ve covered a few of the many ways that the power of expanding gas can be used in life safety applications. There are other ways, too — snuffing out oil field fires comes to mind, as does controlled demolition of buildings. But the number of explosives protecting us from more common accidents is quite amazing, all the more so when you realize how well engineered they are. After all, these everyday bombs aren’t generally blowing up without good reason.
On the morning of September 26th, 2013 the city of Orlando was rocked by an explosion. Buildings shook, windows rattled, and Amtrak service on a nearby track was halted. TV stations broke in with special reports. The dispatched helicopters didn’t find fire and brimstone, but they did find a building with one wall blown out. The building was located at 47 West Jefferson Street. For most this was just another news day, but a few die-hard fans recognized the building as Creative Engineering, home to a different kind of explosion: The Rock-afire Explosion.
The Inventor and His Band of Robots
Many of us have heard of the Rock-afire Explosion, the animatronic band which graced the stage of ShowBiz pizza from 1980 through 1990. For those not in the know, the band was created by the inventor of Whac-A-Mole, [Aaron Fechter], engineer, entrepreneur and owner of Creative Engineering. When ShowBiz pizza sold to Chuck E. Cheese, the Rock-afire Explosion characters were replaced with Chuck E. and friends. Creative Engineering lost its biggest customer. Once over 300 employees, the company was again reduced to just [Aaron]. He owned the building which housed the company, a 38,000 square foot shop and warehouse. Rather than sell the shop and remaining hardware, [Aaron] kept working there alone. Most of the building remained as it had in the 1980’s. Tools placed down by artisans on their last day of work remained, slowly gathering dust.
On the morning of September 26th, 2013 the city of Orlando was rocked by an explosion. Buildings shook, windows rattled, and Amtrak service on a nearby track was halted. TV stations broke in with special reports. The dispatched helicopters didn’t find fire and brimstone, but they did find a building with one wall blown out. The building was located at 47 West Jefferson Street. For most this was just another news day, but a few die-hard fans recognized the building as Creative Engineering, home to a different kind of explosion: The Rock-afire Explosion.
Many of us have heard of the Rock-afire Explosion, the animatronic band which graced the stage of ShowBiz pizza from 1980 through 1990. For those not in the know, the band was created by the inventor of Whac-A-Mole, [Aaron Fechter], engineer, entrepreneur and owner of Creative Engineering. When ShowBiz pizza sold to Chuck E. Cheese, the Rock-afire Explosion characters were replaced with Chuck E. and friends. Creative Engineering lost its biggest customer. Once over 300 employees, the company was again reduced to just [Aaron]. He owned the building which housed the company, a 38,000 square foot shop and warehouse. Rather than sell the shop and remaining hardware, [Aaron] kept working there alone. Most of the building remained as it had in the 1980’s. Tools placed down by artisans on their last day of work remained, slowly gathering dust.
