Optimize Your Paper Planes With This Cardboard Wind Tunnel

March 22, 2023 by Robin Kearey 6 Comments

We at Hackaday are great fans of hands-on classroom projects promoting science, technology, engineering and math (STEM) subjects – after all, inspiring kids with technology at a young age will help ensure a new generation of hardware hackers in the future. If you’re looking for an interesting project to keep a full classroom busy, have a look at [drdonh]’s latest project: a fully-functional wind tunnel made from simple materials.

Built from cardboard, it has all the same components you’d find in a full-size aerodynamics lab: a fan to generate a decent stream of air, an inlet with channels to stabilize the flow, and a platform to mount experiments on. There’s even some basic instrumentation included that can be used to measure drag and lift, allowing the students to evaluate the drag coefficients of different car designs or the lift-generating properties of various airfoils. Continue reading “Optimize Your Paper Planes With This Cardboard Wind Tunnel” →

Reverse-Engineering An Elevator Control Panel Results In Clicky Goodness

February 4, 2021 by Dan Maloney 9 Comments

We have to admit that in the hardware hacking universe, there aren’t generally too many chances to hack elevators. Well, at least not opportunities that don’t also include the risk of incarceration. But fortune favors the bold, and when he found the remains of an elevator control panel in an abandoned Croatian resort hotel, [Davor Cihlar] undertook an extensive and instructive reverse-engineering of the panel.

The video below highlights his efforts, which were considerable given the age and state of the panel. This is a relay-only control panel, after all, with most of the relays missing and a rat’s nest of wires connecting the sockets. So [Davor] put his “RevIng” concept to work. This uses a custom PCB with a microcontroller on-board that plugs into each relay socket and probes the connections between it and every other socket. Very clever stuff, and it presented him with the data needed to develop a ladder-logic diagram of the board, with the help of some custom software.

With the original logic in hand, [Davor] set about building a simulator for the panel. It’s a lovely piece of work, with buttons and lights to mimic the control panel inside the elevator car, as well as the call stations that would have graced each lobby of the hotel. Interestingly, he found logic that prevented the elevator from being called to some floors from anywhere but inside the car. The reason remains a mystery, but we suppose that a hotel built by Penthouse publisher [Bob Guccione] would have plenty of secrets.

We love the supremely satisfying clickiness of this build, and the reverse engineering prowess on display, but we can’t find much practical use for something like this. Then again, DIY elevators are a thing.

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Coandă Effect Makes A Better Hovercraft Than A Quadcopter

October 17, 2019 by Dan Maloney 22 Comments

Leaving no stone unturned in his quest for alternative and improbable ways to generate lift, [Tom Stanton] has come up with some interesting aircraft over the years. But this time he isn’t exactly flying, with this unusual Coandă effect hovercraft.

If you’re not familiar with the Coandă effect, neither were we until [Tom] tried to harness it for a quadcopter. The idea is that air moving at high speed across a curved surface will tend to follow it, meaning that lift can be generated. [Tom]’s original Coandă-copter was a bit of a bust – yes, there was lift, but it wasn’t much and wasn’t easy to control. He did notice that there was a strong ground effect, though, and that led him to design the hovercraft. Traditional hovercraft use fans to pressurize a plenum under the craft, lifting it on a low-friction cushion of air. The Coandă hovercraft uses the airflow over the curved hull to generate lift, which it does surprisingly well. The hovercraft proved to be pretty peppy once [Tom] got the hang of controlling it, although it seemed prone to lifting off as it maneuvered over bumps in his backyard. We wonder if a control algorithm could be devised to reduce the throttle if an accelerometer detects lift-off; that might make keeping the craft on the ground a bit easier.

As always, we appreciate [Tom]’s builds as well as his high-quality presentation. But if oddball quadcopters or hovercraft aren’t quite your thing, you can always put the Coandă effect to use levitating screwdrivers and the like.

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A Crane Fit For Any Workshop

September 26, 2019 by Jenny List 18 Comments

Sometimes we will encounter items in our workshops that are a little bigger than we bargained for. An engine block, an anvil, or a particularly substantial machine tool. Lifting these things may be possible, but doing so risks injury, perhaps a hernia or worse. For these moments a particularly well-appointed workshop will include a small crane, and [Workshop from scratch] has posted a video that we’ve placed below the break showing the construction of a particularly nice model.

The fabrication of a crane is not in itself a difficult task, in that most metalwork-minded readers could probably make one. What’s appealing about this video is the sense of gratification at watching metalwork being done well, and that while he does use a bandsaw and a drill press there’s not a lot in the video that couldn’t be done with more basic tools. The result is a handsome item that is probably better than many commercial offerings, though the gut feeling here is that the pivot points would have been better made with a sleeve and pin rather than a threaded bolt. The lifting effort comes from an off-the-shelf hydraulic ram.

Cranes feature here surprisingly rarely, but at least we’ve brought you a balcony crane.

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Quilting Desk Is An Absolute Unit

August 1, 2019 by Kristina Panos 10 Comments

Most hobbies come with a lot of tools, and thread injecting is no different. Quilting itself may be Queen Hobby when it comes to the sheer volume of things you can buy: specialized templates, clips, thimbles, disappearing ink pens, and so on. And of course, you want it all within arm’s reach while sitting at the machine.

Years ago, [KevsWoodworks] built an impressive custom quilting desk for his wife. He’d added on to it over the years, but it was time for a bigger one. This beautiful beast has 21 drawers and 6 large cubbyholes for plastic bins. At the wife’s request, one of the drawers is vertical. [Kev] doesn’t say what she put in there, but if it were our desk, that’s where we’d stash all our large plastic rulers that need to be kept flat (or vertical). There’s also a lift, so any sewing machine can be brought up flush with the enormous top.

Fortunately for us, [Kev] likes to teach. He documented the build in a series of videos that go nicely with his CAD drawings, which are available for download. Thread your way past the break to see those videos.

Want to do some thread injecting, but don’t want to spend hundreds on a machine? We got lucky with our entry-level injector. If yours is a piece of scrap or has limited stitch options, replace the motor, or add an Arduino.

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Amplifier Controlled Motorized Display

October 6, 2018 by Tom Nardi 4 Comments

It’s easy to get jaded by gadgets like the Chromecast or Sonos, which let the user control AV equipment remotely from a mobile device or computer. You can pick something to play from your phone and send it off to your speakers via the magic of Wi-Fi. But it’s still nice to have a display to look at for music visualizations and that sort of thing, at least occasionally.

To address this only occasional desire to have a display on your media setup, you could follow in the footsteps of [Steven Elliott] and create a DIY motorized display which only pops up when needed. Inspired by seeing videos of TVs rising out of cabinets and other such trickery, he decided to create his own version using an old computer monitor he had lying around.

The monitor is lifted with a beefy linear actuator, which has been placed inside of a square metal fence post to keep from rotating. It already had a power supply and control board with relays for extending and retracting, so [Steven] just needed to find a convenient way of firing them off.

The answer came from a somewhat unconventional source: his amplifier. [Steven] explains that many amplifiers feature a “Trigger Output”, which uses a standard stereo 3.5mm connector and sends a 12V pulse to connected device. This is generally used to turn on downstream devices when the amplifier switches to the respective input. It’s too short and not nearly powerful enough to close the actuators relays, but it’s easy enough to detect.

[Steven] uses a LeoStick microcontroller to wait for the pulse from the amplifier, and then use that to raise or lower the display depending on the selected input. There’s also a SPST momentary switch which can be used to trigger the actuator manually. Beyond the fact the linear actuator is a bit loud, he says the setup works very well and prevents him from having to start up his projector if he just wants to take a quick glance at what’s playing or program his DVR.

We don’t see many motorized display lifts like this anymore, not since wall mounted LCDs became popular anyway. But it’s still a cool effect, and today made quite a bit easier thanks to the fact that TVs and monitors no longer weigh as much as a small car.

[Thanks to Baldpower for the tip.]

A DIY Balcony Crane Lifts Groceries For The Lazy But Patient

September 9, 2018 by Dan Maloney 39 Comments

If necessity is the mother of invention, then laziness is probably its father. Or at least a close uncle. Who hasn’t thought, “There has to be a better way to do this, one that doesn’t involve me burning precious calories”?

Motivational laziness seems to increase with potential energy, as anyone who needs to haul groceries up four flights of stairs will tell you. This appears to be where this balcony-mounted drill-powered crane came from. Starting with a surplus right-angle gearbox and drum, [geniusz K] fabricated the rest of the crane from steel plate and tubing. We like the quality of fabrication and the tip on making slip couplings from bits of square tubing. The finished product got a nice coat of brown paint to match the balcony railing; keeping the neighbors happy is always important. He tested the crane with a 20-kg weight before installing it on the balcony and put it to work hauling groceries up three stories. Check out the build and the test in the video below.

While it won’t set any speed records, at least the drill is doing the work. But what if you’re impatient as well as lazy? Aside from being two-thirds of the way to programming greatness, you may have to up the game. A heavy-lift quadcopter, perhaps?

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