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26 Articles

Photo of AlphaPhoenix looking at an airplane flying through the air

Weighing An Airplane As It Flies Overhead

June 18, 2025 by 52 Comments

Recently, [AlphaPhoenix] weighed an airplane. Normally, that wouldn’t be much of an accomplishment. Except in this case, the airplane happened to be in flight at the time. In fact we’re not sure what is more remarkable, as he not only weighed real actual airplanes but a paper airplane too!

The sealed box essentially acts as a pressure sensor.

To test the concept, a large scale is made from foamcore and four load cells which feed into an Arduino which in turn is connected to a laptop for a visualization. After a brief test with a toy car, [AlphaPhoenix] goes on to weigh a paper airplane as it flies over the scale. What we learn from the demonstration is that any weight from a flying object is eventually transferred to the ground via the air.

In the second part of the video a new, smaller, type of scale is created and taken to the airport where airplanes flying overhead are weighed over the course of three days. This new apparatus is basically a pressure sensor enclosed in a nominally air-tight box, essentially a fancy type of barometer. Measurements are taken, assumptions are made, and figures are arrived at. Unfortunately the calculated results are off by more than one order of magnitude, but that doesn’t stop this experiment from having been very cool!

If you’re interested in weighing things for fun or profit be sure to check out Hackaday Prize 2022: Arduino-Powered Weighing Scale Has A Real Analog Display or Reverse Engineering A Bathroom Scale For Automated Weight Tracking.

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Hefty 3D Printed Quadcopter Meets Nasty End

September 1, 2023 by 26 Comments

You can readily buy all kinds of quadcopters off the shelf these days, but sometimes it’s more fun to build your own. [Michael Rechtin] did just that, with a hefty design of his own creation.

The build is an exploration of all kinds of interesting techniques. The frame itself uses generative design techniques to reduce weight while maintaining strength, while the motors themselves make heavy use of 3D-printed components. The design is modular and much of it slots together, too, and it uses a homebrewed flight controller running dRehmflight. It draws 2.5 kW from its lithium polymer batteries and weighs over 5 kg.

The DIY ethos led to some hurdles, but taught [Michael] plenty along the way. Tuning the PID control loop posed some challenges, as did one of the hand-wound motors being 5% down on thrust.  Eventually, though, the quad flew well enough to crash into a rectangular gate, before hitting the ground. Any quad pilot will tell you that these things happen. Drilling into the quad with a battery still inside then led to a fire, which did plenty of further damage.

[Michael’s] quad doesn’t appear to be specifically optimized to any one task, and it’s easy to see many ways in which it could be lightened or otherwise upgraded. However, as a freeform engineering thinking exercise, it’s interesting to watch as he tackles various problems and iteratively improves the design. Video after the break.

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Trebuchet Sends Eggs Flying

July 14, 2023 by 7 Comments

Without any sort of restrictions on designs for trebuchets, these medieval siege weapons are known to send 90 kilogram projectiles over 300 meters. The egg-launching trebuchet contest that [AndysMachines] is entering, on the other hand, has a few limitations that dramatically decreased the size of the machines involved. The weight of the entire device is limited to no more than 3 kg, with any physical dimension no more than 300 mm, but that’s more than enough to send an egg flying across a yard with the proper design and tuning for maximum distance.

Trebuchets distinguish themselves amongst other siege weapons by using a falling weight to launch the projectile. The rules of this contest allow for the use of springs, so [AndysMachines] is adding a spring in between the trebuchet arm and the weight in order to more efficiently deliver the energy from the falling weight. More fine tuning of the trebuchet was needed before the competition, though, specifically regarding the stall point for the trebuchet. This is the point where the forces acting on the arm from the projectile and the weight are balanced, and moving this point to allow the projectile to release at a 45-degree angle was needed for maximum distance.

The video goes into a lot of detail about other fine-tuning of a trebuchet like this, aided by some slow-motion video analysis. In the end, [AndysMachines] was able to launch the egg over ten meters with this design. Of course, if you want to throw out the rule book and replace the eggs with ball bearings and the aluminum and steel with titanium, it’s possible to build a trebuchet that breaks the sound barrier.

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Jump Like Mario With This Weighted Wearable

May 11, 2023 by 5 Comments

Virtual reality has come a long way in the past decade, with successful commercial offerings for gaming platforms still going strong as well as a number of semi-virtual, or augmented, reality tools that are proving their worth outside of a gaming environment as well. But with all this success they still haven’t quite figured out methods of locomotion that feel natural like walking or running. One research group is leaping to solve one of these issues with JumpMod: a wearable device that enhances the sensation of jumping.

The group, led by [Pedro Lopes] at the University of Chicago, uses a two-kilogram weight worn on the back to help provide the feeling of jumping or falling. By interfacing it with the virtual reality environment, the weight can quickly move up or down its rails when it detects that the wearer is about to commit to an action that it thinks it can enhance. Wearers report feeling like they are jumping much higher, or even smashing into the ground harder. The backpack offers a compact and affordable alternative to the bulky and expensive hardware traditionally used for this purpose.

With builds like these, we would hope the virtual reality worlds that are being created become even more immersive and believable. Of course that means a lot more work into making other methods of movement in the virtual space feel believable (like walking, to start with) but it’s an excellent piece of technology that shows some progress. Augmenting the virtual space doesn’t always need bulky hardware like this, though. Take a “look” at this device which can build a believable virtual reality space using nothing more than a webcam.

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PCB Gets Weighty Assignment

January 5, 2023 by 9 Comments

[Curious Scientist] tried building an integrated strain gauge on a PCB, but ran into problems. Mainly, the low resistance of the traces didn’t show enough change under strain to measure easily. Even placing a proper strain gauge on the PCB had limitations. His new design uses a bridge design to make the change in the gauges usefully large. You can see a video of the project below.

Bridging strain gauges isn’t a new idea. However, the novelty of this design is that the PCB has cantilever beams that facilitate the weighing. Standoffs mount a plate to the beams so that weight on the plate cause deformation on the beam that the strain gauges can measure.

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Does This Lead Make My Car Look Fat?

January 5, 2022 by 64 Comments

When looking at the performance of a vehicle, weight is one of the most important factors in the equation. Heavier vehicles take more energy to accelerate and are harder to stop. They’re also more difficult to control through the corners. Overall, anything that makes a vehicle heavier typically comes with a load of drawbacks to both performance and efficiency. You want your racecar as light as possible.

However, now and then, automakers have found reason to intentionally add large weights to vehicles. We’ll look at a couple of key examples, and discuss why this strange design decision can sometimes be just what the engineers ordered.

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IBM Cheese Cutter Restoration

October 12, 2021 by 31 Comments

For a while now, Mac Pro towers have had the nickname “cheese grater” because of their superficial resemblance to this kitchen appliance. Apple has only been a company since the 70s, though, and is much newer than one of its historic rivals, IBM. In fact, IBM is old enough to have made actual cheese-related computers as far back as the 1910s, and [Hand Tool Rescue] recently obtained one of these antique machines for a complete restoration.

The tool arrived to the restoration workshop in a state so poor that it was difficult to tell what many of the parts on the machine did except for the large cleaver at the top. The build starts with a teardown to its individual parts, cleaning and restoring them to their original luster, machining new ones where needed, and then putting it all back together. The real mystery of this build was what the levers on the underside of the machine were supposed to do, but after the refurbishment it was discovered that these are the way that portions the cheese wheel would be accurately sized and priced before a cut was made.

By placing a section of a wheel of cheese on the machine and inputting its original weight with one of the levers, the second lever is adjusted to the weight of cheese that the customer requested, which rotates the wheel of cheese to the correct position before a cut is made. To us who are spoiled with a world full of electronic devices, a mechanical computer like this seems almost magical, especially with how accurate it is, but if your business in the 1910s involved cheese, this would have been quite normal. In fact, it would be 50 more years before IBM created the machines that they’re more commonly known for.

Thanks to [Jasper Jans] for the tip!

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