OSHW Model Rocket Kit Embraces The Hexagon

July 27, 2024 by Tom Nardi 19 Comments

If you’ve ever built a model rocket, you’ll know there’s not a whole lot to them. Essentially it’s a cardboard tube, a plastic nosecone, some fins, and a little clip that will keep it riding the launch rail as it accelerates off the pad. Extra points awarded if you add in a parachute, but strictly speaking, even that’s a luxury. Stick an Estes motor in that thing and send it.

But pointing out that lightweight cardboard tubes can be tricky to ship without getting crushed, [Concrete Dog] has come up with HEXA, a clever model rocket kit that uses pre-scored cardstock instead. The immediate advantage is that this allows the rocket to be shipped as flat sheets of material, but as a secondary bonus, once folded into its final shape the rocket has an awesome hexagonal cross section.

As with a traditional kit, both the nosecone and fins are plastic. Except here they’ve been 3D printed in either PLA or PETG depending on their proximity to he hot and fiery area of the rocket. [Concrete Dog] says the printed parts are largely ready to fly as-is, but that some quality time with a piece of sandpaper and a coat of paint could improve the aerodynamics a bit if you were so inclined.

Ready for the best part? [Concrete Dog] has decided to release all of the design files for the rocket under the CERN Open Hardware Licence, meaning you’re free to reproduce and modify the rocket as you see fit. In fact, on July 24th, the HEXA rocket was officially certified as Open Hardware by the Open Source Hardware Association (OSHWA) — a first for a DIY rocket, as far as we can tell.

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George Washington Gets Cleaned Up With A Laser

July 27, 2024 by Tom Nardi 5 Comments

Now, we wouldn’t necessarily call ourselves connoisseurs of fine art here at Hackaday. But we do enjoy watching [Julian Baumgartner]’s YouTube channel, where he documents the projects that he takes on as a professional conservator. Folks send in their dirty or damaged paintings, [Julian] works his magic, and the end result often looks like a completely different piece. Spoilers: if you’ve ever looked at an old painting and wondered why the artist made it so dark and dreary — it probably just needs to be cleaned.

Anyway, in his most recent video, [Julian] pulled out a piece of gear that we didn’t expect to see unleashed against a painting of one of America’s Founding Fathers: a Er:YAG laser. Even better, instead of some fancy-pants fine art restoration laser, he apparently picked up second hand unit designed for cosmetic applications. The model appears to be a Laserscope Venus from the early 2000s, which goes for about $5K these days.

Now, to explain why he raided an esthetician’s closet to fix up this particular painting, we’ve got to rewind a bit. As we’ve learned from [Julian]’s previous videos, the problem with an old dirty painting is rarely the paining itself, it’s the varnish that has been applied to it. These varnishes, especially older ones, have a tendency to yellow and crack with age. Now stack a few decades worth of smoke and dirt on top of it, and you’ve all but completely obscured the original painting underneath. But there’s good news — if you know what you’re doing, you can remove the varnish without damaging the painting itself.

In most cases, this can be done with various solvents that [Julian] mixes up after testing them out on some inconspicuous corner of the painting. But in this particular case, the varnish wasn’t reacting well to anything in his inventory. Even his weakest solvents were going right through it and damaging the paint underneath.

Because of this, [Julian] had to break out the big guns. After experimenting with the power level and pulse duration of the 2940 nm laser, he found the settings necessary to break down the varnish while stopping short of cooking the paint it was covering. After hitting it with a few pulses, he could then come in with a cotton swab and wipe the residue away. It was still slow going, but it turns out most things are in the art conservation world.

This isn’t the first time we’ve covered [Julian]’s resourceful conservation methods. Back in 2019, we took at look the surprisingly in-depth video he created about the design and construction of his custom heat table for flattening out large canvases.

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Vintage Ribbon Cable Repair Saves Poqet PC

July 26, 2024 by Jenny List 19 Comments

It sometimes seems as though computing power in your pocket is a relatively new phenomenon, but in fact there have been ultraportable computers since the 8-bit era. They started to become useful around the end of the 1980s though as enterprising manufacturers started cramming full-fat PC XTs into pocket form factors. Of these the one to own was the Poqet PC, a slim clamshell design that would run for ages on a pair of AA cells . If you have one today you’d be lucky if its display ribbon cable is without faults though, and [Robert’s Retro] is here with a fix previously thought impossible.

A large proportion of the video below the break is devoted to dismantling the unit, no easy task. The cable once exposed is found to have delaminated completely, and he takes us through the delicate task of attaching a modern equivalent. We particularly like the way in which the cable’s own springiness is used to retract it. The result has a white cable rather than the original black, but that’s a small price to pay for a machine that works rather than a broken paperweight.

If early pocket computing is your thing, it’s a subject we’ve covered before.

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Analyzing Feature Learning In Artificial Neural Networks And Neural Collapse

July 26, 2024 by Maya Posch 9 Comments

Artificial Neural Networks (ANNs) are commonly used for machine vision purposes, where they are tasked with object recognition. This is accomplished by taking a multi-layer network and using a training data set to configure the weights associated with each ‘neuron’. Due to the complexity of these ANNs for non-trivial data sets, it’s often hard to make head or tails of what the network is actually matching in a given (non-training data) input. In a March 2024 study (preprint) by [A. Radhakrishnan] and colleagues in Science an approach is provided to elucidate and diagnose this mystery somewhat, by using what they call the average gradient outer product (AGOP).

Defined as the uncentered covariance matrix of the ANN’s input-output gradients averaged over the training dataset, this property can provide information on the data set’s features used for predictions. This turns out to be strongly correlated with repetitive information, such as the presence of eyes in recognizing whether lipstick is being worn and star patterns in a car and truck data set rather than anything to do with the (highly variable) vehicles. None of this was perhaps too surprising, but a number of the same researchers used the same AGOP for elucidating the mechanism behind neural collapse (NC) in ANNs.

NC occurs when an ANN gets overtrained (overparametrized). In the preprint paper by [D. Beaglehole] et al. the AGOP is used to provide evidence for the mechanism behind NC during feature learning. Perhaps the biggest take-away from these papers is that while ANNs can be useful, they’re also incredibly complex and poorly understood. The more we learn about their properties, the more appropriately we can use them.

Your QuickTake Camera And Your Modern PC

July 26, 2024 by Jenny List 10 Comments

An object of desire back in the mid-1990s might have been Apple’s QuickTake camera. In a form factor not unlike a monocular it packed a 640×480 digital camera, the images from which could be downloaded to a computer via a serial cable. A quarter century later it’s a great retro camera for the enthusiast, but both the serial ports and the operating systems needed to run its software have passed into history. Time for the junk pile? Not at all, for [Crazylegstoo] has produced a new piece of software for 2024 that works for both QuickTake 100 and 150 cameras with USB serial ports on modern operating systems.

Called JQuickTake, it’s a Java app which has the advantage of building on that early Java promise of running cross platform so can be had for Mac or Windows. It allows retrieval of both metadata and images from the camera, but sadly it doesn’t display any of the images. It also doesn’t work with the QuickTake 200. Happily though, there are instructions for building a serial cable, and suggestions for how to deal with the proprietary QTK image format.

Meanwhile if you lack a PC or Mac all is not lost. You can also use these cameras with an Apple II.

Header image: Hannes Grobe, CC BY-SA 4.0.

Electromagnetic Actuator Mimics Muscle

July 26, 2024 by Lewin Day 11 Comments

Most electromagnetic actuators are rotating motors, or some variation on the theme, like servos. However, it’s possible to do linear actuation with electomagnetics, too. [Adrian Perez] demonstrates this with Linette, his design of a linear actuator that he was inspired to build by the structure of our own muscles.

The design uses a coil of copper wire in a 3D-printed plastic housing, surrounded by a claw full of strong magnets. When the coil is activated, the magnets are pulled towards the coil. When the coil is not energized, the magnets fall away. [Adrian] demonstrates the actuator under the control of an Arduino, which switches power to the coil to move it up and down.

He also notes that the design is similar solenoids and voice coil style actuators, though unlike most his uses discrete magnets rather than a single monolithic magnet. It’s possible to get more capacity out of the Linette design through stacking. You can parallelize the actuators to get more pulling force, with neighboring coils sharing the same magnets. Alternatively, you can stack them in series to get longer stroke lengths.

[Adrian] hasn’t put the design to a practical application yet, but we could see multiple uses for robotics or small machines. We’ve seen some other neat DIY magnetic actuators before, too. Video after the break.