Embedding Lenticular Lenses Into 3D Prints

January 11, 2025 by Donald Papp 11 Comments

A research project shows that it’s possible to create complex single-piece lenticular objects, or objects that have lenticular lenses built directly into them. The result is a thing whose appearance depends on the viewer’s viewpoint. The object in the image above, for example, is the same object from five different angles.

What’s really neat is that these colorful things have been 3D printed as single objects, no separate lenses or assembly required. Sure, it requires equipment that not just everyone has on their workbench, but we think a clever hacker could put the underlying principles to work all the same.

This lampshade (which was 3D printed as a single object) changes color and displays *Good Day* or *Good Night* depending on viewing angle.

The effect is essentially the same as what is sometimes seen in children’s toys and novelties — where a perceived image changes depending on the viewing angle. This principle has been used with a lenticular lens sheet to create a clever lenticular clock, but there’s no need to be limited by what lenses are available off the shelf. We’ve seen a custom 3D printed lenticular lens slapped onto a mobile device to create a 3D screen effect.

Coming back to the research, the objects researchers created go beyond what we’ve seen before in two important ways. First is in using software to aid in designing the object and it’s viewpoints (the plugin for Rhino 3D is available on GitHub), and the second is the scale of the effect. Each lens can be thought of as a pixel whose color depends on the viewing angle, and by 3D printing the lenses, one can fit quite a lot of them onto a surface with a high degree of accuracy.

To make these objects researchers used PolyJet 3D printing, which is essentially UV-cured resin combined with inkjet technology, and can create multi-color objects in a single pass. The lenses are printed clear with a gloss finish, the colors are embedded, and a final hit of sprayed varnish helps with light transmission. It sure beats placing hundreds of little lenses by hand.

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AA Battery Performances Tested, So Get The Most For Your Money

January 10, 2025 by Donald Papp 38 Comments

[Project Farm] has a video in which a wide variety of AA cells are analyzed and compared in terms of capacity, internal resistance, ability to deliver voltage under load, and ability to perform in sub-freezing temperatures. Alkaline, lithium, and even some mature rechargeable cells with a couple thousand cycles under their belt were all compared. There are a few interesting results that will can help you get the most from your money the next time you’re battery shopping.

The video embedded below demonstrates a set of tests that we recommend you check out, but the short version is that more expensive (non-rechargeable) lithium cells outperform their alkaline peers, especially when it comes to overall longevity, ability to perform under high-drain conditions, and low temperatures. Lithium cells also cost more, but they’re the right choice for some applications.

Some brands performed better and others worse, but outside of a couple stinkers most were more or less comparable. Price however, was not.

As for how different brands stack up against one another, many of them are more or less in the same ballpark when it comes to performance. Certainly there are better and worse performers, but outside of a couple of stinkers the rest measure up reasonably well. Another interesting finding was that among rechargeable cells that were all several years (and roughly 2,200 charge-discharge cycles) old, a good number of them still performed like new.

Probably the single most striking difference among the different cells is cost — and we’re not just talking about whether lithium versus alkaline AAs are more cost-effective in the long run. Some brands simply cost twice as much (or more!) than others with comparable performance. If you’re in a hurry, jump to [Project Farm] presenting the final ranked results at 19:45 in.

Relying on brand recognition may save you from buying complete junk, but it’s clearly not the most cost-effective way to go about buying batteries. These findings are similar to an earlier effort at wide-scale battery testing which also determined that factoring in price-per-cell was too significant to ignore.

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Gaze Upon This Omni-directional Treadmill’s Clever LEGO Construction

January 7, 2025 by Donald Papp 16 Comments

Want to see some wildly skillful LEGO construction? Check out [Banana Gear Studios]’ omni-directional treadmill which showcases not only how such a thing works, but demonstrates some pretty impressive problem solving in the process. Construction was far from straightforward!

A 9×9 grid of LEGO shafts all turning in unison is just one of the non-trivial design challenges.

In principle the treadmill works by placing an object on a bed of identical, rotating discs. By tilting the discs, one controls which edge is in contact with the object, which in turn controls the direction the object moves. While the concept is straightforward, the implementation is a wee bit more complex. LEGO pieces offer a rich variety of mechanical functions, but even so, making a 9×9 array of discs all rotate in unison turns out to be a nontrivial problem to solve. Gears alone are not the answer, because the shafts in such a dense array are a bit too close for LEGO gears to play nicely.

The solution? Break it down into 3×3 self-contained chunks, and build out vertically with gimbals to take up the slack for gearing. Use small elastic bands to transfer power between neighbors, then copy and paste the modular 3×3 design a few times to create the full 9×9 grid. After that it’s just a matter of providing a means of tilting the discs — which has its own challenges — and the build is complete.

Check out the video below to see the whole process, which is very nicely narrated and illustrates the design challenges beautifully. You may see some similarities to Disney’s own 360° treadmill, but as [Banana Gear Studios] points out, it is a technically different implementation and therefore not covered by Disney’s patent. In an ideal world no one would worry about getting sued by Disney over an educational LEGO project posted on YouTube, but perhaps one can’t be too careful.

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Turns Out Humans Are Terrible At Intuiting Knot Strength

January 6, 2025 by Donald Papp 36 Comments

We are deeply intuitively familiar with our everyday physical world, so it was perhaps a bit of a surprise when researchers discovered a blind spot in our intuitive physical reasoning: it seems humans are oddly terrible at judging knot strength.

One example is the reef knot (top) vs. the grief knot (bottom). One is considerably stronger than the other.

What does this mean, exactly? According to researchers, people were consistently unable to tell when presented with different knots in simple applications and asked which knot was stronger or weaker. This failure isn’t because people couldn’t see the knots clearly, either. Each knot’s structure and topology was made abundantly clear (participants were able to match knots to their schematics accurately) so it’s not a failure to grasp the knot’s structure, it’s just judging a knot’s relative strength that seems to float around in some kind of blind spot.

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Turning A Lada Into An EV With 50 Cordless Drills, Because Why Not?

January 1, 2025 by Donald Papp 47 Comments

[Garage 54] is no stranger to vehicle-related projects of the “because why not?” variety, and their latest is using 50 cordless drills combined into a monstrous mega-motor to turn a gutted (and extended) Lada into an electric vehicle (EV).

Doing this leans on some of [Garage 54]’s earlier projects, such as replacing the aforementioned Lada’s engine block with a frame containing sixteen chainsaws. That means they don’t need to start completely from scratch, and have a frame design that can drop into the vehicle once the “engine” is constructed.

Fifty cordless drills won’t set any efficiency records for EV engines, but it’s got a certain style.

Here’s what’s in the new engine: each of the drills has its chuck replaced with an aluminum pulley, and belts connect each group of drills to an output shaft. Ideally, every drill motor would run at the same time and at exactly the same speed, but one works with what they have. [Garage 54] originally worked to synchronize the drills by interfacing to each drill’s motor control board, but eventually opted to simply bypass all controls and power each drill’s motor directly from the batteries. Initial tests are done by touching bare cable ends with a turned-away face and squinted eyes, but we expect “Just A Big Switch” to end up in the final assembly.

It looks wild and we can think of more than a few inefficiencies present in a system like this, but the output shaft does turn and torque is being transferred, so the next step is interfacing to the car’s factory gearbox.

If it powers the car in any meaningful way, that Lada might very well become the world’s most gloriously hacked-together EV. And hey, if the power output of the EV motor is disappointing, you can just make your own.

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Porting Dragon’s Lair To The Game Boy Color Was A Technical Triumph

December 28, 2024 by Donald Papp 5 Comments

If you remember the 80s arcade game Dragon’s Lair, you probably also remember it was strikingly unlike anything else at the time. It didn’t look or play like anything else. So it might come as a surprise that it was ported to Nintendo’s Game Boy Color, and that took some doing!

Dragon’s Lair used LaserDisc technology, and gameplay was a series of what we’d today call quick-time events (QTE). The player essentially navigated a series of brief video clips strung together by QTEs. Generally, if the player chose correctly the narrative would progress. If they chose poorly, well, that’s what extra lives (and a stack of quarters) were for.

More after the break!

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Watch A 3D Scan Become A Car Body Model

December 20, 2024 by Donald Papp 1 Comment

Not all 3D scanning is alike, and the right workflow can depend on the object involved. [Ding Dong Drift] demonstrates this in his 3D scan of a project car. His goal is to design custom attachments, and designing parts gets a lot easier with an accurate 3D model of the surface you want to stick them on. But it’s not as simple as just scanning the whole vehicle. His advice? Don’t try to use or edit the 3D scan directly as a model. Use it as a reference instead.

Rather than manipulate the 3D scan directly, a better approach is sometimes to use it as a modeling reference to fine-tune dimensions.

To do this, [Ding Dong Drift] scans the car’s back end and uses it as a reference for further CAD work. The 3D scan is essentially a big point cloud and the resulting model has a very high number of polygons. While it is dimensionally accurate, it’s also fragmented (the scanner only captures what it can see, after all) and not easy to work with in terms of part design.

In [Ding Dong Drift]’s case, he already has a 3D model of this particular car. He uses the 3D scan to fine-tune the model so that he can ensure it matches his actual car where it counts. That way, he’s confident that any parts he designs will fit perfectly.

3D scanning has a lot of value when parts have to fit other parts closely and there isn’t a flat surface or a right angle to be found. We saw how useful it was when photogrammetry was used to scan the interior of a van to help convert it to an off-grid camper. Things have gotten better since then, and handheld scanners that make dimensionally accurate scans are even more useful.

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