Heavy-Duty Starter Motor Powers An Awesome Drift Trike

December 15, 2021 by Lewin Day 11 Comments

Starter motors aren’t typically a great choice for motorized projects, as they’re designed to give engines a big strong kick for a few seconds. Driving them continuously can often quickly overheat them and burn them out. However, [Austin Blake] demonstrates that by choosing parts carefully, you can indeed have some fun with a starter motor-powered ride.

[Austin] decided to equip his drift trike with a 42MT-equivalent starter motor typically used in heavy construction machinery. The motor was first stripped of its solenoid mechanism, which is used to disengage the starter from an engine after it has started. The housing was then machined down to make the motor smaller, and a mount designed to hold the starter on the drift trike’s frame.

A 36V battery pack was whipped up using some cells [Austin] had lying around, and fitted with a BMS for safe charging. The 12V starter can draw up to 1650 amps when cranking an engine, though the battery pack can only safely deliver 120 amps continuously. A Kelly controller for brushed DC motors was used, set up with a current limit to protect the battery from excessive current draw.

The hefty motor weighs around 50 pounds, and is by no way the lightest or most efficient drive solution out there. However, [Austin] reports that it has held up just fine in 20 minutes of near-continuous testing, despite being overvolted well beyond its design specification. The fact it’s operating at a tenth of its rated current may also have something to do with its longevity. It also bears noting that many YouTube EVs die shortly after they’re posted. Your mileage may vary.

For a more modern solution, you might consider converting an alternator into a brushless electric motor. Video after the break.

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Fabulous Flexure Mechanism Makes For Resetting Cat Calendar

December 14, 2021 by Kristina Panos 18 Comments

When we met [Amy Makes Stuff] at the 2019 Hackaday Superconference, we were immediately impressed with the array of flexure mechanisms displayed on a board hanging around her neck. That must be where we saw [Amy]’s original version of the cat calendar — a simple way to know for sure whether the shared house’s cat has been fed once, twice, or not at all on a given day.

Left: a simple flexure that gets heavily stressed when actuated. Right: a slightly more complicated flexure that uses less force.

Awesome as it is, the flexure mechanism doesn’t reset the yes/no indicators when the day clicks over — that has to be done manually. So when [Amy] was offered to try a small desktop CNC, she decided it was time to make a new version that resets automatically. Check it out in the video after the break, which also includes an exploration of [Amy]’s choice of flexure design as well as a bonus review of the CNC.

This is just an all-around great video, especially after [Amy] neglected to mill out the check marks and circles, sending her down a rabbit hole of attempting to make branding bits for these that could be chucked into a soldering iron. Unfortunately, the mill stops short of having the necessary mettle for milling metal.

Although [Amy] is likely known for her flexures, she has a ton of skills. Remember when she resurrected that burned and bubbled laser cutter? Or the time she machined a honing jig for hand-sharpening chisels and planes?

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Adding Wire Races Improves 3D-Printed Bearings

December 13, 2021 by Dan Maloney 35 Comments

Like a lot of power transmission components, bearings have become far easier to source than they once were. It used to be hard to find exactly what you need, but now quality bearings are just a few clicks away. They’re not always cheap though, especially when you get to the larger sizes, so knowing how to print your own bearings can be a handy skill.

Of course, 3D-printed bearings aren’t going to work in every application, but [Eros Nicolau] has a plan for that. Rather than risk damage from frictional heating by running plastic or metal balls in a plastic race, he uses wire rings as wear surfaces. The first video below shows an early version of the bearing, where a pair of steel wire rings lines the 3D-printed inner and outer races. These worked OK, but suffered from occasional sticky spots and were a bit on the noisy side.

The second video shows version two, which uses the same wire-ring race arrangement but adds a printed ball cage to restrain the balls. This keeps things quieter and eliminates binding, making the bearing run smoother. [Eros] also added a bit of lube to the bearing, in the form of liquid PTFE, better known as Teflon. It certainly seemed to smooth things out. We’d imagine PTFE would be more compatible with most printed plastics than, say, petroleum-based greases, but we’d be keen to see how the bearings hold up in the long term.

Maybe you recall seeing big 3D-printed bearings around here before? You’d be right. And we’ve got you covered if you need to learn more about how bearings work — or lubricants, for that matter.

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Snip Your Way To DIY PCB Castellations

December 11, 2021 by Dan Maloney 22 Comments

Castellated PCB edges are kind of magical. The plated semicircular features are a way to make a solid, low-profile connection from one board to another, and the way solder flows into them is deeply satisfying. But adding them to a PCB design isn’t always cheap. No worries there — you can make your own castellations with this quick and easy hack.

[@CoilProtogen] doesn’t include much information in the Twitter thread about design details, but the pictures make it clear what the idea is here. OEM castellations are really just plated areas at the edge of a board that can be used to tack the board down to another one without any added hardware. The hack here is realizing that lining up a bunch of large-diameter vias and cleaving them in half with a sharp pair of scissors will result in the same profile without the added cost. The comments on the thread range from extolling the brilliance of this idea to cringing over the potential damage to the board, but [@CoilProtogen] insists that the 0.6-mm substrate cuts like butter. We’d worry that the plating on the vias would perhaps tear, but that seems not to be the case here.

The benefits of a zero-profile connection are pretty clear in this case, where castellated PCBs were used to replace bulky header-pin connectors on a larger PCB. We can see this technique being generally useful; we’ve seen them used to good effect before, and this is a technique we’ll keep in mind for later.

Sound-Reactive Mannequin Arms Make For Creepy Lounge Decor

December 9, 2021 by Lewin Day 8 Comments

Music visualizers were all the rage back in era of Winamp and Windows Media Player. They’re even cooler when they don’t just live on your computer screen, though, as [Emily Velasco’s] latest project demonstrates.

The build consists of two mannequin arms on a board mounted on the wall. The arms were sourced for just $5 from a Sears that went out of business, and originally fastened to the mannequin thanks to magnets inside. Thus, putting two steel plates on the board allowed the arms to be attached, and they can be freely arranged as [Emily] sees fit.

The ESP32-based Pixelblaze LED controller serves as the brains of the operation, controlling LEDs mounted inside the arms themselves. Using a dedicated controller makes working with addressable LEDs a cinch. As a further bonus, the board serves up a web interface, allowing patterns to be changed without having to hook up a cable to the device. Meanwhile, a sensor board inside the arms uses a microphone to enable the light show to react to sound and music.

It’s one of the more obscure uses for an old mannequin, but definitely one that appeals to our love of everything that flickers and glows. It’s a build very much up [Emily’s] alley; as a prolific maker, she loves to build weird and wonderful creations, as shared during her talk at the 2019 Hackaday Superconference. Video after the break.

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The Ins And Outs Of Casting Lenses From Epoxy

December 9, 2021 by Dan Maloney 10 Comments

If you need a lens for a project, chances are pretty good that you pick up a catalog or look up an optics vendor online and just order something. Practical, no doubt, but pretty unsporting, especially when it’s possible to cast custom lenses at home using silicone molds and epoxy resins.

Possible, but not exactly easy, as [Zachary Tong] relates. His journey into custom DIY optics began while looking for ways to make copies of existing mirrors using carbon fiber and resin, using the technique of replication molding. While playing with that, he realized that an inexpensive glass or plastic lens could stand in for the precision-machined metal mandrel which is usually used in this technique. Pretty soon he was using silicone rubber to make two-piece, high-quality molds of lenses, good enough to try a few casting shots with epoxy resin. [Zach] ran into a few problems along the way, like proper resin selection, temperature control, mold release agent compatibility, and even dealing with shrinkage in both the mold material and the resin. But he’s had some pretty good results, which he shares in the video below.

[Zach] is clear that this isn’t really a tutorial, but rather a summary of the highs and lows he experienced while he was working on these casting methods. It’s not his first time casting lenses, of course, and we doubt it’ll be his last — something tells us he won’t be able to resist trying this all-liquid lens casting method in his lab.

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Molding Complex Optics In A Completely Fluid System

December 9, 2021 by Dan Maloney 25 Comments

Traditional lensmaking is a grind — literally. One starts with a piece of glass, rubs it against an abrasive surface to wear away the excess bits, and eventually gets it to just the right shape and size for the job. Whether done by machine or by hand, it’s a time-consuming process, and it sure seems like there’s got to be a better way.

Thanks to [Moran Bercovici] at Technion: Israel Institute of Technology, there is. He leads a team that uses fluids to create complex optics quickly and cheaply, and the process looks remarkably simple. It’s something akin to the injection-molded lenses that are common in mass-produced optical equipment, but with a twist — there’s no mold per se. Instead, a UV-curable resin is injected into a 3D printed constraining ring that’s sitting inside a tank of fluid. The resin takes a shape determined by the geometry of the constraining ring and gravitational forces, hydrostatic forces, and surface tension forces acting on the resin. Once the resin archives the right shape, a blast of UV light cures it. Presto, instant lenses!

The interface between the resin and the restraining fluid makes for incredibly smooth lenses; they quote surface roughness in the range of one nanometer. The use of the fluid bed to constrain the lens also means that this method can be scaled up to lenses 200-mm in diameter or more. The paper is not entirely clear on what fluids are being used, but when we pinged our friend [Zachary Tong] about this, he said he’s heard that the resin is an optical-grade UV adhesive, while the restraining fluid is a mix of glycerol and water.

We’re keen to see [Zach] give this a try — after all, he did something similar lately, albeit on a much smaller scale.

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