Are You Getting Your Money’s Worth From Threaded Inserts?

Have you ever wondered whether it’s worth the time and expense to install threaded inserts into your 3D-printed projects?Ā [Stefan] from CNC Kitchen did, and decided to answer the question once and for all, with science.

If this sounds familiar, it’s with good reason: we covered [Stefan]’s last stab at assessing threaded inserts back in March. Then, he was primarily interested in determining if threaded inserts are better than threads cut or printed directly into parts. The current work is concerned with the relative value of different designs of threaded inserts. He looked at three different styles of press-in inserts, ranging in price from pennies apiece to a princely 25 cents. The complexity of the outside knurling seems not to be correlated with the price; the inserts with opposed helical knurls seem like they’d be harder to manufacture than the ones with simple barbs on the outside of the barrel, but cost less. And in fact, the mid-price insert outperformed the expensive one in pull-out tests. Surprisingly, the cheapest inserts were actually far worse at pull-out resistance than printing undersized holes and threading an M3 screw directly into the plastic.

[Stefan] also looked at torque resistance, and found no substantial difference between the three insert types. Indeed, none of the inserts proved to be the weak point, as the failure mode of all the torque tests was the M3 bolt itself. This didn’t hold with the bolt threaded directly into the plastic, of course; any insert is better than none for torque resistance.

We enjoyed seeing [Stefan]’s tests, and appreciate the data that can help us be informed consumers. [John] over at Project Farm does similar head-to-head tests, like this test of different epoxy adhesives.

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BikeOn Makes Electric Conversion A Snap

If you’re in a relatively urban area and your destination is within a reasonable distance, it’s hard to argue against riding your bike rather than taking a car. It’s a positive for the environment, and great way to exercise and keep active. But some of us, say folks who write for the Internet full-time, might appreciate a little electromechanical advantage when the going gets tough.

In an effort to make electrifying your bike as easy as possible, [Shushanik] and [Aram] are working on a product they call BikeOn which they’ve recently entered into the 2019 Hackaday Prize. Thanks to some very clever engineering, this small unit can clamp onto the frame of a standard bicycle and transfer the energy from its 350 watt motor directly into the rear wheel; all without any tools or permanent modifications.

In the video after the break, [Aram] demonstrates how the user can install the BikeOn motor assembly in literally just a few seconds. Naturally there’s a beefy battery that needs to get attached to the frame as well, but even that has been made modular enough that it can attach where many bikes have their water bottle holder.

The attentive reader will likely notice that there’s no obvious control mechanism for BikeOn. Instead of having to fumble around with it manually, BikeOn uses a combination of torque sensor, accelerometer, and gyroscope to intelligently determine when the rider could use a boost.

BikeOn nabbed Editor’s Choice award at Maker Faire 2019, and now that it’s in the running for the Hackaday Prize, we’re excited to see more information on the product as it moves towards commercial release.

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Vacuum-Powered Rotary Tool Redux, This Time Machined

We love to see projects revisited, especially when new materials or methods make it worth giving the first design another go around. This twin-turbine vacuum-powered Dremel tool is a perfect example of what better tools can do for a build.

You may recallĀ [JohnnyQ90]’s first attempt at a vacuum powered rotary tool. That incarnation, very similar in design to the current work, was entirely 3D-printed, and caused no little controversy in the comments about the wisdom of spinning anything made on an FDM printer at 43,000 RPM. Despite the naysaying, [Johnny] appears to have survived his own creation. But the turbo-tool did have its limitations, including somewhat anemic torque. This version, machined rather than printed and made almost completely from aluminum, seems to have solved that problem, perhaps thanks to the increased mass of the rotating parts. The twin rotors and the stator were milled with a 5-axis CNC machine, which has been a great addition to [JohnnyQ90]’s shop. The turbine shaft, looking like something from a miniature jet engine, was meticulously balanced using magnets mounted in the headstock and tailstock of a lathe. The video below shows the build and a few tests; we’re not big fans of the ergonomics of holding the tool on the end of that bulky hose, but it sure seems to work well. And that sound!

We first noticed [JohnnyQ90] when he machined aluminum from soda cans to make a mini Tesla turbine. His builds have come a long way since then, and we look forward to what he’ll come up with next.

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Reaction Wheels Almost Control This Unusual Drone

When you think about all the forces that have to be balanced to keep a drone stable, it’s a wonder that the contraptions stay in the air at all. And when the only option for producing those forces is blowing around more or less air it’s natural to start looking for other, perhaps better ways to achieve flight control.

Taking a cue from the spacecraft industry, [Tom Stanton] decided to explore reaction wheels for controlling drones. The idea is simple – put a pair of relatively massive motorized wheels at right angles to each other on a drone, and use the forces they produce when they accelerate to control the drone’s pitch and roll. [Tom]’s video below gives a long and clear explanation of the physics involved before getting to the build, which results in an ungainly craft a little reminiscent of a lunar lander. The drone actually manages a few short, somewhat stable flights, but in general the reaction wheels don’t seem to be up to the task. [Tom] chalks this up to the fact that he’s using the current draw of each reaction wheel motor as a measure of its torque, which is not exactly correct for all situations. He suggests that motors with encoders might do a better job, but by the end of the video the little drone isn’t exactly in shape for continued experimentation.

Of course, dodgy reaction wheels don’t only cause problems with drones. They can also be a problem for spacecraft when the Sun gets fussy too.

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Can You 3D-Print A Stator For A Brushless DC Motor?

Betteridge’s Law holds that any headline that ends in a question mark can be answered with a “No.” We’re not sure that [Mr. Betteridge] was exactly correct, though, since 3D-printed stators can work successfully for BLDC motors, for certain values of success.

It’s not thatĀ [GreatScott!] isn’t aware that 3D-printed motors are a thing; after all, the video below mentionsĀ the giant Halbach array motor we featured some time ago. But part of advancing the state of the art is to replicate someone else’s results, so that’s essentially what [Scott!] attempted to do here. It also builds on his recent experiments with rewinding commercial BLDCs to turn them into generators. His first step is to recreate the stator of his motor as a printable part. It’s easy enough to recreate the stator’s shape, and even to print it using Proto-pasta iron-infused PLA filament. But that doesn’t come close to replicating the magnetic properties of a proper stator laminated from stamped iron pieces. Motors using the printed stators worked, but they were very low torque, refusing to turn with even minimal loading. There were thermal issues, too, which might have been mitigated by a fan.

So not a stunning success, but still an interesting experiment. And seeing the layers in the printed stators gives us an idea: perhaps a dual-extruder printer could alternate between plain PLA and the magnetic stuff, in an attempt to replicate the laminations of a standard stator. This might help limit eddy currents and manage heating a bit better. Continue reading “Can You 3D-Print A Stator For A Brushless DC Motor?”

Electric Drift Trike Needs Water Cooling

Electric vehicles of all types are quickly hitting the market as people realize how inexpensive they can be to operate compared to traditional modes of transportation. From cars and trucks, to smaller vehicles such as bicycles and even electric boats, there’s a lot to be said for simplicity, ease of use, and efficiency. But sometimes we need a little bit more out of our electric vehicles than the obvious benefits they come with. Enter the electric drift trike, an electric vehicle built solely for the enjoyment of high torque electric motors.

This tricycle is built with some serious power behind it. [austiwawa] constructed his own 48V 18Ah battery with lithium ion cells and initially put a hub motor on the front wheel of the trike. When commenters complained that he could do better, he scrapped the front hub motor for a 1500W brushless water-cooled DC motor driving the rear wheels. To put that in perspective, electric bikes in Europe are typically capped at 250W and in the US at 750W. With that much power available, this trike can do some serious drifting, and has a top speed of nearly 50 kph. [austiwawa] did blow out a large number of motor controllers, but was finally able to obtain a beefier one which could handle the intense power requirements of this tricycle.

Be sure to check out the video below to see the trike being test driven. The build video is also worth a view for the attention to detail and high quality of this build. If you want to build your own but don’t want to build something this menacing, we have also seen electric bikes that are small enough to ride down hallways in various buildings, but still fast enough to retain an appropriate level of danger.

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Changing Color Under Pressure

When you saw the picture for this article, did you think of a peacock’s feather? These fibers are not harvested from birds, and in fact, the colors come from transparent rubber. As with peacock feathers, they come from the way light reflects off layers of differing materials, this is known as optical interference, and it is the same effect seen on oil slicks. The benefit to using transparent rubber is that the final product is flexible and when drawn, the interference shifts. In short, they change color when stretched.

Most of the sensors we see and feature are electromechanical, which has the drawback that we cannot read them without some form of interface. Something like a microcontroller, gauge, or a slew of 555 timers. Reading a single strain gauge on a torque wrench is not too tricky, but simultaneously reading a dozen gauges spread across a more complex machine such as a quadcopter will probably require graphing software to generate a heat map. With this innovation it could now be done with an on-board camera in real-time. Couple that with machine learning and perhaps you could launch Skynet. Or build a better copter.

The current proof-of-concept weaves the fibers into next-generation bandages to give an intuitive sense of how tightly a dressing should be applied. For the average first-aid responder, the rule is being able to slide a finger between the fabric and skin. That’s an easy indicator, but it only works after the fact whereas saying that the dressing should be orange while wrapping gives constant feedback.