Changing Color Under Pressure

June 15, 2018 by Brian McEvoy 3 Comments

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.

Arbor Press Modded For Applying Specific Force

March 25, 2018 by Donald Papp 25 Comments

Arbor presses are simple and effective tools made for a particular task: exerting force in a specific spot. A 1-ton arbor press fits on a desktop and is very affordable, but doesn’t offer a lot of particularly fine control over the ram beyond lowering and raising it. [concreted0g] got to thinking about ways to gain more control and knowledge about the amount of force being applied, and made a simple modification to combine his press with a torque wrench.

He removed the spindle which raises and lowers the ram, and drilled and tapped it to fit a bolt. Now, by attaching a torque wrench to the bolt and using the wrench as the handle for lowering the ram, he can take advantage of the wrench’s ability to break at set amounts of force. As a result, he has a repeatable way to accurately apply specific amounts of force with a tool that usually lacks this ability. It looks like this mod is limited to lower forces only (too much could shear off the bolt head, after all) but it combines two tools in an unusual way to gain an ability that didn’t exist before, which is great to see. Mods and presses seem to go very well together; don’t miss this DIY thermal insert add-on for an arbor press, and 3D printed dies for a press brake turned out to be remarkably durable and versatile, not to mention economical.

Mechanisms: Gears

March 16, 2018 by Dan Maloney 29 Comments

Even before the Industrial Revolution, gears of one kind or another have been put to work both for and against us. From ancient water wheels and windmills that ground grain and pounded flax, to the drive trains that power machines of war from siege engines to main battle tanks, gears have been essential parts of almost every mechanical device ever built. The next installment of our series on Mechanisms will take a brief look at gears and their applications.

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3D-Printed Halbach Motor Part Two: Tuning, Testing

June 30, 2017 by Dan Maloney 8 Comments

Building your own Halbach-effect brushless DC motor is one thing. Making sure it won’t blow up in your face another matter, and watching how [Christoph Laimer] puts his motor to the test is instructive.

You’ll remember [Christoph]’s giant 3D-printed BLDC motor from a recent post where he gave the motor a quick test spin. That the motor held together under load despite not being balanced is a testament to the quality of his design and the quality of the prints. But not wishing to tempt fate, and having made a few design changes, [Christoph] wisely chose to perform a static balancing of the rotor. He also made some basic but careful measurements of the motor’s parameters, including the velocity constant (Kv) using an electric drill, voltmeter, and tachometer, and the torque using a 3D-printed lever arm and a kitchen scale. All his numbers led him to an overall efficiency of 80%, which is impressive.

[Christoph] is shipping his tested BLDC off to the folks at FliteTest, where he hopes they put it to good use. They probably will — although they might ask for three more for a helicarrier.

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Cheap Torque Sensor Goes Back To Basics On Strain Gauges

June 20, 2016 by Dan Maloney 21 Comments

Sooner or later, we’ve all got to deal with torque measurement. Most of us will never need to go beyond the satisfying click of a micrometer-style torque wrench or the grating buzz of a cordless drill-driver as the clutch releases. But at some point you may actually need to measure torque, in which case this guide to torque sensors might be just the thing.

[Taylor Schweizer]’s four-part series on torque is pretty comprehensive. The link above is to the actual build of his DIY torque transducer, but the preceding three installments are well worth the read too. [Taylor] describes himself as an e-waste connoisseur and tantalizes us with the possibility that his build will be with salvaged parts, but in the end a $20 bag of strain gauges and an LM358 were the quickest way to his proof of concept. The strain gauges were super-glued to a socket extension, hot glue was liberally applied for insulation and strain relief, and the whole thing wired up to a Teensy for data capture. A quick script and dump of the data to Excel and you’ve got a way to visualize torque.

An LCD display for real-time measurements is in the works, as are improvements to the instrumentation amp – for which [Taylor] might want to refer to [Bil Herd]’s or [Brandon Dunson]’s recent posts on the subject.

[via r/arduino]

High Tech, Low Cost Digital Torque Meter

August 20, 2015 by Dan Maloney 40 Comments

Ever obsessed with stripping the hype from the reality of power tool marketing, and doing so on the cheap, [arduinoversusevil] has come up with a home-brew digital torque meter that does the job of commercial units costing hundreds of times as much.

For those of us used to [AvE]’s YouTube persona, his Instructables post can be a little confusing. No blue smoke is released, nothing is skookum or chowdered, and the weaknesses of specific brands of tools are not hilariously enumerated. For that treatment of this project, you’ll want to see the video after the break. Either way you choose, he shows us how a $6 load cell and a $10 amplifier can be used to accurately measure the torque of your favorite power driver with an Arduino. We’ve seen a few projects based on load cells, like this posture-correcting system, but most of them use the load cell to measure linear forces. [AvE]’s insight that a load cell doesn’t care whether it’s stretched or twisted is the key to making a torque meter that mere mortals can afford.

Looks like low-end load cells might not be up to measuring the output on your high-power pneumatic tools, at least not repeatedly, but they ought to hold up to most electric drivers just fine. And spoiler alert: the Milwaukee driver that [AvE] tested actually lived up to the marketing. Continue reading “High Tech, Low Cost Digital Torque Meter” →

Changing Unipolar Steppers To Bipolar

July 29, 2014 by Brian Benchoff 68 Comments

If you’ve been a good little hacker and have been tearing apart old printers like you’re supposed to, you’ve probably run across more than a few stepper motors. These motors come in a variety of flavors, from the four-wire deals you find in 3D printer builds, to motors with five or six wires. Unipolar motors – the ones with more than four wires – are easier to control, but are severely limited in generating torque. Luckily, you can use any unipolar motor as a more efficient bipolar motor with a simple xacto knife modification.

The extra wires in a unipolar motor are taps for each of the coils. Simply ignoring these wires and using the two coils independently makes the motor more efficient at generating torque.

[Jangeox] did a little experiment in taking a unipolar motor, cutting the trace to the coil taps, and measuring the before and after torque. The results are impressive: as a unipolar motor, the motor has about 380 gcm of torque. In bipolar mode, the same motor has 800 gcm of torque. You can check that video out below.

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