A Look Back On The Oroville Dam With Practical Engineering

May 31, 2021 by Jonathan Bennett 10 Comments

Back when it first happened, we covered the Oroville Dam near-disaster. Heavier-than-expected rainfall in California back in early 2017 led to running the dam’s primary spillway at much higher-than-normal levels. February 17, 2017, the operators noticed something odd about the water flow down the spillway, and when they turned off water flowing down the spillway, it was made obvious that they had a major problem on their hands. Several chunks of concrete were missing, and the water had begun gouging into the earth beneath the spillway. It would need repairs before it was properly up to the task of discharging water, but it was still raining.

The rising water level in Lake Oroville put operators in a tricky situation, as they needed to discharge water in the least damaging way possible. They decided to use the emergency spillway to keep water levels at safe levels. Unfortunately, the secondary spillway began to deteriorate even more quickly than the primary had, and continued use could compromise the structure of the entire dam. The difficult decision was made to evacuate downstream residents, and sacrifice the primary spillway to drain the lake to 50 feet below the nominal full level. It worked, and effectively destroyed the bottom two-thirds of the spillway over those 3 months.

With the water at a safe level, the spillways could be repaired, a monumental nearly-2-year process in itself. We’ve covered all this before, but you may be left with the nagging question, what went wrong? [Grady Hillhouse], of the Practical Engineering channel, breaks it down for us in the video embedded below.

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Thin Coatings Require An Impressive Collection Of Equipment And Know-How

May 31, 2021 by Dan Maloney 15 Comments

Let’s be honest — not too many of us have a need to deposit nanometer-thick films onto substrates in a controlled manner. But if you do find yourself in such a situation, you could do worse than following [Jeroen Vleggaar]’s lead as he builds out a physical vapor deposition apparatus to do just that.

Thankfully, [Jeroen] has particular expertise in this area, and is willing to share it. PVD is used to apply an exceedingly thin layer of metal or organic material to a substrate — think lens coatings or mirror silvering, as well as semiconductor manufacturing. The method involves heating the coating material in a vacuum such that it vaporizes and accumulates on a substrate in a controlled fashion. Sounds simple, but the equipment and know-how needed to actually accomplish it are daunting. [Jeroen]’s shopping list included high-current power supplies to heat the coating material, turbomolecular pumps to evacuate the coating chamber, and instruments to monitor the conditions inside the chamber. Most of the chamber itself was homemade, a gutsy move for a novice TIG welder. Highlights from the build are in the video below, which also shows the PVD setup coating a glass disc with a thin layer of silver.

This build is chock full of nice details; we especially liked the technique of monitoring deposition progress by measuring the frequency change of an oscillator connected to a crystal inside the chamber as it accumulates costing material. We’re not sure where [Jeroen] is going with this, but we suspect it has something to do with some hints he dropped while talking about his experiments with optical logic gates. We’re looking forward to seeing if that’s true.

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Bicycle Flywheel Stores A Bit Of Energy, Not Much

May 30, 2021 by Lewin Day 49 Comments

Kinetic energy recovery systems have often been proposed as a useful way to improve the efficiency of on-road vehicles, and even used to great effect in motorsports for added performance. [Tom Stanton] decided to build one of his own, outfitting a simple bicycle with a flywheel system for harvesting energy. (Video, embedded below.)

The system consists of a 300 mm steel flywheel mounted in the center of the bike’s frame. It’s connected to the rear wheel via a chain and a clutch which [Tom] assembled himself using bicycle disc brake components. The clutch is controlled by a handlebar lever, allowing the rider to slow the bike by charging the flywheel, or to charge the flywheel to maximum speed by pedalling hard with the clutch engaged.

The actual utility of the flywheel is minimal; [Tom] notes that even at its peak speed of 2200 RPM, the flywheel stores a small fraction of the energy content of a AA battery. Practical demonstration shows the flywheel is only able to deliver a small push to [Tom] when riding the bike, too.

Despite the lack of performance, it’s nonetheless an interesting project and one that demonstrates the basic principles of flywheel energy storage. The underwhelming results perhaps serve as a solid indication of why it’s not something we use particularly often, on bicycles at least. We’ve seen [Tom]’s bike experiments before, too. Video after the break.

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Reviving Old Recipe For Faraday Wax Keeps Vacuum Experiments Going

May 29, 2021 by Dan Maloney 24 Comments

Science today seems to be dominated by big budgets and exotics supplies and materials, the likes of which the home gamer has trouble procuring. But back in the day, science was once done very much by the seats of the pants, using whatever was available for the job. And as it turns out, some of the materials the old-timers used are actually still pretty useful.

An example of this is a homemade version of “Faraday Wax”, which [ChristofferB] is using for his high vacuum experiments. As you can imagine, getting a tight seal on fittings is critical to maintaining a vacuum, a job that’s usually left to expensive synthetic epoxy compounds. Realizing that a lot of scientific progress was made well before these compounds were commercially available, [ChristofferB] trolled through old scientific literature to find out how it used to be done.

This led to a recipe for “Faraday Wax”, first described by the great scientist himself in 1827. The ingredients seem a little archaic, but are actually pretty easy to source. Beeswax is easy to come by; the primary ingredient, “colophony”, is really just rosin, pretty much the same kind used as solder flux; and “Venetian red” is a natural pigment made from clay and iron oxide that can be had from art suppliers. Melted and blended together, [ChristofferB] poured it out onto wax paper to make thin strips that are easily melted onto joints in vacuum systems, and reports are that the stuff works well, even down to 10^-7 mbar.

We love this one — it’s the perfect example of the hacker credo, which has been driving progress for centuries. It also reminds us of some of the work by [Simplifier], who looks for similar old-time recipes to push his work in DIY semiconductors and backyard inductors forward.

[David Gustafik] dropped us the tip on this one. Thanks!

Solar Plane Is Like One Big Flying Solar Panel

May 29, 2021 by Lewin Day 15 Comments

Solar-powered plane concepts typically focus on high-efficiency glider-type designs, so as to make the best possible use of the limited power available from the sun. [rctestflight] wanted to try a different school of thought, instead building a relatively inefficient plane that nonetheless packed a huge amount of solar panels on board.

The plane consisted of a pizza-box style design, with a simple foam rectangular wing that was absolutely covered in solar panels. The plane was controlled with an off-the-shelf autopilot, and fitted with cheap, no-brand MPPT modules to handle charging the batteries. The plane faced difficulties in flight, most often with stability, which led to the autopilot getting the plane lost on one occasion. However, one flight was achieved with a full one hour and thirty minute duration, indicating the solar panels were helping to extend flight times beyond what was capable with batteries alone.

Further research on the ground showed that the cheap MPPT modules were wasting power, and there was more to be had. A better MPPT module was subbed in and showed that the panels could generate up to 5 amps under good conditions, while the plane only needed roughly 4.2 amps to fly. This would allow for indefinite flight in sunny conditions, though probably would not allow enough energy to be banked to fly 24 hours round the clock due to the lack of power at night.

We’ve followed [rctestflight]’s solar plane experiments for a while now, and can’t wait to see the next iteration. Video after the break.

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3D Printed Flip Dots

May 29, 2021 by Danie Conradie 9 Comments

Displays have come a long way in the last few decades, but none can deliver the mesmerizing visual and audio experience of a large flip dot display. Both old panels and new panels can be expensive and difficult to source, so [Larry Builds] made his own flip dots with the help of 3D printing.

Flip dots are driven by a pair of electromagnetic posts that attract or repel a magnet embedded in the dot, and [Larry Builds] version is no different. For the electromagnets, he used M3 threaded rod with enamel wire wound around them using a drill. At first, he used a large magnet in the center of the 3D printed dot, but the magnetic field was large and strong enough to flip the surrounding dots in an array. He then changed the design to a small 4 mm diameter magnet in the edge that aligns directly with the electromagnets. This design looks very similar to those used by Breakfast for their massive installations. By modifying electromagnets and adding spacers around the magnets, he was able to reduce the operating current from 2 A to below 500 mA. [Larry Builds] also breadboarded a basic driver circuit consisting of H-bridges multiplexed to rows and columns with diodes.

We will be keeping a close eye on this project, and we look forward to seeing it evolve further. It’s definitely on our “things to build” list. We’ve embedded multiple videos after the break showing the progress thus far.

We’ve covered several interesting flip dot projects, including a water level indicator that doesn’t use any electronics and another that is crocheted. Continue reading “3D Printed Flip Dots” →

3D Printed Mars Rover Smiles For The Camera

May 28, 2021 by Tom Nardi 3 Comments

You’d be forgiven for thinking these pictures of NASA’s Perseverance Mars rover were renderings of the real deal on the Red Planet, if it wasn’t for the golf ball tucked in for scale, anyway. What you’re actually looking at is a 3D printed model made by [Alex Givens] that he brought out to the desert for a photo shoot by his friend [Josh Jalil].

[Alex] printed the parts for the model on the Ender 5 Pro, while [Josh] snapped the shots using a Canon EOS 90D. The realism of the final shots serves as a testament to how well they’ve honed their respective tools, but credit for the 3D model itself has to go to the good folks over at NASA.

The highly detailed Perseverance model came from the space agency’s extensive “3D Resources” collection, which has models for an incredible array of present and historical spacecraft. They’ve also got models for a number of interesting astronomical objects, just in case you’re in the market for a 3D printed asteroid or two.

We know, this isn’t exactly a hack in the traditional sense. But it’s a fantastic reminder of a great resource from NASA, as well as a practical demonstration of how high quality photographs can really bring a project to life.