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Engineering
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A place to geek out about engineering, fabrication, and design. All disciplines are welcome. Ask questions, share knowledge, show off projects you're proud of, and share interesting things you find.
Rules:
- Be kind.
- Generally stay on topic.
- No homework questions.
- No asking for advice on potentially dangerous jobs. Hire a professional. We don't want to be responsible when your deck collapses.
The community icon is ISO 7000-1641.
The current community banner image is from Lee Attwood on Unsplash.
founded 1 year ago
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The dark autumn evenings reminded me of a particular street light in my neighborhood that's an awful purple color. I finally dug into what causes that. The "white" LEDs are really blue LEDs with a phosphor-based coating on the lens. The coating is excited by the blue light and emits other wavelengths, approximating white light. If the phosphor coating degrades or delaminates then more blue light escapes, making the overall light look more blue-violet.
The post image is from an entry on the Dark Sky Consulting blog.
This recent research paper has some pictures of the actual failure on LEDs.
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The original design of the Sydney opera house featured roof sections with unique curves. This caused two major problems: (1) the structural analysis was very difficult, and (2) it made construction more expensive since they could not reuse construction details among the roof sections. Eventually the engineers realized they could approximate the roof sections as segments from a single sphere. This greatly improved both problems.
This post inspired by a recent episode of the Cautionary Tales podcast. I never knew what a messy project the opera house had been.
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Posting a second picture that shows and earlier stage in the process. Multiple charges ignite to remove the canopy from a CF-18 Hornet immediately before the pilot ejects. Photo from ejectionsite.com, which has more info on the incident.
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A post on NCD sent me down a rabbit hole reading about ejection seats. Do we have anyone here who can share some first-hand knowledge about the designs? I didn't fully appreciate these products before: thousands of parts, multiple precisely timed pyrotechnic charges, and big consequences for failure. That sounds like a very stressful development project.
The picture above is a British pilot ejecting from his Harrier in Afghanistan in 2009. He was lucky and was able to resume flying.
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The valve core contains a specially designed wax. The wax expands as it is heated, forcing the valve open and allowing engine coolant to flow to the radiator. When the wax cools and contracts the valve is closed by a return spring.
More modern cars have a "map controlled" thermostat. These incorporate a heating element to melt the wax prematurely if the engine computer demands more cooling.
Here is the full video with narration.
And credit to Jalopnik for the animated gif.
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I wonder how many people understand the planning and work that goes into making hiking trails and shelters for us weekend warriors. For example, here's a sample trail project package following the US Forest Service's standard plans and specifications. A trail is so much more than a strip of bare ground.
The image is a classic plan for an Adirondack shelter. They are common in the forests of New York and along the Appalachian Trail.
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I know there isn't a lot of information available yet, but I'm not above playing Monday morning quarterback. What do you think about this incident?
Russianspaceweb.com has some interesting info on the probe.
CBC has a decent article that doesn't seem to be paywalled.
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In 2021, two University of Washington engineering students completed a pipe-inspecting rover named hydroCUB as a capstone project. The project was proposed by the Washington State Department of Transportation. Full story here.
A year later the WSDOT was experimenting with a further iteration of the same concept, nicknamed Elvis. Here's Elvis:
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Log bridge (crib trestle) on the Columbia and Nehalem Valley Railroad, Columbia County, Oregon.
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An F-16 model in a flow visualization test using smoke and a laser light sheet to illuminate the smoke.
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Image courtesy of the Michigan Department of Environment, Great Lakes, and Energy.
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Shadowgraphs of fluid disturbances around high-velocity vehicles demonstrate how a blunt-bodied vehicle produces a shockwave in front of the vehicle, which allows it to stay cooler during reentry. 1960.
Source: https://rarehistoricalphotos.com/nasa-wind-tunnels-photos/
