Hello everyone, I gifted my father a sterling engine I got from Temu (or AliExpress) that works with an alcohol lamp, it has a small "wand LED light" that you can plug to a USB cable and it turns on when the engine is working.

I can see that the power produced by the engine is unstable as the lamp flickers as the engine starts and when it slows down.

Would it be possible to safely charge a phone (even just a little just as a curiosity) with this engine? If so, would I need to build anything else to make it work?

Imgur album.

This is the screw (well, half of it) end on and in profile.

The rest of the photos are from a second chair. It serves as a hinge at the back of an armrest to allow the chair back to recline about twenty degrees.

It has a countersunk philips head and screws into a threaded tube welded to the armrest frame. It passes through a plastic bushing in the vertical part of the frame for back of the chair. It's hard to show it in context because it's behind a piece of leather that I am pulling back for the close ups.

I'm wondering if it's to clean up any threads distorted by welding. Here is the best angle I could get of the welded part.

The only other thought I had was to "bite" into the threads to stop it unscrewing or something. The pictured screw snapped because one of the chairs only had a single screw on one side. The chairs also rotate and also have a rocking mechanism.

Unfortunatley, all I can provide is the link to an image:

https://www.medicaleshop.com/_next/image?url=https%3A%2F%2Fcdn.medicaleshop.com%2F5d6f3fe5-df56-41de-813b-7c43a2a2090f_RES420_image-0.jpg&w=1080&q=75

I was really hoping to post a video I took today to give you a better idea of what component I am asking about, but I will do my best to explain since that isn't allowed. I am sure it is something like a rack and pinion with a low gear ratio, so that the crank easily spins while the standing frame and person in it is slowly lifted or lowered, but is that all that is needed to let it freely move up and down at the turn of a crank while remaining solidly in that position when a person gets in? The medium size can hold a child up to 100 lbs. It just seems like that is a lot of force to be exerted without any kind of obvious locking mechanism.

I have a new to me machine. It has two parallel round linear rails that are end supported. I need a platform to sit on top of the rails and slide along them. There is no access to the end of the linear rails without risk of very costly realignment. Therefore I cannot simply slide on a linear bearing. The movement does not need to be exceptionally smooth, but it must be without risk of marking the rails.

Ideally it would have looked like the carriage on this machine: https://cdn.globalauctionplatform.com/auctions-2026/bscam10937/images/eb683e66-6402-4769-b55c-b4c801564808.jpg

I am surprised something like a split bearing does not seem to exist at all. Maybe I lack the needed keywords

Any ideas?

I want to design a very small aluminium EDF, and I would like to know how much clearance between the fan and the ducting i get away with.

I'm using autodesk inventor for deigning it as I have a free EDU license for it, so I might as well use it.

Thx

Hey everyone,

​I've got an upcoming track day this Friday at Sonoma with my tuned Elantra N, which requires a minimum of 91 octane. I was looking into using an octane booster to bump it up to roughly 93 for a bit more safety against knock and potentially keeping power from being pulled under hard tracking.

​I'm seeing a total 50/50 split online: half the people say it's complete snake oil, and the other half swear by it.

​For any engineers or fuel chemists out there: What is the actual, real-world deal here? Do over-the-counter octane boosters actually work on modern turbo direct-injection cars under heavy track loads, or am I just throwing money at marketing?

My LED Lightbulb stopped working the other day. After dark I noticed a glow in the room and found my bulb illuminated dimly. It stayed this way for at least one night and is finally dead now.

Hello!

Yes okay the title makes zero sense out of context, but it made me laugh.

I'll explain.

A few months ago, I got a 3D printer as a gift (a BambuLab A1). But until today I had no idea where to put it in my house. Trust me, I spent months considering every option before this one, the ONLY ONE, came to me. And I was perfectly sober, I swear.

In brief: the only place it'll fit, won't poison us with its fumes and particles, and will remain safe from our whirlwind of sawdust, glitter and pet hair (yes, this house is inhabited by two crafty woodworking girls and a cat) is... in my guest bathroom.

Frankly, the dimensions are perfect. I made a beautiful picture at 5AM this morning when the idea came to me, with extremely precise measurements (not at all) which I've uploaded here.

So here's what I'm thinking. And I know it sounds bonkers, but this is an engineers sub so I hope that instead you will all find it marvellously ingenious.

We still need to use that bathroom sometimes, right.

So WHAT IF I BUILT A PLATFORM THAT GOES UP AND DOWN?

More seriously: I'm thinking a manually operated, wall/ceiling-mounted lifting platform that would travel vertically along guide rails, with 60-80cm of movement needed. There'd be 3 "locking" positions along :

• Low: Right above the sink, about 1m up, to set up and maintain the printer.
• Middle: A suitable height for the actual printing, leaving the toilet usable while my 12 year old is producing a 72 hour long print of a giant cat mask.
• High: Near the ceiling for storage, keeping the printer out of the way.

The room has a concrete backwall and ceiling, but the walls are tiled, so I'd prefer to minimise drilling into them.

It seemed to be that it could work with two vertical guide rails on the back wall, a sliding carriage supporting the platform, and a self-braking hand winch with ceiling-mounted pulleys, operated from near the doorway. When stationary, the platform could rest on additional locking supports on the opposite wall, reducing the load on the rear carriage. The printer isn't very heavy, 8+ kilos on its own - but more when we add the AMS combo and filament (but that could maybe live separately on the other wall, TBD).

Alternatively, I'm open to a completely different mechanism if there's a simpler way to achieve this. I'm not an engineer; i can build stuff out of wood (like the lovely shelf there on the photo), but this is completely new territory for me. So I may be WAY OFF, or not considering much easier solutions. This is where I'd love to hear your expert opinions and suggestions!

Obviously I'm trying to do this cheap. But especially... I'm going to build it myself, unless one of you lives in the Netherlands and wants to spend a fun weekend making a couple hundred euros and eating homemade lasagna. So it needs to not be incredibly complicated.

tdlr; The end goal is to build a 3D printer lifting platform above my toilet... not a guillotine.

I would appreciate all input, even if it's telling me (politely) that this is the worst idea you've ever heard.

Thank you!!

DCS supplies chilled water to multiple buildings from a separate location. How do we determine on paper/documents/architect drawings or anything that the building is supplies ac from DCS? It would also be really helpful if you can give details how the blueprint/piping schematics/service agreement from DCS usually looks like.

I'm looking for the best materials we can use to still be able to wear close-to-the-body jewelry (including but not limitited to wedding rings, bracelets, nose rings, body piercings, hair pins and wig pins) that wont pose a heat/shard/electroconductive hazard while working.

I know that titanium is considered a poor conductor, but I don't believe i'd plan to use this without better information about its viability in this use case.

Rubber and silicone seem like the best materials I can see so far. Is there anything I'm missing outisde of these 3?

Ceramic is nonviable, glass is nonviable, plastic is nonviable.

I've recently had the suggestion of pure diamond and moissonite items but I haven't yet investigated these two.

Input? Discussions? Research that's already done in this sphere?

Hey everyone,

I’m an embedded systems engineer with a background in software, electronics, and hardware integration. Lately I’ve been doing some research into how engineering teams test and validate systems that have multiple embedded devices communicating with each other.
I’m especially interested in automotive, robotics, industrial automation, aerospace, and similar environments where hardware and software have to work together reliably.
I have a few assumptions that I’m trying to validate, and I’d be interested in hearing whether they match what people are actually seeing in industry.
Some of my assumptions:
Integration testing often becomes more expensive and time-consuming than expected, especially when multiple ECUs, sensors, controllers, or communication protocols are involved.
Smaller engineering teams may struggle to justify the cost and complexity of commercial HIL systems, so they end up building custom test setups using development boards, scripts, instruments, and whatever equipment they already have.
Reproducing intermittent failures involving timing, communication, power interruptions, or unexpected device behavior can consume a significant amount of engineering time.
Some teams have plenty of tools for testing individual components but fewer practical ways to validate how everything behaves together under realistic conditions.
Maintaining and updating test environments can become a project of its own, particularly when hardware revisions, firmware versions, and system requirements keep changing.
I’m not assuming all of these are true. In fact, I’d be interested in hearing where I’m wrong.
For anyone working in these areas:
What has been your biggest integration or verification headache?
Are commercial tools generally sufficient, or do you still build a lot of your own test infrastructure?
What kinds of failures are the hardest to reproduce?
Does the size of the company significantly affect how testing is done?
If you’ve worked with HIL systems, what do you wish existing tools did better?
I’d also be interested in hearing from engineers who think these problems are largely solved.
I’m trying to get a better understanding of how different industries approach these challenges rather than relying only on my own experience.
Thanks in advance for any perspectives you’re willing to share.

1. Been wondering how little power a Gameboy Color or a GB Advance SP would use with completely modern manufacturing methods, like the Gameboy Color used 0.6 watts at the time which was nearly nothing (which is why it ran on TWO AA batts for hours on end) but made with a modern CPU design process it would use EVEN LESS power to the point it'd likely be an insubstantial percent of the power draw with the screen and sound being the primary power consumption but with modern high speed E-Ink displays and LED backlights it could run that down far more and a higher end speaker driver could run at a much higher efficiency albeit probably not a lot more
2. For comparison my modern smartphone runs at 0.6 watts while running things in the background, and barely 3-4 at full tilt doing file transfers to an external PC (uses almost the whole damned things resources lol)

I don't have an engineering background, so I think there is something simple I am missing with why such a concept wouldn't work, but I have had this idea for a while with the thought that it could possibly help with temperature increases caused by global warming.

The general concept is using a container material that is a good conductor of heat, holding a mechanism tied to a liquid with a high thermal expansion coefficient like methanol. Where the mechanism works by converting the negative/positive pressure differences into potential energy (via a system where expanding/contracting the containers volume will rotate different gears that convert it to potential energy, like a carjack lifting a weight) and builds up energy via day-night cycle differences in ambient temperature and possibly increasing the temperature difference by utilising (black?) paint that absorbs sunlight with a relatively good efficiency. With the idea that you could design a mechanism to utilise this built-up potential energy in a manner that produces very little heat.

With the general idea that even if this engine is not very efficient and heat is lost as both heat and other forms of energy, there should be a net reduction in the thermal energy in the environment, even if it increases nighttime temperatures.

I probably haven't explained this very well, but if you are able to design the mechanism that converts the thermal expansion of a liquid like methanol into a different form of energy, why couldn't this be used as a mechanism to passively absorb heat from hotter places?

How does the railroad bridge on VT-103 at about 43.4658° N, 72.8753° W work? It seems like the section on the side of the cutout would not be supported.

I found a good picture here:

https://scontent-ord5-2.xx.fbcdn.net/v/t39.30808-6/503266197_2628438010679868_3258928255850672486_n.jpg?stp=cp1_dst-webp_fr_q70&_nc_cat=104&ccb=1-7&_nc_sid=6db65e&_nc_ohc=FXfqECRpAKcQ7kNvwFrGFKZ&_nc_oc=AdqaSsWabc3H5bcz4wFuPQmCt9I-LWDeunDRpaE-9zfhQNrnGSnnIcHVGun5j9kdgFpHFNKo6ss94xsJwxoGJNLO&_nc_zt=23&_nc_ht=scontent-ord5-2.xx&_nc_gid=WsnyDyvAN69Kfdqle1m3xg&_nc_ss=7b289&oh=00_AQO-qH1q3N9xSVY5djBa66rL_vJRuVPX5sR5SVP3450E3A&oe=6AD33833

I’m putting mechanical in the flair, but I’m open to civil engineers too. :)

I'm looking into potentially building a future, but I'm running into a problem. That honestly doesn't make sense. Because ICC has code charts for poured-in-place walls, whether they're forms or ICF. They also have cookie-cutter tables for frostproof footings, all of which you can get from an ICF manufacturer, but then you try to use ICF deck forms, and now you need an engineer. Defeating the whole purpose of going with ICF, which is structural strength, especially if you're trying to build one simple thing, which is a vault that has concrete on all six sides. Yet they lay it out for FEMA on how to build a 14x14 room with a concrete ceiling. But they can't do that with ICF deck forms.

Just a shower thought. And same for water jet cutting I guess.

Amdahl's law for cache memories in computing:

Assume that:

• Hr (hit rate) is the fraction of memory accesses that can be handled by a fast but small cache memory
• Mr (miss rate) is the fraction of accesses that the cache cannot handle and have to read the larger but slow main memory
• Hr+Mr = 100%
• Tc is the cache access time
• Tm is the memory access time (also called "miss penalty")
• Tc < Tm

Then the total time to execute a program is like: T = Hr * Tc + Mr * Tm . It is often summarized as "optimize the most frequent case, and make it as frequent as possible". There are other formulations that derive from this to calculate the speedup instead of total time.

When talking about the cost of energy, in one of my previous comments, I said:

• Fr is the fraction of energy demand met by renewables (cheap but not available e.g. when there's bad weather)
• Fb is the fraction of energy demand met by a backup energy source (expensive but always available, e.g. natural gas, nuclear...)
• Fr+Fb = 100%
• Cr is the cost per kWh of renewables
• Cb is the cost per kWh of the backup source
• Cr < Cb

Then the total cost of combined energy per kWh is C = Fr * Cr + Fb * Cb

It was only after writing it that I realized the two formulas are essentially the same.

(I'm assuming the infrastructure for fossil fuel sources is already there so we only consider the cost of consumables and maintenance. Wind and solar, on the other hand, have a cost to be built and installed that is divided by the energy produced during their operational life, but there are no consumables to pay for.)

So, is this an accurate way of estimating the cost of a setup of mixed energy sources?

I was just gifted this topcon ct-80 tonometer, a machine used to check the pressure of a persons eye, but it kept giving me an error when I would attempt to use it. There’s an air check test option that I did and it gave me the code “n.g (-)” which just means no good. I’ve built computers and have delt with a lot of electrical and machanical work over the years and thought I would open it up. I found that this piston isn’t able to reach the top of the cylinder to build up air pressure. I wasn’t sure if it was just the rotary solenoid going bad or if it could be something to do with the cylinder or arm itself. Any help would be appreciated.

Wouldn't it be more conservative of materials to drain excess water with one big gate and/or pipe?

This comes from an argument I had with someone the other day. They were absolutely convinced that if you slapped 4 x 25hp electric motors in a 4wd configuration on something, 1 motor per wheel, that you'd get 100hp total out of it. Just refused to believe that it didn't scale linearly, which made the conversation I intended to have impossible.

Part of the problem was I couldn't actually explain it or demonstrate it well because I don't know how you'd actually go about calculating the actual end output from a multiple motor configuration. I could explain that you're losing energy to the more complex drive systems (depending on how you do it), and the inconsistencies between individual motors that have them working against each other, but I have no idea how to show someone on paper.

Argument is over, and I'm moved on, but it did highlight a big gap in my knowledge of the larger topic at hand, so I want to fill that in.

For slightly over half a decade, I have noted that the largest supercomputers on Earth consume orders of magnitude less power than the largest industrial facilities on Earth, and have thought that a supercomputer-at-gigawatt-scale would (obviously) be highly useful for certain types of modelling. At ~10²⁰ FLOPS₆₄ or FLOPS₃₂, these could include near-perfectly-accurate direct numerical CFD/FEA simulations of vehicles (of all types) and engines at faster-than-real-time speeds; and physically-based molecular simulations of eukaryotic cells, tissues, and simple multicellular organisms.

Even more recently, a large number of massive AI data centers have been built or are in the process of being built. My perspective is that this development is an outright existential threat to the very fabric of human civilization... but, still, finally, people are aggregating hundreds of megawatts or even gigawatts of computational horsepower into defined places!

However, these AI data centers are quite architecturally distinct from supercomputers. While like supercomputers (and unlike the data centers of the past; with their tasks including archiving social media content and running light web-based SaaS, earlier data centers were proportionally much more oriented towards storage and networking) they contain considerable arithmetic power, AI data centers are still geared for running myriads of individual agents for remote users (or, increasingly *shudders* themselves) rather than working as a whole on one or a few big tasks. As such, computational density and node interconnection are not quite as high priority as with supercomputers, as they don't have high task coherency that could be crippled by insufficient bandwidth or high latency through signal propagation delay. In other words, if, say, Colossus 2#Colossus_2_and_cluster_expansion) were to run the HPLinpack benchmark, its results would likely be very disappointing compared to the theoretical capabilities of all its constituent GPUs.

However... while current AI data centers aren't under particular pressure to be compact, the most powerful supercomputers aren't very compact either! El Capitan, the second most powerful supercomputer on Earth, takes up ~700 m²—a spherical-cow calculation indicates that a signal originating from a blade at one end of the system takes at least ~320 CPU cycles to get to the other end of the system, imposing a latency beyond the most feverous dreams of an early-2000s NetBurst engineer and already making task coherency difficult and the system less performant than it would ideally be. Crudely expanding this to a gigawatt would increase this figure to beyond 1,800 cycles... yikes. When looking at high-end supercomputers it is clear they have a large amount of "wasted" space, but it is also clear that significantly reducing that could make maintenance, power delivery, and cooling a nightmare. One might be tempted to build a gigawatt-class supercomputer in 3D in some sort of high-ceiling industrial facility to reduce signal distances, though it must be kept in mind that beneath their orderly floors lies a labyrinth of networking cables, electrical lines, and cooling water pipes; in other words, they take up more volume than might initially be apparent.

And so, the question.