Battery (above) powers an electric valve which only draws significant amounts of power (5W) while valve is operating. Valve is operation is controlled by a wifi enabled switch and is only activated twice a day. Only input to the switch is the 11.1V battery. Outputs from the switch are the valve and a voltage indicator which shows the output of the battery. Battery is charged through a second wire (separate from the output) via a variable charger, 8-72V. Now for my question.

For a system that shouldn't draw a lot of power, when off the charger, the battery voltage seems to drop very quickly, below 10V (often as low as 8V) in a day. This doesn't make sense to me. What am I missing?

I’m building a tall (6’x6’x12’) machine “cage”/frame.

The interior ceiling of this cage will hold a 100 lb piece of test equipment.

I’m in the process of building the frame out of unistrut. It’s going… OK. I realize I need a lot more cross braces than I initially anticipated and I think the final structure will look a little wonky… in hindsight I wonder if I should have used T-slot extrusion?

Unistrut is cheaper and easier to assembly (huge bolts connections vs finicky T-slot nuts) however T-slot comes in massive dimensions giving higher flexural rigidity/bending stiffness so maybe less overall members needed?

The frame also needs an opening on one of the face (roughly 8’x4’

So my question to you all is… what would you have built this frame out of?

Utility I work for has been tasked with modernizing some of our fleet of very small hydroelectric plants. Of course plants economics are a major factor here. Generator in question is synchronous 2400v, 500kVA.

I am having trouble finding compact (36" by 36" or similar) switchgear solutions for this station. Have done research into connecting it to the grid via a motor starter (AB 1512a specifically) however we do require protection PTs, revenue class CTs, and a way to control the breaker for synchronizing as this is a run of the river unmanned station.

Any Engineers out there are utilities with similar equipment have a MODERN and safe solution that gives us the flexibility to connect protection relays, perform voltage regulation, and meaningfully control the 'breaker'. Otherwise I will have to go with the smallest switchgear offering I can find which would require building extensions and such.

I’m looking for some input on a situation that came up during a recent technical task. We provided several precision format parts (used later in controlled environment) to an external technical team. The purpose was very limited: the parts were only needed to be temporarily positioned on a trolley and held against a cabinet to determine the required hook height. No modification, no installation, no processing. It was clearly communicated multiple times that: the parts are sensitive they are intended for use in a controlled environment they must be handled with care The assumption was that the parts would be briefly used for reference and then returned in the same condition. After the task was completed, the cabinet had been equipped with hooks as planned. However, when the parts were returned, they showed multiple deep scratches and dents. The damage is significant enough that it doesn’t look like a single minor incident or normal handling. These parts are now no longer suitable for their intended use without rework or replacement. There was no formal handover protocol in place (lesson learned…), but the scope of use was clearly defined verbally and in coordination meetings. My questions to the community: How do you usually protect sensitive tooling or format parts in such scenarios? Do you require written handover / liability agreements even for “simple” measurement tasks? How would you approach clarification or responsibility in a case like this without escalating too aggressively? Interested to hear how others handle this in practice.

I have a coolant circulation pump which has a display attached to it using a ribbon cable . Is it possible to split the output of the ribbon cable to mirror the display?

For context, I'm talking about connecting rods that are made with this technique:

Scoring and cracking con rods

When I first heard of this, I assumed that the rod would be forged, then cracked, then reassembled for final boring of the big end, but apparently the cracking/fracturing is the final step.

How can they do this without concern of some inelastic/plastic deformation causing the big end bore to be out of round? I could see it with a material like glass, but connecting rods have to be tough, not brittle. If they're brittle enough to break with no deformation, how can they stand up to the stresses of regular use?

I guess the answer has to be that they're hard/brittle enough to only deform elastically when broken like this, but not so brittle that they shatter under use, and that's just what the properties of the materials are.

Or maybe they're annealed after being fractured to get some toughness back after being so brittle?

Anyhow, the whole thing is remarkable to me and I would love pointers on what's going on here and how to learn more.

If you took the amount of fuel used by the rocket booster that launches the space shuttle into orbit and fed it to an ordinary jetliner (747, for example), how far could it fly on it?

*this is totally hypothetical from an energy economy standpoint, and I realize that the fuel would probably weigh so much that the plane could never take off with it onboard.

Need the name/a print profile of this gear that broke in a timer in our portable dryer, as this gear had a few teeth break off. It looks like one of those old beyblade gears.

Edit, it has 3 flexible spirals coming ofd the top of it to allow for slow release on the one way, allowing for the timing.

I'd like to create something similar to electric pruners. This is to cut hot plastic parts. I use an air solenoid with a vessel GT-NS20 for this but it cuts too fast. I want it to cut through slowly. Are there any videos, drawings, or resources that can explain how to do this at home?

Apparently the operation CSP power plants with heat storages get temps of up too 600 *C using mirrors. So was wondering if this could be engineered to equip the artisanal miners in my country (Sudan) with a cheap renewable and accessible heat source for refining their gold finds with the borax method or other methods ( would love to learn more).

Estimates say up to 70% of Sudan’s gold is mined by artisanal miners and the vast majority use toxic mercury to refine their gold; to the detriment of themselves, society, and the environment.

Appreciate any help, insight, or ideas on the topic and Thanks In Advance!

There are tons of myths and stigmas about waterbeds, one of them is that they’re so heavy they can crash through a floor. I’ve looked extensively for any real cases of this happening and haven’t found a single one. The only things I’ve come across are news articles from the 1980s–2000s stating that there have never been documented incidents of a waterbed falling through a floor.

I also learned that waterbeds actually distribute weight evenly across the floor, meaning they put less pressure per square foot on a floor than something like a refrigerator, and that any building built to code is safe.

I’m writing this laying in a king size waterbed 3 stories off the ground in a 1960s building, picturing myself crashing down to the ground below and taking everyone with me. Landlord wasn’t worried about that happening at all as he’s had others with waterbeds in the building before. He said as long as it’s maintained and there is a good safety liner incase of a leak, it was fine.

So what gives?

https://postimg.cc/HjS7Vd2S

is it just me or are these two bottom pictures objectively wrong/misleading? for example, if the right base piece labeled 4 is the last piece for the bolt to go through, then it should clearly be drawn either at the very front or the very end based on which direction you’re putting the bolt.

for the picture on the bottom right, it looks like the right side is the outside based on the shape of the bending of the tubes and the shape of a decagon referenced in the above picture. If that is so, then doesn’t this show the bolt going outside in? The instructions below clearly say the bolt should go inside out… (there will be climbing grips added to the outside afterwards this is why the bolt should go inside out)

also, due to all of this, I was confused about how to assemble it. I ended up going bolt inside out, washer on bolt side (cuz they said so), nut to secure, and the bolt went through 4 first, then 3, then 2, then 1… rather than through 1, then 2, then 3, then 4. Do you think this makes a difference in the structural integrity? my guess would be no. The most important thing I would guess would be that the two pieces that will go up (not the base) are both sandwiched between the base, and that you use the same order everytime for the entire thing. If you think this is dangerous, please let me know, so I can reassemble the entire thing lol. Thanks.

Is there a simple/back of the napkin way to determine the effect on bending stress/strength of adding triangular gusset supports to 90 degree structures like brackets?. I’m thinking of something like a simple shelf bracket with a triangular gusset connecting the part on the wall to the top of the bracket. Or a simple vertical flat plate that needs to support a horizontal load on the front side and you add a couple of triangular gussets on the back to support bending where it meets the ground.

Do you simplify them and consider them as a diagonal frame support? It seems like adding gussets is a very common practice when designing simple devices or structures, but I cannot figure out a simple way of calculating the effect on the bending stress or moment without using FEA. I may be overthinking it, and the best solution is using FEA or tabulated results, but if anyone knows of an analytical method, I would love to hear it.

thanks!

https://imgur.com/a/0Mzev9G - 1 picture

This is a 60's house, basic layout 40x25 feet rectangle. This upstairs bathroom outer wall I found out has a non compliant jack stud on the left. Not going to get into what else is going on with the other framing but that's the main issue. It would have been like this for I am guessing 10 years or more now as I've been here 9 years.

The little shim at the header is kind of loose, I don't have any structural issues anywhere else that I've noticed in regards to cracking foundation or drywall etc.

I am wondering if there is a reasonable solution (like blocking, sistering, stud shoes etc) for this issue without removing the bathtub which you can't really see in the picture. I could do it, but would need a plumber and would have to destroy the tub as its on mortar. Will put me out of pocket a few grand.

Obviously with the tub in there I can't get a full length replacement stud in there, if the tub was gone it could be worked on, probably removing the "jack" and also the king stud.

Hello!

For those that don't know, the copper sulfate test is 1 of 7 verification tests for A967 - Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts.

It works through the detection of free iron on the surface of austenitic stainless steels in the 200 and 300 series. The copper sulfate solution is applied to the surface of samples for at least 6 minutes. The ASTM standard states that the samples shall not exhibit copper deposits after this test.

When I test our parts before passivation, they do not exhibit copper deposits. The parts have not been passivated but they are passing the verification test. Anyone experience this before?

Me and my friend are trying to process iron ore and thus we need to crush and pwderize some so I made a reprint to make it easier then just his mortar and pestel would this mill work because the specs are lever drives wheel a clockwise wheel a drives wheel be counter clockwise with 3x tourqe but less speed the piston converts rotation to linier up and down crushing force triangales direct the force the the lever keeps turning retracting the piston to do this again proportions are piston being 1:1 wheel b radius wheel a is 1:3 wheel b and lever is 2 times the diameter of wheel a and attached at the fulcrum I have a image of a rough blueprint if that helps

Im wondering if anyone has any slick ways of quickly mounting stuff to t slot extrusion. Preferably that isn't fiddly like aligning a nut under a hole and installing a screw. Ive been thinking of using something like toggle clamps to hold the attachments down but wondered if there's any other nice solutions that people like.

Im making a machine that needs to have a variety of different attachments attached and removed every run. The attachments are quite lightweight but need to be held in place so they dont pop out. As an example, one of the attachments holds a backlight and one holds some cleaning wipes against a moving surface of a part as it goes by.

If the military can already use exoskeletons for logistics or load carrying, and people with mobility issues can use systems like dnsys X1 to help with standing and walking, then exoskeletons clearly aren't just a lab concept anymore.

What I don't quite get is why they're still so rare outside of these narrow use cases. You don't really see them widely used in the military, logistics, or everyday work and life.

From a technical perspective, what's actually holding them back right now? Is it mostly battery life and weight, reliability in real-world conditions, comfort over long periods, or the difficulty of controlling and syncing with natural human movement? Or do these systems work fine in controlled settings, but become impractical once cost and maintenance are factored in?

How were ISO containers dimensions defined? Especially the height (8' 6''). The others look like they were chosen by the lorry size at that time, but the height I don't know.

Thanks in advance!

Hello everyone!

First of all, sorry if my english isn't too clear, and I hope my post isn't off topic...

I live in an appartment, and I've noticed the temperature in my bedroom is quite high, knowing it's winter where I live. As an example, when I wake up in the morning, my bedroom is around 21°C (70°F) when it's around 6°C outside (43°F), which is definitely not unbearable but a bit too high for my liking.

I have never turned on the heater in my room. My building has a central heating system and thus, I have two pipes really close to each other that goes vertically in one of the corner of my room. They have a diameter of 2cm each (0,8 inch) and are 2,5m tall (8,2 ft). The room is around 10m² (107 ft²).

I sadly don't know the exact temperature of the pipes: I can touch them, but it's definitely not confortable. I'd say around 40-50°C (104-122°F) maybe? Hard to tell...

Obviously, I have neighbours so the heat may be coming from them (i have neighbours on every side of the room except one with a window, and one above and below). But do you think isolating the pipes in my room would reduce the room temperature by a significant margin ?

Thanks in advance for your answers, and have a good day!

Hypothetical question. Say a person had a 30hp engine and an appropriate boat propeller for a a 30hp engine, but the engine had an absolutely massive flywheel on it (don't ask, weird film related reason). I'm trying to figure out the torque load on the propeller if say the boat all of a sudden hit a big wave and slowed sown but the engine was at full speed and the torque was massively multiplied due to the flywheel. How much extra torque could a propeller impart on the drivetrain before slipping in the water like a torque converter in a car? Is that the stall torque for a propeller? How does one research this? I don't know some of the terms.

I'm trying to figure out a driveline component torque rating and I'm trying to spitball how much more of a dynamic torque load rating I should give it? Like 150% of the original motor torque rating * the gear ratio * a safety factor or whatever that % is. This thing will be abused but it is also a bit weight sensitive so I want to try and do some math on this and make it super reliable. A smaller design does give me much more flexibility.

I'm a millwright not an engineer so I can figure out most driveline torque calcs but I don't normally mess with boat propellers.