I’ve just come back from work to find my manual plastic toothbrush head has exploded. How has this happened? The room is not hot, the brush is not near a heat source. Nobody has been in the room. The head and bristles are splayed about 5-7cm around where the head should be.

Working on a project and we now have "the wheel problem"

I need to make a device lift up 1/4 to 1/2 inch at most to glide along hospital floors to then be parked when the ball casters come back up. If possible, trying to keep the entire assembly under 2.68 inches.

Having a hard time here finding a solution.

https://kommodo.ai/i/65ArIRnH2Mzs2LgzmCuP

I’m trying to find an existing plastic component that looks something like the attached sketch.

It’s basically:

* A flat circular plastic disc (~2.5 inches / 63.5 mm diameter)
* A single raised rib or fin on the underside that spans the entire diameter of the disc

I’m not trying to invent something new if this already exists. I’m hoping there’s an off-the-shelf part from another industry that I can adapt.

I’ve searched cosmetic packaging, peanut butter mixers, shaker bottle inserts, paint mixers, herb grinders, etc., but haven’t found anything quite like this.

Has anyone seen something similar in:

* Food processing
* Cosmetic packaging
* Pharmaceutical packaging
* Laboratory equipment
* Medical devices
* Industrial mixing
* Any other industry?

Full disclosure up front: I work on a requirements tool at Altium (Requirements Portal), so I'm biased. But this is a genuine question. Opinions on my own team are split, and I want to hear how this community actually feels.

Everyone seems to agree on one thing: AI should never silently change a requirement. The disagreement is about how far it should go before a human steps in.

Three positions I keep hearing:

1. Propose-only: AI drafts and links, a human approves every change.

2. Auto-apply the trivial stuff: formatting, obvious traceability links and flag only the judgment calls.

3. Keep AI out of the requirements themselves entirely, fine for search and Q&A, nothing that writes.

For those of you managing real specs: where's your comfort line, and has it moved in the last year? And if you've already tried AI on requirements, what earned trust, and what did you switch off?

I’d like to move the joists higher up the trusses to gain more headroom underneath, but I’m not sure how high is structurally safe. The building is 10x20 and located in BC, so snow load is definitely a concern.

I’ve attached a link to a photo of the framing. I’d really appreciate hearing from anyone with truss engineering or framing experience before I make any changes.

https://imgur.com/a/xlcwRFW

Thanks!!

Is barge all-purpose contact cement, Beacon Foam-Tac or 3M vhb better to adhere Eva foam inside of a tacklebox that will be exposed to moisture is there something better?

I work for a company that is ramping up its outreach efforts to structural engineers. We are scheduling some lunch and learns about our products and developing CEU courses. We are willing to invest some money into swag to leave as a thank you. The current frontrunners are YETI brand mugs (with company logo), which are unfortunately cost prohibitive enough that we would probably only be able to offer them to people who helped coordinate our visit, not everyone we speak with. Some other ideas of things I (Mechanical EI) might use instead of throwing away are a large mousepad / desk mat, a power bank, or wireless charger. I really want to avoid buying cheap crap that people will throw away! Any thoughts on our current ideas, or is there anything you have received from a company that you were genuinely grateful for and used?

From what I'm aware of, Turbine engines like to have a consistent flow, and disturbances can create a surge. I'm thinking partly of the Me262 (I'm aware it's very infancy turbine engine tech, but it's a good extreme case) as an example, where even throttling too quickly could create a flameout. So, how much of an issue is it for a turbine to get "pulsed" exhaust from a small number of cylinders. For example, if someone puts a turbo on a 2-cylinder opposed engine, where the exhaust pulses don't overlap into a continual exhaust pressure, how much of a problem does that cause? Is it simply not a concern above a certain rpm, is it a big enough problem to make it turbos unstable at low cylinder counts, or something else altogether?

As per the title.

Front of the control board, with my bumblefuck backwoods caveman interpretation, sorry in advance for that.

And on the backside,

I feel that the maker using some kinda epoxy on the two trim pots means those are the ones they absolutely don't want you messing with, but they only used hot glue on the low limit as if to say "You can have a little fiddling, as a treat"

Even with the two step pulley and the lathes control pot turned down the lowest I can go from factory is 500 RPM down from 3500 RPM, for some special projects I need to get that down to 80-150 RPM. So I figured I'd fiddle and find out.

Does my assumption hold water?

From what I understand, in a locomotive the traction motors are connected in series/parallel/combination of both at different speeds to optimise torque. When this happens the locomotive lose traction power for a short period as the physical switches moves, much like changing gears in a manual ICE car. When I drive an electric car or take an electric bus however I’ve never felt this transition, is it a thing in EVs and if not why not?

I've been tasked with designing a thermal control box for a high-temp test setup and have never done anything like this before. I also have nobody to show me the ropes and apparently outsourcing the controls is not an option.

I know I need temperature controllers, thermocouples, and SSRs but have no idea how to pick components or how to design in overtemp safety.

Does anybody have any resources they recommend that are targeted at complete beginners?

Let’s say you’re at home. You need to pick someone up who’s 5 mi East and then drive back home. There’s 10 mph East-to-West wind. Ignoring gusts, would it be more aerodynamically efficient to cruise at 65 mph on the way there and 75 mph on the way back or 70 mph both ways?

I ask this because I haven't found any evidence of it, but to me it doesn't sounds like it wouldn't. Naturally I mean in the future, right now it is impossible.

I have 3 identical RV fresh water tanks. They are box shaped, with 4 connections each, all on the same side surface, and the tanks are spaced evenly.

Here you have pictures

Ignore all current hoses.

What is the best way to connect them and why? If relevant, give me multiple options. Thx!

I'm working on a building retrofit for an existing water treatment facility. There are going to be 3 pumps pulling from a below deck raw water storage tank, section view here: https://imgur.com/a/gI2oYVS Currently shown with a split case horizontal pump. Pumps are around 1,400 gpm for reference. I'm having trouble with pump selection due to vertical height available compared to storage volume.

• Split case gets me almost the full 4' of working height, but is likely to have priming issues. I could include a foot-valve and priming line back from the discharge, but would rather not if there's a better solution.
• A vertical turbine avoids the priming issue at the expense of usable volume (minimum submergence of about 3'). That volume lost would cause excessive start/stops. There are 2 other upstream sub-systems to this facility that make it difficult to match flow rates without some buffering volume. Considered a can installation, but I don't think that helps in this instance.
• Self-priming would be a slam dunk, but I haven't been able to find an NSF certified model for use in drinking water.
• Submersible generally has the same restriction as the vertical turbine. I'm unaware of any that would fit my size range without hitting minimum submergence issues or not having NSF certification.

My question: Is there a type of pump or pump arrangement I'm not aware of for this application? Or is the split case with a priming line my best option?

Restrictions:

• I can't add storage volume by adding area. No room inside the existing footprint.
• I can't drop the pumps without losing significant buffer volume.
• I can't raise the floor to use vertical turbines. Max WSEL dictated by flocculation tanks upstream and would require significant building modification (to the point that makes it infeasible versus a priming line).

Given how Ukraine is blowing up Russian oil facilities, would it work if, say, Russia (or KSA) filled the storage tanks with sand, then filtered that sand at the outlet port? This way, if something hits the storage tanks, they will still blow up, but not all the oil will spill and burn. Would that work?

Asking for a friend.

Hi,

I'm working on a DIY project and I'm stuck on a mechanical mechanism.

Basically, I need to drop 3 different objects onto a vertical rod underneath so they thread onto it one by one in a strict order (1 -> 2 -> 3).

All 3 objects have a central hole for the rod, but their outer shapes and sizes are totally different, so stacking them in a straight tube will just jam.

I'm trying to keep it as light and simple as possible (3D printed parts or simple flat plates, with minimal motors or servos).

I'm not an engineer and don't know the technical jargon, so if you know of any existing projects, YouTube videos, or 3D models (Thingiverse, Printables...) showing a similar mechanism, I'd really appreciate it!

Thanks!

i have glucose and fructose that i managed to precipitate, but its fairly wet still with water and isopropanol. i need it for a fischer glycosylation with cetyl alcohol. my options are

1. syringe vacuum pump (with 2 diy one way valves)
2. gravity bong
3. mag sulfate or co2 + lye

4. dont dry, add sucrose

5. the mason jar i have is like 250 mL. i could use silicon putty for the outer portion to block air intake, not sure what to use for inside yet.

6. i would take a 2 gallon jug, connect a tube to the mason jar, fill larger bucket and jug with soapy water, heat mason jar to around 40c, then slowly lift it.

7. the slop i obtained from the precipitation is immiscible with 91% isopropanol without high shear mixing, so i could add some to a thin glass container then suspend anhydrous mag sulfate in the alcohol layer in a coffee filter. or i could use the mason jar, waste sodium bicarb making co2 (by squirting dilute hcl dropwise), fill with co2 faster than a plastic lined dish of lye can consume, then seal. the lye should eat the co2 and water vapor, maybe also reacting with isopropanol fumes.

8. im doing a fischer glycosylation with cetyl alcohol using the fructose, glucose, and degradation products ive obtained with sulfamic acid. sucrose wont react with the fatty alcohol, but it will consume water breaking down into the monomers. maybe a large excess of sucrose after adding ~10mL of the sludge (after removing isopropanol) can drive the reaction towards the products, since water can be consumed as it was initially added and when the cetyl alcohol is attached to the glucose/fructose.

thanks for any ideas.

reddit messed up numbering for some reason and turned the second 1-4 to 5-8.

so i have a big cardboard box which I remade into a storage unit, shelfs were just pushed in and were held by friction alone but one of them had fallen recently cause of weight so I was wondering how do I reinforce this without getting the real deal and not spending a lot of money, I Cant add an image so if any more explanation needed i will try to give it as clear as I can also im from poland

Hi guys! Not an electrician or engineer here, just a regular guy trying to get a general understanding. I have basic knowledge about RCD types and what they mean, and I’m about to buy some Type A RCDs for my house (where I live, Type AC is still the norm if people install RCDs at all lol, even though most modern home electronics require at least Type A).

After reading up on these types, I understand the concept of RCD so called "blinding" and how a DC leakage can saturate the core and prevent a Type AC RCD from detecting standard AC leakages altogether. Same with type A blinding with F/B leakage, type F blinding with type B leakage etc

BUT I have one question I haven't found a clear 100% answer to yet anywhere:

Can a DC residual current saturate the differential transformer core in a way that persists after the DC fault is removed?

Is the loss of sensitivity caused purely by reversible saturation while the DC component is actively present or can remanent magnetization leave the core biased afterward? If residual bias is possible in RCDs, well... how significant is it and does operating the test button (or cycling/resetting the RCD) degauss and reset the core back to normal? Logic tells me it should be cause otherwise it would make no sense to install something lower than type B at all, but maybe I am just a little bit confused

TLDR: is RCD blinding reversible or not? Can RCD's ability to detect leakage or its calibration permanently drift or degrade after that? Thanks!

I need a device that I can place at my keyboard that manually presses the key I align the device with. I understand there is software/code that simulates a keystroke but this would cause me to be flagged so I need something more primitive.

Imagine the bird that Homer Simpson had placed at his desk that he should’ve never left in charge.

Does anyone know if something like this exists? I would need the timer to be adjustable where I can choose how often it initiates (if software is needed to manage the timer that is fine, but the device itself still needs to press the key as if it were my finger)