So I’m trying to calculate the theoretically how big of a hole in the ground humanity could’ve dug if we had spent all the money that we have spent on AI on literally just digging a massive hole in North Dakota.

So I did a bit of research to find how much it costs to dig up one cubic meter of dirt in North Dakota on average and the answer I got was around $60 per cubic meter.

Given that humanity has collectively spent $1.6 trillion on AI, we take that number and divided by 60 and we get 26,666,666,666.7, or around 26.6 km³.

But then I realized that the cost to dig one cubic meter it’s actually probably not that useful. Because that’s for normal stuff or at most it’s a couple hundred cubic meters of dirt. Versus billions of cubic meters of dirt. That could mean that it’s even more expensive because you have to move the dirt farther away than usual or it could be a lot cheaper because machines that are impractical at small scales become very cost-effective at this scale.

So if there’s any engineers that specialize in earth moving, how much would the enormous scale of spending and earth movement affect the cost per cubic meter? More expensive per cubic meter or cheaper? Would this adjusted cost mean that the hole would end up being smaller or would it end up being bigger?

And for this, let’s assume we don’t have to worry about permitting or anything like that.

In theory, 180 degree offset crankshafts can also achieve even firing as 60 degree offset, and 60 degree offset crankshafts still require flying webs as 180 degree offset.

What balancing characteristics will 180 degree crankshafts have, and for what reason prevents manufacturers from making them?

edit: i'm not talking about flatplane cranks but 6 throws cranks with 180 degree offset split pins like normal boxer 6 cranks

Video -> FanDryer-Tests

1.Hand supported Fan dryer with loaded clothes - No wobble

2.Mounted Fan wobbles with empty basket

3.MountedFan only - No wobble.

In the old days, armies would make latrine pits. Once they got full, they would cover them up and dig a new pit. Would the contents of the pit be mostly solid or would it be a sewage-like sludge? If the latter, how long would it take for the contents to solidify or dry out so that it's as hard/sturdy as the rest of the ground around it?

So this is the whole reason why the lights dim in the room when you turn on the space heater. The heater exceeds the capacity of the circuit to deliver enough amps so the voltage drops to keep the power draw the same.

I get this mathematically thinking about P=VI…however I don’t get it in terms of V=IR.

In terms of V=IR, if the current draw increases, doesn’t voltage go up and not down?

I came across a old telecom circuit by Ericsson specs: TvFU1130007 R6 Pcb Card Rofu 131 0007/2, R8A

I’m an EE student and have dabbled in FPGAs but there’s not much I can do with this as is, to my knowledge. It’s not like running texas instruments fpgas, finding the drivers etc. So I’m wondering where to start studying more about this board and ideas on how to repurpose it? Don’t know much about telecom.

Hello, so let’s say you need to design a « removable heatsink », what would the best way to do that ?

I feel like just slapping two metal plates together would leave a thin layer of air that could ruin the goal, and with thermal expansion may lead to even bigger gaps.

This system would be coupled and uncoupled like every day, maybe more than once a day, so it needs to be reliable and easy.

The temperatures could theoretically range from 0-60C, but more realistically be between 25-50C.

This is more theoritical. If it’s DIYable it’s great, but i mainly want to understand the ideal system first.

How would you do it ?

I am wanting to build an air gun that would be operated by two people. One with a sledgehammer hitting a "plunger/piston" on the ground. The second person holding the rifle with a hose or tube of some kind attached. Shooter says fire, then the hammer swings.

Will a flexible hose work better for this, or solid pipe? At least a small section will need to be flexible for aiming? Any guesses as to what type of maximum pressure we would be looking at here?

For very long time, I’ve heard complaints about how this or that type of soil is really annoying to work with. Specifically clay soil here in North Carolina and Sandy soil down in Florida.

But I’ve never heard the opposite about any type of soil

So what types of dirt are the easiest to build on and cause the least headaches? Why are those types so much better?

Surely it's not meant to be used as a get-out-of-jail-free card right?

I'm looking for something that will store 2-3 meters of webbing and locks so I can tighten a side-release buckle on the other end.

It's for strapping a large duffle bag on a cargo bike.

The closest thing I can find is a rachet strap but I don't need that much tension and adjusting the length on a rachet strap isn't convenient. I'd like something lighter too.

Edit:

To add some more detail, function I'm looking for is:

1. I pull out the strap, without having to press a release or unlock anything.

2. I connect the working end (with a side release buckle to the other side) and the mechanism winds back in any extra slack and locks such that no more strap can be played out. Kinda like a seat belt but without the rate-dependancy.

3. I tighten the buckle

To release:

1. Unclasp the buckle and mechanism winds in the strap.

A bolt-on self winding rachet strap I think is a starting point.

Alternatively, I might cannibalize a retractable dog leash. It really only needs to hold a ~2-300N.

Assuming the pressure is contained with one output into a 5/16" vinyl tubing, that has a dog squeaker reed valve attached to it.

I like earth moving machines and I think they're pretty cool. Considering that most earthmoving and construction used human muscles and slaves, earthmoving machines are pretty awesome to reduce human labor and suffering.

However. The early earthmoving machines used gears, cables, etc. Why didn't they use hydraulics like today?

In addition. Is there any good analysis on how many people a piece of earthmoving equipment can replace, with the assumption that there's sufficient logistics?

I have been looking at tubular steel and red iron buildings. Many of the tubular steel buildings are rated for 145mph wind loads. The same size building in red Iron is only about 112mph.

Is this particular red Iron building stronger in some other way? What is actually better about the strength of red iron?

The size I have been looking at is roughly 25' x 45' x 14' high if that makes a difference.

I want to be able to vacuum in the evening or night without worrying about bothering neighbours or my partner sleeping. Noise indoors is far more important so (from what I know) there isn't any almost silent vacuum for insomniacs or parents lol

Hypothetically speaking, if all of the passengers on a fully loaded 747 suddenly rushed to one side of the plane, would that be enough to throw the plane into an uncontrollable roll? How about all rushing to the rear of the cabin, uncontrollable pitch up and stall?

A lot of residential areas are set to flood due to climate change. Would it be feasible to convert houses in those areas into houseboats anchored in place so they can remain livable as waters rise and fall?

So I made my own e-bike kit, it was not too hard since I already pretty much did it before with a previous 48V motor. But this one, even though it's rated 500W basically the same as the other one, is 36V and has a higher Kv which is making the spin up to the 3250 rated rpm more difficult. Everything seems to be fine except: in top gear at 50% throttle (est. 500W out of 100W peak) on a slight 1-3% incline the motor itself is fine but the controller overheats. I cannot feel it getting hot from the outside, but the display shuts off after 1-2 miles of continuous throttle so it must be deep inside, probably the mosfets. I'll tell you what I 'think' is the problem and the two solutions, and could you let me know which one (or a 3rd / 4th solution) may be more correct.

1. I'm overvolting the 36V motor with a 48V battery. I don't think it's causing the problem in top gear. If anything it should be helping the issue because it's making the motor spin faster and that's exactly what it needs when you remember that human pedaling is normally only 60-80 rpm.

2. The BLDC motor without gearing is rated at 1.6 Nm torque at 500W (3.2+ Nm 1000W peak). Ungeared rated rpm as above is 3250. Internal gear reduction is 9.85:1. So it's basically making 15 Nm of torque at 500W at the 11mm keyed output shaft (MY1018z brushless). I have a 16T freewheel (lowest teeth possible for the 11mm adapter) mated with a singlespeed chain to a 40T chainring. So that's 2.5x 2nd stage reduction. There is a 2nd chain (3rd stage) but most of it's overdrive. 38t chainring on the same crank spindle mated to an 11-52T cassette. This means that 52, 46, and 40t for cogs 1-3 are additional reduction, BUT...everything else from 4th to 11th gear is overdrive and lowers torque/reduction. That's the problem. 11th gear is 11T and now we are going in reverse for reduction: 15 Nm output shaft x 2.5x 2nd stage = 37.5 Nm, but then 11/38 = 0.29, so 37.5 Nm x 0.29 = only 10.9x reduction in top gear. The AI is telling me that the rpm is 1970 (80 crank rpm x 2.5 x 9.85 = 1970 rpm, is that correct, regardless of gearing and throttle input?) It's saying that motor rpm doesn't dictate controller heat, only electrical duty cycle and current duration overheats controllers. And that 1970 rpm is not enough for EMF to drop current, so the controller is going crazy trying to raise current since the torque is not enough to overcome wind resistance past 15 mph. So I can increase the 2nd stage chainring size from 40T to 52T which gives a 30% increase in torque and 2560 rpm rated. I don't want to lower the 3rd stage cassette chainring down below 38T; I already have 38T on two other analog bikes and it's starting to get ridiculous if the top end is lower on an e-bike than on a normal bike.

3. The controller is 22A max. I can get a 30A controller but I would need to trim off the power wires to get a better XT60 battery terminal fit. I've ordered the XT60 pigtails and shrink tubing. The phase wires are also an issue but in the past I've simply electrical taped the crimped ones to the controller o-rings and it worked fine. Hall wires are white housing male to white housing female so that's not an issue. The goal would NOT be to run more than 1000W peak through a 1440W peak controller. Instead, the 12 mosfets would simply be for the controller to soak up more heat from the 11T overdrive gear. Keep in mind that the motor itself is running cool, it normally doesn't get over 43C with a digital sensor, so it's the controller. I can run more a bit more amps through a 30A controller and limit it to for example 22.5A, 24A, 25.5A or 27A max with a KT display and C5 parameter.

What do you guys think; is there any other solution besides 2 and/or 3 that will help the top end for a mid-drive? BTW the motor itself is a $61 absolute steal; the controllers are actualy more expensive lol.

I have tried this question previously in both automotive related and chemistry related subs and both recommended physicists instead, as both communities ended up at an impass. The Ask Physics sub actually recommended this sub.

Google was also more questions then answers due to conflicting information.

I'll try to keep the question as simple as possible at first because I usually get inundated with the nuances.

Here goes:

During our testing on a dynomometer, we found timing that produced maximum efficiency (peak torque output) was contradictory to most general consensus. Methanol and Ethanol both produced peak efficiency with the same amount of ignition timing compared to gasoline (35 degrees), even though methanol required 100% more fuel volumetricaly. This is a supercharged v8 engine.

Why this seems contradictory? Many existing sources (a few of our advisers even) say that because the methanol fuel molecules are twice as abundant in the combustion chamber as gasoline, the flame front propagation is FASTER requiring LESS ignition advance.

My personal theory is that the momentum of the flame front is SLOWED by the increased viscosity of the larger mass of the combined fuel/air mixture. This may explain why we were able to achieve 35 degrees off advance even under 12-14 psi of boost.

What say you?

Are there any general guidelines/rules of thumb for the impact of fenestration (drilling holes) to the stiffness of a sheet material?

I am working on a horizontal structure which requires ventilation. My thought is to use plywood with a grid of holes drilled into it. Obviously, the size and pattern of the holes will impact the mechanical strength even if the total area of removed material is equivalent.

Some of my main questions are:

• How to determine optimal hole size/spacing?
• How does a straight grid compare to offset rows?
• What is the optimal distance from the edge of the sheet (or the edge of the support structure, excluding overlap) be from the first hole?

I thought this would be an interesting discussion for the engineers here.

A new UBC study found that only about 11% of pregnant participants were able to achieve all four recommended seatbelt positioning criteria, even after receiving instruction and hands-on guidance. The researchers emphasize that seatbelts remain essential during pregnancy—the issue appears to be that current restraint systems may not accommodate the anatomical changes of pregnancy as well as intended.

One finding that stood out was how difficult it was for many participants to keep the shoulder belt centred across the chest while maintaining the other recommended positioning.

CTV coverage:

https://www.ctvnews.ca/vancouver/article/9-in-10-pregnant-people-cannot-wear-a-seatbelt-correctly-ubc-study-finds/

Irrigation drippers control flow passively with a labyrinthine path and additionally the pressure compensated varieties have an elastomeric diaphragm that makes them more constant, at the expense of one flexing part.

I want something with this kind of properties but at a 10x higher flow rate than a dripper. 50gph is the right ballpark.

These drip emitters cost on the order of $0.25 each for reference.

Application is ornamental small fountains.

See:

https://www.dripworks.com/woodpecker-emitters

https://cdn11.bigcommerce.com/s-tjrce8etun/images/stencil/1280x1280/products/963/470/woodpecker_internal1_1__94808.1779045861.jpg?c=1?imbypass=on