As the Earth rotates on a North/South...ish axis, which hemisphere is the Western one?.......(I've seen the definition, if you accept North South, you don't get to use East West.......or they'd be 2 Earths.)
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Anyone have any random nerdy facts?
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https://en.wikipedia.org/wiki/Western_HemisphereAs the Earth rotates on a North/South...ish axis, which hemisphere is the Western one?.......(I've seen the definition, if you accept North South, you don't get to use East West.......or they'd be 2 Earths.)
If you narrow your definition down, anything can have a record.....
Central Station, Sydney, has the longest escalator in the Southern Hemisphere...
dr wogz
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The Milky Way tastes like raspberries!
In 2009, astronomers were able to identify a chemical called ethyl formate in a big dust cloud at the center of the Milky Way. Ethyl formate happens to be responsible for the flavor of raspberries (it also smells like rum).
https://www.theguardian.com/science/2009/apr/21/space-raspberries-amino-acids-astrobiology
In 2009, astronomers were able to identify a chemical called ethyl formate in a big dust cloud at the center of the Milky Way. Ethyl formate happens to be responsible for the flavor of raspberries (it also smells like rum).
https://www.theguardian.com/science/2009/apr/21/space-raspberries-amino-acids-astrobiology
Flash! This one is literally just out; in Nature on Wednesday.
Why is ice slippery, even when it's well below 0°C? Chinese researchers have observed the image an ice surface at atomic-level resolution, and discovered that the ice surface begins to melt at -153°C.
https://newsen.pku.edu.cn/news_even...440&utm_medium=email&utm_placement=newsletter
Useless anecdote follows:
My favorite grad-school class was surface chemistry, taught by James Wightman, a world-leader in the subject. The fundamental concept is that chemistry (and physics) at a surface can be wildly different from the chemistry of the bulk material.
Wightman was hilarious! Every year he re-enacted Benjamin Franklin's not-famous investigation of oil on water, on the "Duck Pond" at VT. He did so while in full 18th century costume, right down to a tricorn hat. He also did a semester-end collection of classroom demonstrations. One of which involved a pan of flaming alcohol and water; he put out the flame by sticking a finger in his ear and touching it to the surface. Earwax has many uses...
Why is ice slippery, even when it's well below 0°C? Chinese researchers have observed the image an ice surface at atomic-level resolution, and discovered that the ice surface begins to melt at -153°C.
https://newsen.pku.edu.cn/news_even...440&utm_medium=email&utm_placement=newsletter
Useless anecdote follows:
My favorite grad-school class was surface chemistry, taught by James Wightman, a world-leader in the subject. The fundamental concept is that chemistry (and physics) at a surface can be wildly different from the chemistry of the bulk material.
Wightman was hilarious! Every year he re-enacted Benjamin Franklin's not-famous investigation of oil on water, on the "Duck Pond" at VT. He did so while in full 18th century costume, right down to a tricorn hat. He also did a semester-end collection of classroom demonstrations. One of which involved a pan of flaming alcohol and water; he put out the flame by sticking a finger in his ear and touching it to the surface. Earwax has many uses...
They've wanted to get rid of any standard based on an artifact for decades. They can never be replicated with absolute accuracy. Basing standards on fundamental physical constants means they can be replicated anywhere in the universe without referencing one single object that exists in one place.
Fun facts:
For a period of time, the UK didn't have a standard for distance because their primary reference standard for the yard was destroyed in a fire in Parliament.
One reason the USA didn't adopt the metric system early on was that a reference kilogram artifact from France that was being delivered to Thomas Jefferson was hijacked by pirates.
And making flats is done by three against each other, A on B then B on C then C on A, a little at a time rotating through the cycle, switching which is on top each cycle. Since it's not possible to have three things arranged in pairs, the all have to be flat to stay in contact. The same procedure is used for dressing whetstones.
You realize that the M&M Mars company now has to come out with a raspberry flavored Milky Way bar.
Automatic transmissions nearly double the engine torque into the transmission when starting off. Typically 98%, or more, increase. This is due to how the torque converter functions. The most increase occurs when the output shaft is stationary and the input shaft is being driven at a particular rpm (converter is "stalled"). That rpm is usually well below the power band of the engine.
You can get "high-stall" torque converters for people who like smoking the donuts. Foot on brake, engine up to power band, release brake.
You can get "high-stall" torque converters for people who like smoking the donuts. Foot on brake, engine up to power band, release brake.
We had some discussion recently about transmission gearing including the 2-speed automatic transmission that General Motors used for awhile- compatible torque converter design is what makes this work.
I don't know anything about trains, I've always wondered why they couldn't use a torque converter to get the thing moving. Apparently it would not be practical. For that matter I don't know how ships and large boats work either- how is the diesel engine connected to the propeller and disconnected when necessary?
Virtually no trains today use ICEs to drive the wheels. Many passenger trains are all electric. Locomotives, freight and the rest of the passenger rains, use diesel engines to drive generators that drive the motors that drive the wheels. I guess, in a manner speaking, you could call the generator motor pair an electrical torque converter.
Indeed, that's exactly why the word "internal" was used for the new kind.
common term for them like this famous saying "More Powerful than a Diesel Locomotive"
And yes the Diesel generator powers Traction Drives.
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I understand that. Were diesel engine locomotives always diesel/electric?
I understand that a lot of ships these days are also diesel/electric- driving the ship through underwater pods. But I'm sure there are still ships in use that have diesel engines powering propellers without electric motors as intermediaries. How does that connection work?
To the best of my knowledge main stream Diesel Locomotives were Electric Traction for motive power.
No Idea about ships. @boatgeek ?
But I found this: https://www.brighthubengineering.co...re-the-main-types-of-ship-propulsion-systems/
Doesn't say how the propeller is disconnected from the engine- clutch? in/out box? synchronized or unsynchronized?
I would say a clutch. Here is a Wiki Quote "Where more than one engine is geared to a single shaft, each engine will most likely drive through a clutch, allowing engines not being used to be disconnected from the gearbox while others keep running. This arrangement lets maintenance be carried out while under way, even far from port."
boatgeek
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Oh my, there are issues with that link. I will type more when I have time.
goose_in_co
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Not always. Diesel-electric (either AC or DC) is the predominant form, mainly because of the efficiency of conversion and the ability to turn the motors into generators and use them for dynamic braking, which is also used on electric cars as well. The Diesel-mechanical was only used for lower power, since the size and weight of the driveshafts and transmissions would make it too heavy in the higher horsepower locomotives. There were also Diesel-hydraulic, and Diesel-pneumatic engines, among others. Most of the locomotives used on mainline railroads use AC traction motors now with rather sophisticated electronic controls.
Other trivia is that the extra large off-road dump trucks are also Diesel-electric.
Most diesel locomotives and diesel passenger trains (DMUs) in Japan are not diesel-electric; the motor mechanically drives the traction wheels.
They sound more like trucks or buses than trains
boatgeek
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So here's a primer on boat propulsion systems. This is likely long enough that I won't talk about propellers. If there's demand, I can come back with another whole set of nerdy facts. When I talk about efficiency below, I mean mechanical efficiency from the engine flywheel to the propeller. There's other factors in how efficiently an engine runs that I'll talk about in the text, plus more about propellers that I won't get to here. I'm also mainly talking about diesel engines. Gasoline is more or less nonexistent in the commercial world I work in, and gas turbines have a very small niche. The link above has some stuff that I think is off the mark, especially about electric drive systems.
From simplest to most complex, we have...
Direct drive or Direct Reversing
This is the most common propulsion train on large cargo ships. It's pretty much what it says on the box. The engine is directly connected to the propeller shaft and propeller, with no gearbox, transmission, clutch, nothing. If you want to go in reverse, you stop the engine, let the propeller come to a stop, throw a literal or metaphorical lever on the camshaft to change valve and injection timing, and restart the engine in reverse. Needless to say, you don't want to have to do a lot of maneuvering with these engines, so tugs assist these ships in to the dock. These engines are extremely large, roughly the size of a double decker bus, run in the tens to low hundreds of thousands of horsepower, have cylinders you can sleep in, and run at low operating RPM, like 40-120 RPM. They also don't like to change speed very fast, so the process of ramping up to full RPM from idle and vice versa can take an hour or so. The upside is that the engines quite happily burn any kind of fuel (heavy fuel oil isn't too far from asphalt), and are very efficient if you're crossing oceans.
Efficiency: ~98%
Geared Drive
This is the drive system of choice for most of the boats I work on, which are small to medium (50'-400') commercial boats like fishing boats, tugboats, ferries, etc. The engine drives a reduction gear that drops the full throttle RPM from 900 RPM -2300 RPM at the engine to 150-1000 RPM at the propeller. As a rule of thumb, fast boats have small propellers turning fast and slow boats have large propellers turning slow for maximum efficiency. The reduction gear often has a reverse gear in it as well. Both forward and reverse are engaged or disengaged with clutches--the gears stay meshed all the time except for a few specialty gears. The reduction gear then drives the propeller.
You lose a little efficiency because of the gears, but you gain a lot of maneuverability and the engines are quite a bit smaller than the low-speed ones discussed above. Though that's relative. I'm working on a tug right now that has V12 engines that are 12' long and 6' wide. On the small end, you see engines that are more or less the same models as are in heavy duty pickup trucks.
Efficiency: ~95%
Electric Drive
This is the fancy stuff. In electric drive, you convert the power at least twice (mechanical off the engine to electricity, electricity to mechanical on the propeller) with the natural loss of efficiency that causes. It also is more expensive up front and takes a lot more space. So why would you do it? For specialized boats/ships where the overall system efficiency can be improved. First of all, if your electric load for the rest of the ship is roughly the same as the propulsion load, it almost always makes sense to go with electric drive. This is why cruise ships are electric drive--the hotel power is more than propulsion power. Another place is where you have a lot of different power needs that run at different times and/or where the propulsion engines often run at low power. Most diesels don't like running at less than 25%-40% power--you end up with carbon buildup and other maintenance issues. A classic example of this is a dredge. When it's running from place to place with a full hopper of sand, they want to go fast, so they have large main propulsion engines. But when they're dredging, they are tootling along at idle, which is hard on the engines. Add in the cost of major overhauls (usually set by hours of operation) and it starts to make a lot of sense to run everything on electric. On a large dredge, you can actually eliminate 2-3 large engines by going diesel electric, because when you're going fast, the large dredge pumps aren't working, and when the dredge pumps aren't going, the main engines don't need much power. The generators don't care which way the power is going.
Electric drive can also give you better reliability. On a geared drive boat, if you lose one of your main engines, you're SOL until you can get it fixed. With electric drive, you can bring another generator online (you'll typically have 3-5 generators) while you work on the generator that's out of commission.
Efficiency: ~85%-90%
NTP2
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How do cruise ships make all that power? It must take a small power plant and a lot of fuel!
They did make 4 Civilian Nuke Ships, The first was Savannah. I've worked [talked to] the radio room on that ship with my Ham Radio during special events they run from that ship now that it is a museum.
https://en.wikipedia.org/wiki/NS_Savannah
NTP2
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Cool! That led me down a rabbit hole!! It appears that nuclear power is popular for ice breakers because of their lack of ports to refuel at, shame it never became popular!
boatgeek
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They have 5-8 large diesel engines putting out a total of ~100 MW on the largest ships.
Like many things, it came down to economics. Nuclear cargo ships were hideously expensive to crew. Plus, once cargo ships started being run under flags of convenience, you would start running into proliferation issues if you have nuclear powered ships flagged in, say, Liberia.
The Russians are pretty much the only people running nuclear icebreakers, and they’re fairly closely tied to the Russian Navy.
NTP2
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I wonder if modern AI could help alleviate that staff issue. Of course you’d need to have one or 2 people making sure it doesn’t have a fit.
also a ship it the best place for a reactor as water makes a amazing radiation shield as well as a coolant, if you have a meltdown you can dump it in the ocean, that’ll probably stop the meltdown and stop the radiation from bothering anything (except maybe a very unlucky deep sea creature).
boatgeek
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Oh, my sweet summer child. AI won't help. Modern automation (which is not the same thing) may help. But even extremely optimistic views of what staffing will be required put that in the 50-80 people range for 100 MW-1 GW reactors. Since current large cargo ship crew sizes are on the order of 20-25 people, of whom perhaps 8-10 are in charge of the engineering spaces (and some of whom wouldn't be replaced if the diesels were), you're looking at doubling to quadrupling the crew size. Add to that the difficulty in finding crew who are (a) qualified and (b) willing to go on 4-month voyages, and you're looking at a ship that's extremely hard to staff.
And that's before you get to environmental issues. A nuclear ship (rightly or wrongly) would be barred from many of the world's ports. You also don't build hatches into your ship big enough to eject the warp core, and I don't think that you understand the scale of People Will Care if you do dump an overheating core into the ocean.
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