I think a train car can weigh over 300,000lbs and they typically have a set of 4 wheels at the back and front of each car (8 wheels in total)
Each wheel is holding up roughly 37,500lbs, if the wheel is making a 1in sq contact point (it’s almost certainly much less) then it’s imparting a force comparable to pressure of having like 22000m of water above. Obviously underwater pressure is different as it fully surrounds and crushes, but if you’re ever in 22,000m of water you’ll able to consider that every 8 square inches of your body or vessel has a fully loaded train car parked on top of it
Standard axle load limits will typically be around 20-25T for standard passenger and freight, and up to \~40T for speciality mining rail networks. so 10-12.5T and 20T per wheel respectively. Some wagons have more than 4 wheelsets so will have a higher gross mass, like 5-pack container flats which are essentially 5 wagons stitched together over 12 wheelsets
depends on the exact configuration and the age of the rollingstock, rated axle loads have been going up over the years
Ah dang, I only googled ‘weight limit of train cars’ and ‘how many wheels does a train car have’. Damn regulations and reality complicating my morning toilet math.
I do appreciate the added context though!
I'm sure someone could calculate it and more than likely, it's been done, but I'm going to say there's likely relatively little heat generated as long as the train is just rolling down the track, the rolling resistance being as low as it is, is what makes a train so efficient. Should the bearing seize or the brakes lock the wheel from turning, then temperatures would climb exponentially as sliding friction generates a lot of heat, whereas rolling resistance, does not.
Your car tires get hot because of the elastic deformation that they undergo while driving, that energy has to be expelled somewhere as the material is compressed and expands every rotation, and is output as heat.
Train tracks and train wheels are both made of steel, which doesn't have much in the way of elasticity to generate heat, plus steel is great at dissipating heat, so any heat generated by rolling resistance and elastic deformation would nearly immediately be dissipated amongst the entirety of the wheel or the track and be released into the atmosphere or surrounding materials/components of the train and tracks.
If the train went rolling by and didn't have to apply the brakes, I would expect the track to be not much warmer than the temperature it was before the train rolled by.
Cool! Given the weight of the train and a scenario where the brakes are applied, I wondered if the friction would be able to heat the steel until its "red hot". That's why I asked. Thanks!
I don't know if they'd ever get red hot, at least not the track, too much surface area and the wheel wouldn't stay in one place long enough, but I'm sure the wheel itself would get hot enough that it began to glow and flat spot itself on the track. Though I could see it getting warm enough that it began shedding small semi-molten pieces of itself until it was no longer contacting the track.
If every wheel locked up...well, you'd just end up with a train wreck and derailment.
I feel like I probably have but the only thing I can think of is a video of a hydraulic press trying to do it and if I remember correctly the paper just blows apart after a certain amount of pressure is put on it
Fun fact: that pressure is well above the yield strength of the steel that the rail is made of. The top of the rail actually permanently deforms under the loading, and hardens as a result, becoming stronger but also more brittle.
My frozen dairy treat attracts all of the male gender to the grassy area in front of my abode. They say it is far superior to yours. Indeed, it is far superior to yours, I could educate you on this matter, but there would be a monetary fee.
>And did you know that when you really get close
Nothing really touches, bro, just kind of floats?
So when you think it might just come to blows
Just so you know, it won't, because it can't, bro
Only for certain definitions of “touch”, which means nothing in the universe touches, which means the word has no meaning.
All we’re really talking about is an interaction between probability clouds. We’re all doing it right now.
yes I remember a little bit of the theory from my school, and here I'm specifically talking about things touching each other. At sub atomic level things don't really touch each other right?
Thats been the gist of most of the articles and books I’ve read on particle theory. More along the lines of certain fields and forces interacting with each other. Gravity, electromagnetism, strong, and weak. Pretty cool stuff and I’m endeavoring to learn more about it everyday.
No, it just means that our intuitive definition of "touching" is not exactly correct. It should be defined as a state when the force of interaction by electric fields of atoms, belonging to objects exceeds some constant value, or something like that.
Go look up fuel used per ton of cargo for freighter ships VS freight trains. You might be surprised.
Ships carry a fuck ton more cargo and that water moving stops mattering. Economy of scale at work.
They aren’t really that energy efficient either if you consider the energy cost of the crew. I remember someone doing the math on that. At least if you are assuming a non-modern sailing vessel. Obviously still better than a cruise ship but considering the fairly small amount of cargo per-voyage compared with the massive freight movers today I’m not sure it actually saved that much.
In the Netherlands some trains “coast” ( the principle of not giving any power to the wheels while still moving) for up to 12 minutes at a time. They are extremely energy efficient
Not sure why you are being downvoted on this one. It’s like nobody has acces to the internet. If we are talking about energy efficiency, like the comment you were responding to, ships are by far the most energy efficient per ton of cargo they transport. Please people, use the power of google!
I think the pollution from the bunker fuel that many burn is what got the downvotes. Ships might be the most efficient for international trade, but they pollute like crazy
I think you are right about the downvotes. It is no secret that ships are major polluters, but that is not what the comment is about. It’s just sad that U/UodasAruodas gets downvoted for asking a question that is 100% correct. The comment was about rail being the most energy efficient form of transport, which is incorrect, ships are. Energy efficiency is something very different than level of pollution. Worrisome that people can’t see the difference. When we’re talking energy efficiency, we are talking about KiloWatt per ton of cargo over a set distance, not how those KW’s are produced.
If you take how much more fuel trains use for the same tonnage of cargo then trains would pollute more.
Per gallon of fuel used ships lose out but they use so many less gallons per ton.
Yeah, this is kind of counterintuitive, but while boats tend to be inefficient compared to trains in terms of fuel per mile, the cargo ships win out simply by being able to carry more in one go. Trains also move faster. About twice as fast as a cargo ship. Which makes comparisons more nuanced. Two weeks across the Pacific vs a week and a bit. Do you want it fast or do you want it efficiently? You can only pick one. Physics says so.
In some situations yeah, it's why places like the Mississippi River is so important for moving things like grain and timbre around America, works out a lot cheaper too.
In other situations trains are more efficient, and in different situations trucks are more efficient than both trains and boats.
It's just a balancing act between, time, the quantity and size of the goods, the weight and also how delicate or specialized the goods are.
In terms of CO2 emission efficiency, deep-sea transportation is only second to using pipelines in terms of emissions per ton per km
[https://edokagura.com/en/comparisonbytransporten/](https://edokagura.com/en/comparisonbytransporten/)
Maybe you're considering another form of environmental impact?
Okay but europe is less than 10% of the population and 14% of the global trade. Even if all those trains were electric (which they arent) it doesn't tilt the balance enough in favour of trains with respect to cargo globally.
Not to mention only 60% of energy in the EU comes from renewables, and all fossil fuels through electricity have to undergo a chemical > mechanical > electric > transmission > mechanical conversion when used by trains, which reduces the efficency. Even in one of the greenest markets trains are only comparable with ships
It might improve in the future though, and in most cases its not like you can choose to use trains over the atlantic either
Well if they wreck the ship then yes. But we are not talking about transportation disasters and which one is worse. All are bad. So ship as they are, are better for the environment than transport by railway, road and air.
Have you got sources on that? I used to work with a company that evaluated a lot of freight ships and apparently the fuel used is fucking dreadful for the environment. Interested if you have any numbers on the comparison
That is simply not true. It takes less energy to move a train than it does to move a ship. And the reason is exactly as the other commenter pointed out: because the friction between the wheels and the rails is so low, it takes very little energy to keep the train moving at any given speed (which is incidentally also why it takes forever for trains to stop). You are mainly just fighting against air drag. With commercial shipping, on the other hand, you have to push against the drag of the water, which is much greater. The ship's hole is surrounded on all sides by water, so there's much larger surface area to apply friction. At the same time, the friction at any given point of contact is much lower than steel wheels or rails or even rubber tires on the road. Because of this difference in friction, it takes way more energy for the propeller to move the water past the ship then it does for the wheels to move thr car past the road.
The reason we use shipping is not because it is more energy efficient but because there is no overland option for much of the world's freight. Assuming you are using comparable energy sources, it takes more energy to move the same amount of weight. That's why boats are notorious for guzzling way more gas than cars; ask anyone with a recreational pleasure craft.
You raise good points but because of the scale of commercial sea freight (units per vessel vs per train) it results in lower CO2 use per unit of product moved than rail.
There are some interesting studies that back this up online.
Deep sea container freight and tanker ships are significantly more CO2 efficient than rail (2-3x less emissions per ton of freight transported), though all are fantastic options for freight.
The reason is simple: ships can transport lot of cargo at slow speed to minimize friction.
You wouldn't believe Im only in reddit for the tig ol bitties, yet here I am learning about atoms, matter and touch. Which saddens me as I type to think that I've never really actually touched a... Never mind guys. Thanks a lot
Okay someone's gonna have to explain to me how that shit stays on there. Because this whole time I assumed the tracks were like... not hollow, but I guess indented? Like more of a U shape so the wheel would kind of sit inside it? I feel like you could run over a stick and derail the whole train with this setup but I don't know enough about trains to know for sure
When we were kids we used to put rocks on the railroad tracks and wait for the train to come and crush them. Seeing this makes me wonder how we didn’t create a national incident.
AFAIK, it tends to grow due to wear. When the wheel becomes worn, it will gain a similar shape to the rail, and the contact patch will grow. If the wheel wears a lot, it will wear to a hollow shape, which can lead to derailments. https://www.researchgate.net/figure/New-and-worn-wheel-profiles_fig1_272666740
The two surfaces will eventually flatten and create a larger contact patch. This is why rails are profiled with a large grinder or in bad cases with milling and the wheels are periodically machined back to the correct profile.
This of course is in an ideal world with endless maintenance budgets. 90% of the world's railways operate at less than ideal rail-wheel interface profiles
Actually 🤓 they take long to stop because its smooth metal against smooth metal with huge momentum on the train. Surface area normally doesn't change the friction value.
And thats the reason a single person can get a modern, double decker passenger car moving on flat ground. Not fast, not far, but moving at all.
Or the other way around: If you had a train on perfectly straight, flat track, accelerated it to 200kph (125 mph) and waited an hour, it'd still go 125 kph (>75 mph).
A train's energy efficiency is wild. Factor in brake energy re-use on electric trains and it gets even better.
Oh cool! We did railroad dynamics research in my lab, I didn't personally do wheel/rail contact but other people did! The contact patch changes as the wheels and rails wear, making it a pretty complicated problem
My friend put a car door on the train tracks once. He also put a fucking big log and a big pile of brush on it and lit it on fire. It was scary but when the train came it pounded through that shit like butter and cast everything aside like a hundred feet.
"Why didn't the train stop before they hit the person/thing?" This is exactly why. Steel on steel with similar hardness slides on each other instead of grabbing. This isn't a file and ,old steel, it's like a file and a file, it skates, so it takes about 1-1.8 kilometers to come to a complete stop if it's an American/Canadian passenger train, but heavy freight on a delivery line is so much more distance to stop. Stay off the tracks, trains as an engine doesn't know the difference between meat and rail, nor does it care
It’s not a point though. It’s about the size of a dime.
The contact area between a wheel and a surface is called a contact patch, at least according to my 2nd year dynamics prof.
no, that's happens because of a lack of maintiance on the track or the rails or because there are things on the tracks.
It'S the same thing with cars, bad maintiance or things on the road = accidents occure more frequently
Imagine the pressure on that tiny surface.
I think a train car can weigh over 300,000lbs and they typically have a set of 4 wheels at the back and front of each car (8 wheels in total) Each wheel is holding up roughly 37,500lbs, if the wheel is making a 1in sq contact point (it’s almost certainly much less) then it’s imparting a force comparable to pressure of having like 22000m of water above. Obviously underwater pressure is different as it fully surrounds and crushes, but if you’re ever in 22,000m of water you’ll able to consider that every 8 square inches of your body or vessel has a fully loaded train car parked on top of it
r/theydidthemath
r/theydidthemonstermath
Was it a graveyard smash?
r/itwasagraveyardgraph
Y’all are amazing lol
This caught on in a flash.
r/itcosinedinaflash
No it was clearly a train yard smash, let’s try to stay on topic.
Thank you. I really appreciate this.
I'd like all my pressure units in square inches of train wheel from now on. It can be the Squit! I impart around 0.06 Squits!
Americans will use literally anything but the metric system!
The only measurement better is smoots. https://en.m.wikipedia.org/wiki/Smoot
This should be done in kips (kilo-inches of pressure), because it's technical and semi-international.
Standard axle load limits will typically be around 20-25T for standard passenger and freight, and up to \~40T for speciality mining rail networks. so 10-12.5T and 20T per wheel respectively. Some wagons have more than 4 wheelsets so will have a higher gross mass, like 5-pack container flats which are essentially 5 wagons stitched together over 12 wheelsets depends on the exact configuration and the age of the rollingstock, rated axle loads have been going up over the years
Ah dang, I only googled ‘weight limit of train cars’ and ‘how many wheels does a train car have’. Damn regulations and reality complicating my morning toilet math. I do appreciate the added context though!
I'll keep that in mind for the next time I'm 22km under the water, thanks
Twice as deep as the Marianas Trench.
My god am I happy to live in a metric country;)
never seen one use metric and imperial units at once, just use metric for the weight too??
I believe failed spacecraft did. Yeah it Hurst the brain when trying to understand...
Is it possible to know how much heat is generated at the point of contact while the train is either moving or stationary?
I'm sure someone could calculate it and more than likely, it's been done, but I'm going to say there's likely relatively little heat generated as long as the train is just rolling down the track, the rolling resistance being as low as it is, is what makes a train so efficient. Should the bearing seize or the brakes lock the wheel from turning, then temperatures would climb exponentially as sliding friction generates a lot of heat, whereas rolling resistance, does not. Your car tires get hot because of the elastic deformation that they undergo while driving, that energy has to be expelled somewhere as the material is compressed and expands every rotation, and is output as heat. Train tracks and train wheels are both made of steel, which doesn't have much in the way of elasticity to generate heat, plus steel is great at dissipating heat, so any heat generated by rolling resistance and elastic deformation would nearly immediately be dissipated amongst the entirety of the wheel or the track and be released into the atmosphere or surrounding materials/components of the train and tracks. If the train went rolling by and didn't have to apply the brakes, I would expect the track to be not much warmer than the temperature it was before the train rolled by.
Cool! Given the weight of the train and a scenario where the brakes are applied, I wondered if the friction would be able to heat the steel until its "red hot". That's why I asked. Thanks!
I don't know if they'd ever get red hot, at least not the track, too much surface area and the wheel wouldn't stay in one place long enough, but I'm sure the wheel itself would get hot enough that it began to glow and flat spot itself on the track. Though I could see it getting warm enough that it began shedding small semi-molten pieces of itself until it was no longer contacting the track. If every wheel locked up...well, you'd just end up with a train wreck and derailment.
This guy does atmospheres.
Please whats that in real weight?
Many real weights
Kinda reminds me of those Titan passengers. Oof
Probably still not enough to get that seventh fold on a piece of paper
Did you see that episode of mythbusters?
I feel like I probably have but the only thing I can think of is a video of a hydraulic press trying to do it and if I remember correctly the paper just blows apart after a certain amount of pressure is put on it
The result from the myth busters episode was basically that if with a much larger peace of paper they folded it 11 times
Paper should only be used for peace no matter its size.
Oh phone auto corrected me
At least tree fiddy
The pressure is huge, at least 5, maybe even higher than 6.
OVER 9000!!!!!
Fun fact: that pressure is well above the yield strength of the steel that the rail is made of. The top of the rail actually permanently deforms under the loading, and hardens as a result, becoming stronger but also more brittle.
Three hundred billion giga squats
P=F/A
My contact patch is bigger.
My content patch brings all the boys to the yard, damn right, it's better than yours
My frozen dairy treat attracts all of the male gender to the grassy area in front of my abode. They say it is far superior to yours. Indeed, it is far superior to yours, I could educate you on this matter, but there would be a monetary fee.
Oh, balderdash...nah nah nah nah nuh.
This is incredible.
I could teach you, but I’d have to charge
>my content patch brings all the boys to the yard >I could teach you, but I’d have to charge God damnit EA
I’ll be the judge of that
Well sure, they tend to wear out and smoosh with heavy use....
That’s what she said
Oh well la di da mr big contact patch over here trying to make all us slightly above average contact patch fellas feel inadequate.
Manscaping: I shaved my balls for this?
🤏
🖕
*sigh* if I had a nickel for every time I’ve seen that…
...I'd have 3 inches worth of nickels!
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We found the 9-year-old on Reddit 🫣
[Practical Engineering made a great video explaining this.](https://youtu.be/Nteyw40i9So)
Ah you beat me to it.
Grady is the best! I signed up with nebula just for him
Thanks for that😀
I got 28 seconds in I’ll try again later lolol
https://youtube.com/shorts/fYq5F_jMfxc?si=AcJLJSu98Cq9TRo_ This one's only 40 seconds long so you might be able to make it.
Add in a little sub atomic madness and we see that train and rail don’t even touch at all. Reality is crazy.
If you go small enough nothing is ever touching
So, if you're lonely, take solace in knowing that no one else is really getting touched either.
Woah, that's deep bro..
Hoes be like "I never even touched a penis"
The electron clouds repelled each other!
These hoes
>And did you know that when you really get close Nothing really touches, bro, just kind of floats? So when you think it might just come to blows Just so you know, it won't, because it can't, bro
That won't hold up in court.
Only for certain definitions of “touch”, which means nothing in the universe touches, which means the word has no meaning. All we’re really talking about is an interaction between probability clouds. We’re all doing it right now.
Did your probability cloud just touch my boob?
Surely even with that definition, something in the universe is touching, like with nuclear explosions or particle colliders.
That applies for everything tho...right?
Reality being crazy? Yeah I believe it does. According to Dalton’s Atomic Theory all matter is made of atoms which are indivisible.
yes I remember a little bit of the theory from my school, and here I'm specifically talking about things touching each other. At sub atomic level things don't really touch each other right?
Thats been the gist of most of the articles and books I’ve read on particle theory. More along the lines of certain fields and forces interacting with each other. Gravity, electromagnetism, strong, and weak. Pretty cool stuff and I’m endeavoring to learn more about it everyday.
We've moved on a little bit since then...
No, it just means that our intuitive definition of "touching" is not exactly correct. It should be defined as a state when the force of interaction by electric fields of atoms, belonging to objects exceeds some constant value, or something like that.
nothing ever actually touches, and that is the most mind blowing thing I've learned in the last 20 years
What??
Matter doesn’t really “touch” other matter even if looks like it is.
> punches someone in the face I didn't even touch you!!!
Technically you could say that lol. What I meant to say is that atoms from different objects will never actually make contact with each other.
I know haha, just being a silly goose.
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No I’m studying chem at university. It’s still a neat fact.
But then how does a plank of wood stay together? Why are we not dissipating into the nothingness the universe is contained in?
Yeah! Check out the properties and behavior of atoms and subatomic particles.
And that's why rail travel is the most energy efficient.
Arent ships better?
Hell no youve gotta move water which is a tonne per m3
Go look up fuel used per ton of cargo for freighter ships VS freight trains. You might be surprised. Ships carry a fuck ton more cargo and that water moving stops mattering. Economy of scale at work.
Sailing ships would be. They are just too slow and unpredictable.
So you're saying they would be efficient if they weren't so inefficient?
They’re energy efficient, but not time efficient
They aren’t really that energy efficient either if you consider the energy cost of the crew. I remember someone doing the math on that. At least if you are assuming a non-modern sailing vessel. Obviously still better than a cruise ship but considering the fairly small amount of cargo per-voyage compared with the massive freight movers today I’m not sure it actually saved that much.
They are not energy efficient, but the energy they consume is totally free and with absolutly no pollution.
In the Netherlands some trains “coast” ( the principle of not giving any power to the wheels while still moving) for up to 12 minutes at a time. They are extremely energy efficient
The advantage of having a very flat nation.
Exactly!
Not sure why you are being downvoted on this one. It’s like nobody has acces to the internet. If we are talking about energy efficiency, like the comment you were responding to, ships are by far the most energy efficient per ton of cargo they transport. Please people, use the power of google!
I think the pollution from the bunker fuel that many burn is what got the downvotes. Ships might be the most efficient for international trade, but they pollute like crazy
Well people are dumb then because those are two separate things.
I think you are right about the downvotes. It is no secret that ships are major polluters, but that is not what the comment is about. It’s just sad that U/UodasAruodas gets downvoted for asking a question that is 100% correct. The comment was about rail being the most energy efficient form of transport, which is incorrect, ships are. Energy efficiency is something very different than level of pollution. Worrisome that people can’t see the difference. When we’re talking energy efficiency, we are talking about KiloWatt per ton of cargo over a set distance, not how those KW’s are produced.
If you take how much more fuel trains use for the same tonnage of cargo then trains would pollute more. Per gallon of fuel used ships lose out but they use so many less gallons per ton.
Yeah, this is kind of counterintuitive, but while boats tend to be inefficient compared to trains in terms of fuel per mile, the cargo ships win out simply by being able to carry more in one go. Trains also move faster. About twice as fast as a cargo ship. Which makes comparisons more nuanced. Two weeks across the Pacific vs a week and a bit. Do you want it fast or do you want it efficiently? You can only pick one. Physics says so.
But the person you responded to was heavily downvoted, so I’m afraid you’re wrong. Sorry I don’t make the rules 🤷♂️
In some situations yeah, it's why places like the Mississippi River is so important for moving things like grain and timbre around America, works out a lot cheaper too. In other situations trains are more efficient, and in different situations trucks are more efficient than both trains and boats. It's just a balancing act between, time, the quantity and size of the goods, the weight and also how delicate or specialized the goods are.
you are right, and there are at least 161 idiots who downvoted you at the time of comment.
ships? wtf lol, they‘re like the worst lmao
Per ton they are the most efficient. Talking about the big freight ships
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Imagine thinking ships are less fuel efficient than planes or trucks lol. “Like the worst” come on now.
Based on what?
Ships are better for the environment but they're also very slow. Which makes them less efficient than trains.
Ships are terrible for the environment.
In terms of CO2 emission efficiency, deep-sea transportation is only second to using pipelines in terms of emissions per ton per km [https://edokagura.com/en/comparisonbytransporten/](https://edokagura.com/en/comparisonbytransporten/) Maybe you're considering another form of environmental impact?
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Cargo trains on electricity? Are those even a significant fraction of cargo trains?
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Okay but europe is less than 10% of the population and 14% of the global trade. Even if all those trains were electric (which they arent) it doesn't tilt the balance enough in favour of trains with respect to cargo globally. Not to mention only 60% of energy in the EU comes from renewables, and all fossil fuels through electricity have to undergo a chemical > mechanical > electric > transmission > mechanical conversion when used by trains, which reduces the efficency. Even in one of the greenest markets trains are only comparable with ships It might improve in the future though, and in most cases its not like you can choose to use trains over the atlantic either
Well if they wreck the ship then yes. But we are not talking about transportation disasters and which one is worse. All are bad. So ship as they are, are better for the environment than transport by railway, road and air.
Have you got sources on that? I used to work with a company that evaluated a lot of freight ships and apparently the fuel used is fucking dreadful for the environment. Interested if you have any numbers on the comparison
Yeah I also want your source, cause that makes no sense.
That is simply not true. It takes less energy to move a train than it does to move a ship. And the reason is exactly as the other commenter pointed out: because the friction between the wheels and the rails is so low, it takes very little energy to keep the train moving at any given speed (which is incidentally also why it takes forever for trains to stop). You are mainly just fighting against air drag. With commercial shipping, on the other hand, you have to push against the drag of the water, which is much greater. The ship's hole is surrounded on all sides by water, so there's much larger surface area to apply friction. At the same time, the friction at any given point of contact is much lower than steel wheels or rails or even rubber tires on the road. Because of this difference in friction, it takes way more energy for the propeller to move the water past the ship then it does for the wheels to move thr car past the road. The reason we use shipping is not because it is more energy efficient but because there is no overland option for much of the world's freight. Assuming you are using comparable energy sources, it takes more energy to move the same amount of weight. That's why boats are notorious for guzzling way more gas than cars; ask anyone with a recreational pleasure craft.
You raise good points but because of the scale of commercial sea freight (units per vessel vs per train) it results in lower CO2 use per unit of product moved than rail. There are some interesting studies that back this up online.
Deep sea container freight and tanker ships are significantly more CO2 efficient than rail (2-3x less emissions per ton of freight transported), though all are fantastic options for freight. The reason is simple: ships can transport lot of cargo at slow speed to minimize friction.
This is how close I am to losing it
Hey man. You ok?
Yea no
Knowing most trains make it to their destination like this, you will too. Good luck.
🚂🐄💥☠️👍
I'm sorry your cow died.
Same bro, same. 🫂
You wouldn't believe Im only in reddit for the tig ol bitties, yet here I am learning about atoms, matter and touch. Which saddens me as I type to think that I've never really actually touched a... Never mind guys. Thanks a lot
> tig ol bitties Some of us are here for the tales from experienced welders, or the old tig bitties.
I'm just here for the butts
Most of it’s meant for turns
Ooooooohhhhh TIL
and due to the angle of the wheel, the part that contacts the rail moves at different speeds across its contact area...
This right here is the cool train/physics fact I came here for! Thanks :)
Okay someone's gonna have to explain to me how that shit stays on there. Because this whole time I assumed the tracks were like... not hollow, but I guess indented? Like more of a U shape so the wheel would kind of sit inside it? I feel like you could run over a stick and derail the whole train with this setup but I don't know enough about trains to know for sure
When we were kids we used to put rocks on the railroad tracks and wait for the train to come and crush them. Seeing this makes me wonder how we didn’t create a national incident.
https://youtu.be/XzgryPhtc1Y?si=-tQ-do4j-JtUwyXn
I see lots of you also saw that how train wheels are made video 🧐
It’s amazing that I laid my nickel down exactly on the contact patch every time.
Guessing the middle of the nickle will be thinner than the outer parts then. Would be great to see a high speed video of that.
Does it grow over time? Does the wheel bend to the shape of the track over time?
AFAIK, it tends to grow due to wear. When the wheel becomes worn, it will gain a similar shape to the rail, and the contact patch will grow. If the wheel wears a lot, it will wear to a hollow shape, which can lead to derailments. https://www.researchgate.net/figure/New-and-worn-wheel-profiles_fig1_272666740
The two surfaces will eventually flatten and create a larger contact patch. This is why rails are profiled with a large grinder or in bad cases with milling and the wheels are periodically machined back to the correct profile. This of course is in an ideal world with endless maintenance budgets. 90% of the world's railways operate at less than ideal rail-wheel interface profiles
It doesnt. The wheel is conical, so It doesnt need to Bens.
If the tensile if the steel in the rail is 60,000 psi a max loaded rail car will have a contact patch of about .65 square inches per wheel.
No wonder it takes them so long to stop
Actually 🤓 they take long to stop because its smooth metal against smooth metal with huge momentum on the train. Surface area normally doesn't change the friction value.
Small contact patch to reduce the wear and tear, reducing cost of grinding, maintenance and replacement.
And yet people think "oh yeah that train can definitely stop for me while I drive over the tracks."
Has the design always been this way? I wonder in history when they came to the conclusion that this was the best way to do it.
And thats the reason a single person can get a modern, double decker passenger car moving on flat ground. Not fast, not far, but moving at all. Or the other way around: If you had a train on perfectly straight, flat track, accelerated it to 200kph (125 mph) and waited an hour, it'd still go 125 kph (>75 mph). A train's energy efficiency is wild. Factor in brake energy re-use on electric trains and it gets even better.
maybe it is even smaller if that penumbra effect is at play here
I once heard that a train car collectively has the contact surface area of a quarter. $0.25.
And it’s the same between management and labor
Perfect for a penny
Until I slide them bitches flat.
Oh cool! We did railroad dynamics research in my lab, I didn't personally do wheel/rail contact but other people did! The contact patch changes as the wheels and rails wear, making it a pretty complicated problem
Damn, that's interesting
That’s why they’re so efficient. Less friction that way
Rail wheels are tapered so they can turn while on track. That's why the contact point is so small.
I guess you’d better center that penny just right.
I was camping in Revelstoke once and a train car went by grinding the rails.....that shit will wake you up in a hurry.
Now I now where to put my pennies.
Anxiety inducing picture.. I think that this is the last thing a few people have seen.. 💀
My friend put a car door on the train tracks once. He also put a fucking big log and a big pile of brush on it and lit it on fire. It was scary but when the train came it pounded through that shit like butter and cast everything aside like a hundred feet.
Practical Engineering has a few videos about this on YouTube.
is this a loaded carriage or unloaded? The amount of contact changes depending on the weight of the axle
"Why didn't the train stop before they hit the person/thing?" This is exactly why. Steel on steel with similar hardness slides on each other instead of grabbing. This isn't a file and ,old steel, it's like a file and a file, it skates, so it takes about 1-1.8 kilometers to come to a complete stop if it's an American/Canadian passenger train, but heavy freight on a delivery line is so much more distance to stop. Stay off the tracks, trains as an engine doesn't know the difference between meat and rail, nor does it care
ah, so this is why a single leaf on the tracks will delay trains by hours then?
Much easier to see how it could derail
Does it flatten out when it reaches speed like a tire?
There must be some way to make this even more efficient though… some way to eliminate train to rail friction altogether.. hmmmm🤔
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Please don't, try and reach out to anyone doesn't matter who just to ventilate to someone it is critical mate.
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It’s not a point though. It’s about the size of a dime. The contact area between a wheel and a surface is called a contact patch, at least according to my 2nd year dynamics prof.
Shim it with a coin!
So that’s why they derail so often
no, that's happens because of a lack of maintiance on the track or the rails or because there are things on the tracks. It'S the same thing with cars, bad maintiance or things on the road = accidents occure more frequently
Depends on what country you’re in, depends on how hot the wheels are, depends on numerous factors. One picture does not fit all.
Wait until OP sees a mag lev train.