No clue on these last few questions, except to say the power grid will beat the telephone network or internet, or indeed any other data transmission system. Transmitting power requires thick cables, busbars, transformers and generators, and they all use far more metal than their flimsy data-transmitting counterparts. If you count DC and asynchronous interlinks, the entire North American continent can be considered a single grid. So I think you’ll find the power grid will be the largest metal “object”, especially if you count all those motors they’re connected to. Generators + transmission lines + motor loads = basically one giant synchronous continent-spanning machine.
CWR is the preferred technology for any rail really. The Indian Pacific and the Adelaide Darwin lines are most certainly CWR. Whenever an old line is upgraded, it will be done with CWR. In Oz, all the standardisation projects replaced the old lines with CWR.
As you say, breaks will occur for passing loops, and electrical breaks for electrical train detection will break up the individual lengths of rail. But on a long route, there could easily be quite significant lengths of continuous metal. For instance there are operational sections of the Alice Springs to Darwin link that exceed 100km in length. So, no passing loops (there are only two on the entire link) and a section of well over 100 km that requires no internal signalling detection. It would be easy to suppose that was continuous metal.
Wow.
So, in posing my OP, as usual I had no idea what I didn’t understand, or where it would go; Sicks Ate started the casting bit:
That soon-to-be-hard metal, which required simultaneous pouring of five ladles, is a casting, which may or may not be forged? That is, a big old bell either just is, more or less, after being broken out of its mold, without being beaten and re-heated and stressed and taffy-ed. Not “machined from an ingot,” as phrased upthread.
And even Sheffield doesn’t have – even if it could, on order – the normal facility to forge that beast?
ETA: given the above distinction, maybe I meant “What is the largest ingot in the world” as OP.
Which raises the question:
Say
Larger-ingot A results in forged piece-a
Smaller-ingot B results in forged piece-b
Piece b is larger than piece a.
How often does this happen?
The 607 tonne casting might have been for a large forging press. The named customer, SMS Meer, makes them, and the link says the previous 325 tonne casting was for one.
Back to literal question of OP, largest forged piece, the biggest forging presses now can take ingots of 600+tonnes. One reference quotes a few of the biggest presses at that level, though Japan Steel Works claims its press can handle 670 tonne ingots. Forging: taking a piece, an ingot, of metal still in solid form but hot enough to be become plastic, and hammering into a shape. As opposed to casting, pouring liquid metal into a mold. The biggest forgings are often for nuclear reactor components.
http://www.liquisearch.com/forging/equipment/forging_presses
http://www.city.muroran.lg.jp/monozukuri/en/18.html
Very powerful ships’ propellers are generally the largest non-ferrous metal castings produced nowadays, at for example 130 tonnes for Maersk E class container ship propeller. But bells have been bigger in the past (Tsar Bell was mentioned and The Great Bell of Dhammazedi of the 15th century was larger still, ~300 tons, and presumed to still exist in the river in which it sank in 1602 in Myanmar), and some more recent bells nearly as big.
Once you get to fabricated structures it’s IMO somewhat arbitrary to count ships as one object if all welded, but not buildings or bridges because they use other fastening techniques. Especially since one of the reasons might be because they are larger, and the thickness of steel exceeds that at which welding is the easiest solution, or they don’t use steel (but reinforced concrete). I think the more important distinction is between objects with relatively similar dimensions in all three axes, like ships and buildings v. basically one dimensional ones like miles long stretches of welded rail, power lines etc. Bridges can be sort of in between depending if you limit it to a single span or a causeway like the 100+ mile Danyang–Kunshan Grand Bridge.
The Burj Khalifa is over twice as tall as the containership Barzan is long. And it weighs about twice as much as the largest ship in empty weight, 450,000 tonnes not including foundation, v ~250,000 for the biggest ship*.
*the twin hulled oil platform installation and removal ship Pioneer Spirit ex-Pieter Schelte with a light ship weight of 249,500 tonnes per “Significant Ships of 2014” by the Royal Institute of Naval Architects. The biggest tanker Seawise Giant had a light ship weight of around 80k, Barzan around 58k (per 2015 issue of same publication). Pioneer Spirit’s design load displacement also slightly exceeds Seawise Giant’s at 683k tonne, and scantling displacement (what the ship is strong enough to withstand) of 970k tonnes far exceeds it.
How does continuously welded rail handle expansion and contraction due to temperature changes?
Basically it is pre-stretched. They use a (very large) hydraulic ram and depending upon the ambient temperature, pull the rail section out so that it is stretched enough that it won’t buckle when the hottest expected temperatures are reached. The rail can undergo some compression when hot as well, use of concrete sleepers rather than wood, and Pandrol clips rather than spikes, means there is a lot more strength, and a very controlled amount of give in the system, so it is possible to engineer it to work across the temperature range. Here in Oz those lines will drop below freezing at night, and be scalding hot to touch in the day.
I understand this in theory but it still seems like black magic to me. Those compression forces still exist even though it’s pre-stretched. Why doesn’t the CWR line tear apart from the forces when it’s extremely cold? Eg it’s shrinking all over, so pieces are trying to pull apart from other pieces which are also shrinking?
A thanks, oops, given the state of Australia’s infrastructure, I assumed the Indian Pacific was still jointed.
Same reason a guitar string doesn’t break. Steel is strong and elastic.
Steel’s linear thermal expansion coefficient is 12x10[sup]-6[/sup] K[sup]-1[/sup] So across say a 50 K range it expands (or contracts) about 600ppm = 0.06%.
Structural steel has a Young’s Modulus of about 200 GPa. Usefully we see that the thermal expansion coefficient gives us the strain. Structural steel has an ultimate tensile strength of 400 MPa. A 50K temperature change is therefore 0.0006 * 200 GPa = 0.12 GPa or 120 MPa. Which is just over one quarter of the tensile strength.
In reality the rail is laid so that it is unstressed at a chosen useful mid-range temperature, and is able to heat and cool around this temperature without either reaching a point where either tensile or compressive loads along the rail cause problems. So it is unlikely that the rail will get close to anything like one quarter of its tensile strength. Maybe closer to one eighth. Clearly it needs to have enough in reserve to cope with a passing train.
I think the huge bell and cannon at the Kremlin might be high on the list.
or, just search kremlin bell or kremlin cannon
or just read the thread, that was posted earlier.
Awesome name/post combo
One little snippet about the Sheffield casting of 607 tons is that, though it is poured at around 1500C, before it is solid enough to do anything with they have to leave it to cool down to 1000C.
This takes 6 weeks, no that isn’t a typo, 6 weeks.
[QUOTE=Wikipedia]
The pillar was manufactured by the forge welding of pieces of wrought iron.
[/QUOTE]
Not cast in one piece.
No discussion of great moments in casting is complete without Leonardo’s 60-ton monument to Sforza. The Colossus of Leonardo da Vinci (the sketches and project are normally known as the Sforza monument or “Leonardo’s horse”) is a beautifully designed web exhibit on this project, which occupied Leonardo for years, including designing adjunct machinery and processes; all for naught, alas.
A book from a symposium: Leonardo da Vinci’s Sforza Monument Horse: The Art and the Engineering Diane Cole Ahl, ed. Lehigh: 1995.
Huh. I’d read somewhere that it was cast iron. This was in a book on early metalurgy and they used it as an example of how they’d discovered iron casting in the east before the west. The ores in the east often had some other element (phosphorus, I think) that significantly lowered the temperature that iron melts at, thus allowing them to cast iron. I don’t remember the name of the book; it’s been a long time since I read it.
Wrought iron is cast, but the pillar was cast in smaller sections that were then heated and forge welded (hammered) into the final larger shape.
Of course, but It takes far more time for me to read all the posts than it does for you to ignore one you know is a duplicate. When I spend time on SDMB, I like to browse for questions I might be able to contribute something to; frankly, not every topic warrants reading every reply.
Sorry, but no it is not. Cast iron and wrought iron are two different things. Wrought iron is not melted and contains almost no carbon while cast iron has been melted and has high (>3%) carbon. There’s a large amount of difference in the amount of heat needed to make the two. It’s 770° C for wrought and 1170° C for cast (numbers are from memory and could be somewhat off). I think the phosphorus (or what ever element it was) reduced the temperature for cast iron by about 200° C.
At the time the pilar was made it was difficult for European iron makers to get the temperature high enough to make cast iron, so they only made wrought. They wouldn’t make cast iron until sometime in the middle ages, I think.
If that’s the case, then whoever wrote the wiki article doesn’t know the difference between cast and wrought iron.
Say it ain’t so.