Talk:Brusio spiral viaduct

Why
Is it because they wanted to do something cool or was there some reason they couldn't elevate the track in a straight fashion? Moberg (talk) 08:47, 6 February 2014 (UTC)
 * Usually, it's a matter of terrain restrictions, such as not enough room to do it in a straight line. Maybe there was a river in the way, or limits to their right of way.  One general thing you can take for given, is that the railroad would do it the cheapest way possible.  This was apparently the cheapest way.  Let's see... Looking at the map of the location, it's possible that the grade change (increase in elevation) was too much for a train to handle, so they did the loop to make it possible for a train to handle it. - Denimadept (talk) 18:33, 6 February 2014 (UTC)
 * The lead for this article explains it was done purely for gain of altitude. Note the "See also" I just added to Spiral (railway) for more. - Denimadept (talk) 18:41, 6 February 2014 (UTC)
 * I recently acquired some printed reference material on the Bernina railway that probably includes some more information on this point. I will therefore probably be expanding the article in the near future in a way that will provide an answer to Moberg's question. Bahnfrend (talk) 01:00, 7 February 2014 (UTC)
 * I've now made the edit. I hope the new material is sufficient to answer the question. Bahnfrend (talk) 14:53, 8 February 2014 (UTC)
 * Good! I found the wording a bit troublesome, so I've modified it a bit.  Please feel free to revert me or modify it further to make it easier to understand. - Denimadept (talk) 03:50, 9 February 2014 (UTC)
 * No problem. In answer to your further question, the Bernina railway is an adhesion railway, and there's an unsourced statement in the lead of the article rack railway that "... 7% ... is the maximum for adhesion-based rail."  There must be at least one reliable source somewhere for that statement, and when I find one, I will add it to both that article and this article. Bahnfrend (talk) 05:38, 9 February 2014 (UTC)
 * It should not be possible to find a reliable source for this statement, mostly because it's simply not true. There are at least three adhesion "railways" with steeper gradients, the Uetlibergbahn (7.9%), the Pöstlingbergbahn (11.6%) and the de:Linie 28E der Straßenbahn Lissabon (13.5%). Also note that on the Bernina line, a single ABe 4/4 III EMU is able to pull up to 3 panoramic coaches (or 3.5 standard coaches), so it's obvious that the EMU alone could climb much steeper grades and still transport passengers, again showing that the "7% is max." statement is clearly wrong. But that's completely besides the point.
 * The (economic) efficiency largely depends on how much engine power is required to move a train over the line. And how much engine power you need is dictated by the ruling gradient, the "steepest" part of the line (it does not only depend on the gradient, but also whether it's in a curve or not, and tunnels may also be relevant, especially for diesel trains). Thus, the *steepest* bit (no matter how long it is!) basically says how expensive it is to run trains on the railway. That's why one defines a maximum gradient when planning a line (obviously, the whole line gets more expensive to build the lower the ruling gradient is, thus there's a trade-off between initial building and operating costs) and then sticks to it, no matter if it causes additional cost in some cases. In this case it was simply cheaper overall to build this spiral than having to add additional engines just for a few hundred meters of track, and there apparently was no (cheaper) construction available. --Kabelleger (talk) 21:12, 9 February 2014 (UTC)
 * Thanks Kabelleger for your useful comment. Unfortunately the rail adhesion and ruling gradient articles are both (rightly) tagged as having multiple issues, and the rack railway article should probably have a similar tag.  The sources I have on the Bernina railway just don't seem to have any explanation as to why the maximum gradient on that railway is 7%.  All can say is that that, for whatever reason, is the maximum gradient that was chosen when the line was built. Bahnfrend (talk) 09:21, 10 February 2014 (UTC)
 * Yes, I was slightly shocked when I had a look at the ruling gradient article, I didn't remember it being that bad. Anyway. The 7% were probably chosen pretty early in the planning stage, after asking the questions "how difficult is the terrain" (very) and "how much money do we have" (not that much). --Kabelleger (talk) 12:30, 10 February 2014 (UTC)

File:RhB ABe 4-4 III Kreisviadukt Brusio.jpg
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