Talk:Bank engine

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"is a railway locomotive attached to a train that does not have enough tractive effort to climb a steep but short gradient, also called a bank." --Can someone translate this into English? o_O – ∅ (∅), 13:19, 25 June 2006 (UTC)

[edit] Shouldn't the article Helper locomotive redirect here?

These 2 articles appear completely redundant and should be combined IMO Davemeistermoab

[edit] Revert

I reverted an edit by EdJogg because his changes are technically incorrect. "Run-in" is the term used to describe what happens in a train when the slack is abruptly bunched. A run-in could be the result of rough throttle handling while backing a long train, abrupt use of dynamic brakes on a descending grade or improper use of a pusher locomotive on an ascending grade (more rarely on level track). A run-in is not a collision in the generally accepted sense of the word.

If a run-in is caused by a pusher locomotive crew failing to cut off power when the lead crew is applying the brakes, the forces involved are usually sufficient to buckle the train at empty or partially loaded cars, resulting in a massive derailment. A train with empties placed near the head end is particularly vulnerable to this calamity.

Bigdumbdinosaur 20:34, 17 October 2007 (UTC)

That explanation is very good, and could probably go straight into the article as a subsection, as it would appear to be a problem primarily associated with banking!

I do not claim to be any kind of a technical expert in these matters, however I have been a rail enthusiast for many years and had never heard of either 'run-in' or 'slack bunching' (which is why I re-reverted the change rather than editing it). The fact that run-in pointed to a completely erroneous page did not help me determine what was being explained. My edit was partly to try and iron-out country-specific terminology (UK/US differences are a nightmare for rail articles -- see, I even avoid writing 'railway' these days!), partly to avoid some non-WP language (eg 'fearsome wreck'), and partly to try and explain better what was going on, bearing in mind that all WP pages should be accessible by people who are not experts on the subject. Now on the last point, I admit I have obviously failed to some extent, which is unusual, but in my defence I would suggest it was due to the use of jargon that was unknown to me.

Please feel free to adjust the offending sections, but please also consider the areas I was attempting to address with my edit. BTW -- what effect does the type of coupling have on the problem? Presumably, modern (Scharfenberg?) types and buck-eyes will behave differently, and the traditional '2-buffer + coupling' arrangement used on older UK freight stock will be different again.

EdJogg 23:25, 17 October 2007 (UTC)

Well, I understand the potential confusion regarding run-in, especially since it and "bunching the slack" are originally North American terms. Over here, we deal with a lot more mountainous terrain where those sorts of problems can occur.

The point to be made is that a run-in and a collision are different phenomena: the former occurs due to inertial factors peculiar to trains (each car or locomotive is a separately moving entity whose inertial forces can be propagated throughout the train), whereas a collision in the railroad context involves cars or locomotives that are not coupled together.

In my travels during my railroading career, I had numerous occasions to "talk shop" with UK railroaders (and railroaders in Saudi Arabia), all of whom were familiar with the terms "run-in" and "slack bunching." The former is a violent form of the latter. For example, slack bunching is common as a train crests a grade and starts to descend. On the upgrade, the slack was stretched due to the draft of the locomotives. As the train crests the grade, the slack starts to bunch as gravity pushes each car downgrade, these forces referred to as buff loads. If the engineer applies dynamic (rheostatic) braking on the downgrade without also applying the train brakes, all slack will eventually be bunched, as buff loading will substantially increase. If he applies dynamic brakes too quickly, a run-in may occur due to the forward end of the train trying to slow down faster than the rear end.

Bigdumbdinosaur 06:57, 27 October 2007 (UTC)

You do not need to defend yourself! This is genuinely very interesting. Please work out a way of including all this in the article! EdJogg 22:11, 27 October 2007 (UTC)

The following is a trial balloon for yet another railroad article—haven't decided on a title.

Slack action is primarily a North American railroad phenomenom, due to the combination of very long trains and the method of coupling that is employed. The European model of joining cars and locomotives with drawbars and buffers results in almost no slack action, but creates a coupling method that encumbers the quick make-up and break-down of trains in the yard. Over here, everything is equipped with Janney (knuckle) couplers, which facilitate rapid coupling and uncoupling (with no need for anyone to get between or under cars and locomotives), but introduce at least six to eight inches of slack between each pair of cars. With many of our freight trains running upwards of 125 to 150 cars (train length of nearly 1-1/2 miles), the cummulative slack could amount to nearly 100 feet.

In the age of steam, starting a long train was problematic, as unlike a modern Diesel consist, a steam locomotive did not develop very high starting tractive force. Therefore, it was common practice for an engineer attempting to start a long train to take advantage of the slack by backing up his locomotive until all of the slack was bunched (closed up). Once that was accomplished, he'd start forward and since the slack was completely bunched, he would, in effect, be starting one car at a time. Once the first car was in motion, its inertia would assist in starting the second car. The two moving cars would assist in starting the third car, and so on (the poor fellows in the caboose had to hang on for dear life, since the hack would start off with a sizable jerk due to all of that inertia). Of course, it wasn't possible to perform this maneuver on an upgrade, which meant that helper power was often required to start a train that had been stopped on an upgrade.

Once the train is in motion on level terrain or an upgrade, the slack is fully stretched due to draft loads. As the train crests a grade and begins to descend, some interesting effects get into the picture. As long as more than fifty percent of the total train weight is on the upgrade side, the slack will remain stretched. Once that fifty percent threshold is crossed, the slack on the downgrade side will start to bunch, as each car on the downgrade will be pushing into the one ahead of it. At the same time, the train will start to accelerate unless the engineer applies the brakes. The problem he now has to address is one of maintaining a safe speed as more and more cars crest the grade, start on the descent and add their weight to the total weight running downgrade. This sequence will result in rapidly increasing buff loads throughout the train, more rapidly bunching the slack and potentially leading to the phenomenon known as a run-in—the abrupt bunching of slack to the point where a derailment could occur.

A steam locomotive engineer's usual technique for avoiding a downgrade run-in was to start applying the train brakes as the fifty percent threshold was reached, but without cutting off steam (he'd also bail off the independent brake). This technique would delay the onset of bunching because the brake application would keep some draft loading in the train—the pull of the locomotive would be directed back through the cars on the downgrade to those on the upgrade side that were now being held back by the combination of gravity and brake friction. Then, as more of the train crested the grade and speed started to increase, he would gradually cut off steam and drift with the brakes applied. An experienced engineer could do this so well the guys back in the caboose would barely notice anything. An amateur, however, could end up losing control of the train and make a major mess at the next curve.

A similar stretch technique is used with Diesels, except it is now possible for the locomotives to retard the train via dynamic braking. The irony is that an accident induced by a run-in is more likely because of the locomotives resisting forward travel while all that tonnage back there is trying to stay in motion. Therefore, the application of dynamic braking has to be gradual. The usual practice is to utilize blended braking to keep the slack stretched during the descent (again, with the independent brake bailed off). As the train reaches level terrain dynamic braking is gradually reduced.

Bigdumbdinosaur 19:21, 30 October 2007 (UTC)

No, I don't know what article title to give it either. It is more to do with train driving, or more specifically, train braking, than bank engines or helpers and there is the risk that other editors might think it should be placed at 'Wikihow', rather than here. There is also the small matter of providing references for this. The text would benefit from a little adjustment in some areas -- one or two terms explained for the non-railway -minded, a little slang or jargon reworded, that sort of thing -- but it is very clearly explained and well worth putting somewhere!.

Incidentally, the same sort of problems could potentially exist on some British freight trains, albeit to a lesser extent. Right up until the late 1960s there were still 'unfitted', 'loose-coupled' freight trains on the rail network here. These comprised unbraked wagons (they had a hand brake only, for keeping them still in a yard) coupled together with three-link couplings (chains). The couplings were long enough to leave a gap of several inches between the buffers of adjacent wagons when pulled tight. At the back of each train was a brake van (caboose) containing the guard. In addition to his other responsibilities concerning the safety of the train, the guard's job was to use a hand brake to apply the brakes on the brake van as required to keep the couplings tight along the whole length of the train, particularly when travelling downhill. Also, on starting, if the engine had pushed the wagons back so that they were all buffered together, the starting tractive effort would be reduced as only one wagon would be started from standing at any one time; as the coupling between wagons was pulled tight, the wagons were started moving one-by-one.

EdJogg 01:20, 31 October 2007 (UTC)

The technique mentioned above was in fact very common in the UK in the days of steam locomotives and loose-coupled trains. With the old-style UK rolling stock having sprung buffers and a guards van at the rear of the train with its brakes set on, it was possible to reverse quite a long way and build up a significant pressure in the buffers to help start the train, in addition to the aforementioned one-wagon-at-time effect.BaseTurnComplete (talk) 20:58, 17 February 2008 (UTC)

[edit] Question regarding terminology

Would it be proper English to say that a locomotive "banks" a train? If not, what would be the proper verb? "push" sounds a bit too generic... (in German there is a distinction between "stossen" ("push") and "schieben" (??), which makes it sound wrong to me to use "push" in this context) --Kabelleger (talk) 18:40, 2 January 2008 (UTC)

That is correct in UK rail terminology (and also I assume by extension, Australian and some other Commonwealth countries). However as ever there are many rail terminology differences around the English-speaking world and our cousins on the west side of the Atlantic will no doubt say something different! BaseTurnComplete (talk) 20:52, 17 February 2008 (UTC)