Couplings during derailment

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Dave Fortune
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Joined: 18 Sep 2009, 09:41

Couplings during derailment

Post by Dave Fortune »

I have seen loco's turn on their sides and the rolling stock behind run past without derailing and have never thougt of looking at the looked at the couplings. 3404 was one that fell on it's side just outside Ficksburg in the 80's and the dz's behind just ran for about 500 metre's. Do the knucles break up or is there a shearing point at a certain pressure. My first proper look at this site and I am very impressed. Regards Dave Fortune
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Adelbert Stigling
Posts: 63
Joined: 05 Jan 2008, 12:31
Location: Bellville Western Cape

Re: Couplings during derailment

Post by Adelbert Stigling »

Welcome Dave - interesting point you have raised and I'm looking forward to the explanations saw a few of it during my railways career myself. Once the loko is of the rails there should be quite a difference in the height of the buffers and that might cause the uncoupling.
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Steve Appleton
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Joined: 23 Jan 2007, 14:14
Location: Johannesburg, South Africa

Re: Couplings during derailment

Post by Steve Appleton »

Indeed, the most likely explanation is that the couplings slip out (or are forced out) vertically. On the standard Janney couplers used in SA, there is nothing to stop the knuckles from disengaging vertically.
This was regarded as a real problem in the USA where couplers are forced out vertically and then the vehicles could climb up and override each other. As can be imagined, the vehicle bodies are much weaker than the frames and are easily punctured, crushed or sliced by the frame of the adjoining vehicle. This can cause dangerous spillages in the case of liquids and passenger injuries (and deaths even) in the case of passenger coaches.
As a result, the USA has designed and mandates the use of non-climbing couplers (AAR "tightlock" type F and H couplers) on certain classes of trains (using tank cars and passenger vehicles). These couplers have "lips" or projections (black rhino-style) above and below the knuckes to prevent vertical disengagement and consequent climbing up in the case of an accident. This has greatly improved safety.
In Europe, there is a move towards Scharfenberg couplers on new high-speed passenger trains. These are anti-climb by design. The resulting safety improvement is apparently huge. Passenger trains so equipped do not easily uncouple and often come to a stop (albeit abrupt) all in-line in a derailment. Such vehicles do not go flying all around nor do they easily climb over each other. The Blue Train is Sharfenberg-equipped internally.
See: http://en.wikipedia.org/wiki/Coupling_%28railway%29
http://wapedia.mobi/en/Coupling_%28railway%29?t=8.
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Jacob Ossebaar
Posts: 15
Joined: 26 Aug 2012, 13:49

Re: Couplings during derailment

Post by Jacob Ossebaar »

I am a new member and I saw this question . I am a retaired Dutch Railway employee and also I was a member of the Derailmentcrew on Amsterdam Central Station .I try to explane the derailment question with automatic couplings by a derailment . On the Dutch railway are the construction betwwen the Coupling and the Couplingpin a four side welded beam . The beam sprofile ,on the lengt are a long Z . On a derailment the Couplingbeam would the carroserie be lifted from the bogie . On the coupling are connected a bufferspring with a 100Nwt presser to elimineet the first crash .
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John Ashworth
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Joined: 24 Jan 2007, 14:38
Location: Nairobi, Kenya
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Re: Couplings during derailment

Post by John Ashworth »

Jacob, welcome to the FOTR forum on your first post. We look forward to learning more from your experience on the Dutch railways.
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