Buffers

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Derek Walker
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Buffers

Post by Derek Walker »

I have been looking at pics of UK locos and rolling stock and a vast number of them have buffers in place on the engines and coaches. Yet this didnt seem to be the case in South Africa. Why did we not go the buffer route? or did we drop them many years ago? I think buffers give a steam loco a certain "look" about it that is really quite imposing.
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John Ashworth
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Re: Buffers

Post by John Ashworth »

Buffers seem to become redundant when you introduce automatic couplers, as South Africa (and indeed most countries) did quite early on. In the UK the use of chain couplers, which had to be hooked and unhooked manually, continued well into the post-steam age - I'm not sure why.
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Ian Roberts
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Re: Buffers

Post by Ian Roberts »

The automatic coupler was developed in the United States in the late 19th Century as a safety feature to avoid the need to drop a pin in the link and pin couplers and run the risk of being crushed or loosing body parts. These link and pin couplers were similar to those used on the South African narrow gauge.
The chain couplers with buffers could be loose coupled using a shunters pole from alongside the train, hence there was less risk of injury and less pressure to change.
The original South African 3' 6" gauge couplers were the standard British narrow gauge coupler which was known as the chopper and is still widely found today in, for example, New Zealand. This was semi automatic in use, provided at least one hook was placed in the vertical position by the shunter. The change to the auto-coupler in use today was more of a strength issue to enable heavier trains to be run.
Although the auto coupler was better it was the cost and logistics of changing over that left most European railways using forms of chain couplers and buffers to this day.
Some British passenger coaches had automatic couplers which could be dropped by removing a pin revealing a conventional hook for connecting to a chain coupled loco or coach, the buffers here were also retractable when operating in automatic mode.
In Australia the change over on the Broad (5' 3") and standard gauge systems was progressive with the auto coupler being installed, but the buffers left and a coupling chain installed above the auto coupler. The buffers and chains have now mostly dissapeared.
All in all a very complex subject with the dead hand of conservative railway management appearing from time to time.

Ian
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Steve Appleton
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Re: Buffers

Post by Steve Appleton »

The side-buffers are required to absorb the slack and reduce/absorb the impact/pushing shocks of the train. Without them, the wagons would crash into each other whenever the train compresses. For the European screw link-type coupling there is no buffer built-in to its hooks/mountings to absorb such shocks. Shock absoption is accomplished by screwing up the link tightly enough to bring the side buffers into contact and compression. The side-buffers become the shock absorbers, taking up the train slack, not the couplings.
With the central couplers as used in SA (old bell and pin as well as the present automatic couplers) the coupler unit itself is mounted on a non-rigid buffer assembly, a "drag-box", hidden behind the frame (behind the so-called buffer-beam). This mounting consists essentially of a tube containing strong coil springs and damping discs. Hence the train compression/expansion shocks are taken up and absorbed by the central coupler/drawbar assembly itself instead of side-buffers, making the latter redundant. Unlike the screw-link system, the local couplers are therefore dual purpose, replacing the side-buffers.
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