Big trains question about coupling

Yes, roller bearings do make the job a fair bit easier than with the older friction bearings but the problem is still there. I don't know how many
cars you may have in a train and how heavy those cars are when loaded but back when Krauss-Maffei did the 6 locos for the SP and D&RG railroads, they could only test one loco at a time and even then couldn't get the full power out of the loco due to the lack of ability of the train to take the strain. Over here, the locos ran in 3 unit sets, often with another loco(s) of the diesel-electric type to move a train on the SP and D&RG railroads. Stretch that train out and try to start it and there will be a whole lot of power needed to start it moving. Diesels can often get them rolling but steam engines definitely couldn't even today with all of the roller bearings on the axles.
-- Bob May
rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net

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I think that was standard practice in the days of steam, when an engine could pull a train it couldn't start. There was an advantage to back a short distance, then start the train one car at a time.
Anyone else remember the sound of a long train starting? The bang at the head end as the slack was pulled out, then the bang bang bang as the slack pulling moved down the train. That's something you don't hear any more.
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You also don't hear the occasional bang-bang-bang-bang-*CRASH*! as the coupler broke a knuckle, or the draft gear failed catastrophically.
*AH*; the "good old days!"
~Pete
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wrote:

In the case of historic British coal trains, that was the norm. Their trains mostly were pulled by 0-6-0 tender locomotives right up to the 1950s. That was all that was required to move the maximum length trains allowable. Of course they could only achieve something like 15mph and spent most of their time in sidings waiting for 60-100mph passenger trains.

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wrote:

Of course it is, especially when the norm is wagons coupled under tension. (ie nil)

Where on earth did you witness that? (Britain of course not counting as anywhere on Earth, and certainly not Europe ;-)

That "free slack" is the problem. It leads to quite different modes of operation between Europe and the USa.

You probably witnessed a shunting move in a station area.

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Greg.Procter wrote:

[...]
Quite so: "...I observed switching..."
--
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wrote:

Britain used non-screw (3 link chain) couplers on it's goods rolling stock from 1800 to the 1960s. That it lasted so long was due to private owner (coal) wagons being standardised in 1923. (rough handling was hardly a problem with coal) Screw couplers on other goods stock was gradually introduced in the 19th and 20th century.
Greg.P.
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Funny that you say that - after all Thomas the Tank Engine *IS* modeled after British prototypes (which are equipped with buffers). To Europeans Thomas looks quite correctly modeled (not just some silly cartoonish toy with buffers).
I can also relate to what you feel but in reverse. I grew up in Poland (in the 70s) and I had mini TT gauge layout (using buffered European prototype of course). When I arrived in the USA and started researching the local railroads and then modeling US railroads in N scale they all looked really funny without buffers. To me they didn't look like real trains as they were not equipped with buffers! US boxcars looked more like trucks on track than real railroad cars. At this point I got used to that look but when I look at some of my European prototype models, those buffer equipped models still look more "railroady" to me than US prototypes.
I do however remember some examples of bufferless rail vehicles from my days in Poland. All the modern trolleys used center couplings (and didn't' have buffers). Also IIRC, certain types of local commuter multi-unit trains had what looked to me like automatic center couplers (and no buffers again). Those couplings were used to couple several of permanently coupled multi-unit consists together.
Peteski
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Hi,
David Nebenzahl wrote:

Did I say "it's always been done so"? Back in 1840 European trains started out with side buffers and coupling chains (a short piece of chains and a hook at each wagon!). Over time, they developed "three link coupling" - basically three chain links, no more, no less. Still with side buffers. Later on they found out, there is too much slack in three link couplings, but by then the chains were often attached with a pole from beside the wagons (no problem if you have loose chains). So they developed a special link (the middle one in the chain) which needed to be turned after coupling the train. This did reduce slack but did not eliminate slack. The logical next step is the screw arrangement in use today, couplers can be tightened enough to compress the buffers and to allow for (almost) no slack. This works fine and has been in use for the past fifty or hundred years. But then the guy has to go between the cars to do the coupling - we talked about that...
Now, go back to about 1900 and take the ship to North America. They were running longer and heavier trains than the Europeans (or wanted to) and they were facing the same problem. What the Americans did, they changed the system completely (not just improved it). They moved the buffer to the middle (need only one, not two, save money ;-) and put the coupler right into the new buffer (even less parts, even cheaper, save more money). The design (which is still used, though in improved form) was the most advanced one back then and serves today's railroads quite fine.
So you see, most of this has historical reasons ;-)
Now come the "modern Age" - European railroads found out that there is a serious drawback with the hook-and-screw couplers: if you're running passenger trains and want one part to stay on the main line and another part to run the side line from a certain station on, that's highly impractical (this concept has never been used much but is gaining popularity now). So they adapted center buffer couplers as well, but - being Europeans - they wanted the "BEST" design possible. The result is the "Scharfenberg" type coupler, but they did NOT design a common standard for it. There is actually only one company to produce the design, the couplers are (comparatively) complicated and thus are expensive. So they only get used in an insular fashion - the problem with broken-down trains has been mentioned.
Now, just for the fun of it, take a look at Russia. Their couplers are similar to the Janney couplers, but they use a different mechanical design. I don't want to say it's better nor worse, just different. Check it out on Wikipedia if you like. Basically the Russian type coupler was discussed for europe-wide adaption, but they wanted it "gold-plated" and with all extras for the cost of nothing. They did research a feasible design with air and electrical connections, (they even made provisions for reducing the possibility of derailments) but it was expensive. So, as you'll guess, it never got adapted...
By the way, there will always be a little slack between the wagons, but in today's railroad couplers it is reduced enough (if they get used correctly). It's a relative question, an inch is not much in a several-hundred-feet freight train, but it might be too much in an high-speed passenger train...
Now, to get back on-topic with the model railroad theme... Consider the coupling problem solved with knuckle couplers. They could even be applied to models featuring side-buffer imitations, but you'll rather find *huge* (and ugly) hook-couplers (HO) or Rapido-style (N). The wagons will sport side-buffer imitations ;-) And the hook couplers resemble hook-and-chain vaguely ;-)
Ciao...
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On Thu, 23 Oct 2008 07:01:03 +1300, David Nebenzahl

The advantage of the side buffers is the elimination of slack, and the resulting damage to goods. The planned Euro centre coupler was to be the ultimate in fine tolerances so that the inherant slack would be negligable, but of course that level of manufacturing tolerance costs!!!
Regards, Greg.P.
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Hi,
Greg.Procter wrote:

Even with side buffers and screw couplers you will have some slack (although only little). It is still possible to back up against a train (compressing the buffers) and then start forward (releasing them). You'd have to tighten the screws quite a bit to prevent that - and then the buffers would resist the train going around a curve.
So I'd say that with screw couplers and buffers (european style) there is very little "free" slack, but still a bit of "sprung" slack.
If handled carefully, a bit of slack is no problem, but you wouldn't want excessive slack in a high-speed-train. It's all a question of proportion ;-)

Well, there should have been *very* little "free" slack (you still need a bit for the locking plates to slide into place), but you still need the coupler mount to include a buffer. Again, the buffer needs to have some movement allowed which you could use instead of slack ;-) Compare the Scharfenberg couplers - they are close-tolerance meant to fit the form of the opposite one. They even use a sophisticated locking mechanism which "pulls" them together. But when coupling several four-car 130-ton multiple units you definitely need some buffer and you need torsional as well as lateral freedom which makes a very complicated coupler shaft. You wouldn't want that coupling to be completely rigid ;-)
Have fun...
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Bernhard Agthe wrote:

[...]
Back in the days when I stood on open end-platforms and watched the coupler action, I noticed that occasionally the buffers on the outside of the curve would part. The screw couplings weren't tightened enough, I guess.
HTH
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Wolf Kirchmeir

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wrote:

Two points there: - depending on the design of the buffers, some are/were sprung with a semi-eliptical spring behind the two buffers which will equalize on curves. Others have/had self contained coil springs. - On lines with tight curves and with rolling stock fitted with self-contained spring buffers the couplers wouldn't be tightened all the way. If the buffers reach the end of their travel those 4 wheel coaches could derail. (on the principal that something has to give somewhere)
Regards, Greg.P.
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David Nebenzahl wrote:

Standard method (see other posts.)
However, many passenger cars now use centre couplers, some even with buffers. Most are multi-connection couplers, see photos of UK DMUs on alt.binaries.pictures.rail for examples.
British rail installed fold-down knuckle couplers on Mark 1 or 2 cars IIRC. These cars also had the screw couplers. Most Britsih DMUs have ths
HTH
--
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Hi,
Wolf Kirchmeir wrote:

Wait a second, automatic center couplers are seen more often, but mostly in multiple-unit-trains (to ease coupling) and on train end wagons (such as the remote cab in two-way-trains. Again, they are meant to speed up coupling passenger trains. At least in continental Europe, passenger cars still use the screw-type couplers between each other.
On the other hand you'll find permanently coupled multiple units with central couplers at the unit ends more and more often (e.g. with Jacobs bogies). They don't use any couplers internally ;-)
This may actually lead to considerable confusion because the center couplers (Scharfenberg type) are available in different types with different positioning of electrical and air connections.
In general the whole situation is quite difficult in Europe, there are national regulations (the brake pressure gauge needs a red needle in Germany and a yellow needle in Italy, e.g.), european regulations and many different established solutions. While there are different regulations in the american network also, at least the interfaces (couplers) are standard. And I do think, that the Janney couplers are a good solution (while not the best possible). The europeans missed each and every chance in history to adapt something similar... Like I said, nice people individually ;-)
Have fun!
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http://commons.wikimedia.org/wiki/Railway_coupler shows several different looking Europena couplers and I don't think any of them look automatic. But I must confess, I've never seen European trains in operation either.
dlm
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I can't speak for continental Europe but in Britain the majority of passenger trains are multiple units, with automatic couplers to permit several units to be run as one train.
Some longer-distance passenger trains are loco-hauled but these are operated almost as if they were multiple units; they often have semi-permanent couplings between vehicles and are not routinely uncoupled or rearranged - only for maintenance or to deal with problems (eg to swap out a failed loco). These trains are too long to run in multiple-unit formations.
For example, the Class 365 trains which run between my home city of Cambridge and London. These are 4-car units which are very frequently coupled and uncoupled while in passenger service; many of the fast trains from London are 8 cars which run non stop to Cambridge and then divide, with the front 4 coaches carrying on to King's Lynn - and of course in the other direction, a 4-car unit from King's Lynn will be coupled up to another 4-car unit at Cambridge. This takes only a few minutes and a minimum of staff.
Wikipedia has a pretty comprehensive set of basic information about British trains at pages named like this: http://en.wikipedia.org/wiki/British_Rail_Class_365
All European high speed trains (all trains >250kph anywhere?) have automatic couplers although the coupler itself is obviously covered by a panel when not in use for aerodynamic reasons. Certainly the French operate many services with two TGV sets coupled together although I don't know if they routinely uncouple/recouple at the platform, rather than in a siding or a depot, or even do it with passengers on board.
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