Big trains question about coupling

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.

You also don't hear the occasional bang-bang-bang-bang-*CRASH*! as the coupler broke a knuckle, or the draft gear failed catastrophically.

~Pete

It's still normal throughout Europe.

They screw couple against the sprung buffers so that the entire train moves as one unit. The advantage is that there is far less shock damage to goods being carried. The disadvantage is that the loco must be powerful enough to start the train all at once, but as European trains are short and run fast this is not a problem.

Greg.P.

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.

Huhh???? They standardised in 1849!

Britain's railways aren't a part of "Europe" as such.

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.

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.

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 =

allowable. Of course they could only achieve something like 15mph and =

spent most of their time in sidings waiting for 60-100mph passenger trai= ns.

You still need to accelerate the great mass of the train! "Stiction" which is the resistance to movement could be of the order of

Quite so: "...I observed switching..."

No they haven't. There are all kinds of different couplers that are not compatable.

Agreed.

Like Canada isn't part of "America".

-- Cheers Roger T. See the GER at: -

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 astr>

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...

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

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.