Weekend Update 2/22/15

[garethashenden]

Gareth:  Yes, I noticed the model of the 3-link coupling on the car, but thought maybe the prototype used both, so the car could be run with others regardless of how they were equipped.  Do any 2mm modelers use the 3-link couplers as their model coupler?  With a good pair of tweezers it seems that they would work.

I've always wondered why British railways didn't use the European screw-link couplers.  Did they prefer to have slack in their trains, or didn't want the expense/complication/whatever of sprung buffers?

First off, the model I originally posted is 4mm, not 2. Some 4mm modellers do use 3 links and I know of one slightly crazy 2mm modeller who uses them as well. Locomotives and passenger cars use screw links but most freight stock doesn't. Some freight stock uses Instanter couplings which are half way in between 3 links and screw couplings. It is three links, but the centre one can be set either to be loose, like 3 links, or tight, like screw links. Here's a diagram.

[Iain]

So, basically, British rail technology is about a century behind the US?

[nkalanaga]

Well, yes and no.  The couplings aren't much more advanced than a link-and-pin, but much safer.  Instead of having to hold the link in place while the cars come together, one waits for the buffers to touch, then reaches in, lifts the link, and drops it over the hook.  No need to go between moving cars, and no danger of losing a hand, or worse.  For short trains and light cars they're more economical than knuckle couplers, but they do drastically limit train weights.

Pushing a car is even easier, as there's no need to uncouple it when it reaches its destination.  The buffers take the pushing, and the couplers do nothing, unlike our knuckles, which will couple even when they're not needed. 

I seem to remember reading somewhere that the European couplers were limited to about 2,000 trailing tonnes, but wouldn't swear to that, or if that was on level track, or a grade.  Whatever their limit, the British 3-link couplers are probably about the same.

[Ken Rice]

I heard a conversation on the scanner once about pushing against the knuckle - this was in a situation where they needed to move a cut of cars to get clearance to do another move.  So I'm guessing that even with knuckle couplers the occasional shove without coupling happens.  I wouldn't be surprised if there are rules against it, and it obviously doesn't solve the problem of releasing and applying hand brakes.

[nkalanaga]

Yes, one can push against the knuckle, but one first has to make sure that both knuckles are closed.  Usually at least one will be open from the last time that car was uncoupled, and if one is open, they'll still couple.  I would think it would also be hard on the knuckle, but have never heard of an actual rule against it.  It doesn't sound unsafe, and if they break the knuckle, the crew has to replace it, so they have a good reason to be careful.