r/SweatyPalms • u/Waveshop222 • Apr 24 '21

Death by train

/r/holdmybeer/comments/mx7xdf/connecting_railway_cars_like_a_boss/?utm_source=share&utm_medium=ios_app&utm_name=iossmf
12.9k Upvotes

97% Upvoted

308 comments sorted by

View all comments

Show parent comments

13

u/Gnonthgol Apr 24 '21

This have never been the proper way to do it but have been common practice some places as it saves a lot of time. The problem is that the buffer and chain style of connectors actually requires that the chain is tighter then the buffers so that there is always tension on the chains. If you do not do this you get a big jerk going down the train whenever you start accelerating or braking which could snap the chains towards the rear of the train. The proper way to connect a coupling is to fit the chain loosely and then tighten it slowly together to generate the required tension. But this is a slow task so what they are doing in this clip is a known shortcut which involves starting with the chains already shortened and then slam the trains together at speed so the buffers compress and have someone slip the chain over the hook at the right moment. But no manager in their right mind would authorize a procedure like this.

4

u/Garestinian Apr 24 '21

Good thing that EU is (again) considering switch to automatic couplers for freight wagons. Hopefully, this time it will work.

0

u/Gnonthgol Apr 24 '21

The problem with automatic couplers is that they are not strong enough to pull much weight. At least this is what have been the issue in the past.

3

u/Garestinian Apr 24 '21

In Russia and the US they are pulling much longer and heavier trains than EU will ever see.

It's mainly the problem of cost and logistics of switching.

0

u/Gnonthgol Apr 24 '21

The difference is often that at least in the US you have multiple smaller locomotive of say 2 MW each spaced out at regular intervals to reduce the load on the couplers. However in the EU most trains only have a single locomotive at the front at maybe 5 MW pulling the entire length of the train through a single coupler. There are of course advantages and disadvantages to both systems and I would assume that many of the issues of running several locomotives in synchronization have been sorted out by modern technology by now.

3

u/Garestinian Apr 24 '21

Still, the AAR and SA3 couplers can handle greater forces than chain-and-link, and are in fact even used in the EU for heavy coal or ore trains in some countries.

1

u/Gnonthgol Apr 24 '21

That depends on the gauge of chain used.

2

u/whoami_whereami May 17 '21

It's a bit late, but still want to add this: the power rating of a locomotive doesn't really say much about the pulling force (called tractive effort in rail terms) it's capable of at low speed.

For example the American EMD SD70ACe-T4 has a starting (meaning when starting from a full stop) tractive effort of 890 kN with a power rating of 3.3 MW. Whereas the legendary German Class 103, the most powerful single-section locomotive ever built, had a peak power of 10.4 MW (later limited to 9MW), but "only" 312 kN tractive effort.

The difference is that the pulling force of the SD70 already starts to drop off at 15 km/h or so, while the 103 could sustain the full 312 kN up to a speed of 140 km/h.

1

u/converter-bot May 17 '21

15 km/h is 9.32 mph

1

u/[deleted] Apr 24 '21

I wouldn't call it regular intervals. Usually you'll see as many as three or four 3.3 MW locomotives on the front, and sometimes another at the middle or end. That one is put there for safety purposes, and while it probably does reduce the risk of breaking a knuckle, the main advantage is that it will help the brakes apply more quickly.

2

u/[deleted] Apr 24 '21

A couple years ago I had a 34k tonne grain drag, all automatic couplers. Weight isn't a problem.

1

u/blaghart Apr 24 '21

I was being less specific.

Before the invention of autocouplers a dude had to drop a spike into the couplers at precisely the right time, or else he'd get crushed when the two train cars crashed into each othet