Tripcocks

[arun]

Further to a question raised on the Gauge 0 Guild member's forum this afternoon, does anyone know when the MDR, Met, UERL et al started using Tripcocks and Trainstops?

There are certainly pictures of GWR and LNER steam engines between 1930 and 1932 fitted with tripcocks [and of course the LT's forerunner's locos at that time] but when were they first used?

Arun

[goldenarrow]

arun, Papers published in 2010 cite that tripcocks have been used on London Underground metals for over a hundred years.

[arun]

Thank you - On the basis that Met, MDR and UERL were electrified by around 1902-1905, that suggests that tripcocks and trainstops were a fairly early safety measure.

Arun

[greggygreggygreg]

Its amazing that the predecessors to the Underground had devices to prevent trains passing red signals over 100 years ago, but NR has only introduced such devices over the last 10-15 years, and then only at high risk locations

[banana99]

Mar 3, 2018 23:42:32 GMT greggygreggygreg said:

Its amazing that the predecessors to the Underground had devices to prevent trains passing red signals over 100 years ago, but NR has only introduced such devices over the last 10-15 years, and then only at high risk locations

Yes, but NR trains go a lot faster...

[norbitonflyer]

Much easier to fit and operate on a line where everything is electric and all the trains have similar operating characteristics. A mechanical tripcock wouldn't work very well at 125mph, and in any case it would be unlikely to stop a train passing a red signal at full speed in time to make much difference. Which is why ATC/AWS (which has actually been around since the GWR introduced it in 1908) was primarily installed at distant signals. That in itself immediately adds a complication, as the train has to pass the distant signal and whatever transponder is associated with it. Moreover, the home signal associated with the distant may have cleared before the train reaches it, and the system has to be designed to allow the train to proceed if that happens.

[Deleted]

Mar 3, 2018 23:42:32 GMT greggygreggygreg said:

Its amazing that the predecessors to the Underground had devices to prevent trains passing red signals over 100 years ago, but NR has only introduced such devices over the last 10-15 years, and then only at high risk locations

Except that tripcocks and trainstops don't prevent trains from passing red signals at all, they merely get a train stopped if it does pass a red signal. It's SPAD mitigation rather than SPAD prevention. When you have (relatively) quickly accelerating and decelerating trains, running at (relatively) low speeds, with a common fleet (or very similar fleets), you can design a signalling system around stopping trains from full line speed within overlaps and thus provide really good protection. But that sort of thing is much less practical when you have 1-car DMUs mixing with freight trains that can be five, six, seven hundred metres plus long and speeds of 75, 80, 90, 100, 110, 125 mph. TPWS can more or less do it, but it was a much harder nut to crack.

[jamesb]

Mar 4, 2018 0:16:01 GMT tut said:

Mar 3, 2018 23:42:32 GMT greggygreggygreg said:

Its amazing that the predecessors to the Underground had devices to prevent trains passing red signals over 100 years ago, but NR has only introduced such devices over the last 10-15 years, and then only at high risk locations

Except that tripcocks and trainstops don't prevent trains from passing red signals at all, they merely get a train stopped if it does pass a red signal. It's SPAD mitigation rather than SPAD prevention. When you have (relatively) quickly accelerating and decelerating trains, running at (relatively) low speeds, with a common fleet (or very similar fleets), you can design a signalling system around stopping trains from full line speed within overlaps and thus provide really good protection. But that sort of thing is much less practical when you have 1-car DMUs mixing with freight trains that can be five, six, seven hundred metres plus long and speeds of 75, 80, 90, 100, 110, 125 mph. TPWS can more or less do it, but it was a much harder nut to crack.

Aren't tripcocks and trainstops sometimes located half way up the platform to force a train to slow down before it reaches a red signal (if there is a junction ahead) or a buffer at a terminus?

[Deleted]

Mar 4, 2018 1:31:12 GMT jamesb said:

Mar 4, 2018 0:16:01 GMT tut said:

Except that tripcocks and trainstops don't prevent trains from passing red signals at all, they merely get a train stopped if it does pass a red signal. It's SPAD mitigation rather than SPAD prevention. When you have (relatively) quickly accelerating and decelerating trains, running at (relatively) low speeds, with a common fleet (or very similar fleets), you can design a signalling system around stopping trains from full line speed within overlaps and thus provide really good protection. But that sort of thing is much less practical when you have 1-car DMUs mixing with freight trains that can be five, six, seven hundred metres plus long and speeds of 75, 80, 90, 100, 110, 125 mph. TPWS can more or less do it, but it was a much harder nut to crack.

Aren't tripcocks and trainstops sometimes located half way up the platform to force a train to slow down before it reaches a red signal (if there is a junction ahead) or a buffer at a terminus?

With regards to trainstops in platforms, you're absolutely right that there is Trains Entering Terminal Stations (TETS), aka "Moorgate Control". This usually consists of a trainstop at the start of the platform and one roughly in the middle, and it does, as you rightly say, force a train to slow down. It is a good edge case you raise as I believe they are positioned to make sure you don't pass the Fixed Red Lights (FRLs) if you do approach too fast and, indeed, it would potentially be possible for them to stop a train that was not slowing down at all from passing the FRLs and having a buffer stop collision. Which would be SPAD prevention.

However, again, it doesn't actually stop you going past the Fixed Red Lights and into the buffer stops necessarily. It slows you down to make sure you are actually slowing down and can't run straight into a wall if you're asleep at the controls or anything, this also obviously enforces a proper approach speed to reduce the likelihood and consequences of an overrun, but as long as you're under about 10 mph on passing the second trainstop (sometimes there are more) it won't actually stop you running into the FRLs if you don't brake properly yourself. It's still mitigation. And, if you're a little bit over the set speed at the first train stop, maybe 1 mph over, you'll be brought to a dead stop from a speed that was definitely slow enough to stop well before the FRLs. However, I would agree that the speed checks almost certainly have reduced buffer stop collisions by enforcing a proper approach to a terminus and in fact, to be honest, mandating a very cautious approach. So yes, you are probably right, but it's a bit of a footnote. There is a fixed trainstop at the fixed red lights as well, but that'd be very unlikely to stop you before you SPADed them.

Regarding speed control and draw up signals protecting junctions that's an interesting one. What they do is definitely SPAD mitigation. What they do is make sure that you're going slow enough, say 20 mph, so that if you SPAD the signal ahead you'll be stopped before the junction. They're positioned so that if you SPAD them at full speed you'll also be stopped before the junction. So they say, SPAD me and I'll stop you before you reach the junction. Slow down and I'll let you go and then if you SPAD my mate up in front, he can get you stopped before the junction from that speed.

This is actually how TPWS (Train Protection and Warning System) OSS-es (OverSpeed Sensor/System) work - they're SPAD mitigation too.

[roythebus]

One of the problems of train stops on the main line many years ago was the presence of heavy unfitted, loose-coupled goods trains. thee could be up to 1000 tons of say mineral wagons, and the only brake would be on the team loco at the front and the brake van at the back. They were generally limited to 35 mph and took an awful lot of stopping, I speak from personal experience! Also, if the loco had a trip cock and hit the train stop, the guard would get a rather rough shunt as the wagons piled into the loco!

As for the "Moorgate" train stops, I was involved in testing the system when it was installed on the W&C. The testing was done on a Sunday and hey, it worked. 1mph over and the train got tripped. However, 10 mph over the speed and it didn't because the stock rolled so far over the train sop in't contact the trip! It was still possible for a train to hit the blocks at Bank yet not hit the blocks! Simply by very skillfull use of the Westinghouse brake, it was possible to stop with a slight jerk; the centre buffer block would spring forward and leave a greasy oblong on the buffer stop and bounce back, not tripping the track treadle operated by the leading wheels which would set the SPAD alarm off in Bank signal box!