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Author Topic: New Train  (Read 3475 times)
SandTEngineer
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« Reply #45 on: November 23, 2017, 10:34:06 AM »

Sometimes lower overall linespeeds mean increased capacity as braking distances are shorter and signal sections can be closer together.  The lines south of London are a good example of that.  Same applies to ETCS.

The Southern Railway discovered that having lines paired by direction (i.e. UP SLOW/UP FAST/DOWN FAST/DOWN SLOW) was the best option for open stretches of main line, but paired by use (i.e. UP FAST/DOWN FAST/UP SLOW/DOWN SLOW) worked better for capacity at the approach to major terminal stations (a good example being the switch from one method to the other at Wimbledon Flyover on the SWML).

Whoops, topic creep........ Roll Eyes

Note to Grahame: The signalling control element of ERTMS is ETCS https://en.m.wikipedia.org/wiki/European_Train_Control_System

That is true about slower speeds, but then if trains are faster then more services can run just a greater distances apart. I wouldn't be surprised in the future if the old Paddington Parcel depot(now a car park) is made into platforms. As for the up down thing, the Great Western is split with the fast lines together, slow lines together, all the way from Paddington to Didcot. The issue is mainly down to trains coming in late, staying in Paddington longer than booked, and then causing further delays. With the new IET's taking over HSTs timings should improve(which is being seen, and will get better as time goes on) however, the timetable change next year could be an issue, as whilst its taking full benefit of the IET acceleration, is it leaving enough time for a late service to catch up when running late?

Sorry but your logic doesn't stack up for multi-use railways such as the GWML.  Capacity is driven by a careful balance between train acceleration and braking rates, maximum train speed, line speed and station spacing.  It would be great if all trains ran non-stop at the same speed between the origination and destination but that doesn't happen in the UK.  Trains running at high speed (100mph+) need longer braking distances and an appropriate safety margin, and therefore by default need to be spaced further apart thus reducing overall capacity.

The reason Paddington is such a 'bottle neck' is that the track layout in the station throat is not very flexible, and because the signalling is operated automatically (by ARS), many unneccessary conflicts are created due to routes being set in conflict with others that could be used for other services at the same time (i.e. the ARS sticks to its planned route regardless of what else is going on at the time).

...and the GW doesn't have FAST and SLOW lines, they are MAIN and RELIEF lines..... Smiley

Time to start a new topic me thinks...... Roll Eyes
« Last Edit: November 23, 2017, 10:40:54 AM by SandTEngineer » Logged

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« Reply #46 on: November 23, 2017, 10:46:54 AM »

ARS.
Could not ARS be taken out of use at peak times and the system revert to manual control.  Or are there too many movements for a manual operation.
Or even reprogramming of ARS to encompass 'semi logical thinking'?
For the latter I dread to think how many millions that will cost (plus a cost & time over run with 'too many complexities') and also how long it would take to do.
Computer simulation programmes seem to manage Wink
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1st fan
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« Reply #47 on: November 23, 2017, 10:56:36 AM »

Sometimes lower overall linespeeds mean increased capacity as braking distances are shorter and signal sections can be closer together.  The lines south of London are a good example of that.  Same applies to ETCS.

The Southern Railway discovered that having lines paired by direction (i.e. UP SLOW/UP FAST/DOWN FAST/DOWN SLOW) was the best option for open stretches of main line, but paired by use (i.e. UP FAST/DOWN FAST/UP SLOW/DOWN SLOW) worked better for capacity at the approach to major terminal stations (a good example being the switch from one method to the other at Wimbledon Flyover on the SWML).

Whoops, topic creep........ Roll Eyes

Note to Grahame: The signalling control element of ERTMS is ETCS https://en.m.wikipedia.org/wiki/European_Train_Control_System

That is true about slower speeds, but then if trains are faster then more services can run just a greater distances apart. I wouldn't be surprised in the future if the old Paddington Parcel depot(now a car park) is made into platforms. As for the up down thing, the Great Western is split with the fast lines together, slow lines together, all the way from Paddington to Didcot. The issue is mainly down to trains coming in late, staying in Paddington longer than booked, and then causing further delays. With the new IET's taking over HSTs timings should improve(which is being seen, and will get better as time goes on) however, the timetable change next year could be an issue, as whilst its taking full benefit of the IET acceleration, is it leaving enough time for a late service to catch up when running late?

Sorry but your logic doesn't stack up for multi-use railways such as the GWML.  Capacity is driven by a careful balance between train acceleration and braking rates, maximum train speed, line speed and station spacing.  It would be great if all trains ran non-stop at the same speed between the origination and destination but that doesn't happen in the UK.  Trains running at high speed (100mph+) need longer braking distances and an appropriate safety margin, and therefore by default need to be spaced further apart thus reducing overall capacity.

The reason Paddington is such a 'bottle neck' is that the track layout in the station throat is not very flexible, and because the signalling is operated automatically (by ARS), many unneccessary conflicts are created due to routes being set in conflict with others that could be used for other services at the same time (i.e. the ARS sticks to its planned route regardless of what else is going on at the time).

...and the GW doesn't have FAST and SLOW lines, they are MAIN and RELIEF lines..... Smiley

Time to start a new topic me thinks...... Roll Eyes
Thanks for the detailed explanation I've actually learned a lot.
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Tim
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« Reply #48 on: November 23, 2017, 02:29:57 PM »

ARS.
Could not ARS be taken out of use at peak times and the system revert to manual control.  Or are there too many movements for a manual operation.
Or even reprogramming of ARS to encompass 'semi logical thinking'?
For the latter I dread to think how many millions that will cost (plus a cost & time over run with 'too many complexities') and also how long it would take to do.
Computer simulation programmes seem to manage Wink

My understanding is that the ARS can be manually overridden, but that the system and staffing is not set up to do that routinely.  The day will come when ARS technology is more "intelligent", but for every good reasons signalling is a conservative (and expensive) business. 
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devonexpress
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« Reply #49 on: November 23, 2017, 06:43:06 PM »

Sorry but your logic doesn't stack up for multi-use railways such as the GWML.  Capacity is driven by a careful balance between train acceleration and braking rates, maximum train speed, line speed and station spacing.  It would be great if all trains ran non-stop at the same speed between the origination and destination but that doesn't happen in the UK.  Trains running at high speed (100mph+) need longer braking distances and an appropriate safety margin, and therefore by default need to be spaced further apart thus reducing overall capacity.

The reason Paddington is such a 'bottle neck' is that the track layout in the station throat is not very flexible, and because the signalling is operated automatically (by ARS), many unneccessary conflicts are created due to routes being set in conflict with others that could be used for other services at the same time (i.e. the ARS sticks to its planned route regardless of what else is going on at the time).

...and the GW doesn't have FAST and SLOW lines, they are MAIN and RELIEF lines..... Smiley

Time to start a new topic me thinks...... Roll Eyes

Well aren't you a little clever little know it all  Roll Eyes

Main and Relief, Fast and Slow, its still the same thing, just different names. Besides the Fast sorry *cough* Main tracks are limited to 125mph, where as the slow *cough* relief lines are limited to between 60 and 80mph. And actually its much more complicated than that, whilst you say that timings are built in for stops, this is very rare on GWML "main" tracks, apart from the occasional 180 stopping at Slough, and peak services calling at Maidenhead, very few services stop on the fast lines. With electric trains coming, acceleration will dramatically improve, therefore timings will go down, meaning more paths, and more trains can run, however the question is, do GWR reduce journey times, but keep enough back so that trains can keep up during delays, this would also allow for future services to be added by cutting journey times down to the bare minimum. Or do they just cut journey times to the maximum, use as many paths as they can, until they are back to the situation they have been in for the last 15 years?
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IndustryInsider
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« Reply #50 on: November 23, 2017, 08:38:47 PM »

Twice an hour off-peak calls are made at Slough in each direction with a mixture of Turbos, HST'S and 180s (rather more than 'the occasional 180'), and as well as Maidenhead peaks calls, there are also some at Twyford.  Relief linespeed in up to 90mph for the majority of the route for trains that are classed as 'MU' (which is the majority).  Pathing also has to take into consideration crossing from main to relief and vice versa.

Paths will be created by increased performance of the new trains, and having a uniform fleet speed of 110-125mph will help, so that Turbos and their maximum of 90mph are out of the mix - there are up to three per hour in each direction currently.  More paths would be created by getting rid of Heathrow Express, and a reduction in peak time movements from main relief lines and vice versa.
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Four Track, Now!
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« Reply #51 on: November 23, 2017, 10:29:53 PM »

Could you judge if the pressure from that passing HST was more than 1.44 kPa peak to peak? (That's the weight of two forum members per square metre, if that helps. The right two, obviously.) Maybe not.

The pressure of the "standard atmosphere" is 1013.25 hPa at mean sea level (latitude of Paris) and 15°C. 1.44 kPa is therefore a little over 14.22 times the standard atmosphere. It is therefore far from inconsiderable, but I wonder too how the measurement could be done? One for the fluid dynamicists on this forum to answer, I think. Two trains with opposing Pitot tubes attached to some very clever kit passing at high speed maybe?
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stuving
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« Reply #52 on: November 23, 2017, 10:46:14 PM »

Could you judge if the pressure from that passing HST was more than 1.44 kPa peak to peak? (That's the weight of two forum members per square metre, if that helps. The right two, obviously.) Maybe not.

The pressure of the "standard atmosphere" is 1013.25 hPa at mean sea level (latitude of Paris) and 15°C. 1.44 kPa is therefore a little over 14.22 times the standard atmosphere. It is therefore far from inconsiderable, but I wonder too how the measurement could be done? One for the fluid dynamicists on this forum to answer, I think. Two trains with opposing Pitot tubes attached to some very clever kit passing at high speed maybe?

I fear your decimal point has gone walkabout. ICAO standard pressure is 101.325 kPa, so we're talking about 1.4% of that. And it's just static pressure -  or rather hydrostatic, as it's also dynamic.
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onthecushions
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« Reply #53 on: November 23, 2017, 10:52:50 PM »

I'm confused.

The Pascal (Pa) is a Newton (force)/m2 (area). A Newton is about the weight of an apple!

That's very small over more than a yard square, so we put factors of 10 into it, for normal pressures. Mostly these are kilo (10^3) or mega (10^6) but there are lots more that really clever people can quote. Atmospheric pressure is about 10^5 Pa and we have a unit for this - bar.

1.44 kPa isn't very much compared to a standard atmosphere of 101.325kPa, but you'd need plenty of hairspray to save your wife's perm if it rose much higher.

Pressure comes in three forms; static, velocity (or dynamic) and potential. Without friction, the sum at any point in a circuit is constant, because pressure is a form of energy per unit volume - can't be created or destroyed.

My brain hurts.

OTC
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Four Track, Now!
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« Reply #54 on: November 23, 2017, 11:08:38 PM »

The pressure of the "standard atmosphere" is 1013.25 hPa at mean sea level (latitude of Paris) and 15°C. 1.44 kPa is therefore a little over 14.22 times the standard atmosphere. It is therefore far from inconsiderable, but I wonder too how the measurement could be done? One for the fluid dynamicists on this forum to answer, I think. Two trains with opposing Pitot tubes attached to some very clever kit passing at high speed maybe?

Quote
I fear your decimal point has gone walkabout. ICAO standard pressure is 101.325 kPa, so we're talking about 1.4% of that. And it's just static pressure -  or rather hydrostatic, as it's also dynamic.

Er, 1013.25 hPa. 1kPa = 10 hPa, so my decimal point is in the right place. It was a little wrong of me to mix fractions, but I am used to an altimeter calibrated in hectoPascals.

But having read it again, I was wrong for a different miscounting of decimal places, and you are right. 1.4% isn't much, probably less than the difference in pressure at sea level and at the Dead Sea, which you wouldn't notice.

I'm confused.

Me too. It would have been easier just to throw apples at the windows.
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Western Pathfinder
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« Reply #55 on: November 23, 2017, 11:23:14 PM »

Yes it might be but at what velocity and trajectory?. Grin.
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Four Track, Now!
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« Reply #56 on: November 24, 2017, 08:57:13 AM »

Yes it might be but at what velocity and trajectory?. Grin.

More importantly, Braeburn or Golden Delicious? Mrs FT, N! is fond of Cox, she tells me.
« Last Edit: November 24, 2017, 09:15:53 AM by Four Track, Now! » Logged

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Bmblbzzz
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« Reply #57 on: November 24, 2017, 09:33:21 AM »

Time for a musical interlude:
https://youtu.be/N5afiqamGUo
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Day return to Infinity, please.
Western Pathfinder
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« Reply #58 on: November 24, 2017, 09:43:15 AM »

Yes it might be but at what velocity and trajectory?. Grin.

More importantly, Braeburn or Golden Delicious? Mrs FT, N! is fond of Cox, she tells me.

I will set them up  you knock em down !.
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stuving
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« Reply #59 on: November 24, 2017, 10:05:09 AM »

Did you spot this bit in that aerodynamic requirement?
Quote
TS1995
The IEP Trains shall meet the requirements of Railway Group Standard GM/RT2142, Issue 3, August 2009, ‘Resistance of Railway Vehicles to Roll Over in Gales’ without modifications to the infrastructure.

I can't think of any case of that happening in Britain (hurricanes abroad are different), but I suspect it has sometime. But what force on a train's side would it take to roll it off the track? Would 1.44 kPa (as a constant pressure, not a peak-peak transient) do it, I wonder?

Anyone have any idea?

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