Steepest Gradient on GWR?

[whole diary]

[grahame]

Coombe Junction to Liskeard is 1 in 40 plus an 8 chains radius on the curves. No chance of a run-up on that!

My goodness yes ... I made the mistake of walking from Coombe Junction to Liskeard early last month.  Well - more staggering and panting up the road.

The hill gradient between Coombe Junction and Liskeard.  One of the few UK^▸ (United Kingdom) cases where the railway goes a long way round to rise more gently.  See also Dduallt.

[JayMac]

1 in 6.25 (16%)?

Tis but a gentle slope.

www.bbc.co.uk/news/amp/uk-wales-52215151

[smokey]

The Tamar Valley Line has Gradients of 1 in 37 between Bere Alston and Gunnislake.

[froome]

Of course, if GWR^▸ (Great Western Railway) were ever to take over the running of the line between Lynton and Lynmouth... 

[phile]

The climb out of the Severn Tunnel

[IndustryInsider]

How steep is the London end of Portsmouth and Southsea high level?  It always feels quite a sudden gradient...

1 in 61.

The climb out of the Severn Tunnel

1 in 90.

[johnneyw]

Forgive me if it's already been answered elsewhere but do NR^» (Network Rail - home page) have a stated maximum acceptable gradient for new builds and if so, is it less than some of the gradients they've inherited?

[grahame]

Forgive me if it's already been answered elsewhere but do NR^» (Network Rail - home page) have a stated maximum acceptable gradient for new builds and if so, is it less than some of the gradients they've inherited?

I have a suspicion that the new build limiting gradient would be surprisingly steep - look at how Eurostar ducks and weaves out of King's Cross.  For a station, rule are probably pretty tight on gradient and curvature.

[IndustryInsider]

Whilst trying to find the Acton Diveunder gradient I think I remember saying that they had to use concrete slab track due to the 1 in 40 gradient.

[JontyMort]

Forgive me if it's already been answered elsewhere but do NR^» (Network Rail - home page) have a stated maximum acceptable gradient for new builds and if so, is it less than some of the gradients they've inherited?

I have a suspicion that the new build limiting gradient would be surprisingly steep - look at how Eurostar ducks and weaves out of King's Cross.  For a station, rule are probably pretty tight on gradient and curvature.

The modern one that is usually quoted is from St Paul’s Thameslink (aka City Thameslink) up to Blackfriars, which I think is steeper than 1 in 30. That is of course quite short, passenger only, and electrified. I remember when they revamped it to put the line under Ludgate Hill they lowered the northern abutment of the bridge over Queen Victoria Street (i.e. just north of Blackfriars) so that the bridge section was on the gradient, so they must have thought it was pretty tight.

The real game-changer is electric traction. I recommend a 323 up the Lickey, about a minute quicker than a 170 Bromsgrove to Barnt Green (start-to-pass).

[stuving]

I've quoted before that Crossrail has 1 in 27 in three places in its tunnels. Obviously being indoors in the dry makes that less of a problem, but I recall that some high-sped lines have around the same  gradient, and live outdoors: The Schnellfahrstrecke Köln–Rhein/Main has 4% so as to avoid wiggliness. Whether the ICE3s use any trickery to give them better grip than 50% of axles motored would suggest, I don't know.

[BBM]

I've quoted before that Crossrail has 1 in 27 in three places in its tunnels. Obviously being indoors in the dry makes that less of a problem, but I recall that some high-sped lines have around the same  gradient, and live outdoors: The Schnellfahrstrecke Köln–Rhein/Main has 4% so as to avoid wiggliness. Whether the ICE3s use any trickery to give them better grip than 50% of axles motored would suggest, I don't know.

Some years ago I managed to get a front seat with a forward view in an ICE3 along this line and the switchback nature of it was very clear. I was able to see the speedometer in the driver's cab and I was impressed to see how closely it kept to 300 km/h along the route, only dipping slightly on the upward gradients.

[stuving]

I've quoted before that Crossrail has 1 in 27 in three places in its tunnels. Obviously being indoors in the dry makes that less of a problem, but I recall that some high-sped lines have around the same  gradient, and live outdoors: The Schnellfahrstrecke Köln–Rhein/Main has 4% so as to avoid wiggliness. Whether the ICE3s use any trickery to give them better grip than 50% of axles motored would suggest, I don't know.

Some years ago I managed to get a front seat with a forward view in an ICE3 along this line and the switchback nature of it was very clear. I was able to see the speedometer in the driver's cab and I was impressed to see how closely it kept to 300 km/h along the route, only dipping slightly on the upward gradients.

So, you never saw one attempt a hill start in the rain? I wonder if it could do that!

One of the less obvious effects of high-speed travel is that improves hill-climbing. An ICE3 has nothing like enough power to climb 4% with no speed loss - that alone calls for 15 MW, and it only has 8 MW in all (mostly spoken for by drag and friction). However, it has loads of kinetic energy, and can trade a bit of that for the potential energy it needs at the top of the hill. And that trade-off gets more favourable the faster it goes, which somehow doesn't sound right.

For a small time interval (hence small changes in everything else) and a height gain of h, the speed drops by 2gh/v - which gets smaller the higher the speed v (in m/s, for SI units throughout). But this trick only works for short sharp rises, so if you start at 300 km/hr, that falls to 295 for a rise of 10 m, 278 for 50 m, 254 for 100 m, and down to 200 m/s for 200 m. That assumes the traction power is just enough to maintain the actual speed on the level, but if more is available it can top up the energy lost. Those speed drops are the same for any gradient, but the gentler that is the more time there is for any surplus traction power to make up the loss.

On the Köln–Rhein/Main line the overall height range is 50-350 m, but the steep bits will be only small parts of that - I'm not sure exactly where; climbing out of valleys perhaps?

[smokey]

Somebody will know the answer, not GWR^▸ (Great Western Railway) territory, but whats the ruling gradient of the SMR (both of them)?




Snaefell  Mountain Railway 

Snowdon Mountain Railway 

[bradshaw]

Snaefell 1:12 ruling gradient
Snowdon 1:7.86

edit
Many years ago Ian Allan published
British Main Line - Gradient Profiles covering the whole the country
17 profiles covered the GWR^▸ (Great Western Railway), which included some ex-SR^▸ (Southern Railway / Southern Region / Scot Rail / Scottish Region (rather confusing - it depends on the context)) and S&DR lines
Braunton to Mortehoe was around 1:40