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Points/Loops on gradients

You are here: Home > Forum > Miscellaneous > The real thing (signalling) > Points/Loops on gradients

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Points/Loops on gradients 26/01/2022 at 08:59 #143819
BoxBoyKit
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166 posts
Hi all,

I have a query concerning points and passing loops on a single line with a gradient. Essentially wondering if there are, or ever have been, restrictions on the presence of points and crossing loops on single lines with a severe gradient. For specifics if it would ever be “prototypical” (as much as anything on the railway is prototypical) to have a passing loop on a 1 in 103 or 1 in 111 gradients…?

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Points/Loops on gradients 26/01/2022 at 12:52 #143821
bill_gensheet
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938 posts
Looked over a few diagrams easily to hand and it can be seen that an attempt is usually made to reduce gradients at stations, either as built or when (re)constructed.

Tyndrum Lower is on a 1 in 44 / 1 in 49 section of line and reduced to 1 in 85 (or 1 in 113) at the former loop.
Complicated by the original construction and later alterations

Glencruitten Crossing. Was a 1 in 50 plain line summit, 'decapitated' when loop installed to give 1 in 260 and some level.

Some that were pretty much as built:
Dalmally on a 1 in 50, reduced to 1 in 201 at the station.
St Fillans 1 in 70 route, reduced to 1 in 260.
Balquhidder 1 in 60 route, reduced to 1 in 201



Bill

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Points/Loops on gradients 26/01/2022 at 15:13 #143822
jc92
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3454 posts
You can have a passing loop on any gradient (reasonably speaking) provided the risk is managed appropriately.

Take Goathland,albeit a preserved arrangement, the up loop descends steeply through the station, but has a trap arrangement beyond the signal to protect the mainline from any overun.

Its the same as any other converging junction arrangement on a gradient really.

"We don't stop camborne wednesdays"
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Points/Loops on gradients 26/01/2022 at 16:22 #143823
BoxBoyKit
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166 posts
As a Goathland Signalman and a pedantic one at that I’ve got to correct you in that it’s the down loop😉

But you make a good point! Struggling to remember the gradient as haven’t been there fire a while but think it’s about 1 in 126…

Just trying to come up with an argument for somewhere fictional which is never easy. Thanks for the responses!

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Points/Loops on gradients 26/01/2022 at 17:07 #143824
Albert
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1293 posts
Are any of the passing loops on the Carlisle or Motherwell sim on a gradient?
AJP in games
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Points/Loops on gradients 26/01/2022 at 17:26 #143825
Dionysusnu
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465 posts
Carrbridge deserves a mention, being on a 1:60 gradient but leveling out for the station and loop. This gradient was the location of a runaway derailment in winter conditions in 2010, RAIB report here.
Last edited: 26/01/2022 at 17:50 by Dionysusnu
Reason: None given

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Points/Loops on gradients 26/01/2022 at 17:34 #143826
JamesN
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1430 posts
Dionysusnu in post 143825 said:
This gradient contributed to a runaway derailment in winter conditions in 2010, RAIB report here.
It's not mentioned as an immediate cause, casual or underlying factor in the report linked.

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Points/Loops on gradients 26/01/2022 at 17:50 #143827
Dionysusnu
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465 posts
JamesN in post 143826 said:
Dionysusnu in post 143825 said:
This gradient contributed to a runaway derailment in winter conditions in 2010, RAIB report here.
It's not mentioned as an immediate cause, casual or underlying factor in the report linked.
Edited post to include better wording.

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Points/Loops on gradients 26/01/2022 at 18:24 #143828
Steamer
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3724 posts
Albert in post 143824 said:
Are any of the passing loops on the Carlisle or Motherwell sim on a gradient?
The steepest is a 1-in-140 (downhill) at Hardendale, and the rest are much shallower.

There's an obvious advantage to engineering the route such that loops and stations aren't on steep gradients, it makes it easier for trains to initially pull away after stopping.

"Don't stress/ relax/ let life roll off your backs./ Except for death and paying taxes/ everything in life.../ is only for now." (Avenue Q)
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Points/Loops on gradients 27/01/2022 at 22:35 #144854
Late Turn
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693 posts
BoxBoyKit in post 143819 said:
Hi all,

I have a query concerning points and passing loops on a single line with a gradient. Essentially wondering if there are, or ever have been, restrictions on the presence of points and crossing loops on single lines with a severe gradient. For specifics if it would ever be “prototypical” (as much as anything on the railway is prototypical) to have a passing loop on a 1 in 103 or 1 in 111 gradients…?

Newstead Loop (crossing loop on a single line) is on a 1-in-84 gradient, although it was part of a relatively recent scheme (within the last thirty years) so it's possible that the requirements used to be stricter. Both lines are bi-directional, with (unusually?) trap points at the downhill end of the loop line that an Up train (passenger or otherwise) signalled into the loop can approach in the normal position, although they're clear of the overlap at the protecting signal.

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