Prototype curves - How sharp is "sharp"

[HSB]

I like to plan the supposed routes of my fictional railways using Ordnance Survey maps but it is hard to find information on the curvature of prototype railways. Many books refer to 'sharp curves' without telling you what those curves actually are. About the only references I've found for standard gauge are for the Callington line where the curve through Calstock station is given as 7 chains. Can anybody tell me what is (or was) the minimum curve used by service passenger trains in the UK?

HSB

[jamie92208]

a 10 chain radius curve was I think usually restrcited to 10mph and also usually had check rails installed. I also seem to remember being told tnhat a 2 furlong radius curve (20 chains) would have had a 40 mph restriction. There were very strict rules about what speed certain classes of locos coukld go round various sharp curves but I would say that 10 chain was about the minimum on a main line but am happy to be corrected, I know that the curve on what is now the main route rhrough Shipley is very sharp and carries a 20mph restriction.

 

Jamie

[Colin_McLeod]

There's a lot of useful dimensions here, from Chinese high speed rail (301ft in 4mm scale) to London Underground at 31.5"

 

http://en.wikipedia.org/wiki/Minimum_railway_curve_radius

[60163]

The absolute minimum curve for main line use was approximately four and a half chains, as per Iain Rice's Railway Modeling The Realistic Way.

 

The usual minimum curve for main line locomotives was 6 chains, as per the same source.

 

Small pannier tanks like the 136X class and the Class 08/09s had a minimum radius of 3 and a half chains.

The Class 03/04s had a minimum radius of 2 chains and the Class 02 a minimum of only one! Suffice it to say these were extremes. One chain in 00 gauge scales to roughly 10.5" - meaning third radius doesn't even square up to two chains!

[ozzyo]

I like to plan the supposed routes of my fictional railways using Ordnance Survey maps but it is hard to find information on the curvature of prototype railways. Many books refer to 'sharp curves' without telling you what those curves actually are. About the only references I've found for standard gauge are for the Callington line where the curve through Calstock station is given as 7 chains. Can anybody tell me what is (or was) the minimum curve used by service passenger trains in the UK?

HSB

 

Hello HSB,

 

if you don't know what a chain length is it will not help you, 1 chain is 22 yards (66') the length of a cricket pitch stump to stump. So 1 chain is in 4mm = 66' X 4, 264mm (or 10.4")

So the 7 chain rad.. is 22yards. X7, X 3 (to get feet) X 4 to get the rad. in mm. 1848mm or 72.75" = a 6' rad. curve.

 

HTH

 

OzzyO.

 

PS I've just noticed that your in to 7mm so for that here we go,

22X 7chain rad. X3 (feet) X 7 to get the rad. in mm, 3234 or 127.4" or 10.6' rad curve. It's big.

[Fenman]

The absolute minimum curve for main line use was approximately four and a half chains, as per Iain Rice's Railway Modeling The Realistic Way.

I thought the sharpest curves on a British mainline were, until 1959, through Sutton Bridge station on the former M&GN network, with a radius of just 2.5 chains (which is +/- a 3rd radius "train set" curve)?

 

Paul

 

Edit: Now corrected, below -- should have been 3.5 chains.

[IWCR]

2.5 chains would be well into industrial sidings / dock line curves. wagons & short wheelbase shunters only

 

Even small main line locomotives and stock would not handle this.

A Class 2 tank for example is designed for a 5 chain curve.

 

On minor lines curves as tight as 7 chains were not uncommon, these would have to be low speed and as stated earlier could well have a continous check rail.

 

Main lines would be much shallower curves, only within stations and some junctions where speeds are very low would tight curves be used.

 

"Modellers licence" has to apply if you are modelling a main line and wish to fit your layout inside anything smaller than a barn.

 

Pete

[PWSlack]

.....sharpest curves on a British mainline were, until 1959, through Sutton Bridge station on the former M&GN network, with a radius of just 2.5 chains (which is +/- a 3rd radius "train set" curve)?....

Where is the source data?

 

Check the data again, as both 2-6-0s and coaching stock would have difficulty staying on the rails at such curvatures.

[PWSlack]

On standard gauge passenger lines, below 10 chains a check rail is obligatory apart from on light railways and "lines of special interest", where the limit is below 8 chains. Check rails can be found on curves of radius greater than 10 chains.

 

The curve from North Headshunt to Platform 3 at East Anglian Railway Museum's Chappel & Wakes Colne station is 5²/₃ chains, the same as the B & 6¹/₂ junction that feeds it. Passenger trains work round this as a matter of routine. The curve onto the ashpit is a little over 4¹/₂ chains, and it is gauge-widened and check-railed; a Standard 4MT 2-6-4T has passed round this radius "dead slow".

 

Gotham Curve on the Cromford and High Peak line was around 3 chains radius, the value varying depending on where one reads it, and the curves on some of the junctions on the Docklands Light Railway are between 1 and 2 chains radius.

[Fenman]

I thought the sharpest curves on a British mainline were, until 1959, through Sutton Bridge station on the former M&GN network, with a radius of just 2.5 chains (which is +/- a 3rd radius "train set" curve)?

 

Paul

 

I am an idiot. I meant 3.5 chains (which is still monstrously sharp). I'll try to dig out the source.

 

Paul

[HSB]

Hi all,

Thanks for the replies. I did know a chain is 22 yards (or 20 metres as near as dammit) and I am not planning to try and build a layout with scale size curves (unless I change to T Gauge!). It is more an academic interest in working out what the full-size curves would have been on might-have-been routes.

Cheers,

HSB

[roythebus]

The 22 times table is quite useful to know.......especially a few years ago when I worked the IoW beer tent for a weekend and all the beers were £2.20 a pint! Simples.

 

Maybe Martin Wynne of Templot could provide a more scientific answer?

[The Stationmaster]

 

I am an idiot. I meant 3.5 chains (which is still monstrously sharp). I'll try to dig out the source.

 

Paul

So that's why the M&GN went - virtually every BR diesel with bogies had a minimum permitted curve radius of 4 chains (in most cases at dead slow speed).

 

Edit to correct spelling

[roythebus]

I make that about 41.5" radius in OO.

[Fenman]

I am an idiot. I meant 3.5 chains (which is still monstrously sharp). I'll try to dig out the source.

 

Apologies for the severely delayed follow-up. The source of this information is:

 

Clark, Ronald H (1978), Scenes from the Midland & Great Northern Joint Railway, Moorland

 

Clark wrote a number of books on the M&GN, although this is one of the lighter ones. A caution: I've seen a note that there were a number of errors in this book but I've been unable to find the list apparently compiled by the M&GN Circle. So now I have no idea whether or not there were curves of 3.5 chains radius through Sutton Bridge.

 

Paul

[CWJ]

This is a very open-ended question so I'd expect open-ended answers!

 

Curve radii will always be a compromise between the available space, geographical limitations, budget, line speed, and in extreme cases the type of vehicles to run over it. Within those constraints, it can be pretty much any shape so there is no set minium radius.

 

I'm sure there must be someone on here who is a track engineer and could put it into better words than me.

 

Cheers,

 

Will

[The Q]

I note that in British Railways Standard Steam locomotives it states that a 9F is Permitted to use a 6 Chain radius curve or 4.5 Chain Curve at dead slow (to which I would say with some prayers and some ear defenders for the screeching). So someone was thinking of tight bends even then...

 

The Q

[Jack]

In the current GOG Gazette is an article about the "English Shay" which was brought over form the US to work on an industrial line with 50ft radius curves.