Templot Club Archive 2007-2020                             

topic: 3742Crossing Angle Crisis
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posted: 17 Aug 2020 13:54

from:

ikcdab
 
Taunton - United Kingdom

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in the past I have always built b8 turnouts and been happy with them.  On my new layout, I have been brave and pushed the boat out a bit and gone for c10 turnouts on the main line.  And very self-rightous I feel too.However, I have just read the Bot 1933 report on the new crossing loop installed at Leigh Bridge on the minehead line. The inspector quotes the turnouts as being "1 in 16 with 30ft switches". I take this to be a F switch. And this is on a simple branchline with a 50mph speed limit.
I guess its a function of a model railway with its tighter curves and compression. But now I'm having a crisis that I should have gone for shallower crossing angles than my C10.
So my "piece of string" question. What would be "normal" on a main (ish) line?
I've started to build,  so it's now too late to change, I'm just interested in your thoughts. 

posted: 17 Aug 2020 14:39

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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ikcdab wrote:
The inspector quotes the turnouts as being "1 in 16 with 30ft switches". I take this to be a F switch.
Hi Ian,

No, it's a GWR 30ft straight switch:

2_170910_250000000.png2_170910_250000000.png

The GWR had only 3 flexible switches, B, C and D, introduced for new work from 1930. For the other sizes, shorter and longer, they continued to use their older designs.

There is no "normal" crossing angle, everything depends on the site, the traffic, and the line speed. If there is any curving it always means a longer crossing to avoid a severe speed restriction over the diverging turnout road.

1:10 is fine for a station throat or branch terminus area, but maybe a bit short for a running loop or crossover out in the country. On the other hand 1:16 seems generous, unless the turnouts are on a curve.

Often in complex station throats 1:8 is used so that they match 1:8 diamond-crossings and slips (which is the longest angle allowed for fixed K-crossings, and then only if they are all-straight), but it does mean speeds must be kept low.

Bear in mind that for secondary and branch lines, "renewals" were often serviceable second-hand material cascaded down from main-line use. For a fast main-line junction 1:16 would be quite normal, so the fact that 1:16 was installed on a branch line might simply mean that a usable second-hand 1:16 turnout was available, and there was space for it.

If you are basing a model on an actual location such as Minehead, the easiest solution to the conundrum is to load the 25" map from NLS and see what typical sizes were used there.

cheers,

Martin.

posted: 17 Aug 2020 15:21

from:

ikcdab
 
Taunton - United Kingdom

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Martin, that's interesting. Indeed, the loop points were on a curve. At the other end of the loop, the vee was 1 in 20. The loop switched out in the winter so the 40mph limit was through both roads in both directions. Also, both points were fitted with Langley and princes economic point lock.  The box and frame and plain track was secondhand, but I believe the pointwork was new.
My layout (which some posters here have seen on rmweb) is based on the southern. Ijust have an overlapping interest in the minehead line.
Ian
Last edited on 17 Aug 2020 15:49 by ikcdab
posted: 17 Aug 2020 16:34

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Ian,

Just out of interest, I have had a look at the pointwork at Minehead on the 1936 map:

2_171126_010000000.png2_171126_010000000.png

I have matched the switch toes as best I can.

These are old-type GWR loose-heel switches, 15ft and 16ft.

The crossover looks to be 1:10.5 (generic V-crossings).

The turnouts into the yard look to be 1:9 and 1:10.

So your 1:10 turnouts are fine, but bear in mind that nothing would have been running over these turnouts at 50mph.

cheers,

Martin.

posted: 18 Aug 2020 10:29

from:

ikcdab
 
Taunton - United Kingdom

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Hi Martin, thanks. The layout at Minehead was altered in 1905 and 1935. The 1936 map represents the 1905 layout. Neither the 1905 or 1935 inspection reports give any indication about the connections apart from them being "new" and with 85lbs material.
I have an in depth interest in the minehead line, but my own layout is based on the southern. My C10s look very nice on my main line, I guess because of model railway compression.
Back to track laying....
Ian

posted: 18 Aug 2020 10:45

from:

ikcdab
 
Taunton - United Kingdom

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I going seriously off topic now. Crowcombe was also provided with 1 in 16 and 1 in 20 turnouts in the crossing loop. This was probably because the GW installed Whittaker automatic token changing apparatus, and so the whole traffic along the branch could be sped up. Tokens exchanged at 40mph rather than 5mph. Williton and bishops lydeard also had so-called "high speed" turnouts installed, but I don't have details of their geometry.

posted: 18 Aug 2020 11:09

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Thanks Ian.

That explains why the longer than usual turnouts were used on a branch line.

cheers,

Martin.



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