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topic: 2565Speed limits through turnout (to decide which type is most appropriate)
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posted: 28 Oct 2014 22:20

from:

DerekStuart
 
United Kingdom

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Another question from me, I'm afraid...
I have studied as many photos as I can of the trackwork in question and still can't be sure which turnouts are the most likely, although Tony W did help me and agree that a tandem was a B6/B8.
So I am going to go on the "most likely" for the scenario. At a line speed of 25-30 would a crossing through a B8 be realistic, or should it be C9? Equally, at the station throat when the speed limit was at 15mph (or slower) would a B7 be most appropriate?

Scalefour recommends no less than a B7 on a running line. I have looked at one turnout still in use which appears to be a B6- although it is a run around loop that was once the entry to the carriage sidings and not one for general running.
I just know that once I've started, some bright spark who knew the station professionally is going to come up to me and say "oh no, that should have had X sleepers there not Y"

I have just been reading the 'debate' between Martin and others in RMWeb, back in 2007 about point choices. Educational AND entertaining.

Derek
Last edited on 28 Oct 2014 22:20 by DerekStuart
posted: 31 Oct 2014 00:24

from:

Tony W
 
North Notts. - United Kingdom

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Hi Derek.
I have a book somewhere that states what the speed limits through various turnouts would be. When I find it I will post the figures. The difference between a B-6 and B-7 would be negligible. Bear in mind of course that the speed limit through the straight road of even a B-6 could be quite high, but through the crossover road it could be as low as 5 MPH and certainly no more than 10 MPH.
Regards
Tony.


posted: 31 Oct 2014 03:00

from:

DerekStuart
 
United Kingdom

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Thanks Tony. Someone showed me a list that was for FB- he wasn't sure if BH should be the same, greater or lower. The general consensus seems to be B8 minimum on passenger lines (C8 preferred if room), B7 or B6 on yard spurs and for station throats where speed limits are down to 15mph.

Some of the photos I have of Whitby shed show some very tight turnouts A's.

BTW my understanding of all this has greatly improved since you helped me with the tandem design- so again, my thanks for your help- like all people here I suspect, it is a steep learning curve but well worth it.
Last edited on 31 Oct 2014 03:02 by DerekStuart
posted: 4 Nov 2014 18:21

from:

Tony W
 
North Notts. - United Kingdom

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Hi Derek.
I have now had a chance to scan the table I referred to earlier. It comes from a small book called British Rail Handbook by B.K.Cooper published in 1981 and refers to the then modern Flat bottomed point work being installed by BR. Note that the limits for a crossover are often lower than for a single turnout due to the reverse curve. I would expect that Bullhead P&C speed limits would be lower than these figures but it is undefinedundefinedinteresting to see how slowly the limit rises as the turnouts lengthen.
2151_041315_060000000.png2151_041315_060000000.png
Regards
Tony.

posted: 4 Nov 2014 20:02

from:

DerekStuart
 
United Kingdom

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Cheers Tony. Someone did also show me a copy of a BH version of that document, but in the 100s of bits I've got I've misplaced it.

If the 'owner' is agreeable I will upload it to this thread as it would make a good comparison for anyone else between the two tables.

EDIT: That one was for FB as well, but the poster said the speeds would be the same. The doc also shows that for a crossover (or 'return curve' I would have thought) mostly drops 5MPH.
Last edited on 4 Nov 2014 20:06 by DerekStuart


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