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posted: 29 Oct 2009 16:00 from: Alan McMillan
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Hello all. Does anybody know what to do with a crossover (as shown below) on a curve? I can't really see what would be the solution as the normal arrangement for superelevated curves is as illustrated which would lead to the crossover track doing some very strange things to go from one line to the other. Regards Alan McMillan 412_291058_530000000.png 412_291058_330000000.png |
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posted: 29 Oct 2009 16:31 from: allanferguson
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Alan The interim report on the Grayrigg smash http://www.raib.gov.uk/cms_resources.cfm?file=/071003_IR022007_Grayrigg.pdf has a picture of the offending crossover which suggests that both tracks were in the same plane at a cant of 95mm, at least in the vicinity of the crossover. I feel sure I've heard of situations where the cant was taken out through a crossover, but this would involve a speed reduction, and in any case I can't think of examples, so may be havering! Allan Ferguson |
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posted: 29 Oct 2009 17:06 from: Alan McMillan
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Thanks Allan I did wonder if this was how it was done - the only thing was I'd never actually seen it and I wanted to make sure that my approach was prototypical. At least it will make the thing easier to build! Regards Alan |
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posted: 29 Oct 2009 17:31 from: John Lewis
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From Alan McMillanEm dinburgh, United Kingdom Hello all. > Does anybody know what to do with a crossover (as shown below) on a curve? I can't really see what would be the solution as the normal arrangement for superelevated curves is as illustrated which would lead to the crossover track doing some very strange things to go from one line to the other. Apparently the ideal was to keep the rails all in the same plane using very long sleepers under all tracks. However "British Railways Track" has pictures (1st Edn Pg 68) of some "two level" chairs introduced by the LMS where the base of the chair under the rail was thicker than normal to preserve the vertical alignment. The use of these meant the six foot way had to be increased in width. Perhaps Martin or someone can explain furtheer, please? The worse case is double junctions where the branch is on the outside of the curve, but itself curves in the same direction as the main. Care has to be taken to avoid the branch rail on the inside of the curve becoming higher than the outer rail of the branch. |
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posted: 29 Oct 2009 18:03 from: Alan McMillan
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Hi John Your last point is interesting. There used to be a very strange arrangement at Carstairs Junction on the Scottish Region in the 1970s where the Edinburgh branch track deviated from the up main platform road which had a 6 inch cant deficiency for high speed through running. I used to see Brush Type 4s that had brought in the Edinburgh portion of London bound trains use this to reach their stabling sidings. (In those days they swapped motive power prior to electrification of the Edinburgh line). The branch deviated fairly sharply to the left from the main which was heading right. The locomotives effectively climbed over the top of the outer main line rail on a right hand cant and then coggled over alarmingly to the left hand cant of the branch. I've never seen this anywhere else and I'm sure if you modelled it you'd be told by all and sundry that a formation like that would never exist in the real world! Maybe someone has a photo of this? Regards Alan |
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posted: 29 Oct 2009 18:31 from: Martin Wynne
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Alan McMillan wrote:Does anybody know what to do with a crossover (as shown below) on a curve? I can't really see what would be the solution as the normal arrangement for superelevated curves is as illustrated which would lead to the crossover track doing some very strange things to go from one line to the other.Hi Alan, Previous discussion about this is at: topic 150 There is more discussion and a long extract from BRT about 2-level chairs at: http://groups.yahoo.com/group/templot/message/4693 regards, Martin. |
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posted: 29 Oct 2009 18:43 from: Alan McMillan
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Thanks Martin, but I think I'll stick to the "all rails in the same plane" approach. Two level chairs sound like a nightmare and since I'm doing this in flat bottom and using timber and rivet construction, I think I'll raise the white flag and go for the easy option. Regards Alan McMillan |
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posted: 29 Oct 2009 20:54 from: Jamie92208 click the date to link to this post click member name to view archived images |
I think that the same plane idea is the right one. I read an accident report recently that dealt with a freight train derailing on one of the Tyne bridges. From memory one of the causes was superelevation on the main line but not on the diverging route, this combined with a badly maintained suspension on an MGR wagon to cause a derailment. Keeping everything in the same plane solves a multitude of potential sins. Our models aren't as good as the real thin at stayin on the track. Jamie |
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posted: 29 Oct 2009 21:00 from: Alan McMillan
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I just remember how that Brush 4 looked at Carstairs - it was a derailment waiting to happen - and in P87 it probably would! Alan |
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posted: 30 Oct 2009 09:15 from: Jamie92208 click the date to link to this post click member name to view archived images |
Remembering more about that accident report. In 12 inches to the foot minor changes in the set up of the wagon's suspension coupled with poor maintenance of the track brought a wheelset, with several tons holding each axle down, off the track. I don't hold out much hope for our hobby when you are talking about a few gramms of adhesion weight in some cases. Stick to the same plane. | ||
posted: 2 Nov 2009 23:35 from: allanferguson
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For a good illustration of the cant problem see this site http://www.jhowie.force9.co.uk/carstairs.htm#negative%20cant You can get quite seasick watching one of the NXEC sets coming through! Allan Ferguson |
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posted: 3 Nov 2009 10:49 from: Alan McMillan
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It's actually worse than I remember it! Modelling something like that would be nightmarish! Alan McMIllan |
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