Templot Club Archive 2007-2020
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posted: 22 Dec 2012 14:52 from: stuart1600
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I feel sure this (or something very similar) has been covered before but can't find a thread which seems to cover it exactly. So, apologies in advance if the answer is already out there somewhere. Always looking for space-saving arrangements I was considering replacing one (or more) turnout(s) in a scissors crossover with slips. But the problem seems to be a conflict between the slip switches and the central diamond V-crossings. On the basis that a picture is worth a thousand words I've attached a box file showing two double slips joined as one half of a scissors crossover. Am I trying to create an impossible arrangement that would not be used in prototype practice; or is there a way of achieving this? Any help will be much appreciated. Stuart |
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| Attachment: attach_1554_2126_DoubleSlip-20ft-B8.box 212 | |||
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posted: 22 Dec 2012 23:13 from: Martin Wynne
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stuart1600 wrote: But the problem seems to be a conflict between the slip switches and the central diamond V-crossings.Hi Stuart, A curved 1:8 diamond with fixed K-crossings is asking for trouble, especially with the wide GOG-F flangeways. 1:8 is the limit for fixed K-crossings, and then only in straight track. I would strongly recommend changing to a switch-diamond for the slips. Have you considered using 0-MF instead? The V-crossings on the slips can barely be checked properly because of the conflicting diamond rails. By reducing the 90mm track centres a little you may find the check rails fit better. The points of the slip switch need to clear the wing rail on the middle V-crossing. To achieve this you need to move the switch sufficiently to clear. This will shorten the slip road and reduce its radius -- another reason to use a switch diamond (i.e. no K-crossing check rails for the slip road to conflict). The outer switch on the same side will need to be moved in by a similar amount so that the slip road radius will align correctly. The timbering and chairing of the slip switches would need some careful thought, but the rail geometry appears to be possible. It's not unknown as a prototype formation. regards, Martin. |
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posted: 24 Dec 2012 09:58 from: stuart1600
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Martin Wynne wrote: A curved 1:8 diamond with fixed K-crossings is asking for trouble, especially with the wide GOG-F flangeways. 1:8 is the limit for fixed K-crossings, and then only in straight track. I would strongly recommend changing to a switch-diamond for the slips. Have you considered using 0-MF instead?Thanks for this comprehensive reply Martin. I was fairly confident that I could see what the problems were, but I was struggling to identify the solutions! From previous threads on this forum I recalled that 1:8 was the limit for fixed K-crossings, but hadn't noted that this applied to straight track. I could probably change to 1:7, and even with the slip switches moved in a bit could still keep an acceptable radius on the inner slip roads (i.e. at least 6ft). I'm intrigued by your suggestion of reducing the track centres; I had assumed that if anything I would have had to increase them to resolve the conflicts - I shall have a play with that and see what happens. Similarly with 0-MF, which I am considering despite it seeming to be counter-intuitive to make the gauge even narrower. (but going the other way to S7 is definitely out, not least because I own too many wheels!) I do have one scratchbuilt loco with Alan Harris wheels set to 29.4 b-to-b and I will need to check if this is happy with the crucial "check rail to opposite rail-face" measurement in 0-MF. So, all in all quite a few parameters to play around with, and some useful additions to my knowledge of trackwork. Again many thanks for your help, and all best wishes for Christmas and the New Year. Stuart |
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