|
|||
author | remove search highlighting | ||
---|---|---|---|
posted: 7 Mar 2010 01:48 from: allanferguson
click the date to link to this post click member name to view archived images |
I have a double junction at one end of my station (think Gleneagles!), and I'm anxious to keep the curvature through the diamond. Just to complicate matters there's a slew on the main line as well. Now I cannot for the life of me work out how to draw the diamond in Templot (I can usually suss things out eventually, but haven't managed this one!). I can, and have in the past, built the track on the template, making the various crossings to suit. But I'm sure it can be done more sophisticatedly. I don't want to change any of the existing alignments, as I struggled for a long time to get the whole thing to flow. Ignore the timbering -- I'll be using interlaced sleepering a la Caledonian Railway. Can anyone advise me? Please! Allan Ferguson |
||
Attachment: attach_746_1061_Muckhart_north_10_03_07_0124_09.box 318 | |||
posted: 7 Mar 2010 08:48 from: Martin Wynne
click the date to link to this post click member name to view archived images |
Hi Allan, It's not generally a good idea to run a slew through pointwork -- slews are intended mainly for plain track. If possible it is better to use a transition curve instead. I found that this transition matched your alignment very closely: initial radius = 10980 mm final radius = straight length along the initial radius = 0 length along transition section = 995 mm 2_070316_330000000.png I snaked (CTRL+F6) the turnout forward by about 2mm to line up the V-crossing with your existing track: 2_070317_110000000.png The diamond-crossing is an irregular diamond, meaning that the radii in the two roads differ. This means that all the crossing angles also differ. Irregular diamonds are not (yet) supported in Templot. Instead, you would need to create it using partial templates. This is an example of such an irregular diamond which you can download and examine: irreg_double_junct.png Download from (right-click): http://www.templot.com/samples/irreg_double_junct.box Some notes about this design at: message 1640 regards, Martin. |
||
posted: 7 Mar 2010 15:08 from: Dellboy
click the date to link to this post click member name to view archived images |
Martin How did you determine the 48.67mm spacing between the tracks? Derek |
||
posted: 7 Mar 2010 15:16 from: Martin Wynne
click the date to link to this post click member name to view archived images |
Dellboy wrote: How did you determine the 48.67mm spacing between the tracks?Hi Derek, It's the equivalent of 7ft way, i.e.1ft increase on the minimum 6ft way to allow for vehicle overhang on the curves. Just a guess, but it's usually enough. I haven't forgotten your video showing how to check such curves for adequate clearance. regards, Martin. |
||
posted: 8 Mar 2010 10:39 from: allanferguson
click the date to link to this post click member name to view archived images |
Martin Wynne wrote:
Many thanks, Martin, for your very prompt and comprehensive response. I'll have a think about it! I do feel a certain sense of misplaced pride to have found something that Templot can't do -- it's usually me that can't do..... A thought occurs. On the real railway, where this sort of junction was not unusual, how did they lay it out, given that the special chairs were made in a finite range of angles? Regards Allan Ferguson |
||
posted: 8 Mar 2010 11:05 from: Martin Wynne
click the date to link to this post click member name to view archived images |
allanferguson wrote: A thought occurs. On the real railway, where this sort of junction was not unusual, how did they lay it out, given that the special chairs were made in a finite range of angles?Hi Allan, There are two approaches to traditional double-junction design. The early method, for most of the pre-grouping period, was to lay out a ruling curve radius through the diamond, calculate the various crossing angles, choose the nearest available chairs, and fair them into the ruling curve as best they could be made to fit. Prototype radii tend to be much easier than on our models, so this method isn't as clunky as it sounds. The actual errors may be no more than a 32nd of an inch, and normal traffic wear soon removes any rough edges. The later method, applicable to the post-nationalization era, is to establish the nearest available crossing angles as above, and then to redesign the diamond so that these angles fit exactly. That requires using a slightly different radius for each rail leg between each crossing, instead of having a single ruling radius through the whole thing. A range of standard double junctions was available, to be used where they will fit and avoid the need to do a complete design every time. Modern FB uses cast crossings, made to exactly match the required radius and angle. regards, Martin. |
||
Please read this important note about copyright: Unless stated otherwise, all the files submitted to this web site are copyright and the property of the respective contributor. You are welcome to use them for your own personal non-commercial purposes, and in your messages on this web site. If you want to publish any of this material elsewhere or use it commercially, you must first obtain the owner's permission to do so. |