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                 Insert a straight in curved irregular diamond?
     
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1st message | this message only posted: 8 Dec 2020 16:00
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Julian Roberts
 

 

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Hi Martin
As you saw on the Scalefour Forum, I'm making a curving irregular single slip for my Kyle project. https://www.scalefour.org/forum/viewtopic.php?f=5&t=7028&start=25

You explained that the K crossings on a curving diamond have to be within limits, and at 1:7.5  I'm outside the limit in P4, though in S4 it might be OK. 

As I see it I've got three options :-

1 Ignore your warning and carry on regardless (I'm not getting any derailments on extensive testing of propelled vehicles, nor any other except a bit of hopping where wheels prove to have incorrect BB.  However, it is possible to manually steer a vehicle the "wrong way", including a coach bogie)

2  Convert to switched K crossings - which is not realistic, as the photo shows

3.  Redesign the crossing - the assembly is far from complete.  Yes I've spent several days on it but it's my first obtuse crossing, so worth having another go if it will be better.

Thinking about the third option:  as the whole crossing is about 350mm long, would it be possible to "cludge" (is that a possible word to describe what I mean?!) or somehow fit in a straight area where the K crossing is, for say the length of a wagon each way, and move the other rails to suit, retaining the position of the V crossings?   I could probably do it freehand but possibly not very satisfactorily compared with modifying the drawing on Templot first.  I attach the box file - the single slip is at the beginning in the storage box.  I have had a go but not got anywhere, so how would I do this if it is possible?

And if I'm rethinking it, to go back a stage and do what I should have already done, is it possible to say from a photo what the K crossing angle is?

Cheers
Julian









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Attachment: 15 October back up.mecbox (Downloaded 35 times)
 
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2nd message | this message only posted: 8 Dec 2020 18:15
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from:
Martin Wynne
West Of The Severn, United Kingdom



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Hi Julian,

Drawing straight lines on your photo:



shows that this is a straight regular diamond between the V-crossings. The V-crossings are then curved slightly to match the connecting tracks.

Trying on the old map suggests that it is 1:8 CLM:



(but the photo is obviously much later than the map, so may not be a match).

It is extremely likely that the V-crossings are also 1:8 CLM regular, and they can't physically be much different in the space available anyway.

To curve them to the connecting tracks, insert a zero-length transition in front of each V-crossing. It is probably located at the wing rail front joint.

In theory it doesn't have to be zero-length, but I think it extremely unlikely that the designer would have used a mathematical transition curve in such a position.

But if you have your slip built and working ok, I would be tempted to leave it, at least for now. :)

cheers,

Martin.

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3rd message | this message only posted: 9 Dec 2020 08:31
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from:
Julian Roberts
 

 

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Hi Martin
Many thanks.  After I'd posted I took two photos of the crossing as built and see it is almost straight in any case!  But being 7.5 possibly more reliable in P4 than if I'd known it should be 8.  So I think I'll take your advice at the end of your post.

The clarity of the rails in your picture points up what I found to be an issue, that rotating the map on Templot reduces the clarity of the image.  I should have used the map without rotating it, but I wanted to look at the plan as it will be as a layout.  Maybe I could have rotated it while on the NLS site, and made a screenshot then, but I couldn't make that work for some reason, I forget now exactly what I tried to do.

I have wondered what the sign resembling a handwritten 'f' is, on the map.

I've another question on obtuse crossings that I'll post as a separate topic later.

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4th message | this message only posted: 9 Dec 2020 10:40
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from:
Martin Wynne
West Of The Severn, United Kingdom



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Julian Roberts wrote:
I have wondered what the sign resembling a handwritten 'f' is, on the map.
Hi Julian,

The elongated "f" or "S" symbols are called "field ties". They link together areas of the map which are included in a single "field parcel" for which the area is calculated and shown on the map. Each parcel in a parish is given a number -- usually all of a parcel of land would have a single landowner. The area of a parcel is or was used in local taxation, and now in connection with agricultural subsidies.

Ordnance Survey still maintains information about field parcels, but no longer shows it on the maps. See:

 https://www.ordnancesurvey.co.uk/business-government/tools-support/field-parcel-numbers

The difference in map clarity is the result of browser zooming and resampling -- it doesn't actually add any information to the original scan. In the next program update Templot will have its own tools to load the historic map tiles and improve map clarity, see:

 https://85a.co.uk/forum/view_topic.php?id=3823&forum_id=1



cheers,

Martin.

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5th message | this message only posted: 9 Dec 2020 18:00
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from:
Julian Roberts
 

 

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Hi Martin - as people have said, you're a mine of information: thank you for putting me in the picture. I didn't think it could be some physical infrastructure thing, now I know. Great news about the map clarity too.

All best
Julian
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6th message | this message only posted: 24 Dec 2020 14:24
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from:
Julian Roberts
 

 

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Hi Martin
I decided to start again on this curved slip.  It works fine but I don't want the curve to be the limiting factor on future locos.  However I found I just couldn't design a straight one to fit on the layout without rebuilding the adjoining turnout too, and that one is made and works.

You said above, "To curve them to the connecting tracks, insert a zero-length transition in front of each V-crossing. It is probably located at the wing rail front joint."  That is probably why I couldn't design something on Templot, as I haven't needed to learn how to do transitions.

The layout had been fully finished by July with a lot of timber shoving etc done, so I thought I'd see if I could insert a straight diamond in the middle of the existing curved one, with each half to be the length of the maximum fixed wheelbase likely, 21 feet/84mm.  I found it was quite easy to superimpose two straights 168mm long, with a barely noticeable kink in the rails where the joins to the existing slip will be, and with no disturbance to the switch areas.

I then grouped them and moved them away, and "make diamond at intersection".  I propose making this diamond, then lifting it off the template, and fitting it onto the original irregular slip curved template in the same way as I drew it on Templot and completing it from there.

This file shows the slip with the new diamond superimposed on it, so it's a mix up, the other file shows the original slip with the diamond separated off to the bottom left to print.  Ah - I think only one file can load at a time, the next post will have the separated diamond.

I don't know if this would have been possible to do properly on Templot - probably, but involving lots more learning curve.  

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Attachment: 23 Dec Original complete layout with 168mm straight inserted in slip.mecbox (Downloaded 30 times)
 
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7th message | this message only posted: 24 Dec 2020 14:26
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from:
Julian Roberts
 

 

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Oh - and Happy Christmas, thank you for all the help you've given me and everyone, and thanks for the idea regarding vero pins on copperclad
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Attachment: 23 Dec Straight 168mm diamond for slip ready to print.box (Downloaded 35 times)
 
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