Scissors crossing conflict ?

[Tom King]

Dear Templot club members, I hope I am posting this request in the right areas.

I am hoping for some advice on the following scissors formation. The diamond crossings and crossings on the near straight through route are nearly opposite each other. Do you think I might get away with it ? It is in OO-SF, it is for a loco shed, so locos only, slow, and no propelling except tenders. The diamond is straight. The spacing is also influenced by trying to get good alignment of the timbers.
I think I have enclosed a messy box file.

The plan is trying to capture a specific prototype formation though the real one was more symmetrical in the diamond spacing between the top and bottom through routes. This plan is so squished as the bottom right entry is already laid and glued, (it is glued as it was a British Finescale 3D printed base). Then the top right branch goes to a turntable well that has already been cut, and I wanted the entry for that to start as far to the right on the tandem as possible to keep that radius large.

I am planning to extend the K-crossing check rails towards the common crossing, to make interior sort of Vs with machined ends so that the blunt tip is inside the envelope of where an actual "interior V" with 1mm flange ways would be. My representation in the plan is a bit clunky, but hopefully communicates the idea.

I don't think I will need the stumpy residual flared ends of the lower diamond check rails between the turn out crossing rails but I have represented where they might be. I am planning to make use of British Finescale templates at the corners of the formation so they are all Number 7 crossings.

Comments on my folly are welcome. Thanks, Tom

 

[Martin Wynne]

@Tom King

Hi Tom,

The V-crossings are not fully checked. You might get away with it, but there is the potential for derailments. Unfortunately the only way to find out would be to build it and see. After which there would be almost nothing that could be done about it.

I would be inclined to redesign it to ensure all the V-crossings can be fully checked. Here is a quick stab at that:

I moved the double slip a little to the left and changed the tandem exit to a longer 1:8 curviform. The diagonal track is then curved slightly to align with the 1:7 slip, creating an irregular diamond. The two B-7 turnouts are unchanged. All the V-crossings can be checked by extending the opposite wing rails. The tandem needs some reworking.

Scruff unfinished BOX file attached. To complete the diamond use the find intersection function on one of the vees, adjust the K-crossing angle (F10) to intersect on the centre, then tools > make diamond-crossing should complete it. Finally split out the partial templates to remove any conflicts.

I can do that for you if you are happy with the above? Timbering would be over to you to tidy up.

cheers,

Martin.

 

[Tom King]

Dear Martin, that is extremely kind of you. Much appreciated, thank you. I can see how that would be much safer. Let me look at the space again to see if I can make that work before you spend any more time on it. I had already used up some of the left hand room vs. my original plan (wood was cut when I was planning 6.5 for the corners before Wayne released his OO-SF range). It looks like you moved the lower left double slip about 40mm further left I think. The lower left road leads to a fan for 3 loco storage roads (5 in the real location) and I need to check they will still be long enough. Sorry I didn't mention that constraint before !

 

[Tom King]

Dear Martin, many thanks for your help with the above.
I reworked the version with number 7s again moving the lower left turn out 22mm to the left instead of about 40mm in your version. I also kept a number 7 in the foreword tandem turnout instead of the number 8 curviform. I think the 4 crossings in the lower scissors are just checked by the opposite wing rails. Especially if I don't radius the relevant knuckle much.
Do you think I may still run into to issues ? (Slow speed in shed)
Many thansk, Tom

 

[Tom King]

I have redesigned it to have the diamond crossings outside the through route on the near side, and I think this version is fully checked now. Now I will see if I can build it !
Thanks for you help Martin.
Also including a screen shot of a small part of a photo that includes the actual formation this is modelling. Tom

 

[Martin Wynne]

@Tom King

Hi Tom,

That doesn't look fully checked to me?

Are you sure you uploaded the correct file?

Your previous post was much better with all crossings fully checked, one of them by the skin of its teeth, but just about ok:

Green markers fully checked, yellow marker border-line but likely OK.

Your file re-attached below.

cheers,

Martin.

 

[Tom King]

Thanks Martin, I am very glad I asked. I had been thinking that if there was a check rail that would pull the wheels away from the nose in each direction that would be OK, but your response makes me wonder if having the openings around the knuckles so close to opposite each other might allow the wheels to wander too much and not pick up the face of the check rail I intended. Is that the issue ?

 

[Martin Wynne]

Thanks Martin, I am very glad I asked. I had been thinking that if there was a check rail that would pull the wheels away from the nose in each direction that would be OK, but your response makes me wonder if having the openings around the knuckles so close to opposite each other might allow the wheels to wander too much and not pick up the face of the check rail I intended. Is that the issue ?

@Tom King

Hi Tom,

The functional length of a check rail must at least cover the break in the opposite rail, so that wheel flanges are prevented from moving sideways and striking the nose of the crossing. So for a V-crossing that means from the knuckle bend in the wing rail approximately to the centre of the "A" timber:

In practice you can sometimes get away with a shorter checked length, especially if the V-crossing is on the inner rail of a curve. A lot depends on the accuracy of the wheelset -- no wobble, axles square-on to the vehicle, correct back-to-back, etc. Also large locomotive wheels are less likely to mis-track than small wagon wheels. So imperfect checking might be more acceptable in a steam loco shed area than in a goods yard. But have regard to smaller-wheeled pony trucks etc., especially any with poor side control.

More check rail info here:

https://85a.uk/templot/companion/check_and_wing_rails.php

cheers,

Martin.

 

[Tom King]

Thank you Martin, I will revert to the previous version. Tom

 

[Martin Wynne]

@Tom King

Hi Tom,

To keep things tidier I have moved your post to:

https://85a.uk/templot/club/index.php?threads/getting-started-with-3d-plug-track.722/post-8201

and replied.

cheers,

Martin.