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topic: 301Double-junction crossover in space available?
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posted: 5 Jan 2008 01:26

from:

Peter Salathiel
 
Bangkok - Thailand

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Hi Martin,

My previous post didn't show my problem very well so trying again...

The layout design is for a series of modules, approx 1800mm x 900mm which you can see on the attached background shapes file. The dotted line (moveable) represents my initial idea for a "scenic" divider. (The amount of scenery will be limited. I prefer just to run trains. Hence the idea of having a "branch" inside.)

The track plan with sleepers represents my scan from the 1:2500 OS map overlaid on my modules. As you can see, it requires turning at each end to get round the layout corners. I'm reasonably happy with the left hand (West) corner. The right hand (East) is the problem for where the overlaid Templot plan ends is a double crossover junction (from the main SWML to the Barry line with the latter shrinking to a single line.

Being new to 00-SF and 'serious' trackwork I am wondering what radius to employ for the double crossover junction and exactly where to site it so that I can 'get round the bend'. I understand from the group that 30"-36" is probably the minimum radius in 00-SF and that the crossover diamonds should be #8 or less. (They seem to be #8s on the map). I would be happy with the double crossover junction located anywhere between its actual starting position on the map (or maybe a bit before) and the two Templot centre lines which represent my idea as to the minimum radius for the SWML and Barry lines. 

The layout will be "permanant" (ie. no need to move hopefully) and L-girder construction (3" high at the relevnt point) so the modules are not a constraint on the location of the junction.

My question where should the double junction crossover be located, what number turnouts/diamonds should it employ.  Anything you can add to your previous advice would be most welcome.

Regards

Peter

 
Attachment: attach_186_301_08_01_05_0231_34ForMartin.box 237

posted: 5 Jan 2008 06:15

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Peter,

Thanks for uploading your plans. It looks to be an excellent project, and an ideal plan for 00-SF.

There were some misalignments and several unnormalized transitions, so I have taken the liberty of re-working the right-hand part of your plan. I hope I have correctly interpreted your intentions:

mod_for_peter.pngmod_for_peter.png

The .box file is attached below. Use add file... to load it onto the pad in conjunction with the remaining parts of your plan. You are not under any obligation to use it of course, or indeed to take the slightest notice of it. :)

Bear in mind that it's not finished -- I haven't done any timber shoving, and you may want to check the running clearances.

It's interesting that despite appearances both the double-junctions are in contraflexure (negative curving) -- the turnouts at A are right-hand deflections, those at B are left-hand deflections.

All the turnouts and diamond-crossings are 1:8 angle. The diamond-crossing at A is on 960mm (37.8" approx) radius. The diamond-crossing at B is on 1105mm (43.5") radius. The turnouts are B-8s and the minimum radius at A is 910mm (35.8").

At these radii I strongly advise that you don't build 1:8 diamonds with fixed K-crossings. Even in P4 it would be living dangerously. With the wider flangeways of 00 and EM I think derailments and mis-trackings are inevitable. Build them as switch-diamonds instead -- it's easier and ultra-reliable because the wheels don't see any break in the rails. I've made them switch-diamonds (movable K-crossings) on the plan -- both blades are shown in the closed position of course, as on the turnout templates.

Given the likely total cost of this project I feel sure that you can run to the 4 extra point-motors needed (or maybe only 2 if you devise suitable rocker crank linkages). It will be money well-spent to avoid derailments on these junctions.

The trailing crossover at C is using B-8s as in your previous design, but there is plenty of room there to make them C-10s, which would look better.

If I have misinterpreted your plans please let me know and I will see if it can be re-done to suit. The .box file is attached below.

regards,

Martin.
Attachment: attach_189_301_modified_for_peter.box 241

posted: 7 Jan 2008 08:19

from:

Peter Salathiel
 
Bangkok - Thailand

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Thank you! Thank you! Thank you!

First many thanks for "fitting in" the double junction. This had been bothering me for months.
I can now work on finalising the details rest of the plan and start some trackbuilding/tracklaying on the first module (the West end of the station) and get some experience with 00-SF. I hadn't picked up the contraflexure of the double junction but it makes sense as the map is 1940 and prior to the 1923 grouping the GWR and Barry would have had seperate main lines.

Second thank you for the advice re: swith-diamonds. It will be followed (eventually!) scrupuously. I will have enough to do just to build track without attempting to defy the laws of physics.:)

Thirdly, thank you for re-doing the right hand side of the plan. I had completely forgotten about "normalising" the transitions. And thank you for picking up the mis-alignments. It's something I try to guard against but given a largish plan and my lack of templotting skills it's something that happens more often than I would like. Incidentally, when one notices a misaligned template (eg. a turnout in the middle of a plan with one road misaligned what is the best way to correct it? Where to start? How does one systematically hook up the corrected alignment without disturbing the rest of the plan?

One query with respect to your re-doing of the plan. I understand, and will use, a C-10 or C-12 at the start of the Barry double track immediately prior to the facing double junction. It looks something of that order on the map. However the turnout to the RS Hayes siding (#22 on the .bgs file) is close to a B 5.25 on the map (yes, on a major running line!) and I would like to make it as sharp as possible (in keeping with the original) but consistent with trouble free running. Would a B-6 do that or should it be a B-7 or 8? The branch road will only see 4-wheel wagons and 0-6-0 panniers and I wouldn't lose too much sleep if it never worked.  The other 'surprise' was the #15 - #16 crossover, a C-10 with a B 7.5. Was this necessitated by alignemnt?

Finally, thank you once again for Templot. Its differences from 'standard' windows software and the 'learning curve' are a small price to pay for the amazing things it can do.  The project is something that simply couldn't be done with Peco....thank goodness I realised that before it was too late.:)

Best Regards

Peter

 

posted: 7 Jan 2008 23:23

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Peter Salathiel wrote:
Incidentally, when one notices a misaligned template (eg. a turnout in the middle of a plan with one road misaligned what is the best way to correct it? Where to start? How does one systematically hook up the corrected alignment without disturbing the rest of the plan?
Hi Peter,

I'm glad you found the plan suitable. :)

There isn't really a "one answer fits all" to correcting misalignments, it depends on the situation. Ideally if you work methodically you don't create misalignments in the first place! :)

Often where there is contraflexure (negative curving) a big improvement can be made by changing to a curviform type of V-crossing. Then you might use the "make transition" function to replace the misaligned templates. I've made a quick video showing that:

new video: http://www.templot.com/martweb/videos/mis_match.exe

Sorry there are no video notes or captions, adding them is too time-consuming, I will do that later. Press the spacebar to start.

In other cases you might change the V-crossing angle (F5) to get a better fit, or roam one of the turnouts a little way (CTRL+F9). If all else fails you might find that you can get a reasonable manual alignment by slewing the track a little.

regards,

Martin.



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