Templot Club Archive 2007-2020                             

topic: 3326Marcway 3way Tandem Turnout
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posted: 11 Sep 2018 19:24

from:

r_wilton
 
Bangor - United Kingdom

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Hi, i wonder i anyone can help a novice occasional user.
I have a Marcway 3 way tandem righthand turnout with 60" and 48" radius turnouts.
I would like to utilise this in a layout to be completed in templot.

Problem is i'm having trouble trying to make a template for the 3 way.
If anyone can help i'd be most grateful.

Ray.

posted: 11 Sep 2018 19:42

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Ray,

Can you post a photo of the Marcway? Or maybe actually scan it? Or take a rubbing from it and scan that?

It's difficult to advise without seeing what you are trying to replicate. I have no idea what Marcway might refer to as a 60"/48" tandem turnout. Presumably this is 4mm scale, 00 or EM?

To create a tandem turnout in Templot, click the tools > make 3-way tandem turnout > menu items. There are quite a lot of settings and options, you probably need to read this page first:

 http://templot.com/companion/3_way_tandem_turnouts.php

cheers,

Martin.

posted: 11 Sep 2018 20:27

from:

r_wilton
 
Bangor - United Kingdom

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Hi Martin,Sorry i should have been more specific, it is O gauge (fine).

I've attached a photo (hopefully) with a few measurements penciled in, hope that helps.
In the meantime i'll have a read of the article.
Ray.
Attachment: attach_2744_3326_Marcway_3way.jpg     554

posted: 11 Sep 2018 23:15

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Ray,

Thanks for the photo. To make an exact copy I would need something more precise, such as an actual scan of the Marcway tandem.

p.s. I note that it has a check rail missing. :( Also a vee nose hanging in fresh air, and strangely narrow spindly timbering.

I have created this 0-MF tandem which I think may be fairly close. The .box file is attached below. If you print it out, place the Marcway tandem over it and take a photo as square on as possible, I may be able to adjust it for a better fit.

The V-crossing angles in order are 1:4.5  -  1:7.5  -  1:5.5

The radii are 1972mm  (77.6")  -  1287mm (50.7")


2_111801_390000000.png2_111801_390000000.png


2_111801_390000001.png2_111801_390000001.png

cheers,

Martin.
Attachment: attach_2745_3326_short_tandem_for_ray_2018_09_11_2232_38.box     192

posted: 12 Sep 2018 10:37

from:

r_wilton
 
Bangor - United Kingdom

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Hi Martin,Many thanks for the box file. 

Ive attached a scan (pdf) although its in two pages as my scanner is only A4.
The turnout angles of the .box file seem a little too sharp.
I'm not too worried about the accuracy of the switches etc, just the exit angle as i'm not making the turnout, just want to incorporate it in a new layout.

Many thanks for your help

PS i did find that for a starter the REA semi-curve B+V-6 regular V crossing (72.9" radius) is a pretty good fit. 
Attachment: attach_2747_3326_Tandem.pdf     191

posted: 12 Sep 2018 10:38

from:

r_wilton
 
Bangor - United Kingdom

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Heres a photo of the tandem on top of the .box file.
Attachment: attach_2748_3326_tandem_plot.jpg     472

posted: 12 Sep 2018 10:53

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Thanks Ray.

I will have a look at making a better match.

cheers,

Martin.

posted: 13 Sep 2018 19:17

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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    PLEASE -- NO-ONE SHOULD BUILD THIS TANDEM

   
Or if you do, don't tell anyone that it came from Templot !

Hi Ray,

This should be a better match to your scan. Only the rail ends match the Marcway tandem, internally the rail alignments are different, as you can see.

In scaling the scan, I assumed the track gauge is exactly 32mm.

I have put the pegs on the rail ends, ready for you to use this .box file in your track plan.

The crossing angles in order are 1:5.15  -  1:8.93  -  1:6.5

The radii are 2388mm (94") and 1726mm (68"). That's a lot larger than your quoted 60"/48" (which sounds unlikely for 0 gauge -- did you make a mistake there?)

Please don't actually build this tandem, the .box file is solely to allow you align adjacent templates to your existing item of pointwork. The 8.93 V-crossing cannot be properly checked as you can see -- as drawn the wheel flange is obstructed. On the Marcway tandem that check rail is missing, so there is a risk of derailments.

2_131408_490000000.png2_131408_490000000.png

I converted your scan to a negative image, to make it easier to see the rail edges:

2_131409_190000000.png2_131409_190000000.png

.box file attached.

I will post the .bgs and .sk81 files next.

cheers,

Martin.
Attachment: attach_2749_3326_ray_tandem.box     189

posted: 13 Sep 2018 19:23

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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BGS file
Attachment: attach_2750_3326_ray_tandem.bgs     171

posted: 13 Sep 2018 19:24

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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SK81 file.
Attachment: attach_2751_3326_ray_tandem.sk81     201

posted: 13 Sep 2018 21:34

from:

r_wilton
 
Bangor - United Kingdom

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Many thanks Martin, your a star. 72"/48" was written on the packet so i assumed that was the radii. Sorry i got that wrong in my original post.

Excuse my ignorance, but what are the BGS and SK81 file for?
Last edited on 13 Sep 2018 21:39 by r_wilton
posted: 13 Sep 2018 21:50

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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r_wilton wrote:
Excuse my ignorance, but what are the BGS and SK81 file for?
Hi Ray,

So that you (or anyone interested) can load the background scan into Templot as in my screenshots.

You may want to make some adjustments if it doesn't quite match.

cheers,

Martin.

posted: 13 Sep 2018 21:52

from:

r_wilton
 
Bangor - United Kingdom

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Thanks.

Ray.

posted: 25 Aug 2019 10:04

from:

Terry Schroeyens
 
 

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Hi Martin,

I have often wondered what the relationship is between the V-crossing settings and the crossover radius. Marcway label this tandem as 72"/48" (it's on their website) but you clearly disagree with these radii.
72" seems to be the standard Peco radius with an angle of 80 which would be V7.12.
Can you explain how the radius is calculated.

Regards,

Terry

posted: 25 Aug 2019 13:57

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Terry,

I can't speak for Marcway or Peco.

There are 3 different radii which you might mean here:

The Turnout radius is the radius in the rails between the heel of the switch and the end of the turnout curve. For a generic-type V-crossing the turnout curve ends at the FP (fine-point, gauge-intersection). The turnout radius is not usually tangential with the switch front, depending on the design of the switch. For more see: http://templot.com/companion/real_track.php

The Internal Geometric radius is tangential with the switch front and ends at the FP.

The External Geometric radius is tangential with the switch front and at the end of the vee rails. This is also known as the Substitution radius and is the radius normally quoted for commercial model turnouts. It can be significantly different from the other radii where the V-crossing type is not curviform. It has little use or meaning in prototype track design.

In each case above it is important to specify whether the dimension quoted is to the track centre-line or to the outer rail of the curve. Modellers usually mean the track centre-line, but the calculations are made in the outer rail, so it's necessary to remember to subtract half the track gauge from the result.

2_250848_170000000.png2_250848_170000000.png

The Internal Geometric radius to the track centre-line (r) is calculated as:

   R = G/(1-COS(K))

    r =  R - G/2

Where G is the track gauge, and K is the crossing angle.

Templot uses RAM unit crossing angles, so K can be calculated as K = ARCTAN(1/N)

where N is the unit crossing angle.

Remember that this is not the actual radius in the turnout, except in the case of a gaunt turnout with the gaunt offset set to zero.

Bear in mind that prototype pointwork design is far more concerned with lead lengths and crossing angles than with radius. That's because lengths and angles are easily measured on the ground, measuring radius is much trickier (involving measuring versines).

Whereas modellers tend to be pre-occupied with radius because we have to fit layouts in such tight spaces.

The lead length L can be calculated as:

  L = (R-G)/N

cheers,

Martin.

posted: 20 Sep 2019 12:04

from:

RedgateModels
 
Mansfield - United Kingdom

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Martin Wynne wrote:
and strangely narrow spindly timbering.

Marcway have a bit of a thing about using plain track width sleepers on turnouts. Last time I ordered from them they were astounded that I wanted wider strip to build mine, even though they sell two widths.
Like the other model shops in the People's Republic of South Yorkshire they are a bit "quirky" in their customer approach ;)
Last edited on 20 Sep 2019 12:04 by RedgateModels
posted: 20 Sep 2019 19:42

from:

Rob Manchester
 
Manchester - United Kingdom

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Try asking Marcway for the 3rd timber width that is sometimes required on crossing work - equates to the 14" timbers used on the prototype.

Rob


posted: 21 Sep 2019 08:23

from:

Hayfield
 
United Kingdom

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RedgateModels wrote:
Martin Wynne wrote:
and strangely narrow spindly timbering.

Marcway have a bit of a thing about using plain track width sleepers on turnouts. Last time I ordered from them they were astounded that I wanted wider strip to build mine, even though they sell two widths.
Like the other model shops in the People's Republic of South Yorkshire they are a bit "quirky" in their customer approach ;)
May be they follow Peco's lead in this matter making them compatible visually.  Another guess may be that they have jigs set up for the thinner strip.  
Let's face it most of us have grown up using RTR products not knowing any better about their design inaccuracies 



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