seeking tandem turnout template

[jon price]

Is anyone able and willing to produce for me a template for a printed tandem turnout? The type I would require would be based on a Right Hand A5 turnout, with the center track emerging equidistant from the straight and diverging tracks.

[Martin Wynne]

Hi Jon,

Templot can do that (it's free). For a single-sided tandem you need to start with the 2nd turnout, which in this case needs to be an A-7:

jon_tandem1.png

jon_tandem2.png

The timbering will need some final adjustments.

cheers,

Martin.

[jon price]

Thanks Martin. This looks perfect. BUT I am fairly likely to take weeks to learn how to use the program and still get it wrong. I'll give it a go, but if it does take too long I will be back.
EDIT I just downloaded Templot and nope, this is not for me. So back to the original question (which may well involve templot, but with someone who can handle these things being in control)

[Paul Willis]

Thanks Martin. This looks perfect. BUT I am fairly likely to take weeks to learn how to use the program and still get it wrong. I'll give it a go, but if it does take too long I will be back.
EDIT I just downloaded Templot and nope, this is not for me. So back to the original question (which may well involve templot, but with someone who can handle these things being in control)

Hi Jon,

Hopefully this works for you. Martin's instructions meant that I could do it in five minutes flat - and most of that time was remembering which menus to find things in...

Two points (forgive the pune, or play on words):

- I haven't done any "timber shoving" to resolve the sleepering conflicts. I'm sure that you can play with that on the printed version, to see what suits, and looks good as your prototype.

- I've left the approach/exit roads quite short, and I don't know where you would go from here.

I'll save the Templot file, and happily post it up here if anyone else wants to have a play in a more accurate manner...

HTH
Flymo

a5_tandem_in_templot.pdf

[jon price]

Thanks guys, this is brilliant. Thanks Martin for posting the instructions. Thanks Flymo for creating the template.

I printed it out and found it is slightly too large (it comes out at scale 5' gauge, or 20mm). Now all I need to work out is how to print it to P4! Unless there are special instructions specifically relating to Templot templates I should be able to do the scaling calculation and then I will get a print shop to run it off. If this is a specific problem of my printer then the print shop should be able to print out accurately without scaling as well.

Then it is just a case of building the turnout. I suspect that this will be straightforward if I approach it logically as an extension of the step by step instructions which are provided in Exactoscale kits.

[PeteT]

Your printer menu often has a scale option ('fit' etc) which may need turning off to let the PDF determine the size of A4 (and lack of border) for it. That would normally make it too small rather tha big though.

Alternatively, there should also be a %age size option - so you could have a play with that option until it comes out right.

I was wondering how accurately the 1 in 7.4 crossing angle needs forming, but I guess with an accurately printed triangle to build it to match the only slight complication is the lack of standard jig for it.

[Martin Wynne]

I printed it out and found it is slightly too large (it comes out at scale 5' gauge, or 20mm)

Hi Jon,

When you print it from your PDF reader, it is very important to make these settings in the print dialog (which are not the default in most readers):

jon_tandem3.png

However, now that you have installed Templot, Paul could post the Templot .box file instead of a PDF. You could then load it into Templot and print it directly from Templot (print-now! > print all background templates (track plan) now! menu item).

(This has the advantage that you could if necessary calibrate your printer via Templot for the greatest printed accuracy.)

Trim the printed sheets to the red lines to fit them together.

cheers,

Martin.

[jon price]

Re the non standard Vs I would use the fold and file approach explained elsewhere which seems to have pretty good results.

[Paul Willis]

However, now that you have installed Templot, Paul could post the Templot .box file instead of a PDF. You could then load it into Templot and print it directly from Templot (print-now! > print all background templates (track plan) now! menu item).

(This has the advantage that you could if necessary calibrate your printer via Templot for the greatest printed accuracy.)

Trim the printed sheets to the red lines to fit them together.

Martin,

Thanks for the expert advice, as usual...

Here's the .box file.

Cheers
Flymo

A5 tandem for Jon Price.box

[dal-t]

Martin,

This may be a question better put in Templot Club than here (but I'm logged in now so I'll ask it anyway!) - how did you work out the second turnout had to be an A-7? Is it one of those things you just have to know, or am I missing something obvious (I usually do)?

[Martin Wynne]

This may be a question better put in Templot Club than here (but I'm logged in now so I'll ask it anyway!) - how did you work out the second turnout had to be an A-7? Is it one of those things you just have to know, or am I missing something obvious (I usually do)?

Hi David,

Short answer:

1. guess.
2. try it.
3. if result no good click Cancel.
4. total time, 10 seconds max. Try again.

Rambling answer:

Not being a Templot user, Jon was coming at it a bit back to front. Normally for a single-sided tandem you would have the 2nd turnout already in place as part of your track plan, so its size would be a given. Templot then creates the first turnout in front of it, diverging into clear space. The angle of that turns out to be whatever it is, and if necessary can be adjusted (within limits), before completing the tandem.

The make tandem tool in Templot makes a few assumptions. One of those is that both switches have the same deflection angle, so in this case if the first turnout was to be an A-5, the second one also needs an "A" switch. Another one is that Templot doesn't use an actual "A" switch for the generated first turnout -- instead it uses a customized 1:24 switch. This saves a lot of space and simplifies the geometry. Also Templot gives the first turnout a curviform V-crossing for the same reason. So it's not really an A-5, but no doubt it is close enough to one to meet Jon's requirement.

(If those assumptions are not wanted the alternative is to create the tandem entirely yourself using partial templates. Tandems are not simple.)

In this case I tried starting with an A-7 with regular-type V-crossing. The created first turnout had a crossing angle of 1:4.92 . Jon wanted 1:5, so I used the option in Templot to change it to a 1:5 before continuing. The resulting 3rd crossing then had a angle of 1:7.47 , near enough to a standard 1:7.5 crossing for all practical purposes.

Had I started with an A-7 with a curviform crossing, the result would have been 1:4.98, even closer to 1:5, and after changing to that the resulting 3rd crossing would have been 1:7.25 . Only Jon knows which of these two options best matches his need. If the middle road is to be part of loop or lay-by siding or similar, the regular crossing is needed. If the tandem is in a goods yard, a curviform crossing is probably a better fit.

p.s. Jon, you didn't say so, but I assumed you wanted a straight tandem? Templot works just as easily for a curved one, which may fit your site better. With an A-5 size for the first turnout you wouldn't want to curve it much in a similar direction, but it could easily be curved in the opposite direction (contraflexure, or negative curving), thus easing the rather sharp 1:5 turnout radius. Here's what that might look like:

jon_tandem4.png

which at first sight looks like a double-sided tandem -- but in fact the upper road is the main road (on a constant curve), with both turnouts diverging from it to the right, making a single-sided tandem.

Creating this is just the same in Templot as creating a straight one, just start with curved track instead of straight. On any radius you choose.

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

cheers,

Martin.

[CornCrake]

I believe it is also recommended to calibrate the printer using >; output > calibrate printer.

[jon price]

i like the idea that I came to this back to front. Actually I had a track plan with a straight though and a diverging A5, but the real world track plan had a tandem at this point. The A5 curve was fixed as was the straight. I originally discounted the tandem as too problematic but then decided it was worth trying it out. Consequently the middle road had to be fitted in. Maybe not track planning by the book, but maybe closer to the actual practice of my prototype.

[Martin Wynne]

I like the idea that I came to this back to front. Actually I had a track plan with a straight though and a diverging A5, but the real world track plan had a tandem at this point. The A5 curve was fixed as was the straight.

Hi Jon,

If the A-5 is already on a fixed alignment, I'm afraid this tandem won't fit. If you have an existing A-5 P4 template it is likely to have a generic V-crossing and straight exit. To fit an extra road into the middle of such a turnout will need a custom formation in Templot. If you can post your track plan, I will have a go at creating what you need.

cheers,

Martin.

[jon price]

hi Martin

The "plan" is just a standard Exactoscale A5 template fitted into a curved track. The middle road is just going to have to fit whatever comes out. The real track plan is not very accurate and no OS exists as far as I can see.

[Martin Wynne]

Hi Jon,

We seem to be at cross-purposes. Are you saying that the first turnout in the tandem has to be an exact match to an Exactoscale A-5 turnout? In which case the second turnout will need to be something like a B-9 or B-10 to get an even spread of exit tracks (if an even spread is needed?).

Or does Paul's tandem turnout fit the bill reasonably well? The curviform V-crossing means the first turnout will be diverging more rapidly than the Exactoscale A-5, although at an easier radius.

cheers,

Martin.

[jon price]

Hi Martin

The diverging track and the straight through are exactly as the Exactoscale A5. The centre track is equidistant between the two tracks of the A5 at it clears the turnout.

[Martin Wynne]

The diverging track and the straight through are exactly as the Exactoscale A5. The centre track is equidistant between the two tracks of the A5 at it clears the turnout.

Hi Jon,

Unfortunately that produces a sub-optimal tandem. Equidistant straight exits require the two V-crossings to be exactly opposite one another, so that they check each other in the manner of a symmetrical 3-throw turnout. The crossing angle needs to be 1:10.1 (RAM angles):

jon_tandem5.png

This requires the shortest possible switch, and even then there is barely enough distance between the two switches to enable the second one to be opened behind the first. I used a 9ft switch, and there is a short bit of tight 37" radius beyond it.

If you are modelling a pre-grouping layout, it is of course possible that the original was a 3-throw rather than a tandem. Which would ease the geometry, but make it a lot more difficult to build.

If you can tolerate the new exit track being closer to the A-5 exit than to the main road, it produces a more satisfactory tandem with the second turnout as an A-8:

jon_tandem6.png

cheers,

Martin.

[jon price]

Martin
I think your last option with the exit track being closer to the A-5 exit than to the main road, and with the second turnout as an A-8 looks fine for my purposes.