Up and down lines connected to suburban line

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minipix
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Up and down lines connected to suburban line

Postby minipix » Mon Dec 03, 2018 6:40 pm

Here's a conundrum I've been pondering. Say I have two main lines, up (green) and down (red), with a suburban line (yellow) running parallel. The main lines are of course one-way, and for the sake of argument using the UK convention of driving on the left. The suburban line is two-way, so traffic can be going in either direction.

updownsub1.PNG


What I want to achieve is that the suburban line can reach both up and down lines easily, with minimal obstruction to normal main line traffic, and using 'realistic' point configurations. I'm aware that historically track designers have tried to avoid facing points, for example. Would the below be a satisfactory approach?

updownsub2.PNG


In some ways it seems rather simplistic, and does use facing points. Are there any prototypes in the real world for this sort of track configuration? How could it be improved? I guess I could use double slips to combine a point and a crossing, but were those used on busy main lines? Feel free to suggest your own solutions!!
Frontington & Backwoods Railway: https://www.matthewdawkins.co.uk/catego ... way-build/
LocoSound - sound effects for DC model railways: https://mafu-d.github.io/loco-sound

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Bufferstop
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Re: Up and down lines connected to suburban line

Postby Bufferstop » Mon Dec 03, 2018 7:47 pm

You've hit upon one of the requirements that could only sensibly met by facing points, the most frequent is in the entrance to multiplatform termini. The main lines would probably have a speed limit and the facing points would be fitted with facing point locks ( a sliding bolt with two holes on the tiebar) interlocked to prevent the signals being pulled off until the fpl were engaged. The Midland railway who were paranoid about facing points would have probably installed a loop on the other side which then crossed both lines. :)
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minipix
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Re: Up and down lines connected to suburban line

Postby minipix » Tue Dec 04, 2018 2:08 pm

Thanks Bufferstop. Shame there isn't an easy way of avoiding facing points, but I guess in practice it's less of an issue for us modellers?

I still wasn't entirely satisfied though, so I've put together a few other potential solutions.

screenshot-www.traxeditor.com-2018.12.04-14-00-28.png

This is the original design I came up with for connecting the up and down lines to the suburban line. It's like a ladder.

Pros: It's really simple. You can see what's going on, so you shouldn't ever get confused with it. It's just 8 points, so it'll be relatively cheap. And it'll be easy to connect together, both physically and electrically.

Cons: It's quite long, so you'd need a good amount of space for this layout. But the most glaring problem is that it gives every track direct access to every other track, which isn't a good idea! The risk involved here is massive, and you could very easily end up with trains running the wrong way along one-way tracks through a little human-error. I'm also not a fan of the S-bends it makes going through all those points.




screenshot-www.traxeditor.com-2018.12.04-14-01-11.png

My second plan introduces the idea of crossovers, so that the up and down lines are more separated.

(Sorry that some of these pieces are blue, for some reason TraxEditor doesn't like selecting crossovers once they've been placed so I can't change their colour. Use your imagination!)

Pros: Pretty easy to see what's going on, and vastly reduces the chances of an up train heading along the down line, and vice versa. Pretty compact, too.

Cons: There are a couple of 'loops' here, which are slight cause for concern; for example, a train could go from the up line to the suburban line and straight back onto the down line, which is something I'd want to avoid really.




screenshot-www.traxeditor.com-2018.12.04-14-01-28.png

The third iteration is basically two overlaid crossovers, but positioned such that there are no loops.

Pros: Really compact left-to-right, although slightly fatter top to bottom. Since there are no loops, there is no chance of trains ending up on the wrong track. And the diamond shape in the middle is pretty.

Cons: Visually, this looks complex, and I imagine it would be easy for a signalman to get confused with so much intersecting track. I can imagine wiring would be a nightmare too. It's also more costly, with 6 crossovers.




screenshot-www.traxeditor.com-2018.12.04-14-01-39.png

My final attempt (for now) is a variation on the second plan, but with the connections between the down and suburban lines swapped round. This is my current favourite.

Pros: It's really clear visually, so there should be fewer mistakes, and it retains the ease of build. More importantly, though, it's removed all but one of the loops, so that trains from the up and down lines can't end up on each other's tracks.

Cons: There is a loop from the suburban line onto the down line and back onto the suburban line, but at the end of the day this is a minimal risk.


Are there any other configurations you'd suggest? Any other pitfalls to avoid?
Frontington & Backwoods Railway: https://www.matthewdawkins.co.uk/catego ... way-build/
LocoSound - sound effects for DC model railways: https://mafu-d.github.io/loco-sound

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Bufferstop
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Re: Up and down lines connected to suburban line

Postby Bufferstop » Tue Dec 04, 2018 4:59 pm

Your original has the benefit of simplicity. Modern signalling would probably use two crossovers in each direction but would involve a snaking crossing from crossing between top and bottom lines, but your plan using a single slip for each crossing would work as long as you didn't want two way working on your main lines. I think it's probably the ability for two way working that sees the elimination of crossings in modern signalling. I got involved in planning the rerouting of telephone lines away from the electrification of the WCML in the 60s. Once the railway guys found out my interest in the railway I got very detailed explanations of what they were doing and why. At one point they needed the ground clearing for four plain crossovers in place of a scissor crossing. How come I asked expecting some complex explanation, "stringing the wires for a scissor crossing is too much like hard work" was the answer "and simple turnouts are a darned sight cheaper than a complicated crossing too.
Growing old, can't avoid it. Growing up, forget it!
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45655
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Re: Up and down lines connected to suburban line

Postby 45655 » Fri Dec 07, 2018 2:40 am

I think a "single track suburban" line is a bit of an oxymoron. Suburban lines are by their very nature high frequency, which cannot be achieved with single track.


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