Double track tunnel

[Tomathee]

Hi guys, I've created a bit of a problem for myself that I should have seen coming really, wondering if there are any options I haven't so far considered.

I laid my track many many moons ago with the intention of landscaping later, including a tunnel. A bit more recently though still many moons ago I bought a tunnel portal on impulse that I thought would fit the bill. Fast forward to the present day and, if you haven't already guessed, said tunnel portal isn't wide enough for my longer stock to get around the curve it is placed on. The issue is a combination of it being a double track that is slightly wider than set track to allow wider curves, and the fact it is on a curve to begin with. Once I calmed myself down, the options I've so far worked through:

Tried the tunnel on different areas of the curve, some of which do come back down to set track width before ending up at streamline width towards the straight. Still not wide enough until a point far enough along that it would cover too much of the layout, so what I have is unusable really. I thought about cutting it open further but I'm not sure if I can make the edge look the part. I made a Scalescenes single track portal that included a decent enough solution for the edges but I don't think it would work here as it's paper onto plastic.

Considered relaying the track - I think back to all the effort it took getting the curves correct, cork, wiring, canting, the landscaping so far and I don't think it's the outcome I want. I also think I was close to the edge on the tracks being too close for collisions when laying it, so not much space to reclaim anyway. 

Measured the tunnel portal I have (PECO) to look elsewhere, looked at other tunnel products - Metcalfe, Scalescenes, all of which are the same or smaller width. Following that I think my remaining options are:

Found a Noch tunnel portal which may suit as the sides are more vertical below a curved top, though I can't confirm the size online and it's £15 to take the gamble.

Try a bridge type solution over the tunnel exit to cover essentially an undecorated hole in the landscape

Attempt a scratchbuild Scalescenes/other, though creativity isn't my strong point neither is cutting a smooth curve...

 

Looking for any suggestions you helpful people may have

 

Thanks

Tom

[AndrueC]

What I did at one point on my layout (N Scale) was fit two single portals together. I had to shave the sides down on one of them but it worked This was a slightly different scenario (not enough space to fit the wider double).

[Wheatley]

I was going to suggest the same  as Andrue, some examples:

 

Chilcompton

 

Woodhead

 

And if you want something a bit different, Thurgoland had two tunnels built a hundred years apart, a new one being built for the MSW  electrification:

https://www.derelictplaces.co.uk/threads/thurgoland-tunnels-near-penistone-south-yorkshire-november-2018.36741/

 

Or you could just buy an O-gauge portal, although that probably wouldn't hide  anything:

 

Marsh Lane Tunnel

 

 

 

 

[Tomathee]

Thank you both, I've had a look and with the worst case, however unlikely, of longest coaches passing there's less than half a cm to put something in the gap. I had ten minutes at lunch to look at a possible solution of raising the portal a bit, the area causing the obstruction is on the top left/right corner of the opening (poor description) and by raising it, it seems close to working. I need a bit more time to put something solid for backing and get some more scrap wood and card for it to sit on so I can trial and error it to see if it's a legitimate fix, I'll report back. 

[cypherman]

Hi,

My suggestion is similar but using a Hornby brick archway cut in 2 and glued together or cutting down a Hornby Brick viaduct to 2 tracks. They can be bought quite cheap so that you can play around with them to your hearts content.

Edited October 6, 2022 by cypherman

[Pete the Elaner]

I had a similar problem to you. I felt commercially available tunnel mouths were all too narrow & not tall enough. I was modelling a particular location so wanted them as accurate as possible. My "six foot" is also smaller than streamline, which I felt looked too big.

 

My solution was to laser cut them to exactly what I wanted. A friend assured me he could do the artwork for me & he did a great job. I was & still am nowhere near familiar enough with the software required to achieve this.

 

I like the sound of using an O gauge portal as mentioned earlier. Either get a stone one, or re-face it with OO brick card.

[ITG]

5 hours ago, Tomathee said:

The issue is a combination of it being a double track that is slightly wider than set track to allow wider curves,

The following doesn’t really help your dilemma, unless maybe you do decide to relay the track, but if I read this comment correctly, why is your spacing wider than set track, but using wider curves? IIRC set track is approx 67cm track centre spacing, which surely allows all stock (unless I guess if you’re using 1st radius?). Streamline spacing is 50mm. Maybe irrelevant but just trying to picture your dilemma.

[ianLMS]

For my 3 road tunnel, i purchased a Skytrex resin stone arch and cut it down the middle of the mouth. I then inserted a section of similar patterned resin to fill the gap so it stretched over the 3 tracks. I had photos in my layout page but got lost when the website went down. 

 

https://skytrex.com/collections/bridges-arches-tunnels/products/4-017-wide-stone-arch-separate-parapet-unpainted

Edited October 6, 2022 by ianLMS

[Harlequin]

5 hours ago, Tomathee said:

double track that is slightly wider than set track to allow wider curves

 

Wouldn't wider curves allow closer spacing?

 

I don't understand why spacing wider that Setrack would ever be needed for clearance reasons...

 

Can you explain more? What radii are the curves (roughly)?

 

[The Johnster]

Your actual track spacings and curve radii matter little, though I understand why folk are asking about it; it works for you and your decision is that it is down now and the tunnel mouth must fit the track not the other way around, and that's that; fair enough, we'll proceed on that basis.  RTP will not cut the mustard as you've already found out, so you'll prolly have to scratch build a tunnel mouth, but don't panic, it's not hard.

 

I would be very wary of taking a punt on the Noch, which will be 3.5mm/foot scale and, even allowing for the larger loading gauge of European stock, will be cutting things fine in a situation where the core of the problem is that things are already cut fine.  A US produced RTP H0 tunnel mouth may be a possible solution, though. 

 

Or you could have a go at making one yourself.  Use a short, perhaps 6", length of plastic pipe (determine the diameter by taking a stick out with you when you source this, cut to a size sufficient for width and headroom clearance.  You can probably skipraid the peice, just look around on waste tips or for anywhere building or renovation work is being done in your local area, or you might have something to hand.  It'll be out of sight when you've finished so appearance is irrelevant!).  Cut to form with a segment missing from the bottom to provide an impression that the trains are vanishing into a long dark scary hole, and cut the tunnel mouth out of stiff card, along with any wing walls that you need using the pipe as a marker for the cut, and face them in brick or stone sheet or paper.  The actual mouth arch will need facing separately in arch-pattern brick or stone with a keystone/brick at the top.  Or a skim-coat of plaster over the card, and a selection of different sized and shaped loops of wire impressed into it before it dries to represent cut stone, then of course painted and weathered; don't forget the soot marks that survive even now on many tunnel mouths 60 years after the end of steam, and are only visible on the uphill side if there are gradients!  To gild the lily, brickline the internal surface of the plastic pipe bore.

 

Mention of a 3-road tunnel has made me realise that I cannot think of any prototype example of such a thing anywhere, and would now be interested to hear of any for no other reason than my own inquisitivness!  I am not an expert in tunnelling technology or engineering, but I do know that it is expensive, difficult, and dangerous, so I would assume that 2-road tunnels were/are considered the norm, as 2-lane road tunnels seem to be, and that if more roads are required it is cheaper, easier, and less dangerous to build extra tunnels. 

 

To give an impression of just how problematic they can be, the Rhymney Railway was effectively bankrupted by one they built beneath Cefn Onn ridge south of Caerphilly in order to have an independent route to Cardiff Docks; going bankrupt at a time when coal traffic was increasing exponentially is a sort of achievement, and was not the result of mismanagment or poor planning, but a massive budget overrun caused by a spring of groundwater that was struck, killing a number of navvies in the resultant collapse.  3 of their bodies could not be recovered, and so they are still in there, sealed in, leading to the almost obligatory ghost stories as their unshriven and unquiet spirits seek peace in their Long Beds...

 

The Rhymney, a well-run and extremely profitable concern in normal circumstances, was then effectively bought out by the LNWR, which acquired a majority shareholding and access to Cardiff Docks from the Abergavenny-Merthyr line at Rhymney Bridge, but elected to let the Rhymney company continue to operate the railway and retain control over production of locomotives and stock.  The LNW kept a loco at Cardiff East Dock shed, though, to shunt it's Tyndall Street goods depot, a Ramsbottom saddle tank suitably named 'Marchioness of Bute'; the Bute family owned Cardiff Docks. 

[eastglosmog]

Depending on the function of the tunnel in your layout, I would suggest opening it out into a deep cutting (there are several prototypical examples of this happening) and spanning it with a girder bridge.

[Hal Nail]

How about bodging two together to form something like this:

 

https://www.geograph.org.uk/photo/5114235

[Edwin_m]

3 hours ago, The Johnster said:

Mention of a 3-road tunnel has made me realise that I cannot think of any prototype example of such a thing anywhere, and would now be interested to hear of any for no other reason than my own inquisitivness!  I am not an expert in tunnelling technology or engineering, but I do know that it is expensive, difficult, and dangerous, so I would assume that 2-road tunnels were/are considered the norm, as 2-lane road tunnels seem to be, and that if more roads are required it is cheaper, easier, and less dangerous to build extra tunnels.  

I think the reason is that the arch of the tunnel has to be circular (or nearly so) to hold up the earth above it, and usually the curve continues down to trackbed level.  One or two tracks fit quite well into a bit more than a semi-circle, but with three or more the crown of the tunnel would be a long way above the top of the trains, so a lot of earth would be dug out unnecessarily.  Therefore, as you say, anything more than two tracks will generally be a combination of single and double track bores.  

 

There are a few exceptions, but I would hazard a guess that these are cut and cover tunnels, where the earth above the track has to be dug out anyway as part of the construction.  The Marsh Lane tunnel posted above looks like an example of this.  

[Wheatley]

30 minutes ago, Edwin_m said:

 The Marsh Lane tunnel posted above looks like an example of this.  

I wondered that, but it was actually dug. It was part of a longer tunnel which was later opened out into a cutting apparently. 

 

https://en.wikipedia.org/wiki/Richmond_Hill_Tunnel

 

I think it was this one that our Area Ops Manager managed to get removed from the Sectional Appendix as a tunnel and reclassified as a bridge for operating purposes, on the grounds that it was never actually dark inside except when it was also dark outside. Therefore none of the restrictions on what could and could not be done in a tunnel needed to apply. 

[Steamport Southport]

6 minutes ago, Wheatley said:

I wondered that, but it was actually dug. It was part of a longer tunnel which was later opened out into a cutting apparently. 

 

https://en.wikipedia.org/wiki/Richmond_Hill_Tunnel

 

I think it was this one that our Area Ops Manager managed to get removed from the Sectional Appendix as a tunnel and reclassified as a bridge for operating purposes, on the grounds that it was never actually dark inside except when it was also dark outside. Therefore none of the restrictions on what could and could not be done in a tunnel needed to apply. 

 

It's like the approach to Liverpool Lime Street.

 

Many seem like bridges, but they still have the tunnel names rather than numbers like bridges have.

 

 

Jason

[Steamport Southport]

4 hours ago, The Johnster said:

Mention of a 3-road tunnel has made me realise that I cannot think of any prototype example of such a thing anywhere, and would now be interested to hear of any for no other reason than my own inquisitivness!  I am not an expert in tunnelling technology or engineering, but I do know that it is expensive, difficult, and dangerous, so I would assume that 2-road tunnels were/are considered the norm, as 2-lane road tunnels seem to be, and that if more roads are required it is cheaper, easier, and less dangerous to build extra tunnels. 

 

 

 

Four road tunnel but with three bores. Touched upon above but omitted the "new" tunnel.

 

 

 

 

https://s10probus.co.uk/the-lost-woodhead-tunnelstephen-gay-4-feb-19/

 

 

 

Jason

 

[ianLMS]

5 hours ago, The Johnster said:

Mention of a 3-road tunnel has made me realise that I cannot think of any prototype example of such a thing anywhere, and would now be interested to hear of any for no other reason than my own inquisitivness!  I am not an expert in tunnelling technology or engineering, but I do know that it is expensive, difficult, and dangerous, so I would assume that 2-road tunnels were/are considered the norm, as 2-lane road tunnels seem to be, and that if more roads are required it is cheaper, easier, and less dangerous to build extra tunnels

 

I agree that i doubt there is a 3 track tunnel in the real world. It was more a case of "needs must". I could and probably should have placed a support between track 2 and 3 to seperate them but wasnt too concerned at the time. If i re-build in the future, its something i will fix. It was more a case of giving an option to the OP that its easy to extend the width of a tunnel mouth if you need to widen the span for any reason. Whether its right or not is a different story!

[DCB]

The initial problem is not planning the layout to suit your stock.  52 mm streamline spacing works for most stock at 2ft radius, a GW King on the inside and a Mk3 coach on the outside is about worst case scenario so you probably need 55mm for 3rd radius and around 60mm for 2nd. 

But track is laid and Obviously there is no room for anything between the tracks so a double portal is out of the question.  That would be where a single tunnel was bored and found to be inadequate.  An 0 gauge or bigger portal reclad with 00 size size bricks or stones sounds good   Lots of full size tunnels have huge portals and rapidly contract to a much smaller diameter, Box  on the GW main line is a spectacular example.

I have and would use a Peco plate girder bridge on a couple of vertical sided abutments with  retaining wall behind it.  It can hold up a road, shop backs, (In cities)   anything, as in poor ground tunnels are sometimes very shallow or cut and cover to hide the tracks from the local landed gentry (Kemble)   A wide rectangular hole is the optimum, keep it dark inside, spray everything with rattle can Matt Black, and put a retailing wall round the outside of the curve, I darken mine as well so people can't really see inside the tunnel.   See Pics for a few flat top straight side tunnel mouths.

[The Johnster]

The decorative and oversized portals on tunnels like Box were to re-assure passengers of the safety of passing through them, a significant point in the early day especially as Box had been publicly criticised in the press by ‘Dr’ Dionysius Lardner as not only being too long for safety but also dangerous because it was on a gradient.  It rapidly tapers down to the GW’s broad gauge dimensions and is brick lined for some distance from the portals, but the central section is cut through the bare limestone.  Brunel was interested in the discoveries the French had uncovered in Egypt, and the pyramids’ astronomical alignments, which may be why the sun shines directly through the tunnel when it rises on his birthday!

 

 

[St Enodoc]

On 07/10/2022 at 09:00, Wheatley said:

I wondered that, but it was actually dug. It was part of a longer tunnel which was later opened out into a cutting apparently. 

 

https://en.wikipedia.org/wiki/Richmond_Hill_Tunnel

 

I think it was this one that our Area Ops Manager managed to get removed from the Sectional Appendix as a tunnel and reclassified as a bridge for operating purposes, on the grounds that it was never actually dark inside except when it was also dark outside. Therefore none of the restrictions on what could and could not be done in a tunnel needed to apply. 

Alan P?

[Wheatley]

Phil G

[Tomathee]

Thanks for all the replies, apologies for the delay in replying, I had started on the solution and I'll come back once it's finished.

On 06/10/2022 at 15:17, Pete the Elaner said:

I had a similar problem to you. I felt commercially available tunnel mouths were all too narrow & not tall enough. I was modelling a particular location so wanted them as accurate as possible. My "six foot" is also smaller than streamline, which I felt looked too big.

 

My solution was to laser cut them to exactly what I wanted. A friend assured me he could do the artwork for me & he did a great job. I was & still am nowhere near familiar enough with the software required to achieve this.

 

I like the sound of using an O gauge portal as mentioned earlier. Either get a stone one, or re-face it with OO brick card.

I liked the O gauge idea and if my current idea doesn't pan out will probably go back to it. I think the thing putting me off was the intention is to have hills/fields behind it and I didn't want the tunnel taking up too much of the 'view', which I imagine these would add a decent chunk on to the height.

 

On 06/10/2022 at 17:00, Harlequin said:

 

Wouldn't wider curves allow closer spacing?

 

I don't understand why spacing wider that Setrack would ever be needed for clearance reasons...

 

Can you explain more? What radii are the curves (roughly)?

 

This was poorly explained by me and picked up a couple of times. I've done the track as streamline spaced along straights, and opened up to around setrack on the curves, it's a small layout so in reality the outside loop is a bit wider than 3rd radius and the inside a bit wider than 2nd radius. However at some point in my laying of it there's a stretch of around 6 inches where they are wider than setrack, only a few mm or so, but is obviously where I want this portal to go.

 

On 06/10/2022 at 19:29, eastglosmog said:

Depending on the function of the tunnel in your layout, I would suggest opening it out into a deep cutting (there are several prototypical examples of this happening) and spanning it with a girder bridge.

I would have looked at this but for a couple of reasons. The tunnel is to hide a tight curve at the 'far corner' of the layout which I can't do anything with at ground level. I plan to eventually have hills/fields on top of it all. I've also got the other end of the tunnel which comes from the station, off the loop. I wanted that so I could have the loop that passes the station 'hidden' and have a bit of separation between it and the station.

 

On 06/10/2022 at 20:51, Hal Nail said:

How about bodging two together to form something like this:

 

https://www.geograph.org.uk/photo/5114235

Also a good idea and outside the box, I don't think I'd have ever considered anything like this without a picture though it would be suitable for what I want as a backup option.

 

On 07/10/2022 at 03:50, DCB said:

The initial problem is not planning the layout to suit your stock.  52 mm streamline spacing works for most stock at 2ft radius, a GW King on the inside and a Mk3 coach on the outside is about worst case scenario so you probably need 55mm for 3rd radius and around 60mm for 2nd. 

But track is laid and Obviously there is no room for anything between the tracks so a double portal is out of the question.  That would be where a single tunnel was bored and found to be inadequate.  An 0 gauge or bigger portal reclad with 00 size size bricks or stones sounds good   Lots of full size tunnels have huge portals and rapidly contract to a much smaller diameter, Box  on the GW main line is a spectacular example.

I have and would use a Peco plate girder bridge on a couple of vertical sided abutments with  retaining wall behind it.  It can hold up a road, shop backs, (In cities)   anything, as in poor ground tunnels are sometimes very shallow or cut and cover to hide the tracks from the local landed gentry (Kemble)   A wide rectangular hole is the optimum, keep it dark inside, spray everything with rattle can Matt Black, and put a retailing wall round the outside of the curve, I darken mine as well so people can't really see inside the tunnel.   See Pics for a few flat top straight side tunnel mouths.

This for me was the solution I was looking for but unable to imagine myself. I've seen these girder kits used so many times in the bridges as the name on the tin suggests that I hadn't thought of using it for this. With that initial idea you do find other options such as Scalescenes plate girder bridge and others which give the same "misdirection".

 

So I've gone ahead with the Peco suggestion and am working on it, almost prepared the shapes ready for brick cladding and to paint it all, then I'll report back. Thanks again for all the suggestions and input.

[Tomathee]

As promised I've returned with an update. I'm not sure it's quite finished but it's 'built' and roughly in place, and I wanted it moved on from my workspace so I can have a go at something else over Christmas. Quick disclaimer that it probably falls out of realism on a couple of things. Off the top of my head it's a girder backing onto what will probably be a field type scene, so effectively a couple of feet of ground above the tunnel covering part of the girder section (made more sense in my head).

 

Firstly, it was a Wills kit I used (SS57 Vari-girder Bridge), not sure wheere I got Peco from in the last post. This was to go with a supporting structure that I ended up scratch building with 2mm card and a plasticard sheet I found in the model shop (not sure of the brand).

 

 

 

I think I mentioned at the beginning I had tried a Peco ready made tunnel mouth but I couldn't see a picture, so I've added one below, also for comparison with what I came up with. The clearance wasn't really there, with enough wiggling I could get through without scraping the paintwork but it got a bit silly. I'm using the worst case scenario of the longest stuff I have on both lines which is highly unlikely to ever happen, however playing that against sod's law I wanted to be sure.

 

The girder bridge I assembled as per instructions and there's nothing complicated to add, used a paper template to make it wide enough and double faced as some of the back will be visible. The side walls of this I used as a template on to 2mm card, which I did at double thickness for the wing walls, ahead of mounting the plasticard. I cut one corner of the triangle off and flipped it to make a small buttress(?) at the end of the wall. I also did the vertical sides at the front of the entrance for the girder to sit on/in. I did the same again but shorter, these sit behind and are what the girder sits on. I also did a couple of small pieces for the far end of the wing walls.

 

 

 

Once I had all the card pieces I used them as templates for the plasticard sheet. It was new to me, but found it quite easy to cut and fairly cheap (£3.30 for I think an A4 sheet).

 

Before mounting the plasticard I used Halfords grey rattle can primer on it and the girder section, also the card as some of it might be visible for a while until I finish the scenery and it was no extra trouble. Then mounted the plasticard to the card with Copydex.

 

I then embarked on what felt like an eternity of trying to get the right paint colour and technique for the plasticard. I wrote down various things I tried but it ended up getting so out of hand I can no longer make sense of my notes. I had acrylic, enamel, ready made wash, home made wash, sponges, stippling and more. Luckily I had a spare bit of plasticard that I cut out wrong handed for one of the walls to practice on and wipe down several times. I also watched several youtube clips and ended up with a bit of a mishmash of various things, a few examples of attempts.

 

 

What I ended up on was painting an overall grey coat and spot painting individual stones with 3 or 4 different shades. As fresh it didn't look great but adding a wash I think helped a bit. I did an all over grey wash then some dark grey/black for the mortar. I tried a dust type wash but I'm not sure it looked right.

 

 

In the meantime I also spent some time looking for a colour to do the girder bridge, I ended up using Revell bronze green which I'm fairly happy with.

 

On to assembly, I had a bit of struggle getting the girders to stick to the vertical walls either end as the bottom was the only part with a decent contact surface. So I used some card scraps to make the surrounding area level and used a spare bit of mounted plasitcard to kind of sandwich the girder between front and back. Loctite all purpose seemed to do the job with attaching the plasticard pieces together. I had some smaller plasticard pieces around the sides and so on, these are ok but below a point the plastic will start to curl and add an extra issue of keeping it flat whilst the glue dries. On the inside wall of the vertical sides which was a few mm wide I just used a pencil to mark out the horizontal stones.

 

 

On to a couple of finishing touches. To finish the capping on some of the walls I was able to use some of the junk sprue parts from the girder bridge, primed and painted Tamiya buff, looks a bit bright but didn't have anything else and wanted to not have more grey.

 

Lastly pics of it in it's rough final place. The back of one of the wing walls was part of the experimenting for the paint but I've put it so it's almost hidden, between the tight angle against the backscene, when the scenery is added behind it should soon be forgotten.

 

Earlier on I said it wasn't quite finished. I need to put something for capping on the vertical walls and little buttress at the bottom of the wing walls. I've got card options from other kits but if there's a plastic option I'd rather go with that for consistency. I'm also not sure on the wash, particularly the mortar wash which might be too dark, in two minds on that, and something to tone down the buff capping, which I'll do once I paint and add the other capping in the same colour. Also to continue into the tunnel, I have more plasticard for side walls to go inside some distance but I'll go with a simpler painting method. Maybe need it on the roof as well though it will be invisible from almost every angle. Finally the surrounding scenery, particularly the hill/field to sit on the tunnel and come up to the mouth. Some of the wood and insulation board is in the background that I've made a start on, this will extend to this entrance and slope upwards from the tunnel, with some grass banks either side of the wing walls.

 

If there's any comments or suggestions please put them forward. This was the first time doing a number of things and it was mostly enjoyable, but for my procrastinating and indecision. At some point I'll have to do something like this for the other end so anything to improve on this one or that I can take forward for the next one would be great.

 

Thanks again for the tips which was now a couple of months ago.

[DCB]

Looking good.

I would continue the tunnel inside wall around the outside of the tracks where it can be seen through the entrance, I would spray a lot of pound land rattle can Matt black inside the tunnel and keep as much light out as you can.   On mine I used the shadow cast by the shed lights as a guide and transition from the natural colour to a darker version,  so it looks quite impressive as the train appears and disappears, especially ones with lights.

[simon b]

That looks great, it will blend in fine once the rest of the scenery is around it. 

 

Just in case you decide to do something different at the other end, the Hornby tunnels R8511 or R8512 should be wide enough for what you need. There are matching wing walls available to.