Tunnelprofile - dimensions?

KjellAn · Post by **KjellAn** » Sat Jul 09, 2011 8:16 pm

I started construction on my Garden Railway. There will be one tunnel on the layout, and it will partly be in a curve with 30" radius (SM32 SL605) track.

What distance from the center of the track do you think will be adequately to give space for the longest coatches and engines?
And what height from top of the track up to the tunnelceiling?

laalratty · Post by **laalratty** » Sat Jul 09, 2011 8:39 pm

I have a tunnel on a curve, and you should leave as much space as possible. For height, probably at least 20cm from floor to roof (remember the height of the track will reduce this effectively) and then allow at least 8cm from the side to allow for coach end overthrow. This I think is greater then my tunnel which is only on a 4 foot radius curve.

MDLR · Post by **MDLR** » Sat Jul 09, 2011 9:52 pm

Depending on where your tunnel is, I'd suggest (if the line's going round a curve) making the tunnel as wide as possible internally - much wider than you really need - and only having the tunnel portals "built to fit" the locos and stock you're intending to use - nobody will notice the difference!

I have seen a tunnel put under a raised area of decking built in panels, with the panel(s) over the tunnel arranged to lift out, which makes it very much easier to sort any catastrophes in the tunnel!

Narrow Minded · Post by **Narrow Minded** » Sun Jul 10, 2011 12:02 am

I agree with all of the above, but would add my tenpennorth by saying that the amount of "overthrow" (end and middle) will vay massively between different items of rolling stock - depending on wheel arrangement / bogie placement as well as physical length.

The safest bet would be a practical measurement.
Get a curve of the same radius set up, get your largest pieces of rolling stock and run them over the curve.
Have a pencil held vetically at the corners (and centre of long bogie stock) to actually "trace" the path then measure it.

Then take your tallest item of stock, place it on a piece of track and measure it. You'll have to add the extra height caused by whatever method of ballasting you intend to use and add a comfortable clearance.

Alternatively, you could do as I did - use resin cast tunnel mouths, fit 'em then file the portals to fit your stock

:lol:
(REMEMBER resin dust is nasty, but you'll be outdoors!

)

KjellAn · Post by **KjellAn** » Wed Nov 02, 2011 9:01 pm

Thank you all for the good advices.

Here are some pictures from the construction of the tunnel on my garden railway.

The line has a radius of 75cm (2,5 ft). Here is the track temporary in place before construction.

Here is the base of the tunnel. It is wide enough too give space inside the tunnel - about 30cm wide and 26cm high.

A step further. It takes some time to give the concrete time to harden before next step.
Iron grid is used both in the base, the walls and in the top (ceiling).

Here are the tunnel covered with earth, and hopefully the strawberryplants will recover the slope next summer.
The little hut for the "smurfs" stands on a hatch on top of the tunnel witch can give access to the tunnel in case off derailment.

I have testet different engines and coaches to see how wide the tunnelopenings should be, and I have 11cm from trackcenter to the sides.
The tunnelopening are 21cm high. This give space for a beercan loaded on one of my flatcars.

Here are some pictures of my RH Billy when it run through the tunnel.

The northern tunnelopening.

The southern tunnelopening.

Narrow Minded · Post by **Narrow Minded** » Wed Nov 02, 2011 9:04 pm

That looks to be very well engineered

TheChestnutLine · Post by **TheChestnutLine** » Wed Nov 02, 2011 10:10 pm

That's brilliant! Great work

Sir haydn · Post by **Sir haydn** » Wed Nov 02, 2011 10:16 pm

excellent work!

Dr. Bond of the DVLR · Post by **Dr. Bond of the DVLR** » Thu Nov 03, 2011 5:38 pm

I really like the fact that the railway carve through a real hill rather than a tunnel made and then encased in a hill!

invicta280 · Post by **invicta280** » Thu Nov 03, 2011 7:52 pm

Impressive tunnel !

Sir Clothem Cap · Post by **Sir Clothem Cap** » Thu Nov 03, 2011 10:48 pm

Well done it looks great.

KjellAn · Post by **KjellAn** » Thu Nov 03, 2011 11:15 pm

Mr. Bond of the DVLR:60699 wrote:I really like the fact that the railway carve through a real hill rather than a tunnel made and then encased in a hill!

Actually it took a lot of hard work to dig out the pathway for the line.

But now when the soil is back upon the tunnelroof, it is time for the small strawberryplants to take back the landscape and the natural slope as it was before the excavation.

IrishPeter · Post by **IrishPeter** » Fri Nov 04, 2011 2:49 am

My line carefully avoids tunnels because:

1. Ireland had very few tunnels

2. Any attempt to use a pickaxe will be rewarded with a bull's eye contact with a well hidden granite boulder. The resultant raw, rasping pain exiting out of one's elbow ususally leaves one rolling on the ground gasping for breath..

Your tunnel looks good as is part of the landscape, which is where most model railway tunnels fall down.

Peter in AZ

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