curved tunnels

[spodwo]

Here is a rather in depth article from our Tips page:

http://islsmr.homestead.com/ISLSMR_tips_page28.html

Plenty of photos and tips to make a tunnel of length.

[Anonymous]

I have three tunnels that are a total of 90 feet in length on my RR and have been using them for five years. Two are 35 feet long and about 2-1/2 feet deep, and one is a half circle with 4 foot radius, and about 4-1/2 feet deep. Yes, I disagreed with all the experts and built them anyway, and I have no regrets. But they were a lot of work. I had help the help for a contractor to build them. (We removed 2 dumpsters of dirt from our berm).
My method was to build the walls out of 4" thick concrete block placed like brick. Under the bottom row we put a bed of 3/8" rebar. We then built them to within six inches of the surface of the ground. To make them super strong and last forever, we filled the hollow core of the concrete blocks with mortar mix after we stuffed rebar pieces we cut to size. The sides are very strong!

The top was also made of concrete block which were cut lengthwise like pieces of pie to follow the tunnel on curves. Straight sections required no cutting. The sides of the tunnel were spaced to exactly fit these concrete blocks which are standard size. These were then filled with mortar mix to make them stronger as well (and heavier). They are then fitted onto the top of the tunnel like a jigsaw puzzle leaving only narrow cracks between the blocks. Over this I put pool liner material I had left over from the water feature and there has been no mosture in the tunnels. I cut the rubber pieces in three foot lengths, and the overhang the tunnel top by about six inches on either side. Bark dust about three inches thick completes the tunnels and makes it look like there is no tunnel there at all. They are true tunnels boring through mountains.

To access the tunnel, simply push aside the bark dust, pull off the three foot long rubber liner, and remove the concrete blocks that rest on the top of the tunnel. They are loose (just setting there, so it is pretty easy. The 4-1/2 foot deep tunnel is another matter. For that one, I had to build access holes into the side of the tunnel lining I can climb into and reach anything that goes off the track. I build plywood access hatches to fit over the top of the concrete block walls. The plywood is fiberglasses to protect for the rain we have in Oregon.

The roadbed is made of concrete as well with pressure treated 2x4 spaces in 6" lengths placed crossways (same direction as the roof). I used 10 foot long bender board to create the sides, and filled with mortar mix troweling the surface flat. The LGB flex track is nailed with brads to the 2x4" to keep it in position. Don't forget to use rail clamps, solder the rail joints, or put jumper wires around all the rail joints. Using five foot long flex rail keeps joints to a minimum. Graphite paste is also an option, but I prefer soldering with a torch, pulling the ties back to protect from melting.

Finally, you must protect your tunnels from critters. I built wood tunnel portals, and then wood inserts with handles that exactly fit the opening. They are always in place when I am not operating, and no one has made a home in them yet. I used plywood pieces until the tunnel portals were finished.

If you run with track power as I do, you will need the LGB track cleaning engine to clean the track in the tunnel. This cleans the track in front of the engine, and works very well. I try to never push cars through the tunnel, although I have done it with a video camera. After the winter, I run it through three times before sending in normal engines.

I run only reliable equipment with metal wheels on the layout. I have had to pull off the top of each tunnel once or twice in the last five years, and it takes only about five minutes to reach a train, provided you can find it, but about a half hour to put it back properly. I usually send a loco in after one that is stuck to nudge it, and it usually works. I have also had to climb into the manholes (about 3x3x5 in size) a few times to make repairs or retrieve a car. The rocks on top of the manhole cover can be removed in five minutes and you can climb in. I could put the top on when I am inside, and no one would know I was there. The roadbed and track were installed before any of the tunnel walls were begun as you need shoulder width to be comfortable installing the roadbed and track.

As I said, I broke all the rules, but created a railroad with tunnels that visitors actually wonder where they come out. Good luck on your project, and don't be afraid to try it. But be prepared for some work and some expense if you try my methods.
Bill Derville

[vsmith]

If you are planning a tunnel longer than 4 feet you really should plan on a removable access point 1/2 way in the tunnel. The best way is to plan on installing a removable lid over the tunnel that will allow you to retrive a stopped train. One way to build a curved tunnel is to put down a small slab of concret under the curved track section 3" is enough, thats a bit wider than the overall tunnel. Use concrete pavers 12x12 to build up the sides of the tunnel, mortoring them together, then using 8x16 concrete caps to bridge the span of the tunnel, this also allows for the access point at the 1/2 way point, you just leave the middle 2 paver loose and berm the soil around them.

[bman36]

Terry,
I used curved concrete blocks I found at Home Depot. They are smooth on all sides and about three feet long. They don't interlock but stack nicely. What exactly they were intended for I'm not sure, but they were in the landscaping dept. These ones fit about 20' diameter and they came in different sizes. All the best . Later eh...Brian.

[Anonymous]

Thank you everyone! This cold weather is killig me. Want to go ouside and get started.[:D] Terry

[Anonymous]

TIP for Motar- If mortar won't stick to a trowel turned upside down than you need to add portland cement until it can. Most mortars and or concretes purchased in bags from building centers does not contain enough portland cement. I use one bag portland cement for every three bags of mortar or concrete. Even bags labled professional grade often don't have enough portland cement.

[Anonymous]

I've never tried water putty since mortar is so cheap but it may work. Mortar is available just about everywhere so this is what I use.
OLD DAD

[Anonymous]

QUOTE: Originally posted by OLD DAD

Terry; I have built my curved tunnel by cutting "U" shaped wood forms then stapled wire me***o the inside contour of the forms....with the forms upside down. Then I mixed up a batch of brick morter and troweled this onto the mesh. When this had cured I flipped it over and covered it with a "mountain".
My tunnel is only 4' long so I can reach in over half way from both ends to retrieve a derailed train or clean my track. If your tunnel is over 4' long you will need to provide an access hatch of some type in the areas you can't reach from the tunnel openings.

OLD DAD

What else might one use in the spackling of such a structure? Water putty? Is brick mortar the only viable substance for mountains and rivers?
WHat are you

[Anonymous]

Terry; I have built my curved tunnel by cutting "U" shaped wood forms then stapled wire me***o the inside contour of the forms....with the forms upside down. Then I mixed up a batch of brick morter and troweled this onto the mesh. When this had cured I flipped it over and covered it with a "mountain".
My tunnel is only 4' long so I can reach in over half way from both ends to retrieve a derailed train or clean my track. If your tunnel is over 4' long you will need to provide an access hatch of some type in the areas you can't reach from the tunnel openings.

OLD DAD

[Anonymous]

Yes phantom I do know how to do it but I would warn you that all the so called experts advise you not to do it. a) If your train gets caught in there you may not be able to get it out. b) Animals get in there and like to make it there own this includes snakes etc. And They are hard to get right to start with.

What I did was to get 250 mm (10") ID plastic water pipeof more than the correct length.

Make a template out of cardboard using your track as a guide, and then convert this into a wooden base for your track (Use marine ply if you can afford it) and test that your curve fits correctly and is longer than the tunnel to allow quick release connections. Then get in touch with I think it is Hillman clamps they have joiners that make the whole thing relatively removable.

Then with your origonal template or even using your mounting board as a template cut even "V" shaped sections out of what will be the inside of your curved tunnel and bend the pipe to suit your template easily and steadily untill you have it so that your wooden baseboard will slide into your tunnel. Elevated temperatures will help you in this activity ie a very hot day (40 deg C +) and using a very low temperature oven if you have one big enough; failing this run a gas jet up and down it from time to time very gently.

Now when it all looks pretty good you will probably have to throw it away and start again as you have stuffed it up somewhere or other and it will look a mess and not be as water tight as you would like; your second or third attempt should be pretty good. Coat the whole thing with a thick water tight paint type stuff.

You then use a hand made compass out of pegs and string and draw your curve on the ground where you want it and dig the required trench. Put your entire sction into the trench; get everything working before you fill it in.

In theory 1m (40") is about as long as you should go but if you are adventurous up to 2m (80") could be attempted.

Good luck. Ian; Kawana Island Tropical Railway.

[Anonymous]

I need help. We are putting in our first garden railroad and the plans call for a tunnel on a 8 ft radius.
Does anyone have ideas how to do this?
Thank you
Terry