Raised platform roadbed - Width

[fseider]

All, trying to determine a good working size for a raised platform roadbed. The intent is to use ballast as well. (Because I like the look.) So to help keep the ballast at bay, I'll have some short walls to help contain it, and they will be at about rail height based on what I am thinking.
My real question is - For smaller radius track, such as Piko R3 920mm Radius Curve Track, 36.2"R, how far apart should these walls be so that I don't have any interference with any cars traversing just to play it safe? (In theory, with a short wall I should have no concerns. But humor me please, in case I do make them higher.) I will be using shorter rolling stock and shorter (non live) steam locos in general. What would be the suggested minimum - 6, 7, 8, etc inches, wall to wall? I'd like to keep it as narrow as possible and worry free as well. (And yes, I know I need drain holes, etc. This is just size prototyping for now.)

7 (L) and 6.5 (R) inch side by side

6.5 and 7 inch side by side

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6.5 between walls

6.5 between walls

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7 inches between walls

7 inches between walls

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Thanks in advance!

Fred, PA USA

[philipy]

Hi Fred,

I normally reckon on about 6" centre to centre for double track or sidings etc. That allows most stock to pass without disasters! You are looking at single track I think, so allowing 3" either side from the centre should be OK and if you do that, I'd suggest the ballast retaining wall need be no higher than the top of the rails. If you do go higher you'll need to take account of any low bodyside steps on your stock and whether they might foul the retaining walls on curves. Only you can really work that out given your curves and stock.
Are you planning to glue down the ballast, because if not it probably won't last very long. It's surprising how much gets flung about by birds searching for insects, and how rain displaces it, and frost can shift it too.

[fseider]

Thanks Philip. So 3 1/2 inches from center, both sides, (7 inches total wall to wall separation) sounds like it gives me the safety margin.

"Are you planning to glue down the ballast, because if not it probably won't last very long. It's surprising how much gets flung about by birds searching for insects, and how rain displaces it, and frost can shift it too."

A separate topic that I'll be asking eventually. But since you asked - I keep getting mixed messages on that. If I do glue/cement down the ballast, then the track can't move under varying temperature conditions, and may buckle. If I don't glue, then the track can move due to temperature changes, and to your point of losing ballast (due to birds and squirrel in my case I am sure). I'm surprised this topic is a bit all over the map in my research, so there must be some caveats here that I am not aware of. How can one garden railroader have buckle issues, and yet another not? - There has to be more to this story I am sure.

Thanks

[philipy]

Re track distorting, I'm not sure what your climate does in terms of temperature variation throughout the year? Here in the UK, rails buckling due to temp is not a problem that I've heard of but we don't often get temps below about 7 or 8 degrees C, or above the low 30's for more than a few days a year. You will get rail expansion and contraction of course, but part of the trick is to leave a small gap for expansion between rail ends.
Another factor in track buckling is the way your trackbed is constructed. Solid blockwork and concrete are the least likely to move but that may depend on your soil ie sand, clay, etc. Treated solid timber may move a little as it gets wet and/or dries out, but again that hasn't caused me any problems personally. There is a product available in the UK called "Filcris" which is recycled plastic. That has caused some members problems because they have found that it does expand and contract quite significantly.

Hope that helps a little.

[Peter Butler]

Hi Fred, aside from all of the advice given, my greater concern would be of your choice of materials and method of construction.
I guess your preferred material is timber, but unless it is treated and has fewer sectional joins, you will be doing it all over again in a couple of years.
With so much end-grain for moisture to enter, and small section side pieces, it will expand and contract more easily than continuous lengths and encourage it to rot.
Also, if you do intend to glue down any ballast material it will be necessary to use a stable material between them to prevent the movement of timber from destroying the bond.
Now is the time to have a rethink to save your time and money.

[GAP]

Fred,
This how I did parts of one of my layouts.
Been out in the weather in Australia for close on 3 years now and the ballast has not moved at all. Using the cable tray saved me heaps of time and it will last for many years.

https://ringbalin-light-railway.blogspo ... -farm.html

https://ringbalin-light-railway.blogspo ... -farm.html

https://ringbalin-light-railway.blogspo ... -line.html

[fseider]

Great posts and responses! Thank you. My area gets four equal seasons - 100 degrees F (37C) on hot summer days, to 10 degrees F (-12C) on cold days in the winter. 2/3 of my layout (total 450 to 600 ft of track) will be exposed to direct, unobscured, sun, and facing south. So that is my expansion concern.

Concerning materials, I am using pressure treated wood. As it's wood, it will expand and contract by it's very nature. Though it will be surfaced with a water repellant. (I know, water repellant lifetime is limited, for sure.) Concerning the edges (end grain) - I admit I did not think about that factor. Note that many areas will be longer - 8 ft lengths of larger exterior plywood, well protected, for my towns, etc. My current question only concerns curved areas at this time due to their placements. Concerning bonding of ballast to the base - very good point - I did not consider that yet with the wood expansion effect. Not sure of how concerned I need to be there just yet, but thanks for bringing that up! Any more ideas on that will be appreciated.

Pressure treated wood is my choice of material, due to my tools, skills, and budget. Only has to last 10 to 20 years, and then I'll cross that bridge if I ever get to it. I'm starting this hobby much older in life - but either way - it's never too late!

[philipy]

Note that many areas will be longer - 8 ft lengths of larger exterior plywood, well protected, for my towns, etc.

If I were you I'd rethink the use of ply. It never lasts however well you protect it, even using marine ply I wouldn't bet on more than about 4 or 5 years before it starts to delaminate and twist and bulge..

Only has to last 10 to 20 years, and then I'll cross that bridge if I ever get to it. I'm starting this hobby much older in life - but either way - it's never too late!

I'd bet that most ( not all though, before anyone screams!) of our membership are wondering how long before their own loco fires go out for the last time, so you're not alone.