Graveling track on viaduct

[Nowhere man]

I have made a board which spans the doorway of my shed,it has a viaduct between two embankment's, the viaduct is a metcalfe one with twin tracks on cork, A thought just came to me, what happens when you come to graveling the track. Does the process of wetting the gravel then adding the water/pva mix affect the cardboard that the viaduct is made from? What are your thoughts?.

[Tricky Dicky]

I think most people including myself would have continued the plywood trackbed as as you have done on the approaches to the viaduct and would have arranged the risers to coincide with the viaduct piers the viaduct would then just be a cosmetic addition. Most of the ballast would then sit on a timber base rather than card and only the very edges possibly in contact with the cardboard. If your viaduct does not have an internal timber structure I suspect over time running trains across it will cause structural problems.

Richard

[Walkingthedog]

When I had a viaduct the track was laid on ply and the viaduct just hung underneath.

[Steve M]

I suspect that the majority of model viaducts are merely a cosmetic shell to hide the structural bits underneath.
But all is not lost.
Before doing anything more, test the track on this and adjoining boards thoroughly - you mention a shed for so I presume this may be a lift out section? If so test and adjust the track across the joints.
I would also suggest that you don’t lay the track in one continuous length across the bridge as it will buckle when the weather warms up. IMHO have a short length each side of the bridge and a length of flexitrack to join them across the bridge.
Important to get the end sections right with a section across the bridge that you can install separately to the main structure.
Once you are satisfied that all is well, remove the track on the bridge and apply a generous coat of undiluted PVA to the bed of the viaduct where the track will go. Put the track back in place and use a few drawing pins to hold it in place in the glue.
Now sprinkle the ballast over the glue - you will need to experiment to find the best way of applying the right amount and keeping it neat.
Once dry hoover off the excess.
Now you can do patch repairs as necessary.
The worst thing you can do is use a dilute PVA as it will soak into and ruin the work you have done so far.

[Nowhere man]

A bit more info info for you, the board is on the N gauge shelf layout which is 60inches height,the thinking was it was to be fixed permanently because at that height i could just limbo under that. Are we saying I need to put a wooden track bed. Right across the embankments and the viaduct, if so I have some 3mm ply i could put there and drop the board by the 3 mm. Would i still need the cork underlay.by the way what does IMHO mean.

[brian1951]

In My Honest Opinion.

[Walkingthedog]

Can’t comment on cork underlay I always lay track directly on the board.

Yes lay all the track on solid board with or without cork. The viaduct is just a bit of scenery.

[Walkingthedog]

Can’t comment on cork underlay I always lay track directly on the board.

Yes lay all the track on solid board, with or without cork, where ever it is.