Decision made

[Nickk]

Another one made

[jed10]

Why not use 3x1 pse instead? (which is 20x69mm finished planed size). It doesn't cost a lot more and gives just a little more rigidity. The slightly bigger size is also better for drilling nice big hols through for passing your bus wires through, and a separate hole for any other wiring to keep them separated.

When laying your ply, give it a coat of any old emulsion paint (you can water it down up to 50/50) on both sides and on the edges before you screw it down (yes, use screws to fix it down every 150mm). That will stop it expanding and contracting once laid. I used a dark brown paint on my layput which is a good base colour. I have read of others painting the underside white to make it easier to see wiring against it when working under the boards which seems a sensible suggestion.

[Walkingthedog]

When you make the frame cut slots in the top edge for wires to pass through, keeps the wire high up out of the way.

[yelrow]

WTD, I like that idea, pity I read it years too late.

[Walkingthedog]

Same here John, I read it too late as well.

[Nickk]

thank you all for your advice. 3 x 1 is probably a good idea and cost isnt a problem for the timber as ive found a private timber merchant up here in Telford whose prices are literally half those in B&Q in kent which are the prices im used to. The design I propose has a terminus station atan upper level and the main tracks need to run underneath it so that bit will need a little more thought. its only about 6ft x 18 inches so im thinking 2 x 1 strategically trimmed shoud be ok for that. unless you know better of course . always open to suggestions. Thanks again fellas

[jed10]

I am a bit concerned about your proposed size. You won't be able to get a complete loop in at 18" depth - 457mm in new money. You need to really stick to R2 as a minimum radius which is 265mm but ideally, if using flex track allow a little more than that. By the time you factor in running a double track you need at least 600mm (2ft) depth to get around. If you're planning a single sweep around end to end layout then you should be able to make it work at 457mm. Most N passenger train stock will struggle at any radius less thsn R2 and many won't run at all and derail on the curve if it's too tight.

The other thing to think about is inclines. Practically you need to stick to 3% on straight runs and 2% on curved sections. Any more than that and you may run into problems. To run a train under another track the upper track really needs to be sitting at about 70mm above the lower baseboard surface. Assuming the incline is about 50/50 straight and curves you'll need about 2.76m (about 9ft) of track run to get up to 70mm height. Also give some thought to how long you want your platforms to be. Work out the length of your longest train. For something like a 3-car dmu you need about 800mm. Make sure you factor that in with your track design.

[Nickk]

Sorry i think my previuos post was a bit confusing. The 6 ft x 18 inches is the size of the upper level board which will contain the terminus station. the main board will be an L shape with both arms 3ft x 8ft. I reckon I can pretty much get away it arounf 18 i radius curves if i make the boards slightly wider at the ends. thank you for you advice regarding the 70mm clearance. Id sort of guessed about 2 inches and the need for 8ft to make the climb and descent so not too far out. Ill try to take a photo of my track plan (such as it is) and see what everyone thinks. Thanks again

[Nickk]

[jed10]

That makes a bit more sense but don't under estimate the importance of keeping those curves to no narrower than R2 and a bit. You'll find that at small radii like R2 you have to space the tracks out more than you do on the straight or carriage end corners will clash as they pass in opposite directions. As a guide, use the wider setting on the Peco way guage and that, assuming, say, 269mm radius for the inner track, equates to 305mm for the outer track (which works nicely to the size of a standard curved tracksetta). Add on about another 7mm to the outside of the sleepers on the track and that takes you to 312mm. So, to go around 180deg you need at least 624mm surface width (just under 2ft 1in). My layout is built with 269/305mm radii and even that has caused me occasional problems - for example I've had to put some longer couplings than I'd like to have used on Mk3 coaches. It works ok with an occasional bit of improvisation but any smaller and it could have been very limiting.

The figure of 70mm height I quoted is only a guide. You only need about 45mm clearance to pass another train under but you need to factor in the height of whatever type of scenic arch you intend using and possibly the thickness of the base material that the overhead track will sit on. I have found that 70mm is a pretty good practical guide but you could get away with 60mm, especially if you scratch build a straight top arch rather than using a curved tunnel entrance type. I've done that with a road bridge going over the track and it looks fine. For a short span you can get away with using a bit of 3mm thick ply as an upper track base.