50mm Extruded Polystyrene + Ply - practicalities?

[Lacathedrale]

I've got a fairly firm idea of a layout plan I'd like to put together- two boards of 4' x 2' each. Having read Iain Rice's new cameo layout book where he evangelises the use of extruded polystyrene with a ply roadbed, I am tempted. I believe @Re6/6 has also done this on this forum, and as I am informed Gordon Gravett's Pempoul (MRJ 185).

 

The proposed solution is to use a base layer of 50mm XPS that is boxed in with 6mm plywood strips attached via no nails.  Track is laid onto a plywood roadbed and then glued onto the XPS. Obviously, this makes no provision for under-baseboard turnout operation, wiring, etc. and Iain Rice's solution is to have each roadbed section fully wired up in isolation, embedding these wires in the surface of the XPS towards a bus on the rear of the layout. Similarly, using wire-in-tube to run turnout actuating rods horizontally  in the XPS to motors/servos at the back.

 

This raises a question - how do you handle maintenance? With a fully sealed unit - trackbed glued onto XPS and then wire-in-tube glued into a cavity and subsequently covered with scenic material - what happens when a wire snaps, or glue inadvertently drips down under the tie bar? It seems a very fragile solution, but I may be overlooking something...

 

I have wondered about a hybrid approach, with oversized voids cut out of the XPS into which roadbed-mounted turnout motors fit (and are accessible from below).

 

Any thoughts or opinions on this gladly taken!

 

Edited May 7, 2020 by Lacathedrale

[Phil Bullock]

17 minutes ago, Lacathedrale said:

I've got a fairly firm idea of a layout plan I'd like to put together- two boards of 4' x 2' each. Having read Iain Rice's new cameo layout book where he evangelises the use of extruded polystyrene with a ply roadbed, I am tempted. I believe @Re6/6 has also done this on this forum, and as I am informed Gordon Gravett's Pempoul (MRJ 185).

 

The proposed solution is to use a base layer of 50mm XPS that is boxed in with 6mm plywood strips attached via no nails.  Track is laid onto a plywood roadbed and then glued onto the XPS. Obviously, this makes no provision for under-baseboard turnout operation, wiring, etc. and Iain Rice's solution is to have each roadbed section fully wired up in isolation, embedding these wires in the surface of the XPS towards a bus on the rear of the layout. Similarly, using wire-in-tube to run turnout actuating rods horizontally  in the XPS to motors/servos at the back.

 

This raises a question - how do you handle maintenance? With a fully sealed unit - trackbed glued onto XPS and then wire-in-tube glued into a cavity and subsequently covered with scenic material - what happens when a wire snaps, or glue inadvertently drips down under the tie bar? It seems a very fragile solution, but I may be overlooking something...

 

I have wondered about a hybrid approach, with oversized voids cut out of the XPS into which roadbed-mounted turnout motors fit (and are accessible from below).

 

Any thoughts or opinions on this gladly taken!

 

 

We are facing the same dilemma with our Abbotswood rebuild - exhibition layout, is yours static? I would not trust going for everything sealed in and suspect we will adopt the voids approach to ensure we can gain access when things inevitably fail....

 

 

[Harlequin]

Hi William,

Slightly Off-Topic but can you give us a reference to the book, please?

Thanks,

 

[Phil Bullock]

Would it be this one perhaps?
 

https://www.amazon.co.uk/Creating-Cameo-Layouts-Iain-Rice/dp/0953877175/ref=sr_1_4?dchild=1&qid=1588923137&refinements=p_27%3AIain+Rice&s=books&sr=1-4

[Harlequin]

4 minutes ago, Phil Bullock said:

Would it be this one perhaps?
 

https://www.amazon.co.uk/Creating-Cameo-Layouts-Iain-Rice/dp/0953877175/ref=sr_1_4?dchild=1&qid=1588923137&refinements=p_27%3AIain+Rice&s=books&sr=1-4

 

Thanks. He's written so many I wanted to know I was looking at the right one!

 

(Ooph! That's a bit steep!)

 

[Happy Hippo]

I've used Kingspan sheet with 3 mm ply for the sides and 18mm ply for the ends.  (It could have been thinner with reinforcing blocks behind the pattern maker's dowels bu I had it in stock.)

 

Point and signal control is by servo via a Megapoints control system  The servos are recessed into the base board tops with a short wire in the tube operating rod.The servos and the operating arms are below the top of the foam and  drop on covers which are secured with velcro to hide them.

 

The electrics are all run back to the surface of the foam behind the back scene and are all connected via chocolate box connectors.

 

I have cut recesses into the foam which drops thing to below baseboard height, but allows access from the top and have holes that go all the way through where required.

 

It does require a bit more forethought when you are planning.

 

As you have mentioned Iain Rice has built his track on a sub base, his is mdf not ply;  mine is 3mm ply and the next layout will also have a track bed but thicker.

Replacement of a point operating rod would be a bit tricky but not impossible, although by the time a 0.5 mm hard steel rod has snapped inside the tube, I'll have long moved on to stamp collecting.

 

[TheQ]

If track such as points are built and tested before scenery is built.  then cover the track with masking tape it should prevent anything getting in the works. 

 

Note that Expanded foam is often 1200 mm wide,  4ft is 1220mm, I found it easier to design and build to 1200mm rather than mess around  wastefully cutting foam to fit. Though 1200 plus 2 lots of 12mm ply for the ends is pretty close. I do inset small wooden blocks in the corners to glue and screw them ends and side together,  not just relying on the no nails.. 

 

The cutting of foam, gluing a ply panel in beneath track is I believe what Gordon Gravett and others have done on point motored turnouts. A hollow only about 3 inches square is needed. 

 

Wire in tube is pretty reliable, the most likely failure is at the point itself where you have some access. 

 

When I can my base boards have two layers of foam.  The track is then above base board level so you can have land above and below track level.  Scenery is a mixture of extruded and expanded foam 

 

 

[Lacathedrale]

As has been rightly pointed out the area of failure/most danger is around a turnout's tie bar

1 hour ago, Phil Bullock said:

Would it be this one perhaps?
 

https://www.amazon.co.uk/Creating-Cameo-Layouts-Iain-Rice/dp/0953877175/ref=sr_1_4?dchild=1&qid=1588923137&refinements=p_27%3AIain+Rice&s=books&sr=1-4

Exactly this one. @Harlequin it's a great book - I don't believe I paid that much, but very much an enjoyable sojourn.

 

46 minutes ago, Happy Hippo said:

Point and signal control is by servo via a Megapoints control system  The servos are recessed into the base board tops with a short wire in the tube operating rod.The servos and the operating arms are below the top of the foam and  drop on covers which are secured with velcro to hide them.

 

...

Replacement of a point operating rod would be a bit tricky but not impossible

 

 

Hi Richard, do you have any pictures? I'm assuming there are recesses in the foam lined with something else (styrene? wood?) into which the servos are placed - with a channel under baseboard level connecting this location with the tie bar. Do you have your velcro covers over the servos portholes, or the whole thing including the channels?

 

32 minutes ago, TheQ said:

If track such as points are built and tested before scenery is built.  then cover the track with masking tape it should prevent anything getting in the works. 

 

Note that Expanded foam is often 1200 mm wide,  4ft is 1220mm, I found it easier to design and build to 1200mm rather than mess around  wastefully cutting foam to fit. Though 1200 plus 2 lots of 12mm ply for the ends is pretty close. I do inset small wooden blocks in the corners to glue and screw them ends and side together,  not just relying on the no nails.. 

 

The cutting of foam, gluing a ply panel in beneath track is I believe what Gordon Gravett and others have done on point motored turnouts. A hollow only about 3 inches square is needed. 

 

Wire in tube is pretty reliable, the most likely failure is at the point itself where you have some access. 

 

When I can my base boards have two layers of foam.  The track is then above base board level so you can have land above and below track level.  Scenery is a mixture of extruded and expanded foam 

 

 

 

Glad to hear that a recess/hollow with a bottom mounted point motor is also feasible. Maybe the solution is a passive provision for both? 3" square recesses in the foam underneath tie bars as well as cut-and-cover channels from those tie bar locations to the rear of the layout.

 

Thank you all for the tips on the corner blocks and the particularis of the foam. This is the stuff, right? https://www.ebay.co.uk/itm/XPS-Insulation-Boards-Floor-Underlay-Panels-for-Electric-Underfloor-Heating/153630539630?hash=item23c517ff6e:m:msGiZmS-EaPCjahsYdj2ozw

 

 

[Phil Bullock]

Are we talking static or exhibition layouts gentlemen? 

[hayfield]

I have seen one gentleman (I think at one of the CMRA shows when at St Albans) use a thin sandwich of 1mm ply and a thin strip of polystyrene for baseboards, admittedly in small scale modelling but made a very strong, thin and light baseboard,  

 

I am in the process of planning and building a small layout based on one of Iain's plans, thinking of how to use thin ply and pine strip for a light weight board. However I fear it may get a bit heavy as it progresses, some think removing material in the supporting struts helps others think the savings are minimal and not worth it

[Lacathedrale]

@Phil Bullock my question was realistically for a layout built for my own pleasure, but I would like to exhibit it at some point.

 

@hayfield what caused this pondering was while a ply lattice is definitely better than the old 3/4" sundeala-on-softwood, my 4' x 1' tim horn board isn't a dead weight, but it's definitely not lightweight - a 4' x 2' equivalent would start to be decidedly unwieldy, I think!

Edited May 8, 2020 by Lacathedrale

[Phil Bullock]

Many thanks am interested to hear any comments based on a large multi board exhibition layout. Something will fail every time it is moved and repairs need to be quick and easy...

[jonhall]

6mm ply seems awfully thick - 3mm would be more like it in my mind? Its not providing great structural strength, just protecting the edges of the poly from damage.

 

Jon

[rodshaw]

For a smallish layout it may be worth considering balsa. I made an 8ft by 2ft layout from 4-inch widths fixed side by side on top of more balsa around the sides, much as you would fix sheets of ply or foam to strips of pine. It was 3/4 inch thick, I think, with no warps or bends. It's very easy to work with. Not cheap but it was very light and quite robust. I glued small squares of ply underneath to take screws for point motors.

[hayfield]

2 minutes ago, Lacathedrale said:

@Phil Bullock my question was realistically for a layout built for my own pleasure, but I would like to exhibit it at some point.

 

@hayfield what caused this pondering was while a ply lattice is definitely better than the old 3/4" sundeala-on-softwood, my 4' x 1' tim horn board isn't a dead weight, but it's definitely not lightweight - a 4' x 2' equivalent would start to be decidedly unwieldy, I think!

 

 

 

I am thinking along the same lines but using 3.6 mm ply, it will be 59" x 18"  plus a removable fiddle yard/board. I have a 48" x 12" ply baseboard out of 5 mm ply and it weighs 5lbs, I could be tempted to build it out of 5 mm for the added strength, or at least for the top piece that the track will lay on

[Harlequin]

I would worry about the generation of "micro-plastics" when cutting the polystyrene. I might still go ahead but I would worry.

 

I would also worry about the bond between the ply and the foam breaking down over time.

 

Edit: To clarify about micro-plastics: The worry would be about where the particles end up in the environment as well as breathing them in during cutting.

 

Edited May 8, 2020 by Harlequin
Clarity

[Lacathedrale]

@jonhall - I believe it's also stopping warping. I also imagine it depends on whether you are having the sides purely boxing in the foam, or providing an additional depth beyond the bottom of the foam. For example, clearance for bottom-mounted cobalts is ~70mm - so not feasible with a single layer of 50mm foam providing the sum-total distance between underside of roadbed and bottom of the 'baseboard'. If you were using 3mm I would have thought that would get bashed up pretty quickly along the bottom edge? I'm not speaking from experience, mind you.  I guess it does mean if you're using a single layer of foam to provide the base then you can't use cobalts!

 

@Phil Bullock as I said I believe the big Balcombe viaduct layout is using this method, and that's ginormous!

 

[TheQ]

I do wear a mask if sawing the sheets, a lot of dust is generated,  but for simple carving I don't. 

That eBay reference is the correct stuff. 

 

I've not had a bond fail yet between ply and foam,  but I do spread the no nails type adhesive on then clamp and weight for two days or more before doing anything else to it. 

Whilst the end plates have locating dowels in them the strain between boards is taken by adjustable toggle latches pulling along the ply. 

 

I use 6 mm ply for the edges simply because it's cheap and easily available.  There is no need for Baltic ply in this type of construction.  Yes 3mm ply would be lighter and would probably do the job. 

 

If you are really wish to use cobalts then use 75mm foam. I'm intending to use servos to replace the peco/ seep points on the current and future layouts. 

[Lacathedrale]

@Harlequin no more than the use of polystyrene, using a hand file to smooth off sheet plastic, etc.? As for debonding you could be right - seems that corner blocks to hold the sides/ends on is a good idea regardless, maybe even a lip around the bottom of the ply to hold the polystyrene inside the shell? As for very long term - it seems not unreasonably to expect 30-50 years without degradation - by which point I imagine the layout will be well past its usefulness. With a substantial ply subroadbed however, one could in stages remove the polystyrene from the shell (probably very messily and no doubt ruining the ground-layer scenic treatment) - and replace it with ply risers in the normal fashion.

 

That has given me cause to do a bit of maths around the baseboard (If we assume the weight of the average 6mm ply 8' x 4' board is 10kg (https://www.inchcalculator.com/how-much-does-plywood-weigh/)) - 3mm boxed-in XPS (3" tall (front), 12" tall (back) and 7.5" (average of gradient - for sides) x 4' is a weight of approx 800g, plus the weight of the XPS (approx 1kg) for a total board weight without scenery, lighting, etc. etc. of approx 2kg.

 

The equivalent outer framing in 6mm is of course, 1.5kg., and it seems that with longitudinal and transverse ply risers, one can get very little deflection of on a span of 407x305mm (using https://www.woodbin.com/calcs/sagulator/) and an internal lattice based on this (plus 2" square softwood blocks on every corner) adds about 2kg to the weight of the layout for a total of 3.5kg.

 

So we are saving some 40% in weight and providing a surface to apply scenics directly - but it does seem like there's alot more than just 'glue ply to polystyrene off you go'...

 

Edited May 8, 2020 by Lacathedrale

[Izzy]

I think the idea to use expanded polystyrene coated in ply is to provide a structurally stable and warp/twist free result with, probably, lowish noise levels. The ply off-setting the ability of the polystyrene to deform if lent/pushed on or knocked too hard.

 

My experience of thin ply alone (6mm/1/4”) to build a baseboard, even well braced, was that it was heavier than desired but also easily twisted laterally. It felt too flimsy. The cheap (diy) stuff also tends to splinter quite badly. Sometimes getting warp free sheet to start with can be a challenge. 
 

Izzy

[Lacathedrale]

@Izzy - Tim Horn baseboards are (I believe) 6mm ply and I think it would be a stretch to say they are easily twisted or flimsy - but that may be due to the precision of the laser cutter and egg-crate bracing.

 

 

My previous calculations (2kg XPS vs 3.5kg ply) do not factor in the weight of lights, a notional proscenium arch/backscene/etc. which inevitably will have to be made of ply (I appreciate foamboard is possible, but I think the most staunch advocates couldn't vouchsafe a warp and bump-free width/height of foamboard of more than a foot in all dimensions?) - an 18" end and back board of a 4' x 2' baseboard is an easy 5kg - unless it is self supporting and into which the baseboard slides/clips/is bolted.

 

Low noise levels isn't something I'd considered but that's a very fair point, as I suppose is the ease of construction!

Edited May 9, 2020 by Lacathedrale

[Izzy]

1 hour ago, Lacathedrale said:

@Izzy - Tim Horn baseboards are (I believe) 6mm ply and I think it would be a stretch to say they are easily twisted or flimsy - but that may be due to the precision of the laser cutter and egg-crate bracing.

Yes, I would agree that a design with a (fairly ) high integral backscene as part of the structure will not, and of course depending on the depth of the side members. I was particularly referring to a flat type of longish length, and particularly with open framework, no more than about 50mm deep, as per the expanded polystyrene size. Those I made were 60”x16”. They also ‘sounded’ a bit, acting like a sound enclosure I would guess. 
 

Now I use layered mount board! Each to their own as they say...and all knowledge is useful.

 

Izzy

Edited May 9, 2020 by Izzy