Wiring on Foam Baseboard

[regme]

Hi 

 

Before I make a final decision, if I use 50mm XPS foam as my base board, what is the best way to attach all the wiring underneath?

 

I've seen people have a 3mm ply and glue the foam to that and others that have just glued to the foam to the supports. 

 

If I go without the 3mm ply, I thought about using cable nail clips and push them straight into the foam, not sure how long that would last, maybe drop some glue on the nail before pushing them in.

 

Any thoughts. 

 

Cheers

[The Stationmaster]

I would recommend a test first because some types of expanded foam are very good at melting pvc insulation on electrical wiring.  I don't know anything about this sort of foam so maybe it is safe but well worth checking before you find out the hard way.

[TheSignalEngineer]

Be careful mixing different types of plastics. We had lots of problems on the big railway, different cables reacting with each other and some types reacting with certain plastic trunking.

My boards are ply. Main cables are in pvc mini trunking along the edge. Local wiring is run through holes in the frame and where extra support is needed underneath I use self adhesive cable clips.

[regme]

The foam board I'm using is  XPS Foam.  XPS Multi-Use Foam Board is a high performance, water-resistant and lightweight board of extruded polystyrene. 

 

I'm not sure if the expanded foam you mentioned is the same thing.  My understanding of "expanded foam" was used to seal gaps and come out of can.

 

Also, I have never heard of plastics reacting with each other especially without a heat source.  I guess depending on the amps being carried that could heat up the wire but wouldn't that take some serious amps to do?  I'm not a sparky so I limited knowledge on the subject.

[TheSignalEngineer]

All plastics will change their nature eventually depending on their environment.

The cables we had trouble with were usually carrying very low currents so not much heat from those, more usually where a lot of heat was generated by other equipment. Various factors could affect the severity and type such as air temperature and humidity. A warm sunny day can generate a lot of heat on a small space.

On a plastic loco I had about 40 years ago pvc wiring insulation reacted where tape had been used to hold it to the chassis. I don't know if it was caused by ingredients from the chassis, insulation, tape or adhesive but it just ended up with the conductors covered with goo. 

[Vistisen]

I have used 8mm plywood for frames with 5mm ply top and 5 cm thick extruded foam. I experimented with glues and found that good quality wood pva glue was fine for foam to wood joints. Cheap pva was not strong enough, The good quality glue made joints so strong the when using a crowbar to separate them I ended up splitting the plywood rather than the wood from the foam. For foam-to-foam joints I used 'Gorilla' glue which is again very strong. I have a picture of me sitting on a 1.2-meter board supported at each end. It can bare my 80+ kg, but it only weights 2 Kg.

I decided to use above board points motors. But I have since regretted this decision. What I would do now is lay a plan of the coming track on the top of the foam and cut 5cm round holes with a hole saw attached to a drill at the right locations. After gluing the plywood on top, you can then attach underboard motors as you would normally do. As for wiring what I have done is as follows:

·       Leave a 5-10 cm section at each end of each baseboard free of foam. This makes it easier to install whatever you want to use to fasten baseboards together.

·       In this section I have also fitted a four pin XLR socket, (I use one bus for track power and one for dcc accessories) so between each board there is a short XLR cable connecting the two busses to the neighbouring board(s)

·       I use a twisted pair of cables for the track bus and bought a 7cm long 2mm drill bit to bore holes through the foam to attach dropper wires to the track bus and all wires for points, signals etc

·       On open-frame boards, I have cut a strip of extruded foam with a jigsaw to glue on the underside of the track beds. This allows me to have a much larger distance between supporting frames. To fasten wires to the underside of the frame

·       I use wire staples which the foam is solid enough to hold wires in place, but easy to remove/move.

·       One design feature I am pleased with is the method of attaching trestles I make a strip of Ply across the underside of the board this consists of 5 cm wide strip of 5mm plywood with two 2 cm wide strips glues to each side of the 5 cm strip leaving a 1 cm channel in the middle. The top of the trestle sits in this channel. AS you can see from the photo, there is no string to hold the trestle’s legs at the right angle. I discovered it was not necessary when the legs are on a carpet.

 

Edited July 10, 2022 by Vistisen

[brossard]

I laid 2" (~50mm) thick foam on top of my 3/8" ply boards.  The idea was to allow for some contouring beneath track level.  That hasn't happened.

 

Thick boards pose a problem for point motors.  My solution for mounting Tortoise motors was to cut holes using a vibrating saw and install 1/4" ply on top.  This allows the motors to be fixed to a firm substrate.

 

 

As noted above good PVA (the yellow stuff) works well to stick the ply to the foam.

 

Personally, I wouldn't use solely foam for the boards.

 

John

Edited July 9, 2022 by brossard

[regme]

Thanks for the write up @Vistisen and @John there is so much info out there it's hard to know where to start.

 

@John I was going to use the same approach for the point motors, but I going to use servos instead

 

@Vistisen I like the latch you used

[Vecchio]

XPS (extruded polystyrene) doesn't contain softeners so there shouldn't be any problem in contact with other plastic materials. I used it for almost (used also some expanded material as I run out of xps...) all mountains in Donnersbachkogel, light but strong enough and not the crumbly effect of expanded polystyrene when grinding. Where a station (points, signals) is, a 3 or 4 mm light ply is used. 

 

I covered the surface of the XPS mountain with plaster bandage. 

[Re6/6]

19 hours ago, Vistisen said:

 

 

 

 

 

 

Since finding those adjustable toggle latches, they've been invaluable to me for baseboard joining for our Balcombe layout which has seventeen boards plus six add-on scenic boards. Previously it was a back breaking job (for an old 'un!) getting underneath and using bolts and tee-nuts. They now reduce setup and takedown times by 50%! 

[meil]

20 hours ago, regme said:

The foam board I'm using is  XPS Foam.  XPS Multi-Use Foam Board is a high performance, water-resistant and lightweight board of extruded polystyrene. 

 

I'm not sure if the expanded foam you mentioned is the same thing.  My understanding of "expanded foam" was used to seal gaps and come out of can.

 

Also, I have never heard of plastics reacting with each other especially without a heat source.  I guess depending on the amps being carried that could heat up the wire but wouldn't that take some serious amps to do?  I'm not a sparky so I limited knowledge on the subject.

XPS is extruded polystyrene as opposed to expanded polystyrene used for disposable cups, packaging etc. This will attack PVC insulation in time.

 

What you describe as expanded, coming out of a can, is polyurethane foam.

[regme]

So after a bit of research on migration of plasticisers from PVC Cables into XPS polystyrene there seems to be a solution:

• you can either use a cable with a migration resistant plasticiser
• or prevent the cable from contacting the XPS polystyrene

Plasticiser migration from PVC cable in contact with EPS can also be effectively minimised. If the cable temperature can be kept relatively low (50–60°C for a 50% usage situation), the rate of migration will be slow and will not cause a problem over 50 years.   Not sure how hot the cable gets for model rail layout and how often would you be running locos and etc 24/7 and also in 50 years I won't be around so is it a problem?

 

If I seal the foam (there's another question) on the underside of the XPS foam will I have a problem, only the dropper wires would be in contact but being that small in diameter and only 50mm of foam, is that a concern.

 

 

[johnhu]

I've been using XPS for layouts over many years and never had an issue with any of the wiring (plastic insulation) causing issues. Maybe I've just been lucky.

Back to the original question - I normally just 'glue' the wiring to the bottom of the XPS foam board.  My go to adhesive for the majority of my construction is "Sikaflex 111 Stick & Seal". This is readily available in Australia - I'm not sure about other parts of the world.  There is bound to be other alternatives. It's basically an 'adhesive caulk'.

 

On my current layout (aluminium frame, XPS deck, sign board / foam board back scenes - I've used it to;

- Glue the 50mm XPS to the aluminium frame

- Glue the sign board to the aluminium frame and top of the XPS (for the backscene)- Glue the cork sub roadbed onto the XPS

- Glue small pieces of MDF to the XPS (to mount servo point motors)

- Glue cork sub roadbed onto the XPS

- Glue the track onto the cork

- Glue the wiring onto the aluminium frame and XPS (depending on if run along the bottom of the XPS or along the aluminium frame).

Definitely the 'jack of all trades' with non wood layout construction :-)

 

I hope the info is of some use....................

John

[regme]

Hey John

 

That was helpful, any chance you can post some pics

 

Cheers

[DCB]

Why not let them hang down and put a 3mm ply sheet or Hardboard or two underneath to support them.  I use cable trunking but don't have the forest of droppers which DCC users seem addicted to.

[regme]

10 hours ago, DCB said:

Why not let them hang down and put a 3mm ply sheet or Hardboard or two underneath to support them.  I use cable trunking but don't have the forest of droppers which DCC users seem addicted to.

Sounds interesting, but I can't really picture what you mean, is the 3mm ply glue to the foam or a separate structure?

[Captain_Mumbles]

Foam boards were pretty loud with fast trains on my first layout. I had the foam stuck directly to a ladder frame. The bonus with the foam was that it was super easy to work with. That layout had to be destroyed and I am building a new one now, (with 7mm ply and on a ladder frame and note it is also loud :-) and the wiring that came out of it was all fine to use again.