Track underlay - Yes or No?

[Tullygrainey]

I usually glue track down directly onto the baseboard and solder rail ends to gapped copper-clad strips at board joins. That has worked ok for me.  I've been thinking about using an underlay with the current project. I know cork sheet is regularly used for this but I've been looking at the dense foam membrane normally laid underneath wood flooring. It comes in various thicknesses from 5mm down to around 2mm. Has anybody tried it?

Generally, what are the pros and cons of flexibly mounted track? 

Specifically,

Would flexibly mounted track help or hinder locos' electrical pickup, particularly ones with rigid chassis?

Would it cause problems keeping track lined up accurately at board joins? How might you secure these to avoid damage during transportation?

Cheers

Alan

[Mol_PMB]

As ever in modelling, there are many schools of thought!

One of the main benefits claimed for a resilient underlay is sound-deadening, and this is probably true, especially for a layout with relatively lightweight baseboards that can amplify sounds and vibrations.

On the other hand, if you then ballast your track with stone ballast stuck down with PVA, that makes it pretty rigid and probably counteracts most of the benefit of the underlay.

Having said the above, this is exactly what I usually do! 

Some people use ground cork and Copydex (or other rubber-based glue) for ballasting, so that the track remains flexible.

 

One thing to avoid is using pins to nail down track on underlay - this definitely contributes to uneven track geometry and would worsen pickup on rigid locos.

My view is that the the typical underlay (3mm cork or foam) is sufficiently stiff that it won't be compressed noticeably by a loco, even a heavy one, and so I wouldn't expect an improvement in pickup though that. 

 

Personally I like my track to be a little higher than the trackbed, making it easier to represent ballast shoulders, trackside cess drains etc. Underlay is a convenient way of lifting it a few mm, purely for appearance.

I tend to use 3mm thick cork underlay. I have a friend who uses 3mm dense foam sheet with great success. 

Open-celled foam (as once supplied by PECO etc for track underlay) is a bad idea as it deteriorates over time. 

 

As for fixing rails at board joints, I'd say these need to be rigidly and firmly fixed to protect them. As an alternative to copperclad, some people use brass screws screwed down into the board and then the rails soldered to them.

If you did want a flexibly-mounted baseboard joint, a possibility would be to terminate the tracks an inch short of the baseboard edge, and have a short removable section to bridge the gap. You would need a couple of teaspoons of loose ballast applied each time the layout is erected.

 

[Mayner]

These days I use dense foam sleeping bag underlay as underlay for flexible track. Track, pointwork and (loose Woodland scenics) ballast laid in a bed of PVA. Suprisingly good sound deadning qualities even on an all Ply (10mm) baseboard. The resilience/slight give in the track probabably improves running and power pick up.

Interestingly running is quieter and smoother than on a layout I built about 20 years ago which used (expensive) Anita Decor foam underlay on a MDF baseboard surface, the loose ballast glued in place using the dilute PVA with a wetting agent in a eye dropper technique (which set like concrete!).

Worst layout in terms of nosie transmission (but reliable running) track (partially handlaid) was glued to cork underlay glued to a baseboard formed in ply using Barry Norman techniques for some reason I used 6mm rather than 9mm ply a real sounding board, looked nice and ran reliably though and was even exhibited at Warley following a no of Irish exhibitions

 

[Mike 84C]

I laid my track on a dense foam underlay called Tessamol which had a high strength glue on one side, I used the glued side to stick onto cork floor tiles. Ballasted the track with loose ballast and eye dropper. It worked well, did not transmit much noise and was quite quick to lay. Also tried it reversed with little difference. The Tessamol was used by an HGV Trailer builder I used to have to visit for servicing and was easy to buy from their stores.  Like all good stuff not so cheap!

Different subject, Mayer, do you remember Colin Dukes from the Festiniog Railway From your Wales days?

[Northroader]

I like using cork tiles 3mm thick, a foot square, with an adhesive back. They come from Wickes builders merchants. I think the EU has a thing about cork products, they’re not so common these days.

At board joins the track is soldered onto a wide piece of copper clad glass fibre strip, with a securing screw in the middle (where the cladding is filed away.) There’s a thin ply packing strip underneath to make up the level with the cork underlay. If the track is fixed securely at both ends of the board like this, you must allow for expansion due to temperature change along the track, somewhere along its length on the board.

The track locates across the join using lengths of brass tube soldered on the outside of the rail web, with a brass rod having a sliding fit in the tube soldered inside the tubes on one side or the other of the join.

(there’s no securing screw in the picture, as the track is glued down on a 10mm foamboard baseboard)

[amdaley]

4 minutes ago, Northroader said:

I like using cork tiles 3mm thick, a foot square, with an adhesive back. They come from Wickes builders merchants. I think the EU has a thing about cork products, they’re not so common these days.

At board joins the track is soldered onto a wide piece of copper clad glass fibre strip, with a securing screw in the middle (where the cladding is filed away.) There’s a thin ply packing strip underneath to make up the level with the cork underlay. If the track is fixed securely at both ends of the board like this, you must allow for expansion due to temperature change along the track, somewhere along its length on the board.

The track locates across the join using lengths of brass tube soldered on the outside of the rail web, with a brass rod having a sliding fit in the tube soldered inside the tubes on one side or the other of the join.

(there’s no securing screw in the picture, as the track is glued down on a 10mm foamboard baseboard)

Can I ask what size is the brass tubing & rod you used ?

Thank you.

Tony.

[Mike 84C]

Northroader, I really wish I had thought of your wire in tube locating device for our club layout Bantry. May have saved a lot of stress lining track up at exhibitions !  

[Northroader]

No real engineering tolerances here, it’s really what you can lay your hands on at a show. Pick up a bit of rod, or small tube,  and slide it in and out of a bigger piece, trying not to have a suggestive leer as you’re doing it, to find a sliding fit, not force. I think the rod in the picture was Slaters .050” brass, and the tube is around 3mm outside diameter, but do check the fit. The rod ends up slighted cocked over, with rounded end, and will transfer the electrics as  well, which will simplify the job.

[David Holman]

It has always been cork floor tiles for me, simply because they come flat, are easy to cut and glue down nicely. That said, am fairly sure there is no benefit at all in sound deadening, but find this doesn't matter because at exhibitions there is always enough background noise to render such things redundant. Hence all about providing the ballast shoulder of mainline track.

 Baseboard joins are a real issue on exhibition layouts, with earthquake cracks often very evident. Trick I learned from Gordon Gravett is to used car body filler between the joints. Put a layer on one face, then cover with cling film and clamp/bolt the boards firmly together overnight. Gives an almost invisible join, though same sort of thing required For whatever scenic go on top. For ballasting, I fix about 5cm worth either side of the join with undiluted pva. Again, leave overnight and, crossing everything beforehand, break the boards apart when dry and this (usually) leaves a nice irregular join which disappears when the boards go together again.

[amdaley]

I have used both underlay and cork on my layouts. I think I prefer cork. You can buy 3mm cork on pre cut rolls or sheets & cut it into trackbed strips yourself.

I stick the cork to the baseboard with PVA & stick the track on top using copydex. Use track pins to hold the track lightly in place until the adhesive goes off. Then remove the track pins as the copydex will hold the track in place.

[Tullygrainey]

Lots of good practice here. Thanks everyone

[Broithe]

There are several basic aspects to stopping noise from flat panels, as baseboards essentially are. Stopping the energy being transferred into the panel and stopping it coming back out as sound, in a form that causes annoying noise.

Reducing the input from trains running on the tracks would require fairly soft and 'dead' material - not easy to achieve in real life, whilst maintaining reliable running.

Much easier to do is changing the manner in which the energy is re-emitted. Lightness and stiffness of the panel are not helpful in this matter, and plywood is a great resonator - string instrument bodies are a good example of the opposite requirement.

You can change the re-emission characteristics fairly easily, though, by the addition of some weight to the central area of the panel - this is largely the effect that sticking cork tiles on actually has. It drops the frequency of the re-emitted sound. You will find this technique used all over car bodywork, although it is usually hidden by trim panels. A better technique is to add the weight, but have it attached to the panel via 'soft ' material - a heavy sheet, with an intervening 'soft' sheet stuck to the panel.