Plywood disaster

bobwallison
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Plywood disaster

Postby bobwallison » Sun Nov 10, 2019 6:32 pm

I finally bit the bullet a few weeks back and invested in some quality birch ply, 9mm thick, Grade B/B, lovely stuff. The trackbed was cut to shape and Febond adhesive applied to the top surface (that's the flexible PVA stuff recommended by Norman Solomon) followed by a layer of Exactoscale's 3mm foam. So far, so normal.

24 hours later - disaster! The trackbed has bowed up in the middle and now resembles a hump back bridge, probably because the moisture in the top surface has caused the wood there to expand more than the botom surface. Of course, scientifically speaking this might be considered entirely predictable, but I cannot be the first person to use these materials in this combination, so I wonder if anyone else has come across this problem and if so, how they got around it.

The board is presently in a warm dry room to encourage the wood to dry out, but I am conscious that with a moisture proof membrane on top and waterproof glue between the plies, that might take a very long time.

Any helpful suggestions would be very welcome. Currently wishing I had stuck to tried and trusted MDF at half the price (speaking of which, is anyone able to confirm that 9mm MDF is able to span 300mm between supports without sagging?)

Bob

nigelcliffe
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Re: Plywood disaster

Postby nigelcliffe » Sun Nov 10, 2019 9:59 pm

Options I can see:

1) Wait for it to dry.
2) Wait for it to dry, but also add weights to flatten it.
3) Glue some matching foam on the other side with similar quantity of glue (as one does with plasticard to even out warping)
4) Make a vertical piece to glue to the underside, to form a T-section beam. That will need clamping to keep it flat whilst stuff sets.
5) Scrape the foam off, and the glue remnants and use something else between ply and sleepers, including "nothing" if that suits the ballast formations. I've not looked at the Exactoscale foam, but experience of foam on other layouts makes me think "don't do it". Experience is of a track-bed which can become easily dented (with or without track in place), and thus the track isn't level, and becomes an absolute pain to get back to level .

There must be more options. And, MDF also warps and is heavy.

Terry Bendall
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Re: Plywood disaster

Postby Terry Bendall » Mon Nov 11, 2019 8:25 am

It is not unknown for plywood to bend like this when something is applied to one face. That is a reason why when veneering is done, a plain veneer is applied to the other face to even up the forces. I have found the same thing happens when two pieces of styrene are glued face to face.

Solutions are as suggested by Nigel in his options 3, 4 and 5. It is old fashioned but I still use 3mm cork for the surface and would not use anything thinner than 12mm plywood for the track bed. All the layouts I have built so far have used a sheet of ply across the whole of the baseboard since that is what the deign needed. If the proposed ground formation means that there will be an embankment or other raised trackbed then I would use a beam glued to the underside.

Personally I think far too much fuss is made about noise and methods of reducing it. It may be a problem for a layout used at home but at exhibitions the noise is not noticed even in quiet locations.

I would never use MDF for any baseboard surface.

Terry Bendall

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Tim V
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Re: Plywood disaster

Postby Tim V » Mon Nov 11, 2019 9:46 am

I agree with Terry, MDF is not suitable for baseboard use, it is heavy, delaminates easily. Might be OK for kitchen units (just), but not for our purposes.

You say you cut the track bed, is it attached to any framing?
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David Thorpe
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Re: Plywood disaster

Postby David Thorpe » Mon Nov 11, 2019 11:51 am

Start again - it's essential that you get your baseboard right. I find 9mm ply fine when braced. Paint or varnish both sides, then I suggest you use cork rather than foam for the trackbed - I've heard too many stories about problems with foam whileas good old cork is tried, tested and generally found to be satisfactory.

DT

bobwallison
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Re: Plywood disaster

Postby bobwallison » Mon Nov 11, 2019 1:17 pm

Thanks for the replies.

Tim - I use L-girder construction as per American practice; cross beams and risers to support the trackbed are at about 300mm centres. My model is set around Buxton in the Peak District - all cuttings, embankments, and flying junctions so a traditional British flat top baseboard was really not suitable. The layout is very permanent, which may explain why I am reasonably happy with the 12mm MDF I used for Phase 1 - the only real difficulty I had was lifting the 8x4 sheet onto the trestles to cut out the track bed.

After four days in a warm room the curvature seems no better, so I think I'll be stripping the underlay off to see if the ply then dries flat. The two lengths of trackbed in question support the sorting sidings (Buxton up yard) so I will think carefully about whether I need to replace the underlay here - nothing will be moving faster than scale walking speed so hopefully noise will not be an issue. The same goes for the loco depot which is Phase 3 of the layout.

As an aside, I have various forms of underlay in the temporary parts of my layout. Closed cell foam from Exactoscale and Depron rigid foam seem equally quiet, whether track is glued to them, pinned to them (about 500 centres) or just resting on top. The noise begins when the track is ballasted, and seems unaffected by the type or thickness of underlay. That suggests that nearly all the noise is generated in the sandwich comprising rails, sleepers, ballast and glue, in which case the only benefit of underlay is to isolate this noise source from the baseboard to stop it acting like a sounding box. Which leads to the $64,000 question - does a relatively heavy baseboard really act like a sounding box? I think I need to experiment with some spare track and trackbed.

Regards,
Bob

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Le Corbusier
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Re: Plywood disaster

Postby Le Corbusier » Mon Nov 11, 2019 2:20 pm

bobwallison wrote: My model is set around Buxton in the Peak District - all cuttings, embankments, and flying junctions

:thumb :thumb :thumb :thumb :thumb :thumb :thumb :D
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David Knight
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Re: Plywood disaster

Postby David Knight » Mon Nov 11, 2019 2:29 pm


bobwallison
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Re: Plywood disaster

Postby bobwallison » Mon Nov 11, 2019 3:14 pm

Thanks David. I always wear a face mask when cutting MDF and have recently started to wear a lab coat as well, to keep the dust out of my clothes.

Regards,
Bob

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Tim V
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Re: Plywood disaster

Postby Tim V » Mon Nov 11, 2019 3:55 pm

bobwallison wrote:Thanks for the replies.

Tim - I use L-girder construction as per American practice; cross beams and risers to support the trackbed are at about 300mm centres. My model is set around Buxton in the Peak District - all cuttings, embankments, and flying junctions so a traditional British flat top baseboard was really not suitable. The layout is very permanent, which may explain why I am reasonably happy with the 12mm MDF I used for Phase 1 - the only real difficulty I had was lifting the 8x4 sheet onto the trestles to cut out the track bed.

Regards,
Bob


Ah, the trackbed is unsupported - over 300mm sections. I used that system in the past on a permanent layout. You need to put pieces under the trackbed to form T shapes, this will stop the trackbed warping.
Tim V
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allanferguson
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Re: Plywood disaster

Postby allanferguson » Mon Nov 11, 2019 4:27 pm

My layout, built 6 or 7 years ago, is entirely 12mm MDF, supported at 300mm centres throughout, and has shown no sign of warping, either on the bare boards, or where foam is attached to it (with spray carpet adhesive).

Interestingly, in view of other comments made, I found that trains running over the foam (6mm camping mat -- and that was a mistake!) are as noisy as if on bare boards. But on some track which I had laid temporarily and was only fixed at the ends, there is virtually no noise.

I concluded (a) that all foams are effectively solid under the weight of our trains, and transmit loco noise to the baseboard, and (b) completely decoupling the loco from the baseboard is the answer to silent running. But I don't know how to do that!

Allan F

Rdunning
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Re: Plywood disaster

Postby Rdunning » Mon Nov 11, 2019 5:07 pm

This is straying off the original thread a bit but a method of building "floating" track for quiet running is described in Ray Hammond's article on his layout "Buntingham" in MRJ 49 and also in Iain Rice's book on Finescale Track, published by Wild Swan. It uses an inverted channel of stiff card for the trackbed which makes contact with the baseboard only through the lower edges of the channel section. I haven't tried it myself so can't comment on its effectiveness or otherwise but the theory looks sound to me.

Richard

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Le Corbusier
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Re: Plywood disaster

Postby Le Corbusier » Mon Nov 11, 2019 5:39 pm

This may seem heresy .... but I quite like to hear the noise of the trains running along the track ... particularly the clickety clack over the joints .... or is this not what we are talking about ?
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Knuckles
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Re: Plywood disaster

Postby Knuckles » Mon Nov 11, 2019 5:51 pm

Same for me, sound deadening and take a hike. NFI.

:thumb
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Knuckles
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Re: Plywood disaster

Postby Knuckles » Mon Nov 11, 2019 5:53 pm

David Thorpe wrote:Start again - it's essential that you get your baseboard right. I find 9mm ply fine when braced. Paint or varnish both sides, then I suggest you use cork rather than foam for the trackbed - I've heard too many stories about problems with foam whileas good old cork is tried, tested and generally found to be satisfactory.

DT


Unless you're me, then it warps like a mofo. Well, it did on an older layout. Never again, same as card, never again.
“He who dares not offend cannot be honest.” Thomas Paine

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bobwallison
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Re: Plywood disaster

Postby bobwallison » Mon Nov 11, 2019 6:29 pm

allanferguson wrote:My layout, built 6 or 7 years ago, is entirely 12mm MDF, supported at 300mm centres throughout, and has shown no sign of warping, either on the bare boards, or where foam is attached to it (with spray carpet adhesive).
My experience of 12mm MDF is the same as Allan's - no warping over a period of several years. If the only way to stop warping in ply is to paint both sides and/or add a vertical rib underneath, I'm beginning to think I was wrong to invest in it. But thanks, Tim and others for your suggestions re. my current problem.

allanferguson wrote:Interestingly, in view of other comments made, I found that trains running over the foam (6mm camping mat -- and that was a mistake!) are as noisy as if on bare boards. But on some track which I had laid temporarily and was only fixed at the ends, there is virtually no noise.Allan F
Allan - I was beginning to wonder myself if underlay actually reduced the noise. Was the permanent, noisy track ballasted, and if so, with what materials and glue? The warped boards, and the boards I will need for the loco depot, will have no ballast shoulders and running speeds will be very low so perhaps I don't need underlay at all. I have some spare track and trackbed so I think I'll try a little experiment myself.

allanferguson wrote:(b) completely decoupling the loco from the baseboard is the answer to silent running. But I don't know how to do that!
Sprung suspension! I have four locos with rigid suspension and one which is sprung (CSB's as it happens): the sprung one is soooo quiet.

Regards,
Bob

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Tim V
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Re: Plywood disaster

Postby Tim V » Mon Nov 11, 2019 7:04 pm

I didn't have a noise problem on Clutton.

Baseboards were 4mm ply, in box sections. Track was glued to 1/8" cork, with stone ballast.

But my locos were built to be quiet, most noise came from the rolling stock!
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Philip Hall
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Re: Plywood disaster

Postby Philip Hall » Mon Nov 11, 2019 11:34 pm

Some years ago I had a customer who built a lovely layout in EM, with PCB based pointwork and SMP plain track. The track was lightly pinned to a cork underlay, but mostly the track was held in place with dilute PVA painted over the sleepers, which seeped under the sleepers. Pointwork was pinned as far as I remember.

I built or modified a number of engines and some rakes of carriages for the layout and the running was very quiet indeed. Until it was ballasted, which was with loose ballast and dilute PVA dropped on. It still had a degree of flexibility but was noticeably noisier.

Foam rubber may well turn out to be OK as an underlay, but as soon as you start gluing the track to any underlay the noise level goes up. Adding granite ballast just cranks up the noise even more. So I think I shall try gently pinning track down with the minimum of glue underneath the sleepers. Not sure how I will get on...

My final comment is a memory I have of one of the first pieces of PCB based track I ever built, a little station on an upper level of an 00 layout my father and I were building. We pinned the track down to the baseboard, a flat piece of wood that happened to be lying around. It ran quite well, but we decided to ballast it with the (then) new Kings Cross self adhesive granite chippings. Big mistake, huge. Solid as a rock doesn’t adequately describe it - all running then sounded like we were running concrete mixers full of boulders rather than trains.

Not sure how any of this might help, other than to promote learning through mistakes!

Philip

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Le Corbusier
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Re: Plywood disaster

Postby Le Corbusier » Tue Nov 12, 2019 6:58 am

Tim V wrote:I didn't have a noise problem on Clutton.

Baseboards were 4mm ply, in box sections. Track was glued to 1/8" cork, with stone ballast.

But my locos were built to be quiet, most noise came from the rolling stock!


Apologies for going off topic again, but I am failing to understand why silent running is seen as something of a holy grail.

My memory of Clutton .... which I spent a reasonable time watching at a couple of exhibitions .... was as follows -

The first experience (I can't remember exactly where) was at a general exhibition - the background noise in the hall was such that I have no recollection of running noise what so ever.

The second experience was at Scaleforum .... where the noise levels where far more muted and I watched during a particularly quiet period. The noise this time was quite discernible and for me added considerably to the experience. My impression was that predominantly it was the sound of the wheels on rails, and not transferred motor noise. There was definitely a clickety clack which added nicely to the realism. The real thing after all was far from silent. :thumb

I would also add that when watching some of the professional BRM videos of Tony Wright's Little Bytham, the sound of the wheels on track is prominent and adds to the feeling of weight and speed in the trains. :D

Just my opinion and certainly what I shall aim for. ;)
Tim Lee

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Jol Wilkinson
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Re: Plywood disaster

Postby Jol Wilkinson » Tue Nov 12, 2019 8:06 am

My experience with noise levels is similar to Philip's. When building the extension for London Road I found that when testing the track while temporarily held in place with pins there was very little noise, as the track was effectively decoupled from the underlay. When glued down with rubber carpet adhesive (theoretically more flexible than pva) and ballasted, the noise level rose considerably.

The same adhesive was used to fix 3mm closed cell foam underlay to the 6mm ply tops of baseboards. This foam was also used on the original London Road baseboards built in the 1980's but fixed and ballasted with pva and is still in good condition.

Did not Iain Rice suggest in his book building the track on paper templates and then putting this onto the underlay, only fixing down the edges of the paper templates to the baseboard at the edges of the underlay? This should effectively decouple the track from the underlay and give quieter running. While possibly suitable for a permanent layout,it might be so good for a portable exhibition layout.

bobwallison
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Re: Plywood disaster

Postby bobwallison » Tue Nov 12, 2019 11:40 am

Le Corbusier wrote:Apologies for going off topic again, but I am failing to understand why silent running is seen as something of a holy grail.


Hi Tim: noise and underlay seem inextricably linked with the form of baseboard construction, so I reckon your comments are very much on-topic.

I think one's perception of model train noise is very subjective: some people like it, others don't. From personal observation of Little Bytham and Garsdale Road, both layouts were at the noisier end of the spectrum and Messrs Wright and Jenkinson are on record as liking it that way, so you are in good company. For me, the noise made by a model train is a litle tinny to be convincing. The other problem for me is that noise doesn't scale, so a train in my loft 18ft (a scale 1/4 mile) away is nearly as noisy as one right by me: the crescendo of noise as a real train approaches, passes and then moves away is missing. I do like to hear the clickety-clack at selected rail joints.

Having said all that, I don't think I'll be bothering with underlay for goods yards and loco depots in future.

Regards,
Bob

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Tim V
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Re: Plywood disaster

Postby Tim V » Tue Nov 12, 2019 11:59 am

One of those little pleasures I get is when I am blocking at Pendre (Talyllyn Railway) seeing the engines shunting around silently. Steam engines (on their own) can move around virtually noiselessly. Hence blowing the whistle before any movement, to attract attention.

Diesels, on the other hand ...

So working on noise levels is very important.

I found most noise was generated by our model locomotives, so look there for noise reduction. The boards merely amplify the noise.
Tim V
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steve howe
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Re: Plywood disaster

Postby steve howe » Tue Nov 12, 2019 5:33 pm

Getting back to the ply problem. The principle of the open-top system in my understanding is that any horizontal plane is stiffened by a vertical one either below or above it. In other words, a strip of ply forming a base for the track should have at least one corresponding strip glued and pinned, or screwed, on edge below it along the centreline forming the ubiquitous 'T' or 'L' section. Where wide trackbases are needed the underpinning strips (I always make mine 100mm) can be supplemented by others running at right angles or 45* forming an 'eggbox' frame. Even quite thin (6mm) ply gets really rigid when braced like this.

Steve

davebradwell
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Re: Plywood disaster

Postby davebradwell » Tue Nov 12, 2019 6:00 pm

To pass by the original thread briefly, isn't it good practice to stack the wood for a job in the room it's to be used for a few days before starting? I'm no joiner but I seem to have this in my head from somewhere way back. Perhaps it was just a strategy my Father used to delay a job.

If you're going for floating, that is decoupled, track then a danger I've seen is it floats so much it no longer lines up with adjacent panels and leads to constant derailments. Right from LMS Society days in the 'Modeller the emphasis has been to start with a flat surface and stick successive flat bits on top of this. Result is, of course, noise but isn't this why we spring our stock? If you add low gear ratios and separating motor and gearbox to avoid direct noise transmission to track then it's doing quite well. Re-wheeled and weighted rtr wagons are noticeably noisier than proper ones. It's the inappropriate noises that irritate - grinding gears and whining motors.

I've also noticed that when trains pass from thin ply top across substantial baseboard joints there's a considerable drop in noise so perhaps kitchen worktops would be a quiet surface but its difficult to find flat ones! Meanwhile the foam is an interesting development and there's been a number of articles in 'Railroader over recent years. I've always intended to try sticking scrap bits of ply under my thin ply baseboard tops with contact glue to reduce drumming as the glue layer would act as a damper. This inspired by some metal sheet somebody used once at work to cure noise from a motor - it had 2 layers with a thin, rubbery layer between. A stiffer board isn't necessarily a quieter one - deliberate vagueness here!

DaveB

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Tim V
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Re: Plywood disaster

Postby Tim V » Tue Nov 12, 2019 7:11 pm

steve howe wrote:Getting back to the ply problem. The principle of the open-top system in my understanding is that any horizontal plane is stiffened by a vertical one either below or above it. In other words, a strip of ply forming a base for the track should have at least one corresponding strip glued and pinned, or screwed, on edge below it along the centreline forming the ubiquitous 'T' or 'L' section. Where wide trackbases are needed the underpinning strips (I always make mine 100mm) can be supplemented by others running at right angles or 45* forming an 'eggbox' frame. Even quite thin (6mm) ply gets really rigid when braced like this.

Steve

Reminded me that the L girder system was devised by Linn Westcott (former Model Railroader editor). I was introduced to the idea by David Jenkinson in his Little Long Drag project (19702 Railway Modeller).

Looking at the concept, the roadbed was 1/2" ply, with Homasote on top for the track (Homasote is the equivalent of our Sundeala - remember that?). No particular sign of any longitudinal girders though.
Tim V
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