Sealing wood on a turntable fiddleyard

[Wyvern]

Hello everyone,

 

I am building a turntable fiddleyard for my first 2mm finescale layout and have produced the following to date;

 

 

 

basically the turntable is two pieces of 4mm birch ply separated by 18mm pine strips to produce a barry normanesque ply beam box. The intention was that this would produce a stable turntable for good long term track alignment. unfortunately the turntable has warped very slightly since orginally built and the track and locating lugs have had to be realigned - and now work fine.

 

What I would like to try and do is to stabalise the wood to prevent anymore movement. As I understand it warping is caused by the uneven drying of wood and so sealing the wood with a shellac sealer ( I have bought Zinsser sealcoat ) would appear to be the way forward. I have however built the turn table as a box so sealing the inside will be difficult. I therefore have the following options;

 

1) seal the outside surface of the turntable.

2) seal the outside surface of the turntable and drill some holes (20mm diameter) and pour in the sanding sealer to each of the box compartments and empty to leave sealed inner surfaces.

3) leave it as is.

 

Any advice would be greatfully recieved.

 

Cheers

 

Wyvern

[amdaley]

Hi Wyvern.

You don't say how long the turntable has been built or how long you have had the wood. If it is built some time then the chances are that it has dried fully & is unlikely to warp any further unless it is in a damp environment. If there is any dampness or low temperature present the I would suggest you seal what you can see. If the unit is a sealed box then any dampness in the atmosphere is unlikely to get inside the box structure.

If anyone is building a layout I suggest that they put any materials they plan to use in the layout room lying flat on the floor or a level surface for a couple of weeks before they commence work. The temperature & moisture content in the material then has a chance to stabilize & any warping or twisting will occur within that period.

Incidentally your turntable looks like a very fine piece of work.Well done.

[bertiedog]

I don't want this to sound to pessimistic, but wood does not really stabilise, it takes on whatever moisture is around it and moves quite a bit.

 

Sealing the outer surfaces only will indeed help, and if you can get sealer inside this will help as well. The best example are violins, where all surfaces are sealed on relatively hard wood, and even here they alter tone with damp levels changing.

 

 

Wood is never a really good engineering material, however the uses are sound, but may need allowances made for the movement, adjustments built in to the design to take up and allow for future changes.

.

An example would be a box or tray, with a "loose" top and bottom, held in place with flat head bearing screws, rather than countersunk headed, so that they hold the wood properly, but the wood can move slightly sideways under the flat heads, potentially stopping the warping pressure..

Hope this helps,

Stephen.

[beeman]

I would agree entirely with Bertidog.It would seem that perhaps the method of construction could be a culprit having the various pieces causing varying expansion/contraction. I would have made this out of one piece of thick material such as chipboard flooring, thick ply or MDF. These would be less likely to be affected by moisture as the wood breathes it in/out. I have a Laser beam detection system in operation on my layout. These initially were the cheap keyring lasers with a 'spot' of about 3mm, I found that these needed regular adjustment to stay aligned to the opto transistor targets.This being due to movement over the distance of approx 2,3 metres. I overcame this by replacing the lasers with a focussing type to increase the 'spot' on the targets. Shows though,even with substantial mounts I made how the deck and in fact lining of the building can move with humidity/temp change. Beeman.

[Wyvern]

Firstly thankyou to you all for your advice. Amdaley, thankyou for your complement, with the exception of the wood movement I am pretty happy with it! The turntable was made 6 months ago with the wood purchased approximately one month before that. I expect some drying out will have occured over that time and it is kept indoors. I think I will thoroughly seal the outside surfaces and look at sealng the inner surfaces to prevent further changes in the moisture levels in the structure. In future it may be better to make the structure from MDF, sealed afterwards or I could look at acylic sheet or even aluminium honeycomb. I have even thought about carbon fibre honeycomb - until I found out how much it cost, at which point I put that idea swiftly to bed.

 

thanks again

 

Wyvern

[corax67]

Unfortunately timber is a necessary evil in layout building but I have had a lot of success with acrylic structures in the past - it is often possible to pick up discarded acrylic from shop fitters (my main source) and you can build boxes that are lightweight, rigid and most definitely temperature stable.

 

 

The material is easy to cut (with a degree of care in thicker sheets) and glues well with a wide range of liquid cements as well as being suitable for drilling & tapping to take machine screws.

 

 

Looking at the excellent turntable you have already built I believe you would have no difficulty whatsoever reproducing the same item in acrylic.

[bertiedog]

In one corner of the workshop resides about 40 ladies legs.........in perspex, ex stocking display dummies, it has provided free 1/4 inch perspex for years! ..yes.. perspex would be the best for the turntable or any mechanical surface or mechanism like it.

 

 

MDF is best sealed first, before sawing etc, then the edges sealed, the best sealer I found is Blackfriars MDF sealer!!, but a solution of waterproof grade PVA works about the same. Old fashioned Shellac,(French Polish, or Button Polish), also seals MDF very nicely, rubbed in.generously. MDF is not a bad material, I have items 20 years old in it and they are stable.

 

(Backgound,, step fathers business was reproduction antique furniture manufacture).

Stephen.