Baseboard construction

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Will this be strong enough?

Evening All,

I'm planning a new N gauge layout, I don't have too much real estate so will be fairly small and be round a stairwell in my man cave.

I'm proposing to have a 4' x 2' board cross braced at 1' centres, joined by a 2'4" x 2' board in a line. This board will be cross braced at 14" and longitudinally at 1'. An additional board will join the second board in a L shape and be 2'6" by 1'4" crossed braced at 10" centres.

I want open frame baseboards and my plan is to use 3" x 6mm ply for the sides and cross braces with 6" x 9mm ends. The risers will be 6" tall using 6mm ply to allow for differing scenery levels. The framework joints will be strengthened with 20mm x 20mm softwood.

The track bed will be 6mm ply with only the track bed used to allow for the scenery.

Along the front I'm planning on an additional 6mm profile board, so the bottom 3" will be 12mm thick leaving the top 3" as 6mm.

The backscene board will be 3mm hardboard coated in fairly thick lining paper and fastened to the rear 6mm frame. I'm not yet sure of the height of the backscene but thinking about 1' above the track level so total height of 18".

The wood be from a local woodyard who will also cut it to my cutting list. The ply will be either Baltic Birch or hardwood depending on cost. I think it will use 2 of 8' x 4' sheets of 6mm ply plus the ends in 9mm. I have to be sure what to use as I may have to buy the whole sheet for some types (thinner hardwood ply can be purchased as part sheets but not sure about Russian Birch)

The website includes the following:

"Our Russian Birch T/O Plywood BB/BB is compliant to E1, EN314-2 Class 3, Specification EN636-2."

"Our hardwood plywood is CE marked and BB/CC Compliant to EN636-2S EN314-2."

My main concern is whether the 3" tall framework will be torsionally robust or should I increase it to 4"? I'm not planning on cutting holes in the framework, all wiring etc can be located between the framework and track bed. 

Sorry for the long post, but I want to get it right the first time round and not have to worry about it twisting and warping. I'm planning on sealing the plywood with either 2 coats of dilute paint or varnish.

Your comments and observations are much appreciated.

Thank you

Andy
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A lot of questions but I'll share my thoughts FWTW.

Frame strength,

Gauge less important than the timber characteristics here. What works for OO will be fine for N but trying to scale down the framing is likely to be a false economy. There is a commercial supplier of Kits making modular baseboard units and imitating their specifications should avoid any problems of being under spec.I think they used 6mm tops.

Holes for wires.

I think this is a furphy #. Put those holes in as they won't weaken the cross braces at all. See my topic for examples. The benefits of running your wires through the cross beams are huge.


# Furphy

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If you haven’t seen my open plan benchwork, which is similar to your plan, have a look from page 3 of my Newcastle Emlyn layout thread.
L girders, 6mm ply boards and laminated MDF spline road beds. Worked a treat and super strong.

Might give you some inspiration.

Be wary of long unsupported, thin sections of ply for your track roadbed. I had a few that sagged and needed shoring up.

Your plan sounds fine otherwise.

I do like the spline road beds, very therapeutic.

Cheers
Edit: oh…and I agree with Colin, holes in the joists are fine and very useful.


Last edit: by Marty


Marty
N Gauge, GWR West Wales
Newcastle Emlyn Layout.
Newcastle Emlyn Station is "Under construction"
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Thank you Colin and Marty for your comments. I've looked at Marty's thread and other layouts and had a minor rethink.
I rang the woodyard this morning; a 8' x 4' sheet of 9mm exterior grade hardwood ply is £29 and £21 for 6mm and they cut everything for free. As the CEO of the railway, the Treasurer and project manager I made an executive decision to increase the depth of the framework to 4" and use 9mm ply for the sides and ends with the internal cross and longitudinal bracing 6mm with the tops also being 6mm. The longest unsupported length of road bed will be 13" on a curve but can have an additional riser support in if needed (I'll probably add one in anyway to make sure).

As much as I like Marty's spline and open frame baseboard my woodworking skills leave a lot to be desired hence letting the woodyard cut everything.

I've just a few odd bits to finalise, prepare the cutting list and I can order the wood

Thank you again

Andy
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I have tended to "over-build" the woodwork but the results have been sturdy layouts which, in the end, have resisted almost anything and even proven difficult to dismantle.  The suggested plan seems to have more than enough timber for enduring rigidity but it's the quality of that timber as much as anything which is critical.  Eye-up the true of the long pieces if you can; check for warp and weft and reject anything you're not happy with.  Avoid pieces with knot-holes, excess knots or other potential weaknesses.  I use the local hardware supermarkets and - being a little selective about the timbers - have no problem there.

Rick
Layouts here and here
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Thanks Gwiwer,
My local diy supermarkets are horrendous for timber so I'm going straight to a proper woodyard who are experienced in timber. I've used them before and the plywood has been good quality. My aim is to build them straight away and seal the wood with diluted paint or varnish to avoid any unexpected twisting or warping. The drawings and cutting list will detail they are being used for a model railway so the timber should be absolutely flat and true.

When I rang them this morning I was the third person this week to contact them about model railway baseboards.

Cheers

Andy
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Hi Andy,

Looks like you are mixing open frame with regular box baseboard techniques. If you want to do open frame try and get a copy of Linn Westcott's booklet (How to build model railroad benchwork). If you want to build open frame then it's probably better to go with decent wood rather than ply (I use Radiata pine, which is knot-free and stable as it's straight-grain, not sure if you can get it in the UK). If you want to use Baltic birch then 12mm or even 18mm is probably best for framing.

 Not sure I would trust a lumber yard to cut it given the cost of the ply. I can only get it in 5 x 5 feet sizing, if your yard has it in 8 x 4 feet that's better. If you can access the yard select a piece that's not warped and make sure the first cut is a straightening cut. If you are gluing up beware of the differences between urethane and PVA glues - urethane swells and requires a lot of clamping. If you want bullet-proof framing 4" minimum height (whatever the metric equivalent is). 6" is better. 1" width nominal gives plenty of space for screwing. How are you going to support the framing?

Yes, you will get torsional issues with differing heights and thicknesses. Baltic birch ply shrinks and contracts with temperature changes. Doesn't need a coat of sealer except on the ends to protect against moisture. Most sealants are water based these days, sort of counter-intuitive.

Nigel



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Hi Nigel,
Thank you for your comments, I'm going for 4" framing; the sides and end will be 9mm ply, the inner framing, again 4" tall will be 6mm ply. The risers will be 6mm ply 5" tall and overlapping the framing by 2" to give a 3" rise. Framing strengtheners will be 1" x 1". The trackbed will be 6mm ply. I've also allowed for front profiling using 6mm ply at 8.5" tall.

I'm planning on using 2" x 2" for the legs secured together by 2 pieces of 6" tall 6mm ply cross pieces.

All joints will be PVA glued and screwed

When I go to order the timber, its a proper woodyard so I can select the wood and talk to the sawman with regards to the squaring cut. I've used the same woodyard for previous jobs including a new cockpit floor on my boat which has stayed twist free despite getting soaked a couple of times.

I suspect I may be over engineering things but rather that than under engineered and the boards twist later.

Regards

Andy
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Hi Andy,

You might be better off using 9mm for the inner framing, not 6mm. Even then some cross braces could be useful. I've found that 4" high framing will take 1.5-2.0" holes. 

3mm Ba!tic birch Is fine for a baseboard top, a PITA to drill and screw.

If you are planning on using switch motors now is the time to plan where they will go. Otherwise Murphy will strike and you will find a piece of riser in the way.

I did try what you are proposing a couple of years ago with some spare 12mm ply but using L girders and cross joists Turned out OK, but easier in dimensional wood (and cheaper). Best of luck, keep us up to date with the build.


Nigel



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Hi Nigel,
2 of the three boards (4' x 2', 28" x 2') will be braced to make 8 No. 1' approx squares and 4 No. 1' x 14" approx squares respectively. The third board being only 16" wide will be cross braced only at 10" spacings. On your recommendation I'm going use 9mm on the sides, ends and inner framing.

Taking a 4' x 2' L girder board with cross bracing would a central longitudinal member be required to make a grid of 1' approx squares or 4 rectangles of 2' x 1' approx? I'm just wondering which would be the better/stronger method.


Andy
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Hi Andy,

Any of the methods is going to be strong enough (I use 6mm ply to make conventional topped modules, 12" spaced cross supports up to 24" wide will support 200-300lb). The issue is torsional (flexing) stability. Recommendations? There is no "best way", what works for you is the best.

1. Closed box construction with a solid top. Works with all wood or all ply framing. The ply top locks the framing,
2. Close box construction using the cookie-cutter approach to elevate the track. Works with all wood or all ply framing. Fiddly with small modules.
3. Open box construction (your method) using risers. Here the track bed is used to lock the frame. Best done with dimensional timber, and needs decent track bed.
4.  Open frame construction using L-girders, joists and risers. Best done with dimensional timber. Doesn't work well for small areas.

My experience with 3 is that it can be done with ply, but dimensional lumber is best as there is no ply top to lock the framing. Option 4 is the easiest, only requires the ability to join lumber at 90°. You don't actually have very large modules, so a 12' square framing approach may not be necessary, especially if you use some triangular bracing pieces screwed to the tops and bottoms.

9mm should be OK, 12mm or even 18mm would be better (but heavier than dimensional timber). 9mm Baltic birch ply is probably equivalent to 12mm dimensional lumber, in strength but is more flexible. Cross-bracing into 12" squares gives lots of stability, but is always susceptible to Murphy later on. Corner blocking using dimensional timber is fine, but adds a lot of weight, and dimensional timber as supplied is rarely truly square. Best to make your own if you can using a decent table saw.

Using screws with thin ply can be problematic at the ends as there is no such thing as small, long ones and the screws break the glue and ply. The modules I make do not use any screws for the framing (wood or ply), only for the top. That said, I normally rabbit dimensional timber (not ply, it splinters too much).

You can overthink bench work, so go with what suits you. Some track planning before you start will pay dividends - I suspect everybody here has had the issue of trying to install a switch machine after building the base board only to find a piece of wood in the way, leading to a lot of comments best heard alone.


Nigel

p.s. Baltic/Finnish/Russian birch? I once went into my local big box home improvement store and asked if they had any Finnish Birch ply. Yessir we do. They were just about to cut it when I said that's not it. But it's finished on one side they said. Since then I go to my local lumber shop that specializes in hardwoods and cabinetry. The Baltic birch I use is partially made in Russia, with the final 2 outer layers done here with cabinet grade B/BB Birch. The cores are nowhere BB grade but do not have as many voids as construction ply.



 

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Thank you Nigel for all the advice
Andy
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