L girder baseboard construction

[bordercollie]

Hi

 

I am contemplating using L-girder construction for part of my layout. 

 

I have been reading Iain Rice's books.  In one book he suggests 4,5,6 mm plywood for girders. uprights etc. and in another 6-10mm. I was wondering if 6mm  plywood has been proven to be strong/durable enough in the long term ( 6mm is the only bitch plywood that I can get).

Regards

[DCB]

L Girder?      Check out Brian Lamberts website      www.brian-lambert.co.uk        I associate L girder with  44 X 12 (or 18)   and  70 X 18mm timber screwed and glued together to make the L's (or T's )   Old floor boards ideally.  6mm ply is fine but not for L girder framing .
The great thing is L girders get the train off the floor or table top and  onto track bases so that the scenery can go below as well as above the trains . 

Edited November 12, 2023 by DCB

[BR60103]

I can't locate my book on benchwork tonight.

I used 1x2 (poplar?) for mine.  I have used larger -- 1x3 with a 1x2 top when I had longer spans.

I'm not sure about plywood as part of the process involves screws going into the edge of the board.

(I just saw DCB's post.)

 

[bordercollie]

Hi

I did think about the problem of attaching the two parts of the girder. However, the adhesives available today are very strong and it appears that the wood would break before bond. Extra support can be had by supporting blocks at intervals. However, it is not easy to take them apart if needed. 

 

I may consider using some old hardwood skirting boards.

 

Thanks

[Chimer]

Isn't a single girder in this context two strips of ply sandwiching bits of softwood?  So  the ply can be 6mm but the whole girder will be something more like 30mm?

[bordercollie]

Hi

I think what you are talking about is another type of construction, I can not remember what its called. What I am talking about is what is called L-girder. This where to bits of wood are joined at 90 degrees to each other. apparently this forms a strong structure where various forces act in different planes.

Regards

[Chimer]

3 hours ago, bordercollie said:

Hi

I think what you are talking about is another type of construction, I can not remember what its called. What I am talking about is what is called L-girder. This where to bits of wood are joined at 90 degrees to each other. apparently this forms a strong structure where various forces act in different planes.

Regards

 

Yes, but each "bit of wood" (girder) is the ply sandwich I described, not a single strip of ply.

Edited November 11, 2023 by Chimer

[AndyB]

I've used lengths of skirting board glued at right angles on twonof my layouts. Seems to work OK. 

[Giles]

3 hours ago, Chimer said:

Isn't a single girder in this context two strips of ply sandwiching bits of softwood?  So  the ply can be 6mm but the whole girder will be something more like 30mm?

 

A 'box' member - you can happily use 4mm ply for the sides of of this. Very strong and very stable. I built a pair of baseboards this way many years ago, and very good they were too. We also use this method for strong, light scenery that has to stay straight! Domestic doors are often made this way as well.

[DCB]

Originally  the L girders were longitudinal members from which cross pieces support the track bases. Often using risers.  The cross pieces can be positioned anywhere along the L's. That has been diluted and any L shaped "girder" is called an "L Girder."  so...

An L girder (or a T girder,)   is two pieces of material joined together to form a girder which resembles a T or an L when seen end on  or a single piece of material cut to resemble an L (or a T) when seen end on.
A bit or 2X1 screwed and glued to a bit of 3X1 is typical  It gives most of the strength of a 3 X 3  (75mm X 75mm) with 2/3rds of the weight
Some people cut a 2 X 2 section out of a 3 X 3 to give the L shape .    If using 2 pieces then a T makes a better job. and H is even better, see RSJs.
Using  ply you cannot really screw or glue two pieces together as you ae screwing or gluing end grain so you need a wooden strip along the inner edge of the join to screw to so that's 3 parts.    Two pieces of ply sandwiching  wooden spacers to form a box girder is probably the  best way to use ply. 

[Harlequin]

On 11/11/2023 at 08:09, bordercollie said:

Hi

I think what you are talking about is another type of construction, I can not remember what its called. What I am talking about is what is called L-girder. This where to bits of wood are joined at 90 degrees to each other. apparently this forms a strong structure where various forces act in different planes.

Regards

 

Yes exactly, it's the orthogonal planes that give the structures their strength.

 

I made 3 identically sized open frame baseboards out of 9mm ply. They use L girders along the sides with cross pieces joining the two side girders together to form a grid. So the ply was joined in the X Y and Z planes, each piece giving the others more strength. Not a pure girder construction as Rice conceived it, but the same basic principle. No timber fillets were used at the joints.

 

The first two units were screwed and glued and in places pinned and glued. By the last unit I realised that the pins and screws were really redundant and so it, and a further bridging piece, are glued only. Absolutely no problems - they are super strong, super rigid with no warping 5 1/2 years later.

 

The ply edges are uniform enough to be glued if cut by a plunge saw using a guide rail or a table saw. And you need some means of holding the parts together correctly while the glue dries.

 

I haven't tried the same technique with 6mm ply yet but I’m reasonably confident it would work.

 

Edited November 12, 2023 by Harlequin

[BR60103]

The original concept used two boards. The different orientation of the grain let the warping effects fight to keep everything straight.

The girders were screwed together, then unscrewed and glued. Screws re-introduced until the glue set, then removed again.

I damaged an expensive drill bit by forgetting to take out the screws.

To keep them square for working, I make a solid box of 4 boards clamped together.

 

The rest of the construction has crosspieces on edge joining the girders. Shorter (usually) sticks go up from the cross pieces and have the roadbed mounted at the top, using a brace. Scenery can dangle from the roadbed or have its own verticals. 

The crosspieces do not have to be evenly spaced and at 90 degrees to the girders. They may be shifted to avoid complexities and set radially to follow curves.

Crosspieces can be mounted with screws through the flange of the L. The flange should be wide enough to get the chuck of your drill in.

Grades can be made by fastening the ends and fitting the risers in the middle.

I modified the system by replacing the legs with IKEA shelving. The Ls were put on top with the vertical board on the outside.

 

(I have built 5 layouts over the years using L-girders.  The best book is How to Build Model Railroad Benchwork by Linn Westcott, but it's not kinda old.)

 

[kevinlms]

2 hours ago, BR60103 said:

The original concept used two boards. The different orientation of the grain let the warping effects fight to keep everything straight.

The girders were screwed together, then unscrewed and glued. Screws re-introduced until the glue set, then removed again.

I damaged an expensive drill bit by forgetting to take out the screws.

To keep them square for working, I make a solid box of 4 boards clamped together.

 

The rest of the construction has crosspieces on edge joining the girders. Shorter (usually) sticks go up from the cross pieces and have the roadbed mounted at the top, using a brace. Scenery can dangle from the roadbed or have its own verticals. 

The crosspieces do not have to be evenly spaced and at 90 degrees to the girders. They may be shifted to avoid complexities and set radially to follow curves.

Crosspieces can be mounted with screws through the flange of the L. The flange should be wide enough to get the chuck of your drill in.

Grades can be made by fastening the ends and fitting the risers in the middle.

I modified the system by replacing the legs with IKEA shelving. The Ls were put on top with the vertical board on the outside.

 

(I have built 5 layouts over the years using L-girders.  The best book is How to Build Model Railroad Benchwork by Linn Westcott, but it's not kinda old.)

 

I agree totally about the method of constructing such baseboards, using Linn's book. Doesn't matter that the book dates back to the 1980s, as wood is still grown the same way!

Importantly, the book contains tables, showing the maximum distances between legs (or brackets if screwed to wall) depending on the size of the L girders. My last one at 6 metres in length had 2 pairs of legs and I could stand, inconveniently, on it.

 

The L girders are the supporting structure for the track bed with risers and yes, the screws are definitely only there to hold things together while the glue sets - things can only go wrong if left behind.

Stuff like risers and track bed, should only be screwed from underneath and NEVER from the top, because it will eventually be covered in scenic materials. That means that they can't be removed (perhaps for track relocation), without wrecking things. But if from underneath - no trouble.

 

His books (at least 2 versions, the last I have was updated by someone else, Rick Selby in 1997) explain this in more detail, although some photos show screws inserted from the top!

 

The method of construction, means that cheaper timber types can be used - pine is fine and indeed for the actual girders, don't need to be perfectly straight, as the 2 pieces at right angles will pull each other straight! Easier if they are, but doesn't need to be 100%. Try that with other baseboard methods!

[DavidB-AU]

I've generally used 19mm for frames and 12mm L girders. Way back I used 3/4" pine for both frames (with folding legs) and girders, based on a Dave Lowery project that was featured in a 1980s home video. Anyone else remember that video narrated by Bob Symes?

[St Enodoc]

In the Australian context, I use 64x19 and 42x19 for L-girders. I did try 42x19 only but they weren't robust enough.

 

 

[DCB]

1 hour ago, St Enodoc said:

In the Australian context, I use 64x19 and 42x19 for L-girders. I did try 42x19 only but they weren't robust enough.

To Mis quote Crocodile Dundee " that's an L girder"    I don't see making one of those out of plywood ending well.

[bordercollie]

Hi

Thanks for replies.

If starting again I would use structural wood. Locally I cannot get laser cutting done and I have not achieved perfectly straight edges. However, I committed myself to birch ply. For the L-girders I would have preferred 9mm. but this is how unavailable close to me and to get it transported from Eastern States is prohibitive. I have 6mm birch ply. On reading. the comments I may adhere two pieces together to make a 12mm thick pieces  for the flanges. If I run out of birch I will finish with  structural pine of old skirting board.

I am thinking of using small shelf brackets (approx 50x50 mm) screwed temporarily until glue  has cured so won't need to drill and screw into end grain.