Saturday, October 24, 2009

A start

Today your intrepid correspondent has dusted off his long lost (some would say still lost) wood working skills, and made a start on a layout. I had purchased some real wood (no more of this MDF crap, unless I can't use anything else) earlier in the week. To get it home in the back of the car I had it cut into 4' by 2' sections. I also purchased some cheap 19mm by 90mm pine boards.

What follows is a bit of a departure from the normal methods of building layouts. Instead of solid wood frames, I'm building wood beams like a real engineer would. This idea comes from Barry Norman, who's work I have followed in the model press for quite a while, but mostly from the book 'landscape modeling'(which once belonged to the late great Brian Cross), where he describes a (then) new method for building baseboard structures. A weakness of using plain wood form the structure is that over time it can warp unless a fair bit of bracing is involved. Mostly in these cases adding strength means adding weight, to the point where the main structure feels like it has been made from concrete. Barry's answer was to build the baseboard from beams. The sheet of plywood (in this case 7mm thick, and the cheapest I could find) was cut into 90mm strips on a sawbench. Some 90mm pine planks were also cut up to the same dimensions (cut everything on the same setting and at least one dimension will be the same during assembly). Taking a ply strip, glue and nail (with brads) a block of pine at each end, making sure that they are square, and that the end grain of the pine is facing upwards. Then glue (and nail) 2 intermediate blocks to the beam.

The second piece is then nailed and glued to the other side. Why are we bothering? because we now have a 4' long beam that will not warp or bend (due to a few engineering principles that I'm not overly sure about, but which are apparently used in the real world) and is also quite light. I'm going to cut out some holes in the beams to see if they can be made noticeably lighter without sacrificing any strength.

The product of tonight's work, six beams which are enough for 12' of layout.


Next up I'll be doing the cross bracing and working out how to tie it all together. I do wish I had paid more attention in woodworking class.

7 comments:

manaia said...

don't make the holes any biger than 1/3the size of the wood,
I havan't biult a house for 3 years now so would need to consolt my 3604 biulding bible for presis mesurments.

manaia said...

post a mess.. broken?, after 6times doing the same thing it fialy posted my message.

Andrew Hamblyn said...

Good work, and as always very inspirational.

I have read about similar methods of construction within the pages of that popular American model railroading magazine.
One such article showed use of "luan" style gluing ply together and using ply as layout sides and such like.....

Will be interested to see how the modules develop.

Drew

RKBL said...

what about making I beams from just ply, light and strong

Motorised Dandruff said...

I'm pretty sure my 2nd form woodwork skills are not up to that. This method also has the plus that you can screw into the pine blocks for added strength. plus I've used it before and know its pretty strong, where as I have never used an I beam.

worzel said...

I beams work by placing all the steel at the top and bottom where it does all the work - the central rib is really only there to keep the other bits the right distance apart. (See I was listening in structural engineering class)

Two ways to do an I beam for a layout. Method 1 would be to try and glue a strip at right angles - not so easy and relies on glue.

Method 2. Attach two thin strips of ply about quarter the height of the central beam or less (or even better use aluminium) glued/ screwed to each side along the top and bottom. Does that make sense? Drill holes in the central rib to reduce weight even further, just make sure you leave enough wood behind to hold together. Sounds like a lot more work than what MD has done though.

By the way, the small blocks in the middle won't add any strength (over simply glueing two sides together) but they do increase thickness with minimal extra weight.

Good work MD!

worzel said...

The huge benefit of doing the beams as MD has done over I beams is joining them at right angles - those wooden blocks give something solid to screw into. An I beam wouldn't have that and would have a tricky shape. You would have to use metal L brackets or separate blocks of wood to screw into at every joint.