Designing a shadowbox diorama

[Lawton Maner]

I'm glad to help.  Finally some of the more esoteric knowledge from my college classes in wood morphology is being put to use. 

We've all seen how an outdoor environment changes the color of wood.  Moisture and warmth encourages the growth of mould which darkens wood.  Sunlight will bleach it, and windblown dirt will erode it. 

An indoor environment is trickier because the wood is protected from moisture and sunlight and changes are subject to more subtle forces.  Once the moisture content of wood is below about 18% there is little likelihood of mould growth so unless there is a leak in the roof or uses of the building which generate moisture (such as a dairy barn) all changes over time will come from other sources.  A furniture factory will have a totally different interior climate from a railroad car repair shop for example. 

In the last picture the streaks on the upper section of the wall might be tar from a roof repair.   

[Hauk]

I value all input and suggestions, and it is incredible what people on this forum knows!

Regarding the stains, they could very well be stains from repair work. At some time in the twenties the skylights in the roof were covered with tarpaper, and I would guess this was due to leakages in the roof. It is plausible that more repairwork was done around the same time.

But I still think the inside of the roof was painted or stained. This could also have been for esthetic reasons. In the early years the Railroad did a lot of things for purely estetic purposes. For instance, all poles for the overhead wire were painted white for the opening.

Back to the drilling of the holes for the rods, I made a simple jig for drilling the holes in the upper beams:



For the holes on the underside I used an even simpler "jig". The trusses were held in position between to absolutely square pieces of MDF. It was quite simple to line up the centerline of the rods and to hold everything in place by hand while drilling:



While I am happy that the roof trusses are finished, I am not too pleased with the overall precision of the parts. I should have paid  more attention in the early stages of construction to ensure that the roof trusses where identical and with tight and prescise joints. When you line up all the trusses, every imperfect angle is easy to see:



But when the diorama is finished I count on that the roof trusses will fade into the background and no one will notice the imperfections. Too much work to start over!

[finescalerr]

I can't see the imperfections as I look at the photos. Maybe they are less obvious than they seem at this stage. I also think your jig may look simple but actually is pretty sophisticated. Few of us have the tools to create one like that. -- Russ

[Hauk]

I can't see the imperfections as I look at the photos. Maybe they are less obvious than they seem at this stage. I also think your jig may look simple but actually is pretty sophisticated. Few of us have the tools to create one like that. -- Russ

Good to hear that you cant see the imperfections! And when everything is in place there will hopefully be more interesting things to look on than the roof rafters. Maybe even a CHB/SierraWest lathe if I am lucky in the eBay auction the coming weekend...

Regarding the jig, the only machine tool involved was the disk sander. I really think it is the most useful powertool in my workshop

[Bill Gill]

Hauk, I can't speak about roof trusses, but recently I watched a documentary on rebuilding the the world's longest single span covered bridge in upstate New York. The original was washed out in a flood after a major storm. The company building the new replica had to assemble the new timber frame on a open, flat piece of land parallel to the water near the old bridge and then turn the the whole frame almost 90 degrees to be able to maneuver it onto the original abutments.

Craftsman were shaving 100ths of an inch from the mortice & tenon joints, so their work was very precise, yet when they rotated the bridge they had miscalculated and had to stop and add additional fill in one area and cut down part of an embankment in another spot to get it into position. What I'm hinting at is even if the craftsman who built the trusses you are modeling were just as careful, over time stresses would shift things around a bit. I don't see any discrepancies.

Lawton is right about different species of wood weathering quite differently under different environmental conditions. On my monitor the color of your trusses in the two photos of your drilling jig look very much like the color of timbers in some hay barns and lumber sheds that I have seen. Perhaps the lighter areas on the trusses could be a little darker and less yellow, but the general color looks good. A touch of weathering should serve nicely.

[Ray Dunakin]

Looks great to me. Whatever discrepancies might exist are minor and will likely not be noticeable at all once the model is complete.

[Hauk]

Thanks for the encouragement!

For the moment I am wondering what material to use for the walls.  I will need a board of some sort that is stiff and light, and can either be milled or lasercut. It can not be a sandwich type of material (no foamcore or Kapa-board or such things) as the reveals for the windows will be quite visible and must have the exact same finish as the walls.  As it might be necessary to cover the walls with some waterbased compund to give color and texture, the material should not buckle if it is exposed to moisture. As the reveals for the windows are about 8 mm , this is the thickness required. Suggestions?

I would also like suggestions for the painting of the walls.  We are talking plastered brick, and as you can see in the prototype pictures, it is quite rough in places. There are also lime deposits showing. So it is probably not good enough to just airbrush the interior with matte paint. Some texture is needed, but how to make it? Talcum powder in wet paint? Plaster dusting or something?

I will of course dive into my collection of Modellers Annuals, I think there is no other magazine or book that has covered this topic in more depth.
But I would really enjoy a discussion on the subject here on the forum! As this probably could be of interest independent of this thread,  I will of course not mind if the discussion branches off in a separate thread.

[Bill Gill]

Hauk, Look into acrylic sheet for your walls. It is much less likely to warp than styrene and it can be cleanly laser cut. it is easily glued. It is stable and will not warp when wet. The surface can be laser engraved, which may be a way to create the surface texture that you need. (I have seen laser engraved "sidewalks" made by CMR, the link listed below, that had a variety of surface textures and cracks much finer than anything engraved with hand tools.)

Acrylic comes in Cast and Extruded sheets. Both can be laser cut, but there are differences to consider.

Here is a link to making architectural models using acrylic sheet that can give your laser friend an introduction to cutting acrylic:
https://www.instructables.com/id/Architectural-Model-Making-Using-A-Laser-Cutter/

To see a wide range of what can be done with acrylic, here is a link to a company, CMR,  that makes elaborate models for model railroads from acrylic:
http://www.custommodelrailroads.com/cmr-train-kits.html

Acrylite is one brand of acrylic sheet and here is a table of available thicknesses and thickness tolerances. The table for Acrylite GP (cast) sheet lists one available thickness at 7.9mm, very close to what you want.
https://www.eplastics.com/blog/thickness-tolerance-plexiglass-acrylic-sheet

Plexiglas is another common brand in the U.S.  Perspex is a high quality acrylic made by Lucite.

Depending on how much you need, you might be able to get end cuts from a sign shop.

[Lawton Maner]

As for the surface finish there was an artist's compound suggested for imitating stucco on this forum about a year ago.  It is water based, about the thickness of sour cream, and has a very fine sand mixed into it.  I don't know where you live, but the Micheal's here in Williamsburg has it on the shelf.

[Hydrostat]

Hauk,

Forex (German brand) is a millable pvc based material which comes in different thicknesses. If sprayed with a plastic primer it can be colored with usual wall paint for example. I tend to rather dab paint to the surface to avoid brush traces. I think at your scale there'll be enough texture from the rough wall paint pigments and the unevenness of the dabbed on color.

Cheers,
Volker

[Hauk]

Thanks for all the sugggestions for wall materials. I should perhaps have mentioned that weight is a concern, as it would be fun to show the diorama at a modellers exhibition in the future. So milling the walls from Forex seems like a good option.

Regarding machinery for the shop, I won the auction for three CHB/SierraWest machines  on eBay, and with Paul´s offer for the milling machine, I have four machines secured for the scene.

That will have to do. In addition, I think that a scratchbuilt wheel lathe would be a great addition to the scene. I really like the look of the wheelset hanging from the gantry crane in one of the prototype photos.

I found a great picture of a similiar lathe in a Swedish workshop:


But if anyone has additional information (pictures or drawings), I would be very interested!

Googling for images of old machine shops I found this nice picture:


It is not "my" workshop, I am quite happy that I do not need that many machines!

[Lawton Maner]

The next time you are near by, give me a heads up and I'll arrange for a tour of the East Broad Top shops in Rockhill Frunace and allow you to fondle a wheel lathe and other belt driven machinery which all still work.

[Ray Dunakin]

Googling for images of old machine shops I found this nice picture:

Wow, that's a lot of drive belts!!

[Hauk]

Some progress on the roof trusses:



Several hundred GrandtLine nbws have been installed. I could not really believe my luck when I found around 600 of just the right type of nbws in one of my drawers!

Recently I also found a little piece of prototype information for the workshop. In this picture it is obvious that there is a round window high up on the wall in the back:



But i had no I idea what it looked like, as I have no drawings of the original building.  But then I found this image in a database online:



To my surprise it was possible to zoom in on the image to an extreme degree:



Examining the image close up it was possible to see the design on the window in question. It is of a quite unusual design of circles inside a circle, and I could never have guessed how it looked. Not exactly an earth-shattering discovery, but it is small discoveries like this that makes research fun.

[Bill Gill]

Hauk, Finding the details of that round window is a terrific bit of tenacity and luck. I love it when some detail I have almost given up looking for unexpectedly shows up.
Now when you build that window you'll KNOW it is correct, and that feels good.