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Laser Etching a Stone Arch Bridge's Facade

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Posted by Overmod on Thursday, May 14, 2020 1:06 PM

jjdamnit
Check out this web site for patterns... Textures.com.

Hmmmmm... I wonder...

... if he sprayed the printed image with appropriate impervious varnish, and then applied something like Mod Podge that would dry clear, he could stipple up the surface (with techniques like those for making realistic water, perhaps) to give some 3D surface effect in light and shadow.  That is about 100% the effect that can be seen in the full-scale picture of the 'flat' arch and voussoir faces of the Thomas Viaduct linked above...

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Posted by railandsail on Thursday, May 14, 2020 11:52 PM

Interesting idea,...I'm new to these scenery technics, but I think I get what you are saying?

I had another gentleman suggest,

While that color picture may be great, making a dozen copies or more of the same one won't look so great. That photo has very distinct color markings on it, and if every arch had the exact same markings, it wouldn't look very good.

I assume this 'technic' of yours could be used to make the different/same arches appear 'different' ??

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Posted by railandsail on Friday, May 15, 2020 12:06 AM

Also, the width at the base of each where each arch meets should be the same width, even though the arch is getting shallower.

 

 Glad you brought this subject up, ....so I had a new look at the situation today. Turns out I CAN made those base dimensions more uniform,..simply by the way I cut and paste the master image. I did this quick little experiment today when I cut the original 6" wide image down to 5" wide for those shorter arches in the lower portion of the viaduct. This cut-and-paste cardstock method allows for such possibilities,...that would have been much more involved if I were using plaster moldings.

 

Lets see if my crude photos show the difference.

original wider bases




....narrower bases on those last 4

 

BTW, that's the famous clock tower in downtown Baltimore (background to be there in that corner). Going to have to make a cardstock image of that as well.

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Posted by railandsail on Wednesday, May 20, 2020 7:38 AM

Single Track Portion

Couple of days ago I finished the substructure of that portion of the viaduct that supports the single track that sits behind the turntable area and in front of Balt. The roadbed and the vertical supports are all constructed of that cellular PVC material I've spoken of,...and glued together with PVC cement.


In this photo I picked the whole structure up and moved it out to my carport work bench for some final tweaking, and tapering down that end that reaches ground level.

 

Here is a little close up of some scraps of that PVC material I used.

BTW, having a chop saw was really handy in getting those very straight cuts,...and a piece of 180 sandpaper lying flat on the table top made cleaning any flash a breeze.

 

Now I can get on with a the final accurate location of my turntable and its roundhouse,...and subsequently the trackage associated with it. I was going to go ahead with cutting the big hole in the 3/4"plywood deck for the turntable, but my friend suggested wisely that I wait to do that outside the shed, as the router cutting that big hole would make quite a mess.

 

 

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Posted by Overmod on Wednesday, May 20, 2020 8:37 AM

railandsail
I assume this 'technic' of yours could be used to make the different/same arches appear 'different' ??

It can, but a better one in your case will be to get one of those sets of art markers in a wide variety of colors, or watercolors, and dab on a few random spots of color blended in with appropriate thinner afterward.  A little will go a long way.  You can use opaque grays or tans if something doesn't come out the way you expected.  Note that you could also cut and tile the laser-printed image 'stone' and fill in any gaps with a little handwork if patterns are still a bit too obvious...

Then surface and tool with translucent or 'clear' material over the top.

Someone gave you dubious advice about 'all those arches being the same'.  An arch of this kind will have its 'springings' adjacent to the vertical "column" and will have its proper form for best strength between those two points.  It will not, as yours currently does, look as if the arches are sagging down into the earth like some ancient-Roman-ruin folly.  As noted, in all probability this approach would be built as a fill -- longer-lasting and much cheaper -- up to the point an arch is necessary, say for a street or passunder, at which point it will have retaining wall(s) and arch construction to suit.  Then the fill, perhaps with stone lower retaining walls as with PRR's elevated construction through places like Mount Union, would continue until the elevated arch structure can be commenced with proper shape.

In the age when stone arches for structure was the 'done thing', making fills without power equipment was a long and tedious process (see for example all the Chinese with baskets on the Central Pacific) whereas construction in stone was more expensive in materials or craftsmanship but more permanent, easier to 'foot', and easier to keep free of effects from water drainage of various kinds.  Later, railroads would consciously use the idea of 'timeless stone construction' (as with many of Cassatt's projects) for an added sense of monumentality, perhaps as stone 'veneer' over concrete.  My suspicion is that your approach uses the latter.

Now, I'd argue that this would be done with 'sections' that have a consistent arch size, starting with smaller 'bays' and going to the full size as you gain height, or get to the point a greater span/fewer footings are required.  To avoid the Chinese-wall effect you might go to small arches as soon as you get to 'human head height' underneath, with appropriately-scaled column thickness, and transition to larger arches as soon as you have room to carry the arch down to proper transition to springing.

Part of the fun here is that longer elliptical arches were certainly used, but they would seldom be built in this type of rounder-headed stone construction.  There is a recent thread discussing both the appearance and construction of this type of bridge or viaduct on the Trains Magazine forum (helpfully in the 'non you-know-what forum' thread) and some other useful thoughts in the 'Filling in a trestle" thread.  

Still shallower arches are possible in viaducts, but there you would have to remember that vertical and horizontal load on such an arch are handled differently, and explicitly, via the form of support at the springing (which can be very high up on a support column or pier, but has to be balanced in thrust on the 'other side').

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Posted by railandsail on Wednesday, May 20, 2020 9:54 AM

@OverMod,

Very eloquently written reply. I might just try some of your detailing suggestions.

But I am still inclined to continue the arch shapes a bit further down the line. I think I was influenced by this photo, even though it is hard to discern the exact construction as things get lower

https://thecourier.typepad.com/alongtherightofway/2014/08/bellaire-viaduct-then-now.html

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Posted by Overmod on Wednesday, May 20, 2020 10:03 AM

railandsail
I am still inclined to continue the arch shapes a bit further down the line. I think I was influenced by this photo, even though it is hard to discern the exact construction as things get lower https://thecourier.typepad.com/alongtherightofway/2014/08/bellaire-viaduct-then-now.html

You can certainly do that; just be aware of what the footings on each of those smaller arches have to be doing even if (for whatever reason) they are below ground level.  Part of the issue is that you're by necessity using selective compression on the approach angle, so you need to use a little care in how the 'arch' stones are arranged under the courses of stone that are effectively forming the 'ballasted deck' of the overall viaduct.  You might have to do some careful cutting out and rotating of the arch stone sections within the 'portal opening' to get the keystones actually at the top of the opening and the springings symmetrical for the lower arches...

In areas of uncertain soil, for example, or if you wanted a more 'permanent way' construction for anything elevated (perhaps as in the example) you could easily prepare the 'foundations' as piers right down close to the ground (as I think I see being done when I blow up the picture and do a little contrast tinkering on it).

The stone above the arch heads to the level of the 'deck' remains constant for all the arches, as it should for this kind of construction*.  I would suspect that all the approach arches are similar in dimension as well, although I'd be very, very happy to see a picture taken at 'right angles' to the provided one that shows the arch detail on the OD of that approach curve.

Under these circumstances carry right on taking the arches close to ground level.

 

*Something to be careful of is to maintain the PROTOTYPE thickness of 'deck' stone courses over the heads of the arches for your particular scale.  As I look at some of the work in progress it looks as if your 'scaling' of the printed arches may not be close to 87:1 and the deck therefore skimpier than it should be for the 'low-down' portions to be quite right...

On the other hand, if you look at 'Starrucca' you may be struck by the relative lack of stone between arches and track.  If I hadn't known that Erie operated considerable Berkshires over this at speed I'd have said it wasn't safe, but it is.

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Posted by richhotrain on Wednesday, May 20, 2020 2:26 PM

railandsail

I am still inclined to continue the arch shapes a bit further down the line. I think I was influenced by this photo, even though it is hard to discern the exact construction as things get lower

There is something interesting going on in this photo. The track may or may not be descending, but the roadway next to it is clearly rising. That raises an interesting question. Is your railroad climbing to cross a waterway or grade level tracks, or is it crossing a ravine or some such depression from grade? Perhaps you can keep the stone arch system level at full height over the depression. I hope this makes sense.

Rich

Alton Junction

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Posted by railandsail on Thursday, May 21, 2020 8:44 AM

richhotrain
That raises an interesting question. Is your railroad climbing to cross a waterway or grade level tracks, or is it crossing a ravine or some such depression from grade? Perhaps you can keep the stone arch system level at full height over the depression. I hope this makes sense. Rich

My single track viaduct there is rising from ground level to fly over another track that is entering the central peninsula (with double stack containers traffic). It is also connecting up with the double track portion of the viaduct that is entering the back wall tunnel to proceed up the helix on the other side of that back wall. Bottom line is that track has to gain a minumum of 3.5 inches elevation.

BTW, its a fairly steep grade, and I hope that most trains using it (at least longer ones) will be using the downgrade rather than upgrade.

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Posted by railandsail on Thursday, May 28, 2020 9:07 PM

Finalize Subframe Structure of Double Track Portion of Viaduct
(and perform open heart surgery...ha...ha)

I went back over to the double track portion of my viaduct to finalize and tweak its vertical support piers.

 
I have this long piece of stiff aluminum 'door sill' that I have been using to get the grades smooth,...ie..




I was under the impression that I had the upper portion of the viaduct done already. But then I discovered I needed to provide slightly more clearance under the bridge portion so as to clear double-stacks coming into port from that access track underneath. Plus, I discovered that I need to re-level the basic plywood deck down that side of the layout (long explanation deleted). So all my previous measurements, and the already cut support piers were going to have to be replaced or re-cut to new dimensions.

As if that wasn't enough of a disruption I discovered another problem affecting the viaduct on that side. It turns out I have two sheets of plywood deck meeting in that area,..and forming a corner piece.
(hidden under that paper template)

 

I was going to have to perform surgery ( I kiddingly referred to it as performing open heart surgery),...cut back the covering paper template, roll it up, so I could access the innards.




I put a 'backing plate' of ¾” plywood under neath such that it got glued and screwed to both deck pieces of deck material, plus it got an extra corner piece glued and screwed in as well.




That is wax paper hanging there to keep from gluing all this mess to the metal bench work

 


Now I can get on with the FINAL cutting and fitting of the viaduct frame.

 

 

 

 

 

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Posted by railandsail on Thursday, May 28, 2020 9:19 PM

Lower Portion of that Viaduct

As the viaduct approaches deck level, the arch structure is no longer utilized,...just stone sides, no arches

(there is that alum grade tool again)


Turns out there is not much need for visible arches here anyway, as they would likely get lost behind some of the buildings I might place along here,..for instances


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