Double track 160-to-200-ft Parker-type truss bridge options

[samusi01]

@thomasjmdavis

I spent a lot of time trying to find diagonal braced columns- I need about a scale mile of columns with bracing like those- for my trainshed project- the only source I can find are Walther's water towers- and I can't see buying enough water towers to yield the columns I need.

Why not 3d design and print them?

[Scottl]

When I built my Cisco bridge, I used quite a few of the CV cross lace parts and still have a lot left over in a junk bag (along with a lot of ME bridge components).  I know you can buy all the CV parts separately so that is a good place to start with a custom build.

I also made up a lot of cross braces, beams, walkways and gusset plates for etching.  I plan to do another bridge or two with my new layout in custom brass and modifying them is quite fast.  Depending on the bridge design, there may be a lot of overlap as the bridge I want to do looks like this https://railpictures.net/photo/369936/ (there are two identical spans like this).  Happy to share/collaborate on the design.

3D printing is likely to able to do this work but I expect it won't be as clean as a brass or plastic build. 

[John]

user kabrumble in thingiverse has a number of nice looking bridges that might work for you .. 3d print files in HO

https://www.thingiverse.com/thing:3722103

https://www.thingiverse.com/thing:3739955

https://www.thingiverse.com/thing:5235898

https://www.thingiverse.com/thing:5328310

https://www.thingiverse.com/thing:4536114

[thomasjmdavis]

@thomasjmdavis

Why not 3d design and print them?

I don't want to hijack Bryan's thread (sorry all, I should not have said anything in the first place). But, briefly, I do not have a 3D printer, and even if I did, I can't imagine how much time and effort would go into the dozens of throw-away failures necessary to come up with a load bearing column with virtually no artifacts, not to mention the learning curve on designing something like that.  If I decide to accept "plastic" thickness for the lattice, I can easily enough just make molds from a kitbashed  (for length) Walthers sprue of water tower parts, and cast them in resin.  Alternately, either use GMM parts for the lattice, or have my own etched if I get that picky about exact sizes, and some styrene, and make them that way.

[Angus Shops]

If you can lay your hands on the old Kalmbach nugget “Bridges and Buildings for Model Railroads” you can find the instructions for a 140’ Pratt truss (single track) bridge. If you substitute strip styrene for the card stock in the article it can go to together pretty quickly. The secret of the project is that it is broken down into manageable subassemblies, including the ‘laced’ columns and diagonals. Wth some drafted/printed templates and some reconfiguring for a double track bridge…

I’ve built 2 for my layout - they look pretty good with all the open laced columns and diagonals and the detailed top and bottom cross bracing. No rivet detail on mine, but I don’t notice it.

[bbussey]

If you're trying to represent the original Shaw's Cove Bridge, isn't the New Haven era bridge a straight Pratt truss, and not a Parker truss?

Originally I was going to model a bridge further west but there’s nothing suitable. Modeling the cove will take more real estate but I’ll make it work.

I actually think I can fabricate a reasonable facsimile from four standard CVMW Pratt truss bridges. That’s the route I will pursue.

[nkalanaga]

Sirenwerks:  It does look like a lot Northwest highway bridges, doesn't it?

[bbussey]

Some of the Central Valley truss bridge dimensions are on the website.  There is a near-straight-on side shot of the bridge in the Library of Congress archives.  I was able to rough out the dimensions of the prototype juxtaposed with the model.  It turns out that the length probably is 153 feet, which matches the CVMW model (my drawing is 3 feet longer but that probably is due to the perspective of the photo).  More vertical supports are in the prototype than the model (8 instead of 5) and it's double-tracked of course, but it's looking probable that many of the stock model components can be used as is and that a good Shaw Cove facsimile can be kitbashed from two CVMW kits plus some extra parts.  I touched base with my contact at the NHRR Archives at UConn, and they are going to search for the bridge blueprints.  Once I have those I will proceed, but I probably have enough information to proceed regardless if the drawings aren't found.

Thanks everyone for your input and suggestions.

[propmeup1]

I have three of those Tomy bridges. If you paint them black and give them the dirty works then they're pretty good. Out of the box with either the green or red they're too new looking.     They work for me because I don't have time right now to invest in scratchbuilding three for the length I needed.  They do hold up well and I've had not one derailment on them.

[NtheBasement]

Good old Bridgehunter has some nice links and detail shots of the swing mechanism: http://bridgehunter.com/ct/new-london/bh61595/  His site is a must for all things bridge.  Modern bridges don't have the lacing, much easier to model.

[bbussey]

That site has the length of the span at 136 feet, which implies the CVMW model is taller than the prototype. So hopefully I can get the blueprints before proceeding.

[samusi01]

The Northern Pacific had a 'bridge book' that listed vital statistics for bridges and trestles. As an example, one bridge is listed as a 186' Strauss bascule, with 56' and 30' deck plate girders, and a 15 pile trestle for 501' overall length; did the NH have anything similar?

[mmagliaro]

This is one of those times where I say, AGAIN, boy I sure wish TrainCat were still around.

He had, I believe, exactly what you want, and his bridge kits were AMAZING.  Pin-connected, 163-foot, N Scale,
double track bridge:

https://www.traincat2.com/d_ilchester.htm

I guess you could scour around and see if one of these is in a shop somewhere.

[randgust]

The spotting features of bridges are just as distinctive as boxcars.   The big differences that evolved - as steel bridges developed - was the change from pin-connected to rivited gusset plates for the connectors.   Pin-connected are distinctive with what looks like truss rods connecting members in tension on diagonals, and what looks like great big pins connecting the individual chord members across the bottom, top, and the pins.   There may be riveted plates and diagonals as well, my Hickory Bridge, in 1896, had both, but was still primarily pin-connected on all major members.

Such spans were easy to erect, just like kits, when properly designed they could be assembled on-site with minimum time and effort.  Those wire-like tension members are a dead giveaway, and they are on Brian's bridge as pin-connected.

Pin connected bridges were often done in the iron-bridge era as well, and were really problematic as unlike steel, iron just snapped and didn't bend, and could have interior inclusions.   Still, even today, pin-connected bridges are difficult to inspect because there is NO redundant backup in case a single pin fails, the entire structure may drop.   And inspecting the pins is problematic without removing them, for either physical or NDT testing.   It's better, but as a matter of practice, pin-connected trusses were never built to handle 286K railroad loads anyway.   My West Hickory bridge was rated for 50 tons, OK for a 47 ton Heisler and 50-ton boxcars, more than enough for trucks, but as the railroad was abandoned in 1934, it survived as a one-lane highway bridge until 2007.

So on my Central Valley bridge, I cut off all the riveted gussets and replace the bottom chord one with .035 styrene rod simulating the major chord pins, removed the tension braces and replace them with wire to get the spidery older bridge look.   That's not impossible on one of their trusses.   The diagonal braces across the top chord, however, proved to be disturbingly fragile in their styrene.

If you're a railroad bridge fan, you need to look at this, because this is the all-time scariest bridge I've ever seen myself, all pin-connected, with just tension rods holding on the center span between the two cantilever towers.  One of those breaks......   NO RIVETED PLATES people.

https://historicbridges.org/bridges/browser/?bridgebrowser=kentucky/tyronehighbridge/

I can pucker just looking at this thing...   This is the one that SRR refused to take a train crew over at the end and ran it with an SW1 and a crew at either end of the bridge, put it in Run 1, let it go across with nobody on it, and pick it up at the other end....

https://historicbridges.org/kentucky/tyronehighbridge/elaine_tyronehighbridge5.jpg

[Rossford Yard]

I have three of those Tomy bridges. If you paint them black and give them the dirty works then they're pretty good. Out of the box with either the green or red they're too new looking.     They work for me because I don't have time right now to invest in scratchbuilding three for the length I needed.  They do hold up well and I've had not one derailment on them.

I've used the twice, and had nice results.  I made one into a highway bridge over my yard (was similar to the old road bridge over IHB's Gibson Yard, since replaced.