Author Topic: Invert a Kato through truss for a deck truss?  (Read 2012 times)

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Cajonpassfan

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Re: Invert a Kato through truss for a deck truss?
« Reply #15 on: July 22, 2020, 10:19:29 AM »
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Well, isn’t that because the deck truss has a significantly longer span?
The google photo Linked above does illustrate that railroads always choose a bridge type most appropriate (and economical) for a given set of circumstances, something many modelers seem to overlook. It also illustrates a basic tenet of truss design, and that is that components in compression tend to be heavier than those under tension. Just something to consider when kitbashing or inverting truss bridges...
Otto K.

Cajonpassfan

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Re: Invert a Kato through truss for a deck truss?
« Reply #16 on: July 22, 2020, 10:20:56 AM »
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Here is a picture of the entire bridge span.


That’s pretty amazing; well done,
Otto K.

wm3798

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Re: Invert a Kato through truss for a deck truss?
« Reply #17 on: July 22, 2020, 11:21:54 PM »
+4
Those are some beautiful bridges, guys.  Now for contrast, here's how I did mine.  First, I started 35 years ago...


Back then in N scale.  There wasn't much available to build much of anything much less a fancy deck truss bridge.  The Vollmer model was around, but didn't do what my larval skill level was up to doing...  So I took the next best thing...  Yup.  With apologies to @randgust , I turned to snap track bridges.  Starting with the Atlas deck truss, which has Randy describes, works through a combination of skyhooks and anti-gravity rays, and went after them with a Dremel tool to square up the ends.  I combined several to make the bridge you see above.  It was part of the old display layout at the WMRHS museum in Union Bridge.  I added bits of strip styrene to beef it up a little, and we crossed it with Micro Engineering c55 track...  Not bridge track mind you.. it wasn't available back then, or if it was, I wasn't smart enough to ask for it....
Here it is in all of its murky VHS glory. 

Anyway, it served long and well with that layout remaining in place for about 10 years before the project was dismantled and a new layout was built in the basement by a new crew of volunteers.  Cast aside, I collected the bridge, along with a few other mementos of the old railroad, and put in the stockpile of stuff as I commenced to build my WM layout.  Eventually, I cut it back to the length I needed to install it at Hinshaw, seen here...



Oh wait... that's before we put in the bridge.  Here it is...



It was combined with some Chooch abutments and piers and Micro Engineering deck girders and quickly became my second favorite photo location...Hosting visiting engines like @Dave V 's exorbitantly expensive brass K-4 among others.



Well, time caught up with that layout, too, so back into the box of stuff it went.  I now have the same bridge installed on my new hollow core door layout, serving to once again carry the Western Maryland across the Potomac River.  I used different piers, built new abutments, and have different approach spans getting to it, but it still soldiers on.



With a little weathering and a few details, I think over the years it has held it's own.  Sure, it's not all lacy and super detailed like the other masterful works shown here, but it has gotten several railroads across some pretty steep canyons, and I think it may have cost about $6 originally to build (I needed four of them for the museum layout, and I think they were $1.50 each back then).

Anyway, if nothing else, maybe this will inspire you to make your bridge look like the ones those other fellows built.

Lee
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Lee Weldon www.wmrywesternlines.net

nkalanaga

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Re: Invert a Kato through truss for a deck truss?
« Reply #18 on: July 23, 2020, 01:43:26 AM »
+6
Here's mine - old AHM HO "Pony Truss" trusses, and a lot of plastic strips.



This bridge is 40 years old, has been rebuilt at least twice, is on its third layout, and once had a 12 pound cat go through it, sideways.  It's been a good one! 
« Last Edit: July 23, 2020, 01:44:59 AM by nkalanaga »
N Kalanaga
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randgust

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Re: Invert a Kato through truss for a deck truss?
« Reply #19 on: July 23, 2020, 08:46:08 AM »
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You guys are doing great.   This is what I mean by the design that makes my resident bridge engineer inspector PE burst out laughing

https://cdn11.bigcommerce.com/s-g1ecax/images/stencil/1280x1280/products/6828/19277/d6078ab0-29d2-5e6a-9bc7-350bd122270d__92741.1547769595.jpg?c=2&imbypass=on

Uh, yeah.

And I'll admit that on my very first N layout in 1972 I invented the 'two-track curved deck girder bridge from hell' that was equally structurally impossible.   Even then, I knew it couldn't work in reality, and rarely photographed it.  A lot of Plastruct died in vain, but the plate girders I made then are still showing up in odd places on the current layout as I salvaged those.

Think the SP Redding, only make it 2 track, put it on a 2% grade, and bend it around an 11 and 13 inch radius, and put a turnout on one end.

So no apologies necessary, Lee or anybody else!

And yeah, for deck truss and deck girder fans, if you've never seen it, go on to Google Earth and see it.   Something like 4350' long, completely curved, over a valley and a river, combination truss and deck girder, WAY up on steel tower piers.  Just breathtaking.

I'd love to start a thread on 'crazy bridges, real and model', but it would probably get buried on another header.   I've seen some truly nuts designs in the field over the years.

« Last Edit: July 23, 2020, 09:08:10 AM by randgust »

amato1969

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Re: Invert a Kato through truss for a deck truss?
« Reply #20 on: July 23, 2020, 09:13:00 AM »
+5
As long as we're sharing, here is the Delaware River bridge I scratchbuilt years ago (old house, old layout):



  Frank

Specter3

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Re: Invert a Kato through truss for a deck truss?
« Reply #21 on: July 31, 2020, 02:58:16 PM »
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Awesome work, especially from the olden days, I mean golden era, of modeling in N scale.

Specter3

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Re: Invert a Kato through truss for a deck truss?
« Reply #22 on: August 09, 2020, 08:33:18 PM »
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OK so the bridge is here and and is sitting on some temp piers. From the proto pics the truss is supported from the bottom by the pier. The approach bridge deck looks like a deck girder. In a lot of pics such as some in this thread there is a metal support on the pier that supports the deck girder. But for this bridge there is nothing obvious that supports it down to the pier. I think it attaches directly to the truss but I am wondering how. Kind of like this.

[ Guests cannot view attachments ]

DOes anyone know how this actually attaches? I am sure I can just snug it up and glue it but I would actually like to know how it is supposed to work.

Thanks!

nkalanaga

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Re: Invert a Kato through truss for a deck truss?
« Reply #23 on: August 10, 2020, 01:34:46 AM »
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I have seen such designs, including one of the ex-SP&S bridges on the BNSF between Wishram and Bend, OR.  The end of the truss has a girder between the end posts, at least as tall as the deck girder bridge girders, and the deck girder bridge is supported on that. 

It barely shows, but my Loudwater River bridge is built the same way.

In the case of the picture you posted, it looks like the deck girder is almost as wide as the trusses, and is supported on brackets on the inside of the truss end posts.  Not a typical design for a deck girder, but in this case it's a ballasted deck deck girder.  That can be seen by the solid wood "deck" on top of the girders.  The oversized guard timber above the "deck" holds the ballast in place, with regular ties on that, so the girders can be farther apart than usual.  Combined with the open-deck deck truss, it looks a little unusual.
N Kalanaga
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Lemosteam

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Re: Invert a Kato through truss for a deck truss?
« Reply #24 on: August 10, 2020, 07:00:09 AM »
0
OK so the bridge is here and and is sitting on some temp piers. From the proto pics the truss is supported from the bottom by the pier. The approach bridge deck looks like a deck girder. In a lot of pics such as some in this thread there is a metal support on the pier that supports the deck girder. But for this bridge there is nothing obvious that supports it down to the pier. I think it attaches directly to the truss but I am wondering how. Kind of like this.

(Attachment Link)

DOes anyone know how this actually attaches? I am sure I can just snug it up and glue it but I would actually like to know how it is supposed to work.

Thanks!


@Specter3   What I am guessing I am seeing here is two 45 degree gussets (white) on the inside of the truss bridge's end vertical supports (orange) that the deck girders (yellow) are resting on.  It is likely that there is a stringer across those vertical beams to prevent them from bowing outward which may be part of the deck girder portion of the bridge.  Sorry for the crappy sketch:



randgust

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Re: Invert a Kato through truss for a deck truss?
« Reply #25 on: August 10, 2020, 10:31:00 AM »
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I think that's what you're seeing, but the basic rule of railroad bridges is try to keep stuff in a compression load rather than tension, and beware the shear forces as well.   Pin connections on bridges are notoriously hard to inspect for hidden cracks, and so are cracked rivets in shear.   Even the Kinzua Viaduct in PA, which was really well designed, succumbed to acid rain eating the vertical pier members off at the base like swiss cheese.  Rode over it several times, often its better you don't know.   Then it blew over due to flaws on the mounting bolts to the piers.

Until I started in the industry I never studied much of this, now, you learn to spot trouble in designs quickly.   As posted earlier, the one I still marvel at is the Youngs High Bridge cantiliver, pin-connected cantilever deck truss dating back to 1889 and when you get out to the center span between cantilevers, holding it all together in pin-connected tension.   Toward the end under Southern Rwy. no crews would ride over it, they sent cars and an SW1 across and another crew picked it up on the other side.  One cracked pin somewhere and it would be all over.

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

Specter3

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Re: Invert a Kato through truss for a deck truss?
« Reply #26 on: August 10, 2020, 05:44:56 PM »
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Oh that Youngstown bridge made parts of me hurt looking at it. I have been across the Poughkeepsie bridge on a bike but it was reinforced multiple times over its life. Thanks for the info on the bridge connection. That is going to be helpful.


Chris333

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Re: Invert a Kato through truss for a deck truss?
« Reply #27 on: August 10, 2020, 05:57:53 PM »
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There is a platform in the center of it now with a walkway leading to a building called Vertigo Bungee:
https://www.google.com/maps/@38.0410172,-84.8464551,3a,60y,144.02h,92.45t/data=!3m6!1e1!3m4!1s6IyLhN8aLj7wh4Z8ts6qjA!2e0!7i16384!8i8192