Author Topic: Invert a Kato through truss for a deck truss?  (Read 1360 times)

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Specter3

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Invert a Kato through truss for a deck truss?
« on: July 19, 2020, 01:41:08 PM »
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I need a reasonable facsimile of this deck truss bridge on my railroad.
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I think an inverted bash of this Kato bridge will get me where I need to be.
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Any different ideas about how to do this? Maybe the Central Valley 1815?

Thanks,

Ryan

nkalanaga

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Re: Invert a Kato through truss for a deck truss?
« Reply #1 on: July 19, 2020, 02:58:17 PM »
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I built a deck truss from the old Vollmer through truss +/- 40 years ago, from an article in either MR or RMC, so the same could be done with the Kato bridge. 

The main difference is that the Vollmer bridge was a kit, so it could be assembled "inverted", simply by putting the floor pieces on top, and the top bracing on the bottom.  A few extra vertical beams to support the ends of the deck and the job was finished.  With the Kato bridge, it's going to look a little odd if simply turned upside-down, because most deck truss bridges have the end posts vertical, not leaning out.  That could be fixed with a little cutting and fitting, so I'd say the job is definitely doable.

I've never built one of the CV bridges, but it should go together in just about any configuration you'd want.
N Kalanaga
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dem34

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Re: Invert a Kato through truss for a deck truss?
« Reply #2 on: July 19, 2020, 03:08:21 PM »
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Kato's Bridge would look pretty close, remember too that you can invert the girders on Kato trusses without even having to modify the bridge. You'd probably just need to clip the end angles and add shoes.










*The one you posted obviously looking closer to the picture reference.
-Al

Specter3

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Re: Invert a Kato through truss for a deck truss?
« Reply #3 on: July 19, 2020, 03:19:27 PM »
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Oh wow, that makes it even easier. ANd the one I posted a pic of is on the bay for $7 plus 4 shipping. That is no brainer pricing.

Thanks

Ryan

davefoxx

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Re: Invert a Kato through truss for a deck truss?
« Reply #4 on: July 19, 2020, 03:25:32 PM »
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The Central Valley bridge will look nicer, but the Kato bridge should work.  Years ago, I removed the truss portion of the bridge to get access to the deck to replace the track with ME bridge track on my old Virginia Central layout.  I wanted to trim off the ears that hold the Kato track.  I’m guessing, but I think that the truss portion could be inverted, as @dem34 suggested.

Here’s another Kato bridge on my daughter’s layout.  I apologize for the crappy shot up the skirt, but it shows those slots where you have to get an Xacto knife blade in there to release the tabs that hold the top on.





Hope this helps,
DFF

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wazzou

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Re: Invert a Kato through truss for a deck truss?
« Reply #5 on: July 19, 2020, 04:16:50 PM »
+1
I think the obvious issue using the KATO in order to closely match your prototype is the angles of the trusses are much steeper than what you wish to portray.
I think the other thing is that it looks to be about twice the height or depth of the prototype.
Bryan

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Specter3

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Re: Invert a Kato through truss for a deck truss?
« Reply #6 on: July 19, 2020, 05:11:34 PM »
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I dont know about twice the height. In the top photo that small thing on the water under the bridge is a person in a kayak. It seems really tall to me. But other than this pic there is very little info about it. But I do know the trolly between Tuscumbia and Sheffield used to run along the creek here and went under the deck girder to the right side. I intend to be sure to have an obvious old right of way in this scene.

Skeebo

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Re: Invert a Kato through truss for a deck truss?
« Reply #7 on: July 20, 2020, 10:39:46 AM »
+7
When it came time for me to span the gorge on my layout, modifying Kato bridges to be deck warrens is exactly what I did. It was easy and quick to square the ends, add interior detail and add a few cross braced I channel to what was the bottom, (now the tops) of the bridges. I did both 240 foot spans in a few evening sessions. Notice in my pictures the interior detailing I did, is exactly the square panels and X bracing that is shown in the bridge that spans the water in your picture. Kato bridges are perfect for what you want to do.


Skeebo

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Re: Invert a Kato through truss for a deck truss?
« Reply #8 on: July 20, 2020, 10:41:24 AM »
+5
Here is a picture of the entire bridge span.


Skeebo

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Re: Invert a Kato through truss for a deck truss?
« Reply #9 on: July 20, 2020, 10:47:23 AM »
+10
To give you an idea of scale with trains on it, here is a picture of some Alco C855's crossing it. Keep in mind they are huge double diesels, standard dash two and such, the bridge may appear a bit larger?


davefoxx

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Re: Invert a Kato through truss for a deck truss?
« Reply #10 on: July 20, 2020, 11:04:46 AM »
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Well done, @Skeebo, on the bridge and the C855s!

Off topic: I never noticed the old tunnel and trestle remains under the bridge before.  Love it!

DFF

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randgust

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Re: Invert a Kato through truss for a deck truss?
« Reply #11 on: July 21, 2020, 11:50:11 AM »
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The 'dumb thing' typical to a lot of modeling efforts on this is to flip the bridge and not put the pier supports on the bottom chord of the truss, but do like Atlas used to do on the HO one and put the pier up under the track and then magically suspend the truss between piers.    That is what makes the difference on having it look right or not.  Also remember that a deck truss has the advantage that if you derail (heaven forbid) you don't wreck the bridge, on a through truss you do.  So if you have the clearance underneath, the deck truss wins.   If you need vertical clearance over a waterway, road, track, whatever...the through truss wins.     Pretty much the same thing with a girder bridge on whether or not it is a through or deck girder.

And, remember that to keep vertical stiffness, the girder bridge expands the girder size in proportion to the span length, so there's a point in span length where the girders are just too darn big and cumbersome and it has to be a truss - less expensive.    But short spans are almost always girders, longer ones start looking like trusses or something else.   So if you're justifying a deck truss, it should be probably longer than what a girder bridge could accomplish.

And all that kicks in to whether it looks believable or not as a model.    We've come a long way from snap-track bridges.

If you want to see one of the worlds scariest-looking pin connected cantilever deck trusses, highly recommend you look at Youngs High Bridge near Lexington, KY.   It's a bungee jump site now.   But for a pin-connected cantilever, it's so incredibly spindly looking you can't believe it's still standing, and WAY lighter in design than what the Kinzua Viaduct was up here that got demolished by a tornado.    Youngs bridge would make an excellent model across an entranceway as it has a clear-span cantilever of 551 feet or 41" in N scale, and it's 283 feet above the river  21" in N.

NtheBasement

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Re: Invert a Kato through truss for a deck truss?
« Reply #12 on: July 21, 2020, 03:12:38 PM »
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If you are on nscale.net check my bridge album for details.

pedro

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Re: Invert a Kato through truss for a deck truss?
« Reply #13 on: July 21, 2020, 08:18:40 PM »
+2
I had the same need: here is my not yet competed Central Valley inverted truss.  Note that both the Kato and CV trusses out of the box are going to give you verticals that are most likely too tall/close together. Look at the opening pic and how the diagonal bracing is nearly 45 degrees. I chopped the verticals on mine to bring each section close to square. The girder sections at the ends are Micro Engineering, to which I’ll be adding deck girder approaches per my prototype. It won’t be perfect, but “it’ll do.”



m_nanson

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Re: Invert a Kato through truss for a deck truss?
« Reply #14 on: July 22, 2020, 02:37:02 AM »
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I had the same need: here is my not yet competed Central Valley inverted truss.  Note that both the Kato and CV trusses out of the box are going to give you verticals that are most likely too tall/close together. Look at the opening pic and how the diagonal bracing is nearly 45 degrees. I chopped the verticals on mine to bring each section close to square. The girder sections at the ends are Micro Engineering, to which I’ll be adding deck girder approaches per my prototype. It won’t be perfect, but “it’ll do.”



[/quote]
Some prototypes have the same underside clearance as the they need for the through truss.  The Immediate example for me is the Grand Trunk Pacific Bridge in  Saskatoon SK were the CNR Main crosses the South Saskatchewan River.  Note the height of the through truss portion is the same height as the deck truss portion in this side shot on google.
https://goo.gl/maps/n16K2xy3QzN8r4AB7