Author Topic: Crossing small stream/river on a curve...  (Read 2307 times)

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ljudice

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Crossing small stream/river on a curve...
« on: March 07, 2013, 11:34:28 AM »
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Any thoughts on the best options for crossing a small stream or river on a curve?  From a model standpoint,
we're talking about 6 inches across, and about an inch or so from the railhead to the bottom of the stream.

My thought is a ballasted deck plate-type deck or through bridge, although I believe it would have to be scratchbuilt - I believe
I have seen these or seen photos of these.  Another possibility would be a wider straight bridge that could accomodate
the curve - we are talking about a 24" radius curve here.  Another thought was a culvert or something.... 

Any other/better ideas???

Scottl

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Re: Crossing small stream/river on a curve...
« Reply #1 on: March 07, 2013, 11:44:55 AM »
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If the steam is small enough, the preferred solution is a culvert, up to about 8-12' in diameter.

Nilmadic

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Re: Crossing small stream/river on a curve...
« Reply #2 on: March 07, 2013, 11:51:07 AM »
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6" sounds like close to 80 scale feet or so. Im not sure what era you are modeling' but I wanted to try taking the BLMA segmental concrete bridge and either widen it for use on a curve, or just build it curved buy sanding the segments down so they will fit together on a curve. Or yeah a culvert.

DKS

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« Last Edit: March 07, 2013, 12:08:14 PM by David K. Smith »
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Flagler

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Re: Crossing small stream/river on a curve...
« Reply #4 on: March 07, 2013, 12:20:16 PM »
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Stone Viaduct would look cool

rogergperkins

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Re: Crossing small stream/river on a curve...
« Reply #5 on: March 07, 2013, 04:13:31 PM »
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My solution to this problem was the retain the plywood base in the area where the bridge crossed the stream on a curve.
Then I cut the middle (track area) out of a deck bridge and attached the upright portion to the plywood.  Sorry I cannot find a picture in my archives
of this area of my layout in MN.

ljudice

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Re: Crossing small stream/river on a curve...
« Reply #6 on: March 07, 2013, 04:35:42 PM »
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Thanks everyone...  So a plate type deck bridge can be engineered for a curve - I guess it is
composed of individual plates bolted together in some way and the ends can be manufactured at
a slight angle to create a curve?


davefoxx

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Re: Crossing small stream/river on a curve...
« Reply #7 on: March 07, 2013, 04:58:26 PM »
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Thanks everyone...  So a plate type deck bridge can be engineered for a curve - I guess it is
composed of individual plates bolted together in some way and the ends can be manufactured at
a slight angle to create a curve?


Lou,

On my Virginia Central, I built a deck plate girder bridge on a curve by installing an Atlas through plate girder bridge upside down on two Chooch abutments, building a "concrete" bridge surface to hold the ballast, and installing the track over that.  Worked great, but mine was approximately 2-1/8" from railhead to the bottom of the stream.

So, if your height is only 1" from the railhead to the bottom of the river, you can't use a deck bridge.  Your plate girder would be in the stream!  I'm in agreement with the others for a culvert or small trestle for your use.

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DKS

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Re: Crossing small stream/river on a curve...
« Reply #8 on: March 07, 2013, 06:07:31 PM »
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Thanks everyone...  So a plate type deck bridge can be engineered for a curve - I guess it is
composed of individual plates bolted together in some way and the ends can be manufactured at
a slight angle to create a curve?

With extremely rare exception, railroad bridge components are never curved, or even bent at an angle. All "curved" bridges are composed of straight segments. So if you make a through plate girder bridge, it will need to be wide enough so that the ends of the straight plates can rest on abutments. For a deck bridge, each straight section needs to be supported individually, although you do not have the vertical space for a deck bridge. In your situation, either a stone culvert or fill over a pipe is likely the best choice.
« Last Edit: March 07, 2013, 06:09:16 PM by David K. Smith »
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Ed Kapuscinski

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Re: Crossing small stream/river on a curve...
« Reply #9 on: March 07, 2013, 06:55:29 PM »
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I used a stretched single arch from the Atlas viaduct.

nkalanaga

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Re: Crossing small stream/river on a curve...
« Reply #10 on: March 08, 2013, 02:00:07 AM »
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IF the creek never rises, you have room for a 2-span deck girder bridge, as a 40 ft (3 inch) girder is only about five ft (3/8 inch) deep.  But if you have any chance of high water, a through girder, trestle of some kind, or culvert(s) would be your best bet.

Do you mean that the creek bed is 6 inches, or that the creek itself is, filling the entire width of the bed?  If it's a six inch bed with a small creek, one culvert will do.  But the open span of any bridge or culvert needs to be at least as wide as the stream itself, or you'll create an obstruction, back up water and debris, and eventually wash out the railroad.
N Kalanaga
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robert3985

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Re: Crossing small stream/river on a curve...
« Reply #11 on: March 08, 2013, 05:53:16 AM »
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Any thoughts on the best options for crossing a small stream or river on a curve?  From a model standpoint,
we're talking about 6 inches across, and about an inch or so from the railhead to the bottom of the stream.

My thought is a ballasted deck plate-type deck or through bridge, although I believe it would have to be scratchbuilt - I believe
I have seen these or seen photos of these.  Another possibility would be a wider straight bridge that could accomodate
the curve - we are talking about a 24" radius curve here.  Another thought was a culvert or something.... 

Any other/better ideas???

I built a couple of straight bridges using the ME 40' Open Deck Girder Bridges, both shortened a little, one built pretty much stock except for the walkway on either side and HO scale bridge feet...the other with narrowed girders replacing the stock girders on the Atlas 55 bridge kit (a nice model by the way) with Styrene plates on top with Archer rivet decals, also with HO scale bridge feet.  Both bridges are almost exact models of the Lincoln Highway bridges which were built in the '40's, eliminating a dangerous grade crossing on Echo Curve.

Here's a photo of both bridges.  The distance from railhead to bridge foot ledge on the rear bridge is .622".  The distance from railhead to bridge foot ledge on the forward Atlas 55 kitbash is .322".


The span of these bridges is about 3"...just a little less to comply with the actual bridges that they're modeled from.  In your case, a good solution would be to use two standard ME 40' Open Deck Girder Bridge kits with concrete abutments on either end, and a concrete pier in the middle that's wide enough to support the bridge feet of both ends of the two 40' bridges, which will be set at an angle so that the overhang of the bridge ties in the center of the bridges and on the ends is roughly equal, but on opposite sides of the spans.

Of course your track will have a radius of 24", and the bridges are straight, and that's prototypical.

Also, because they're shorter, the girders are about half as tall as a single 80 span, which gives you plenty of room under the bridge for high water if you only have 1" to work with.

I haven't installed guard rails yet, nor have I installed the white, wooden railings on the rear bridge or the U.P. Shield in the centers of the girders on both spans, nor have I painted the rails or weathered the ties.  These bridges were only a few years old in my time period so they wouldn't be all rusty and beat up yet.

Although I like the Atlas 55 kitbash, the ties and plastic guardrails are an integral part of the kit, so it would be difficult to eliminate those details and lay curved track instead, but you might look at the kit and see if that would be something you'd be willing to do, 'cause the Atlas kit is a good looking and detailed model and two of them on a curve with a pier between them would be interesting.

Here's another shot of these just east of my Echo Curve. The abutments are a complex structure on these as one track is higher than the other and they're not parallel.  The road underneath is not at a right angle to the trackage either, so the ends of the bridges are not even.  Still got some work to do to tie the abutments together according to prototype photos.  It's a fun project.
« Last Edit: March 08, 2013, 05:54:58 AM by robert3985 »

ljudice

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Re: Crossing small stream/river on a curve...
« Reply #12 on: March 08, 2013, 07:44:05 AM »
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Thanks again for all the ideas....   

I looked a little bit more carefully at the crossing, and when you add in the banks on either side, it's likely that I can get the
actual water crossing down to around 3" - so my thought is an embankment on either side and a short deck type span
like Bob's (the one further from the camera)....   - or a stone culvert....

It's too big a stream to use a pipe type culvert, I believe....

Another thought is the CSX bridge on the second page here (Chris' photo from Youngstown)

https://www.therailwire.net/forum/index.php?topic=29079.15

It looks like a modified double track truss type bridge model could be modified to carry a curved track...  I have never seen such
a creature before, but there must be a lot of them...


« Last Edit: March 08, 2013, 07:49:02 AM by ljudice »

pnolan48

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Re: Crossing small stream/river on a curve...
« Reply #13 on: March 08, 2013, 10:26:20 AM »
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Lou,

For that span, build a wide straight bridge with curved track on it. I've personally seen one bridge actually built with askew sections--but still pretty much straight in engineering terms, so I wondered why the builder bothered.. Since the track is curved, I'd ballast it, if only for the illusion of holding its alignment. And I'd build it one size up in terms of girders, perhaps 60" girders instead of 48", or 72" instead of 60".

Jesse6669

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Re: Crossing small stream/river on a curve...
« Reply #14 on: March 08, 2013, 11:20:27 AM »
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Here are a couple reference photos of both deck and through plate girders on curves (B&O prototype).  The through plate girder bridge is skewed as well.  I'd shorten if needed to fit the radius of the curve.  Obviously both were formerly double track.