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short abutments for low bridge over a small river?

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  • Member since
    February 2021
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short abutments for low bridge over a small river?
Posted by crossthedog on Tuesday, April 27, 2021 6:45 PM

I live to keep you guys busy.

My mainline will be at zero level. At the place where it crosses a not-wide river, the subroadbed is about two inches off the grid. I want to put a simple bridge here -- not sure what it's called but it's just a deck with short metal walls, not even as high as the train, no undertruss. It will sit pretty low to the water. I mean, Uncle Amos won't crack his skull on the bridge if he's baiting a hook while drifting along from upstream, but if he stands up in the boat and tries to cast he may well "catch a local freight".

Some of the abutments I see sold for this kind of bridge tend to be pretty tall, because they're expecting that you want to use this bridge to cross a highway or another track. Have any of you got a low bridge like this over water, and if so what kind of abutment did you make/buy and how/where?

Why so low over the water? Because, my friends, I have designed the layout so that at that same exact point, the branch line crosses over the main. So about 4 inches above this I will have another bridge deck, and I want to make sure there is clearance for the lower bridge walls.

Ideas? Thoughts? Recommendations? Bridges and abutments for sale cheap? Bring it on!

Thanks again in advance,

-Matt 

Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.

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Posted by crossthedog on Tuesday, April 27, 2021 6:56 PM

Here's the most recent incarnation of the plan. I've actually built the subroadbed for the mainline and yard.

It's a little difficult to see but there's a river entering the layout from the left edge of the upper area. It's where the branch (purple) crosses over the main (red-orange). At that point, both tracks are crossing over the river. The upper bridge will necessarily be much longer, a Warren truss, m'thinks.

By the way, this plan makes me really happy. Some of you gave me lots of good feeback on how to make it work better. There's still goofy stuff here that I'll get schooled in when the time comes, but I'm on my way and this plan allows all my dealbreakers: continuous run on a mainline that will allow modest-length passenger cars, a branch for spotting freight cars up in the small city, and a yard for noodling around in with switchers.

-Matt

Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.

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Posted by 7j43k on Tuesday, April 27, 2021 7:28 PM

That'll be a through girder bridge.  A good choice.  Micro Engineering makes a 50' one.  I think Atlas makes a 60' one.  I see Walthers makes a 90' one.

Your can get your short stubby abutments by sawing off the bottom of tall ones.  You can also cast your own by making wood forms (just like the prototype) and casting Hydrocal.

Track plan looks quite nice.  I'd worry about the grade being too steep--looks to be 4%.  It looks like you may have little choice, however.  In that case, go fer it!

Ed

 

PS:  I model SP&S, myself.  And some other peripheral roads, both in time and in distance.

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Posted by Lastspikemike on Tuesday, April 27, 2021 8:55 PM

Not far from where I live, on the CPR mainline at Johnston Creek just such a very low through girder bridge crosses said creek.  A modern line would use a fill over a culvert. In the olden days they'd pre-fabricate a short through girder bridge and plunk it over the creek. Abutments would be minimal concrete structures.

Now I realize "the Plan" was subject to much discussion in another thread.

http://cs.trains.com/mrr/f/11/t/287402.aspx?page=1

Your current Plan gets you the broader radius continuous loop you were looking for and your combination of that and branch line and yard gets you interesting point to point options. 

Anyone planning a new layout should take a look at the progression of planning in that other thread. Often quite small alignment changes, both of the benchwork and the track  can yield big improvements. Also, eliminating excess track can actually produce a more enjoyable and better looking layout. Real railroads built as little track as they could. 

Draw lots and build once (or try to!)

Alyth Yard

Canada

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Posted by doctorwayne on Wednesday, April 28, 2021 12:30 AM

I built this little "concrete" arch-type bridge using sheet styrene after the 3/4" plywood sub-roadbed was in place...

The bridge's sides were attached to the plywood with contact cement.

For most of my other bridges, I cast the abutments and piers using Durabond-90 patching plaster in homemade styrene moulds.

This one is likely high enough that Uncle Amos won't likely crack his head, although if he drifts too far out into the fog over

Lake Erie, he may end up in the States...

The moulds were built to accommodate the various bridge types used for this river crossing, hence the stepped tops.  The bridge is also removeable as a one-piece assembly, useful for when the surface of the "water" needs cleaning...

All of the moulds were built upside down and taller than would be needed, which allows some of them to be useful for other locations and different styles of bridges, too.
My plan (untested at the time) was to fill the moulds a little higher than I thought would be needed, then, where necessary, I could remove the excess from the bottoms, using a utility knife, autobody file, or coarse sandpaper.  It actually worked as well as I had hoped it would.

This bridge, in the foreground, was done in a similar manner, but the piers were all cast in the same mould, again each being filled to what seemed to be close to the height needed (the bridge is on a 2.5% grade).  This was possible because the footings on the bridge spans were identical, and all fit perfectly into the depressions cast into the top of each pier....

The abutment at one end of the bridge used another pier casting, cut to match the slope of the plaster-on-screen terrain, but the wings were cast-in-place on the layout...

...while the abutment at the other end of the bridge...

4300040

...was done with a different mould.

I have a couple of other large bridges, but they're on steel towers, with "concrete" footings, made by stacking .060" sheet styrene, then filing it into a suitable shape.

I have one other bridge on "concrete" piers and abutments, but much of it is not readily viewable, due to the trees and other scenery around it...

The entire bridge has two deck-type trusses, plus a normally-not-seen deck-type girder span.  The two piers are the same, as I chose to use the same "steel" support-work for both the trusses and the girder bridge, while the unseen abutments suit the type of span at each end.

Here's a aerial view of the truss spans...

...and of the seldom-seen girder span...

If you're interested in possibly creating your own moulds for casting bridge piers and abutments (or perhaps other items, too) here's a LINK to how I made my bridge piers.

Wayne

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Posted by riogrande5761 on Wednesday, April 28, 2021 8:09 AM

Calling Rob Spangler.  Rob has some excellent abutments for his bridge over small rivers that are excellent examples.  Hopefully he'll come in here with some photo's.  They are probably more suitable for what you are asking about.

Rio Grande.  The Action Road  - Focus 1977-1983

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Posted by selector on Wednesday, April 28, 2021 3:39 PM

You could use large timbers if the line is dated enough in your theme.  Something like this, holding up the far end of the trestle:

Otherwise, I could agree that you can saw off the excess from a standard pier/abutment.

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Posted by crossthedog on Wednesday, April 28, 2021 6:22 PM

selector
You could use large timbers if the line is dated enough in your theme.

Selector, I could indeed have a trestle like this in my mid-1950s layout. If anyone says it wouldn't be prototype, "I'll fight them in a car park" as our British friends say, because I grew up in the '60s and '70s with a massive wooden trestle inside the city limits of what was once my little town of Bellevue, Washington.

I'm talking of course about the justly famed Wilburton Trestle, longest trestle in the west for quite a while, a monument under which my friends and I caught crawdads in the creek. It looked like this back in the 1990s when a dinner train shared the line with Burlington Northern, who still had a few customers up the line.

Now, of course, it has a lot of spandex on it, and no rails. Image copyright Steve Sloan, I believe.

As a very young child I was often confused because when we drove further east a few clicks, there was another trestle that looked to me like the same one, and which confused me even more when I came back to live in the home turf after being gone for many years and discovered that it was not there. That was the similar but shorter Issaquah Trestle. A Northern Pacific joint, I think:


That one wasn't being used by the railroads anymore and got knocked down circa 1983 for new freeway onramps coming from the hill to the right, which was shaved of trees and made into a new colony of McMansions. This photo was taken maybe 15 years before I was born (can anyone get an "earliest" by ID'ing that car?), but I remember my dad parking off the side of the road about where that mailbox is -- this is Interstate 90, by the way, now seven lanes wide -- so we could go fishing in the crick just off in the woods. Totally off topic. Sorry. But selector's picture got me thinkin'.

I still mean to respond to others of you who have replied, but this is enough for now.

-Matt

Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.

  • Member since
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Posted by crossthedog on Wednesday, April 28, 2021 6:27 PM

Wayne, your second photo is about the height I'm thinking of for my lower track, but it won't be such a long bridge. Lovely photos, by the way. And thanks for the link to the how-to. It looks only slightly daunting to make those abutments.

Edit: Actually, height-wise, your FIRST photo is more what I'm thinking of, but instead of a little arch like that I'd want the through girder.

-Matt

Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.

  • Member since
    February 2021
  • 85 posts
Posted by crossthedog on Wednesday, April 28, 2021 6:39 PM

Lastspikemike
Now I realize "the Plan" was subject to much discussion in another thread. http://cs.trains.com/mrr/f/11/t/287402.aspx?page=1 Your current Plan gets you the broader radius continuous loop you were looking for and your combination of that and branch line and yard gets you interesting point to point options. Anyone planning a new layout should take a look at the progression of planning in that other thread. Often quite small alignment changes, both of the benchwork and the track can yield big improvements. Also, eliminating excess track can actually produce a more enjoyable and better looking layout.

Mike, (can I call you Mike?),

Yes, thanks for remembering that parliamentary epic surrounding my first Plan, which was actually my second. I didn't know whether I should add the new drawing to that post, or what the best practice is here.

Yes and yes, the process of tossing it before the experienced members here yielded great improvements. There were good ideas I did not incorporate, too, but I had to follow my heart. Chief wins I would say are exactly those you mentioned, plus being able to get around to the northwest corner without ducking under (by shifting the north section to the east a bit), and I'm very excited about it. I didn't really want to hear people tell me less track was better, but it proved true, at least on paper.

Instead of spurs and double tracks willy-nilly everywhere, I've got a simple but elegant mainline, a siding on the mainline, a bit of a clunky jog over to a small but workable yard, and a branch line out of the yard to a handful of industries.

Hours of riotous fun, I'm hopin'. Thanks for your part in its taking shape, LastSpikeMike! (but seriously, can I just call you Mike?)

-Matt 

Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.

  • Member since
    February 2021
  • 85 posts
Posted by crossthedog on Wednesday, April 28, 2021 6:46 PM

7j43k
Track plan looks quite nice. I'd worry about the grade being too steep--looks to be 4%. It looks like you may have little choice, however. In that case, go fer it!

Ed, thanks for sayin'. Yes, the grade is just under 4%, but there's nothing for it. I couldn't really see any other way to get up to the town in the southwest corner without doing something on the inside of the loop that looked "rampy". I can still start the climb a smidge earlier by moving the turnout south toward the yard, but I want to make sure I can get into the yard with all its turnouts first. Also, I won't be pulling but five or six cars up that grade most of the time anyway. All my long trains will run on the mainline, and I'll break them up for delivery.

-Matt

Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.

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Posted by cowman on Wednesday, April 28, 2021 7:03 PM

If you have some scrap exruded foam you can make one as tall or short as you want.  One of the club layouts that I see at shows  has several.  You can leave them smooth to look llike concrete or draw in lines with a black ballpoint pen, then paint and weather.

Good luck,

Richard

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Posted by BATMAN on Wednesday, April 28, 2021 10:26 PM

The one on the right is extruded foam.

 

Carved it with an I-beam while watching hockey.

Brent

It's not the age honey, it's the mileage.

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Posted by crossthedog on Wednesday, April 28, 2021 10:36 PM

Thanks Richard and Brent.

BATMAN
Carved it with an I-beam

Brent, in the second photo there, are those lines really carved "out" of the foam or is it an impression? It looks like the line was made by simply pressing the beam into the foam. If so, won't it eventually reclaim its original flat shape?

-Matt

Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.

  • Member since
    July 2006
  • From: 4610 Metre's North of the Fortyninth on the left coast of Canada
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Posted by BATMAN on Thursday, April 29, 2021 9:39 AM

crossthedog
It looks like the line was made by simply pressing the beam into the foam. If so, won't it eventually reclaim its original flat shape?

Yep, it is just pressed into the foam, and the verticle lines were done with a dried-up pen. Years later it has not changed, it still looks the same. Can't remember what the mortar is, but likely tile grout or thin-set.

Brent

It's not the age honey, it's the mileage.

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