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Allen Gaspers

Posted - 2006 July 26 :  2:18:49 PM  Show Profile
I need to replace a 9" curved Atlas track section with a curved bridge. Anybody know who makes one?

Country: USA | Posts: 472

Doc Holliday

Posted - 2006 July 26 :  3:50:36 PM  Show Profile
How 'bout scratch building or kitbashing a trestle kit? I just finished kitbashing a timber trestle kit to fit an 18" radius by cutting the deck in small sections and angling the bents radially.
Doc


Ridin' the Rails in a BAD Western

Country: USA | Posts: 274 Go to Top of Page

Edwardsutorik

Posted - 2006 July 26 :  5:19:34 PM  Show Profile
For a bridge this size, I think railroads would typically use a ballasted girder bridge, either a deck type or a through type. The big difference between the off-the-shelf straight track type you might find in model form and the curved one you need is that the girders will probably have to be space further apart. You can do this by just cutting the girders off a stock part and attaching them to a wider base. The ballast will pretty much cover up your homemade floor so it won't show. Incidentally, railroads prefer to use the deck type bridge unless they need the clearance underneath--it's cheaper.

Ed



Country: USA | Posts: 1671 Go to Top of Page

BillD53A

Posted - 2006 July 26 :  5:21:37 PM  Show Profile
Bridges aren't curved. They are built in short straight sections connected at angles. The sides toward the center of the curve are shorter than on the outside. A deck bridge has the track on top, with the bridge structure below. If you can use one there will be no clearance problems on the sides of the track. If you dont have the space under the track for a deck bridge you will need a through type, where the structure is to the side and above the track. Try using a double track straight bridge to carry a single curved track. Be careful about side clearance.

Playing choo-choo exclusively since 1952

Country: Kiribati | Posts: 227 Go to Top of Page

charlief

Posted - 2006 July 26 :  7:56:17 PM  Show Profile
There are some curved model bridges out there, but from my experience having them match the radius you need is a big problem.

To solve this dilemma, I made my own from some scrap paneling [about the same thickness as cork roadbed], and then as suggested above put straight girders under them for support.

Another possibility would be a culvert rather than a bridge, in which case you could keep most of your present roadbase.



Edited by - charlief on 2006 July 26 7:59:33 PM

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smudgeloco

Posted - 2006 July 26 :  8:34:41 PM  Show Profile
You can have a curved trestle, or a curved viaduct - you cannot have a curved bridge! A bridge is an unsuported span between two points. I know it can be an arch or a suspension bridge, and as such supported. You get curved bridges holding up roadways, but these have supports along their length, usually concrete pillars.

Michael.



Oh for the days when coal was king and steam ruled.
For pics etc -

http://www.flickr.com/photos/smudgeloco/

http://community.webshots.com/user/smudgeloco

http://www.youtube.com/user/smudgeloco

Country: USA | Posts: 1996 Go to Top of Page

chljohns

Posted - 2006 July 26 :  8:55:20 PM  Show Profile
What is your bridge over?

I don't know of any drop in replacements, but there are many options available that would work.

Unless it's over a road or another track, I find that timber trestles, ballast or open deck, look better on sharp curves than longer span steel bridges because the offsets aren't as great. If you can find it, Campbell makes a nice wood trestle kit that can be built at any radius. Walthers and others also make plastic trestles that can be used. There are other manufacturers out there, or you can roll your own from stripwood.

If you want steel or concrete, I'd go with a ballasted deck bridge. A fairly convincing plate girder bridge can be made by gluing the girders from the Atlas thru plate girder to the sides of your roadbed. Low to represet a deck plate girder with a simulated ballast deck is my preference, but you can put them high to represent a thru plate girder.

Walthers makes several overpasses, and smaller manufacturers make some that could work as well.

Chris



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chljohns

Posted - 2006 July 26 :  8:57:20 PM  Show Profile
quote:
Originally posted by smudgeloco

You can have a curved trestle, or a curved viaduct - you cannot have a curved bridge! A bridge is an unsuported span between two points. I know it can be an arch or a suspension bridge, and as such supported. You get curved bridges holding up roadways, but these have supports along their length, usually concrete pillars.

Michael.



Actually, you can have a curved bridge, they just aren't common on railroads (but they do exist). And a bridge is more than just a simple span, it's the whole structure to cross whatever you need to cross. Viaducts, trestles, arches, etc. are all kinds of bridges.

Chris



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Allen Gaspers

Posted - 2006 July 26 :  9:27:47 PM  Show Profile
This is the track plan I'm working on, I need to replace this section of track to have a small stream running under it, (the nephews think we need a bridge :) Download Attachment: plan 8X12.jpg
176.27 KB



Edited by - Allen Gaspers on 2006 July 26 9:29:28 PM

Country: USA | Posts: 472 Go to Top of Page

D.Harrison

Posted - 2006 July 26 :  9:35:49 PM  Show Profile  Visit D.Harrison's Homepage
quote:
Originally posted by chljohns

quote:
Originally posted by smudgeloco

You can have a curved trestle, or a curved viaduct - you cannot have a curved bridge! A bridge is an unsuported span between two points. I know it can be an arch or a suspension bridge, and as such supported. You get curved bridges holding up roadways, but these have supports along their length, usually concrete pillars.

Michael.



Actually, you can have a curved bridge, they just aren't common on railroads (but they do exist). And a bridge is more than just a simple span, it's the whole structure to cross whatever you need to cross. Viaducts, trestles, arches, etc. are all kinds of bridges.

Chris



Chris, I have to agree with Michael, but I would like to know more about your "they do exist" examples. This has been debated before all over the internet. Yes, we have a curved bridge on the CTA "L" system where the former Lake-Dan Ryan turned east-west at 18th ST. It was a welded steel plate box girder supporting a concrete ballasted deck. But "L" car loadings are no where near railroad loadings.

David Harrison



Country: USA | Posts: 2770 Go to Top of Page

chljohns

Posted - 2006 July 26 :  10:28:08 PM  Show Profile
quote:

Chris, I have to agree with Michael, but I would like to know more about your "they do exist" examples. This has been debated before all over the internet. Yes, we have a curved bridge on the CTA "L" system where the former Lake-Dan Ryan turned east-west at 18th ST. It was a welded steel plate box girder supporting a concrete ballasted deck. But "L" car loadings are no where near railroad loadings.



David, I design bridges for a living, so I'll stick with the industry definition (and the dictionary).

Unfortunately, I don't have any specific examples of curved span railroad bridges. I have seen them in industry literature, but never saved the examples. They're rare, but there's generally nothing physically preventing a curved span railroad bridge. It's not an efficient or cost effective solution most of the time.

Curved span highway bridges are fairly common.

Chris



Edited by - chljohns on 2006 July 26 10:50:44 PM

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chljohns

Posted - 2006 July 26 :  10:36:40 PM  Show Profile
Allen, that looks like the perfect spot for a timber trestle.

As I said, I like the Campbell kits, if you can find them.

http://www.walthers.com/exec/productinfo/200-303[/url

http://www.walthers.com/exec/productinfo/200-301[/url

http://www.walthers.com/exec/productinfo/200-302[/url

This one should be similar to the Campbell ones

http://www.walthers.com/exec/productinfo/184-167

If you prefer plastic kits, this might be a good one. I haven't used it, but I've seen good results with it.

http://www.walthers.com/exec/productinfo/5-9333147[/url

Chris



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Dutchman46

Posted - 2006 July 26 :  10:39:50 PM  Show Profile
Valley Model Trains might have the Campbell curved trestle in stock.

http://www.valleymodeltrains.com/website/200ho.html

Personally, I'd build one from scratch, as Doc and others have suggested.


Bruce
Modeling the railroads of the Jersey Highlands in HO and the logging railroads of Pennsylvania in HOn3

Country: USA | Posts: 1167 Go to Top of Page

chljohns

Posted - 2006 July 26 :  10:44:49 PM  Show Profile
quote:

Personally, I'd build one from scratch, as Doc and others have suggested.



That's what I do now, but the Campbell kit has good plans and directions if you haven't built one before.

I'd also reccommend the Paul Mallory book "Bridge & Trestle Handbook", available from Carstens publishing. It's the best guide for modeling RR bridges I've seen.

Chris



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csxnsdan

Posted - 2006 July 26 :  10:47:11 PM  Show Profile
There is a curved trestle on the old L&N short line to Louisville.It is now the LCL division of CSX.The trestle is located close to Covington KY.If you look up some of the old Seaboard System promotional photos you will see this bridge.This line runs very close to KY 17.The trestle is located close to where Pleasure Isle used to be.I believe CSX has also used this trestle for promotional photos.This could give you an idea of what a curved trestle would look like.Dan

It aint easy being cheesy.

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CDF

Posted - 2006 July 27 :  09:26:54 AM  Show Profile
Hello all, here is a photo from Ann Arbor MI. This is where the Ann Arbor RR crosses the Huron River.



Photo credit goes to Steppenwolf photo's


CDF

Country: USA | Posts: 226 Go to Top of Page
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