# HO scale 22 inch radius bridge sections



## Stejones82 (Dec 22, 2020)

Can anyone please point me toward curved bridge sections, I'm thinking girder bridge maybe but open to anything. HO scale, 22 inch radius. I only need about 30 - 45 degrees. 

Thanks, 

Steve


----------



## 65446 (Sep 22, 2018)

There are no such things as curved bridge sections..
You have multiples of trestle 'bents', deck bridges, or any other type of suspensions, each which are straight, installed on a curved route one after the other, and flex or sectional track (blank rail in 1:1 scale) is then curved to go on top of them.


----------



## LateStarter (Mar 12, 2016)

Campbell is one company that made curved trestles. There were (are) others, but I don't recall right now.








Campbell Scale Model 70' Curved Trestle -- 9-21/32 x 1-3/8" - HO


Check out the deal on Campbell Scale Model 70' Curved Trestle -- 9-21/32 x 1-3/8" - HO at Train Sets Only




www.trainsetsonly.com


----------



## LateStarter (Mar 12, 2016)

Noch, Marklin, and Faller also make curved bridge sections.


----------



## 65446 (Sep 22, 2018)

The Campbell trestle in post #3 above is technically not a curved bridge..It's separate 'bents' in a curved route with radiating ties and curved rails on top as I explained..
If you want a European look there are curved, all molded concrete or brick viaducts.
Modern Asian RRs use curved concrete as well; perhaps in Africa, too....
But, North American prototype rarely, if at all, has done it this way, other than short ramps, say.
BUT..It's your railroad !! You are the CEO of it..You do what YOU like..
Especially if it's a fictitious RR; if it's plausible, juz do it...

*I have edited this several times for syntax / better clarification of my intent... M 🌄🛤


----------



## aaron_roch (Mar 31, 2021)

LateStarter said:


> Noch, Marklin, and Faller also make curved bridge sections.


these are likely to be much tighter radius than 22”. The Noch bridges certainly are.

For sure worth looking up the other two though.


----------



## Old_Hobo (Feb 20, 2014)

Curved Railway Bridge


----------



## mesenteria (Oct 29, 2015)

Despite what may appear for our models, railroad bridges are only ever made in chords, and that means straight. I think there could be a case for reinforced concrete bridges, but I am not able to provide an example, maybe a modern one in Europe. But because of the dynamic forces and heavy tonnages, bridge spans are limited in length and will 99% of the time be straight between piers or abutments. However, if they are wide enough, they can support curved rails and ties or ballasted ties so that they can be set in the middle of a curved path, whether S curved or a continuous arc.

The end of the CN Bridge across the Fraser River in Southern BC. There is a symmetrical path outside this image, to the left. Note the chorded segments in the portion depicted:










This example is the CN bridge across the Thompson River at Lytton. Distinctly corded construction, but the S-curve doesn't seem to mind.


----------



## MichaelE (Mar 7, 2018)




----------



## aaron_roch (Mar 31, 2021)

Lol!

So the European manufacturers all make curved bridges, but I haven’t found one more than 18” radius.

That Noch bridges above are 450mm radius.

This guy will apparently build you a curved wooden trestle to your specs (see the note in the description).









Model railway HO/OO Scale, Modular Wooden Trestle Bridge. Straight Section | eBay


Find many great new & used options and get the best deals for Model railway HO/OO Scale, Modular Wooden Trestle Bridge. Straight Section at the best online prices at eBay! Free delivery for many products.



www.ebay.co.uk





P.S. If you’d like that Noch plastic one, I’ll mail you mine for the cost of shipping.


----------



## Lemonhawk (Sep 24, 2013)

I suspect the masonry arches are straight also.


----------



## CTValleyRR (Jul 26, 2014)

MichaelE is fond of showing prototype pictures when people are looking for hobby products. While it does serve to validate the "there is a prototype for everything" theory, it's not much help to the modeler looking for parts.

However, while masonry structures can be built on a curve, it's much more difficult and expensive to do on steel and wooden structures. Most of the time, the support structure underneath these structures are a series of short, straight segments, or chords (or trapezoidal, if you connect the ends of the beams across) underneath curved roadway or rails. MichaelE's top and bottom photos actually show corded structures, if you look carefully, as do the ones posted by mesenteria. 

It's actually fairly easy to kitbash or scratchbuild. The only real trick is to make sure you have enough clearance that any walkways, parapets, lights, etc, don't get sideswiped by the overhang of your equipment due to the radius of the curve.


----------



## MichaelE (Mar 7, 2018)

This is going to be too wide for your purpose with a 30" radius, but if you don't want to scratchbuild a plate girder or trough deck bridge, the Vollmer product is the only bridge I could find that was greater than 18" radius.

This product has been discontinued but is still available from sources in Europe.


Vollmer 42547











For the radius you need, scratchbuilding may be your only option.


----------



## Stejones82 (Dec 22, 2020)

Thanks everyone. I guess I am somewhat surprised that given our modeling real estate concerns that there are not curved bridges available in all the standard radius. 

I'm thinking about maybe modding my own. Like I said, I only need about 30 degrees of arc. so if I make a, say 2x4 form cut to 23" outside and 21" inside radius, maybe I can carefully 'bend' girder pieces using a heat gun and clamps. I could get away with a bed of cut hardboard. 

Thanks for looking and I am still open to ideas! 

PS - - I really don't need the supports so much. 










This is why I'm thinking girder. Will be a really nice viewing spot for the trains as they roll by on that 22 inch curve. And it buys me a little more run length for another loco (as in crazy, not locomotive) idea I am toying with. 

Supports would be triangle wood or hardboard brace from the table edge fascia. 

Before the bridging idea, I was thinking merely of a surface extension from the table of that arc, but I think the bridge would be a nice touch


----------



## GeeTee (Dec 23, 2020)

bridges all have to be chorded construction , including masonry ,otherwise it generates huge cantilever forces , and the bridge will collapse .


CTValleyRR said:


> MichaelE is fond of showing prototype pictures when people are looking for hobby products. While it does serve to validate the "there is a prototype for everything" theory, it's not much help to the modeler looking for parts.
> 
> However, while masonry structures can be built on a curve, it's much more difficult and expensive to do on steel and wooden structures. Most of the time, the support structure underneath these structures are a series of short, straight segments, or chords (or trapezoidal, if you connect the ends of the beams across) underneath curved roadway or rails. MichaelE's top and bottom photos actually show corded structures, if you look carefully, as do the ones posted by mesenteria.
> 
> It's actually fairly easy to kitbash or scratchbuild. The only real trick is to make sure you have enough clearance that any walkways, parapets, lights, etc, don't get sideswiped by the overhang of your equipment due to the radius of the curve.


If you look at other photos of those same bridges you'll see that all of them are chorded. 

pretty much all bridges all have to be chorded construction , including masonry . Forces on either side of the pillar have to balanced,otherwise it generates huge cantilever forces , and the bridge will collapse under its own weight. To design something to counter that would cause the cost to skyrocket. The only way to build a curved masonry bridge that doesn't want to collapse is make a single continuous pillar .

If you take a curve object and try to support it at the ends you'll see what I'm talking about. It will fall over. 

You could do it with steel if you had enough strength and enough concrete to anchor it . It would be highly stressed structure and prone to metal fatigue and collapse .


----------



## Steve Rothstein (Jan 1, 2021)

Stejones82 said:


> This is why I'm thinking girder. Will be a really nice viewing spot for the trains as they roll by on that 22 inch curve. And it buys me a little more run length for another loco (as in crazy, not locomotive) idea I am toying with.


Just remember that if a crazy idea works, it was genius and not crazy.

I was thinking of how to do this as easily as possible and all I can come up with, based on others comments, is to take a regular straight bridge and cut some very narrow wedges out of it to force it to curve when you glue it back together. I think that might be beyond my skill level but I might be tempted to try it anyway.


----------



## MichaelE (Mar 7, 2018)

After you cut out the wedges for the curvature gap, you will be stretching the opposite side when you bring the cut edges together. This may still work if the opposite side girders are not too thick. Gentle heating with a hair dryer to soften the plastic slightly should work.

You could also scratch build the bridge to your desired radius with Evergreen structural plastic. Scratch building will allow you to construct a precisely fitting bridge to your exact requirement.


----------



## traction fan (Oct 5, 2014)

Stejones82 said:


> Thanks everyone. I guess I am somewhat surprised that given our modeling real estate concerns that there are not curved bridges available in all the standard radius.
> 
> I'm thinking about maybe modding my own. Like I said, I only need about 30 degrees of arc. so if I make a, say 2x4 form cut to 23" outside and 21" inside radius, maybe I can carefully 'bend' girder pieces using a heat gun and clamps. I could get away with a bed of cut hardboard.
> 
> ...


Stejones82' & Steve Rothstein;

A real railroad bridge with curved girders, supported in normal fashion, (only at the two ends) would collapse under the first train to cross it. And that's assuming it would even support its own weight. There would be nothing but air to support the middle of the bridge. It would simply roll over to the outside of the curve.
A far better choice would be to use the series of straight chords that many have mentioned. Steve, this is not only something that actually exists, and indeed, is fairly common, its also easier to build, than trying to cut little pieces out of a straight girder and force it into being a "curved girder." Which, if such a thing exists at all, would be an oddball exception, and not normal construction, especially for a bridge that has to be strong enough to support trains. The whole point of a girder's design, and construction, is to prevent any bending and to stay rigidly straight.

The steel trestle in the photos is an N-scale model on my own layout. It does carry a curved track, at about a 36" radius, but the individual plate girders are each quite straight, and joined at angles to each other. You can use the same technique, and similar kits, to make a trestle in any radius, and any scale, you wish. Mine is a kitbash of several of Micro Engineering's N-scale plate girder bridge kits, and a Micro Engineering "Tall steel viaduct" kit. The same kits are available in HO-scale.
If you don't need a long span, one of the tall steel viaduct kits by itself, may work for you. I only used the N-scale plate girder bridge kits because I model in that scale. The viaduct kit is actually HO-scale, and includes HO-scale girders. I substituted the N-scale girders, and modified the viaduct towers to look more like N-scale, and like the Milwaukee Road prototype trestles.

Traction Fan


----------



## mesenteria (Oct 29, 2015)

If you cut an arc of scrap plywood, say 2 feet in length, wide enough to hold a single or double track in any scale, with a radius of about 18-24", and place the ends on an abutment of some kind as a straight truss or girder would be, see what happens. As alluded to some posts back by someone else, the bridge will fall over on the outside of the curve because it has so much torsion wanting to pull the mass at the apex of the arc toward the center of gravity...the Earth's. This is why the typical weight-bearing transportation bridge will be chorded. The deck, yeah, you can play around with it to an extent, with tracks or a roadway to follow, but the supporting structure has to be chorded.


----------



## CTValleyRR (Jul 26, 2014)

Steve Rothstein said:


> Just remember that if a crazy idea works, it was genius and not crazy.
> 
> I was thinking of how to do this as easily as possible and all I can come up with, based on others comments, is to take a regular straight bridge and cut some very narrow wedges out of it to force it to curve when you glue it back together. I think that might be beyond my skill level but I might be tempted to try it anyway.


As others have pointed out, a true curved bride is neither strong nor prototypical. Instead of cutting one side and trying to curve the other, cut a series of evenly shaped and spaced wedges out of the straight bridge structure. His will create several trapezoid shapes, whichcan be glued together to form your chorded structure. Place your curved rails on this.


----------



## Geno the Viking (Feb 29, 2012)

Stejones82 said:


> Can anyone please point me toward curved bridge sections, I'm thinking girder bridge maybe but open to anything. HO scale, 22 inch radius. I only need about 30 - 45 degrees.
> 
> Thanks,
> 
> Steve


I spent ages looking for one with a 24" radius and gave up. I built my own trestle using Walthers Shinohara code 83 bridge track and curving it. Lots of work but worth it. The short girder sections are straight.


----------



## Yoppeh7J-UPmp954 (Nov 23, 2014)

The Campbell trestle can be made Straight, or with 36, 34, 32, 30, 28, 26, 24, 22, 20 or 18 inch radius curves. If I remember right the one I made back about 15 years ago was 26 inch radius. Yes to the all the perfect rivet counters it is short straight sections but it produced the base for the 26 inch radius curved track to sit on.
A through plate-girder bridge got a new wider bottom section as it is on a the edge of a curve. Big Boys, Cab Forwards and 4-12-2s need extra room and as it has been a while I think one end is wider than the other.


----------



## CTValleyRR (Jul 26, 2014)

Yoppeh7J-UPmp954 said:


> The Campbell trestle can be made Straight, or with 36, 34, 32, 30, 28, 26, 24, 22, 20 or 18 inch radius curves. If I remember right the one I made back about 15 years ago was 26 inch radius. Yes to the all the perfect rivet counters it is short straight sections but it produced the base for the 26 inch radius curved track to sit on.
> A through plate-girder bridge got a new wider bottom section as it is on a the edge of a curve. Big Boys, Cab Forwards and 4-12-2s need extra room and as it has been a while I think one end is wider than the other.


This isn't a case of rivet counting at all (and thank you for being obnoxious enough to suggest it). It's a case where emulating the prototype SOLVES the problem that the OP is wrestling with, with an understanding that it is sound physics to build it properly. The Campbell trestle doesn't have a prototypical structure underneath it (a rivet counter would recommend not using it for THAT reason, which no one has), but because of physics, requires narrowly-spaced trestles to hold up a bridge that would otherwise fall down due to the forces of gravity and the centripetal acceleration of the train. And, in fact, all people you snidely refer to as the "rivet counters" have already observed that you do, in fact, place CURVED rails in these chorded structures, and that you have to be careful of the overhang.


----------



## DOOFUS (May 20, 2013)

CTValleyRR said:


> As others have pointed out, a true curved bride is neither strong nor prototypical. Instead of cutting one side and trying to curve the other, cut a series of evenly shaped and spaced wedges out of the straight bridge structure. His will create several trapezoid shapes, whichcan be glued together to form your chorded structure. Place your curved rails on this.


----------



## DOOFUS (May 20, 2013)

I just tried to place a 22" radius track on an old Ahm plate girder bridge section. checked it with NMRA Clearance and plenty of room. I believe the Atlas plate girder bridge also has same dimensions. Problem is the 30 to 45 degrees of radius you require. You might be able to put 2 or 3 together with the generous use of a razor saw, and you will need appropriate support piers. Most plate girder bridges were had ballasted track, so placing the track without removing the existing bridge track wound not be a problem. if you need more inspiration take a look at Western Pacific's Keddie Wye.


----------

