I am looking for some ideas and suggestions for building curved trestles and/or bridges. The radius is 24” with a length of approximately 30”. I am using code 83 track. I am considering the JV Models curved wood trestle or the Micro Engineering Tall Viaduct and bents.
I've build my curved trestles from a pile of wood.
Wolfgang
Pueblo & Salt Lake RR
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Prior to the very recent developments in curved-beam construction, there was no such thing as a curved bridge. Bridges are built under curved track by connecting short tangent bridges at angles appropriate to the curvature.
A timber trestle on a curve will have each bent on a radius line of that curve. The center of each floor beam between bents will be perpendicular to the curve radius half way between bents, and floor beams will meet at an angle equal to the angle between adjacent bents. Extra floor beams may be added to assure that the rails will always be over a floor beam.
The same rules apply to steel viaducts with single-panel bents. If the viaduct has box bents, the entire box will be perpendicular to the curve radius passing through its center, floor beams within the box will be of the same length and the differential length between inner and outer floor beams will be absorbed by the spans between box bents.
One of my favorite prototype bridges has deck girder spans supported by masonry piers. Since the piers are circular in cross-section it isn't obvious that the girders of each span are of unequal length.
Chuck (Modeling Central Japan in September, 1964 - with lots of bridges on curves)
The instructions in the ME tall viaduct kits have a section on how to construct the girders to achieve almost any radius you want. It's a matter of using a template and clipping the inside girders. I've got a fairly long ME viaduct on a 36" curve built from two of the kits. Follow the directions in their very detailed construction manual, and it works like a charm.
Tom
Tom View my layout photos! http://s299.photobucket.com/albums/mm310/TWhite-014/Rio%20Grande%20Yuba%20River%20Sub One can NEVER have too many Articulateds!
My 2 cents, things to remember (from "bridge engineering" in an old MRR).
1. Most railroads preferred to fill cuts with dirt and culverts to avoid bridges (cost). Exception was mountains - too far to bring dirt in, or tall spans (over 30'H), or traffic.
2. 80% of trestles were "pile", only 20% were "framed timber". It's easier to drive trees, if available and if the ground allows it.
3. Framed bents should rest on a foundation. Don't forget the girt or horizontal bracing thru the bents near the track centerline. Make bents with the sway braces, then connect bents together with girt beams, and then add the side braces (and not every bent needs them). Last add fire barrels and upper walk deck.
4. If you have a curved wood trestle connected to a steel bridge (a common approach), don't forget to have double bents at the steel, or better put a pier between them. If there's a fire the steel part won't collapse.
Terry
"Curved" bridges are only possible utilizing masonry--stone or concrete--arches. Track can curve atop a bridge but, as has been pointed out, the bridge structure itself, except in the case cited above, consists of short spans of straight sections joined together atop some sort of tower. There are examples of these towers being masonry but the track-carrying sections themselves will always be straight.
Masonry bridgework--stone (Starrucca) or concrete (Tunkhannock)--are imposing works-of-art but 21st Century labor expenses would prohibit their construction today--unless, of course, they were being payed for using your tax dollars. (Several astronauts, by the way, have attested to the fact that the mass of both Starrucca and Tunkhannock, as also the Great Wall of China, makes them observable from outer space.)
From the far, far reaches of the wild, wild west I am: rtpoteet
tomikawaTTPrior to the very recent developments in curved-beam construction, there was no such thing as a curved bridge. Bridges are built under curved track by connecting short tangent bridges at angles appropriate to the curvature...
Lika so....
eds-trains I am looking for some ideas and suggestions for building curved trestles and/or bridges. The radius is 24” with a length of approximately 30”. I am using code 83 track. I am considering the JV Models curved wood trestle or the Micro Engineering Tall Viaduct and bents.
The choice of bridge has a lot to say on the style and time period of your railroad. In most eras and situations, I wouldn't model a wooden trestle more than one or two stories tall. Steel was the norm.
Mark
Well, it kinda depends on the terrain, budget, materials, capabilities of the engineering department, commitments for deliverables....so for example. the line of the E&N Ry running between Parksville and Port Alberni on Vancouver Island runs on the north shore of Cameron Lake. Four summers ago I walked the five miles along the north side of the lake on the now abandoned right of way. That right of way was used last in the late 80's (I seem to recall...I could check) and it includes three substantial timber frame bent trestles, none of which is less than 40' high or 60 yards long.
Here is a shot taken of the largest from the south side of the Lake. It was about 90 m long and about 35 m high at the deepest point.
Crandell, that bridge is on a backwoodsy shortline. Typical of girder bridges carrying more traffic were like this:
markpierce Crandell, that bridge is on a backwoodsy shortline. Typical of girder bridges carrying more traffic were like this: Mark
Mark:
Ooh, we've been up on the High Line lately, haven't we?
twhite Mark: Ooh, we've been up on the High Line lately, haven't we? Tom
Tom, this is near the west end of the Feather River Canyon (some tens of miles west of the Keddie Wye) on the former WP, now UP, line. The BNSF has trackage rights here for its trains coming from Oregon on this portion of the UP. In fact, the only trains I saw on this line during the drive were BNSF's.
Photos like the above keep reminding me about what has always bothered me about Micro Enginering's viaduct model. Most such prototype bridges have the vertical thickness of the bridge girders the same, while ME has thinner 30'-girder-bridge sections than its 50'-girder-bridge sections.
Okay, I think I know where it is, now. I'm just not used to seeing it photographed from that angle. You must have driven up the side-canyon road access from the highway behind it to get that shot, right? Really nice.
You're right about the ME girders--I was going to mix and match when I built mine, but decided to stick with the 30-footers. But it DOES give that viaduct a really 'spidery' effect. I think you remarked when you saw my photo that it looked 'scary', LOL!
twhite Okay, I think I know where it is, now. I'm just not used to seeing it photographed from that angle. You must have driven up the side-canyon road access from the highway behind it to get that shot, right?
Okay, I think I know where it is, now. I'm just not used to seeing it photographed from that angle. You must have driven up the side-canyon road access from the highway behind it to get that shot, right?
Tom, my Sweetie took this picture while I was driving west on the main road avoiding a fall into the Feather River.
And then again, there are combination wood/steel bridges, although this is a contemporary narrow-gauge example.
markpiercePhotos like the above keep reminding me about what has always bothered me about Micro Enginering's viaduct model. Most such prototype bridges have the vertical thickness of the bridge girders the same, while ME has thinner 30'-girder-bridge sections than its 50'-girder-bridge sections. Mark
I'm not sure, but the M.E. 30' and 50' girder bridges may have been developed before the tall viaduct, and using the disparate heights was merely a matter of expediency when used with the viaduct.
Wayne