Is it necessary to have a straight section leading into and out of a straight bridge, or can you run a curve on either end?
Bear "It's all about having fun."
You can have curves on an end of the bridge. That is entirely prototypical, somewhere, somehow.
But, on my layout, I make sure that any track on either side of the bridge track is straight for at least the length of the longest piece of rolling stock.
Rich
Alton Junction
I have curves adjacent to some of my bridges, and it doesn't cause a problem. It wouldn't surprise me if the prototypes tried to put a straight before a bridge, just to reduce the already low possibility of a derailment.
It takes an iron man to play with a toy iron horse.
they sure do, but real railroads have to face lots of problems. Usually a bridge is able to move a wee bit to allow some shrinkage and expansion, due to changes of temperature. The added force on the tracks and also on the supports of the bridge, due to the start of a curve, could lead to derailments. At least an easement will have been used, speeds limits as well.
On model railroads the forces are no issue at all. Overhang of long engines, coaches or cars could be a problem; depending on the design of the bridge. The above is important in the trackplanning stage. Must you allow space for easements and straights? Your combination of radius, equipment and bridge design should be tried out before omitting space for easements and a straight. Finding the extra space later might be impossible.
Also on a model railroad speed limits could be part of the game.
Paul
Ok, good, thanks! Originally I had a short straight sectionon ether end of the bridge but for some reason the gremlins took over between the drawn track plan and the laying of track, and the straight sections have to be eliminated to accommodate the bridge.
Speed limits and easements are more than possible in this case
I would be less concerned about derailments than I would about inadvertent uncouplings.
Hi Rich
inadvertent uncoupling is due to lack of easements or to tight radii, has nothing to do with a bridge. A kink just before a bridge lead to desaster. Immaculate trackwork is important, ty Tomikawa.
Paulus Jas Hi Rich inadvertent uncoupling is due to lack of easements or to tight radii, has nothing to do with a bridge. A kink just before a bridge lead to desaster. Immaculate trackwork is important, ty Tomikawa. Paul
Paul,
In an earlier layout, I had a curved track coming off the bridge. For some reason, the bridge track into the curved track caused uncouplings, not derailments, at slower speeds.
Derailments, uncouplings...the hits just keep on coming.
I've had never a problem with this trestle bridge.
In progress picture:
Wolfgang
Pueblo & Salt Lake RR
Come to us http://www.westportterminal.de my videos my blog
Due to the odd shape of my layout room, much of the track is curved. Due to the fact that I have quite a few bridges, it's not surprising that both features often occur at the same places.In the photo below, both curves lead to and continue onto the bridges:
Here's a view of the same area from a different angle. The lower track straightens out on the bridge, while the upper one is curved throughout the length of the bridge and beyond:
This small concrete span is right in the middle of a curve:
This multiple span crossing starts on a curve...
...and after a short length of straight track, ends on another:
This one begins on a curve to the right...
...and ends on a curve to the left:
...as does this one:
I also utilise speed limits, although in many locales, trains of any consequence would be hard-pressed to reach them:
Wayne
Ah, Doctor Wayne, that Warren truss bridge is the subject of this thread. Thank you.
Just to clarify for those not familiar with the various truss types, the through bridge shown in the 6th and 7th photos is a Pratt truss (Central Valley kit), while the deck trusses seen in some of the other photos are Warren trusses (Atlas kits). The type of truss, obviously, matters little to its use on a curve, although the style (deck or through-type) may: using long cars on curves which are on or near through bridges may present side clearance issues.
I am using 40' cars and 4 axles locomotives. I don't think that that will result in the problems you identify doctorwayne.
A little "trial and error" testing might be the best answer. If the bridge is fairly narrow you might find some engine's pilots might hit the bridge end on some types of bridges when there's a curve leading into it, where it would work OK with a short straight section (maybe only 4-6" on either side of the bridge).
My take?
Curves into and out of a through truss bridge - possible clearance issues.
If the bridge is a fairly low sided through girder - not high enough to interfere with the Big Boy's boiler, less of a clearance issue.
Deck bridges - no problem.
Unless you have a vertical kink at the abutment line, there shouldn't be any false uncouplings.
Looked at purely from the point of view of track geometry, it really doesn't make a difference if there's a bridge, tunnel, cut, fill or just track laid directly on flat foam or plywood. There will be cosmetic differences (which, in 1:1 scale, are actually engineering differences) if the bridges have open decks, but those should have no effect on rail geometry. If they do, corrective action is in order.
Chuck (Modeling Central Japan in September, 1964 - with lots of bridges, mostly deck girders)
tomikawaTT My take? Unless you have a vertical kink at the abutment line, there shouldn't be any false uncouplings.
Quit picking on my track work - - - LOL
Lots of prototype bridges are curved, with curves leading up to them. The thing to remember is that for a real railroad, a curved bridge is a series of straight spans with a kink at each joint. Straight beams are much stronger than curved beams. The track itself is curved on top of the beams, either directly or in ballast depending on the bridge and railroad.
You want to see some curves into and out of a bridge? I'm gonna show you some curves.
The first curve in comes off a switch; the second is flex track which simply continues on the mainline. The reason why you see a three-truck shay pulling some heavyweights is because I am testing my curves with long cars and locomotives to make sure they not only work but don't look toy-like with goofy overhangs. So far so good...
They work fine, as I say....but I got a bit of a problem this morning.
Anyone have any ideas about a maintenance of way vehicle to clear up this problem? I'm thinking maybe a hair-dryer mounted on a flat car?!
The St. Francis Consolidated Railroad of the Colorado Rockies
Denver, Colorado
In order to make the rest of my track plan work, I have one 22" radius curve on my layout. It just happens to lead right into a Central Valley plate girder bridge. I had to remove the end interior stiffener along the outside rail because it was catching the pilots of my steamers as they entered the bridge. There's another curve with, I think, a 24" radius leading into the other end of the bridge and all of my engines negotiate it just fine.
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