Hey all,
I have a ~32inch span I was planning to bridge the first 150 feet with the nice ME deck plate girder bridge (already built). The last 12 inches are over the approach my yard throat and my reversing loop/mainline (used for continuous running). I am trying to decide between a deck truss (warren) kitbashed Atlas for 12 inches (2 kits required to make 1...) or a warren through truss... any thoughts? I like the look of the deck girder, but since this spans an area where trains could REALLY crash to the cement, I am thinking through truss, and extending a scratch built hand rail and walkway on the plate girder outside. I would love your thoughts regarding this... would it look un-prototypical (I am NOT a rivet counter)? Any of you done this and have pictures? Let me know...
Oh, BTW I am HO scale...
Brian
Atlas have a nice new bridge out soon... A big through truss.
I wouldn't join two trusses end on to make a long one as the depth of the sides would not represent a girder sufficient for the span.
As far as looking reasonably realistic the question you have to answer is "why is one bridge and under girder and the next an over girder"? Come up with a good reason and you have an okay bridge combination. From pics I've seen quite a few through trusses in the US are approached by deck girders.
It would help if someone like Mark B. would offer an opinion since he is an engineer, but I have seen pictures with some odd combos, so ...take yer pick. Make something up! Make it unique.
Personally, I would use a Warren truss because I have one left over from the previous layout. Aren't the Atlas ones about 10"?
Thanks, Dave. That is what I am leaning towards..., but just wanted ideas... As for the Altas, it is cool looking... a bit long for me...hmmm need like a 12-15 inch bridge.
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Yeah the problem I have is I need like 12 inches. By modifying the deck bridge I would just add a panel. The problem with their deck truss bridge is that it is not symetrical, meaning the middle panel is larger than the ends. This is a PAIN if you want to kitbash or make skewed, which was part of my plan
You probably don't want a 12"-span truss next to a 20"-span plate girder, unless they can be weathered to represent two widely divergent construction dates (as in the newer plate girder replaced an older truss in the same location). In terms of modern engineering & construction practices, a plate girder is more economical to build and maintain for short and intermediate spans, although trusses remain the way to go for long spans (like crossing major rivers and such). Up through the first half of the 20th century, when steel was expensive and labor was cheap, a truss design was more economical in more cases. So, barring some extenuating circumstance like clearance restrictions, you're not likely to find many instances of a short truss adjacent a long plate girder on the prototype.
"I am lapidary but not eristic when I use big words." - William F. Buckley
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Is the 20" plate girder span one continous span? Or a series of shorter spans supported with piers? Plate girders spans are usually only 30 to 50 feet, although newer ones can approach 70 feet.
For the truss section, have you looked at the Walthers or the Central Valley kits? If they don't work, the CV bridge girders are a good way to scratchbuild what you need.
Nick
Take a Ride on the Reading with the: Reading Company Technical & Historical Society http://www.readingrailroad.org/
Here is a picture I found that shows several combinations along its length.
http://www.monon.monon.org/railpixs4/07-12circustrain-merrimac.jpg
Selector,
That is EXACTLY what I am building (except trains, not water, going under my bridge). The span is 90 feet, so I am thinking a through truss would be more prototypical according to some of the input.
Here is what I was thinking of...
http://bridgehunter.com/mo/ste-genevieve/rough-creek/
Not sure if the span would be too long for the deck truss...
mononguy63 wrote: You probably don't want a 12"-span truss next to a 20"-span plate girder, unless they can be weathered to represent two widely divergent construction dates (as in the newer plate girder replaced an older truss in the same location). In terms of modern engineering & construction practices, a plate girder is more economical to build and maintain for short and intermediate spans, although trusses remain the way to go for long spans (like crossing major rivers and such). Up through the first half of the 20th century, when steel was expensive and labor was cheap, a truss design was more economical in more cases. So, barring some extenuating circumstance like clearance restrictions, you're not likely to find many instances of a short truss adjacent a long plate girder on the prototype.
Sorry if not clear here...
Lead up to the area of question is 5 x 50' deck girder bridges (ME 150' kit).. this gets me to the area of question, about 12-15" (90 scale feet) over my yard throat and run-arround, of which 12 need to be a single span (pretty hard to squeeze a support in). What I was wondering, is if a warren through truss bridge or a or warren (or pratt) deck bridge would be more prototypical... I have seen both in prototype (see previous post), just not sure on the spans they would be able to cover without mid support.
Railroads prefer deck designs unless clearance issues dictate otherwise. Keep in mind the longer the span the deeper the bridge trusses.
Here's the center span of the now abandoned PRR viaduct spanning the Brandywine Valley at Downingtown:
Here's one end of PRR's through truss bridge over the Main Line at Whitford, PA:
I'm thinking that a deck truss bridge would be cheaper (for a real railroad) than a through truss. For one thing, the bridge is narrower--less steel. And when there is that consequent less steel, there's still less, because you don't need the bridge to be as strong because there's less dead weight. I hope that just made sense.
Anyway, I think that's why deck trusses are generally preferred unlesss there's a clearance problem underneath. When the bridge passes over waterways, besides the clearance for boats/ships, you've also got to deal with flood waters and the consequent trash hitting the lower part of a deck bridge.
I think the above would also apply to girder bridges.
Ed
ShadowNix wrote: Hey all,I have a ~32inch span I was planning to bridge the first 150 feet with the nice ME deck plate girder bridge (already built). The last 12 inches are over the approach my yard throat and my reversing loop/mainline (used for continuous running). I am trying to decide between a deck truss (warren) kitbashed Atlas for 12 inches (2 kits required to make 1...) or a warren through truss... any thoughts? I like the look of the deck girder, but since this spans an area where trains could REALLY crash to the cement, I am thinking through truss, and extending a scratch built hand rail and walkway on the plate girder outside. I would love your thoughts regarding this... would it look un-prototypical (I am NOT a rivet counter)? Any of you done this and have pictures? Let me know...Oh, BTW I am HO scale...Brian
It seems everyone has forgotten this major point. I may be missing something here, but I would build it plate girder leading into a warren truss exiting on plate girder. All supports for the bridges being UP to cover any derailments. Plate girders may be easier to kitbash, so, maybe reversing that to cover that odd length?? I am using a warren truss bridge in a spot just to be certain any trains dont fall off a (straight away) area in the back of the layout. Of course the 9" length is ok for mine.
Of course, I guess CSX can tell you if a train is going to leave the tracks, then leave the tracks it shall!!!!
-G .
Just my thoughts, ideas, opinions and experiences. Others may vary.
HO and N Scale.
After long and careful thought, they have convinced me. I have come to the conclusion that they are right. The aliens did it.
Hmmm... great replies guys... thanks for the info! I may do a little of both... a deck girder (warren) with a hefty safety rail (well, brass with piano wire?)... I like that look better. I may modify my area underneath so there is a "safety net" of scenerey below rather than open space...
Why is everyone worried about damage to locomotives from derailments? Derailments anywhere other than at a mis-aligned turnout indicate serious track issues. If you are concerned about tracking on a bridge, slow to yard speed on it, and keep an eye on things. Better yet, do a patient and good job of fixing the bridge into place, and then to laying solid trackwork atop it.
That said, I would also favour the Warren through between two girders...looks prototypical, I think.
My
So I decided to build the warren truss deck bridge tonight... I combined 2 atlas kits, making the two 3 panel warren deck bridges into one 5 panel deck bridge... here is the frame (unpainted without rail)... I figured I would try since all it cost me is 8 bucks and 3 or so hours of time...
And a close up... I added one support (courtesy of central valley); I also added some old rivet plates cut off an old ?bachman bridge... NOW, I know why I have all that old junk lying around!
Thanks for the help deciding...
selector wrote: Why is everyone worried about damage to locomotives from derailments? Derailments anywhere other than at a mis-aligned turnout indicate serious track issues. If you are concerned about tracking on a bridge, slow to yard speed on it, and keep an eye on things. Better yet, do a patient and good job of fixing the bridge into place, and then to laying solid trackwork atop it.
Where is train is crossing a bridge high above the basement floor, I'm more worried about a carelessly placed elbow than bad trackwork.
Luckily, in the spot this bridge is, one would have to TRY (very hard at that!) to hit the train as it crosses the bridge... I will post a finished pic in a few weeks!
ShadowNix wrote: That is EXACTLY what I am building (except trains, not water, going under my bridge). The span is 90 feet, so I am thinking a through truss would be more prototypical according to some of the input.Here is what I was thinking of...http://bridgehunter.com/mo/ste-genevieve/rough-creek/
Got some Pennsylvania Railroad prototype for you:
[1] Here is a 1950s semi-overhead picture at Dave's Electric Railroads of the Pennsy's (4-track mainline) Stone Bridge over the Conemaugh River and over a steel mill-access road (on the right) and a state highway (on the left). You can even see a Johnstown Traction Company PCC trolley emerging from the PRR's Stone Bridge underpass.
http://www.davesrailpix.com/john/htm/john186.htm
[2] Here is a series of 100 year-old pictures dating to the 1889 Johnstown Flood. Note the unique "layered" stone-laying on the underside of each stone arch in picture two which is structurally still in place on the Stone Bridge...
http://www.jaha.org/edu/flood/why/img/stonebridge_gallery/pages/Stone_Bridge_drawing.html
[3] Here are two pictures of the Stone Bridge overlooking Point Park apx. 1/4 down on the webpage that provides current-day perspective...
http://webpages.charter.net/gdsbmmllp/city/city.htm
Conemaugh Road & Traction circa 1956
Dave-the-Train wrote: As far as looking reasonably realistic the question you have to answer is "why is one bridge and under girder and the next an over girder"? Come up with a good reason and you have an okay bridge combination.
As far as looking reasonably realistic the question you have to answer is "why is one bridge and under girder and the next an over girder"? Come up with a good reason and you have an okay bridge combination.
One reason for changing from under- to over-girder is for additional clearance below the bridge for road, rail or river traffic to pass safely.
The main problem with through-truss/girder bridges is that they limit the width and height of the train. The maximum width and height of any load being carried by a train will be determined by the minumum horizontal and vertical clearances along the line. Tunnels, bridges, buildings and other structures that are close to the tracks are critical factors that can limit train size. Wherever possible, railroad companies prefer to use under-truss/girder so as to maximize the size of the loads they can carry. Over-size loads have to be re-routed along other lines with the necessary minimum clearances. This can lead to increased costs and travel times -- both of which aren't good for a railroad's bottom line.