Good monring MRR's.
I need some advice on how I can span across about 29" from where my foam risers stop to where my next shelf level begins. I thought at first it might have to be a curved bridge/trestle, but I think I can get over it with a long straight bridge/trestle. It's spanning over my Loco service shop so I can only have 2 maybe 3 supports for it. Or I might say the heck with the supports and just bridge it. IMRR. :)
thanks for any advice.
GC
There are a number of bridge kits that could be used together with some modification to span your space with only one support pier. If you can modify your end supports, there is a 200' kit available which is just over 27" for a single bridge.
Good luck,
Richard
"One difference between pessimists and optimists is that while pessimists are more often right, optimists have far more fun."
Just to be clear, is this to be free-standing, a single span? So a viaduct is out of the question?
I believe that, depending on the construction and materials used, a span much greater than about 200' is pushing it for a railroad. The information I have seen says 250' is the practical limit for a Pratt truss, but the article didn't state it was for a particular application...no railway use mentioned.
selectorI believe that, depending on the construction and materials used, a span much greater than about 200' is pushing it for a railroad. The information I have seen says 250' is the practical limit for a Pratt truss, but the article didn't state it was for a particular application...no railway use mentioned.
selector Just to be clear, is this to be free-standing, a single span? So a viaduct is out of the question? I believe that, depending on the construction and materials used, a span much greater than about 200' is pushing it for a railroad. The information I have seen says 250' is the practical limit for a Pratt truss, but the article didn't state it was for a particular application...no railway use mentioned.
In the spirit of selective compression, one might need to apply some selective expansion.
My brother has a span of around 34 3/16" (248 scale feet) and needs a lift-out section because of a door leading to the garage.
Here's a design I came up with for a Pennsylvania through truss bridge. It also has a conduit to carry four conductors of power between the two layout segments, with DIN connectors at each end.
I haven't worked out a way to hide the connectors, but they are somewhat below sight lines and we might just not worrry about it.
It's designed to use banana plugs for alignment and to carry power to the rails.
It was looking pretty good until I started pricing the Plastruct pieces to build it—pretty pricey. But if I decide to fund it, I think it might look pretty cool.
I built a 36” HO trestle for my layout, that was 33 years ago. I used bass wood scale lumber and used oak stain to finish it with a thin coat of Krylon Clear Matt as a sealer.This book has great bridge and trestle info.Mel
My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California Turned 84 last July, aging is definitely not for wimps.
RR_Mel I built a 36” HO trestle for my layout, that was 33 years ago. I used bass wood scale lumber and used oak stain to finish it with a thin coat of Krylon Clear Matt as a sealer.This book has great bridge and trestle info.Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California Turned 84 last July, aging is definitely not for wimps.
Mel, seeing your post made me chuckle. Around 35 years or so ago I built that exact same trestle for my layout. Still have that book.
This past October I finally retired and joined our local model railroading club. Currently another modeler and myself are teamed up on building the same trestle (dubbed the "Big Mama" trestle by the club members), along with the timber deck truss bridge in the center, for the club layout. Definitely a trip down memory lane but much nicer having a partner to share the load with (no pun intended) this time around.
Thanks Richard, do you have brands or anything? Heck, I'll make my bridge span out of wood if I have to and find supports. :)
I would like to have at least one and more so two to make the span. Worst part yet, I'd prefere it to be a curved bridge.
selector I believe that, depending on the construction and materials used, a span much greater than about 200' is pushing it for a railroad. The information I have seen says 250' is the practical limit for a Pratt truss, but the article didn't state it was for a particular application...no railway use mentioned. Gidday Selector, this is one of the references, a PDF, I used to check that I wasn’t putting the OP crook in regards to the plausibility of a single span railroad bridge for a 29” (HO scale 211’) gap. If you’re bored, see from Page 9 on. The maths is far too much for my tiny brain, but I can handle drawings, and I do like pretty pictures! https://onlinepubs.trb.org/onlinepubs/IDEA/FinalReports/Safety/Safety25.pdf Cheers, the Bear.
selector I believe that, depending on the construction and materials used, a span much greater than about 200' is pushing it for a railroad. The information I have seen says 250' is the practical limit for a Pratt truss, but the article didn't state it was for a particular application...no railway use mentioned.
BNSF has a bridge in Bismarck, ND, with a longest span of 400'.
If you really want to get crazy, though not likely to see anything like it in the United States, the Najiehe Railway Bridge has a longest span of 1,155'.
Era and prototype have something to do with how to resolve this interesting challenge. Also knowing just what it is this bridge is over.
Dave Nelson
You could use two central valley kits as they already have metal bracing hidden inside which could be modified to a stronger peice of metal spaning both bridges, also those kits cand be reduced in size which I needed and have on my current layout. Also, just looked at their current offerings, they have 200' bridges now.
rrebell You could use two central valley kits as they already have metal bracing hidden inside which could be modified to a stronger peice of metal spaning both bridges, also those kits cand be reduced in size which I needed and have on my current layout. Also, just looked at their current offerings, they have 200' bridges now.
I've built a shorter bridge from a Central Valley kit. It came out very well. It's a single span truss bridge.
It's not a simple kit. The girder pieces must mostly be cut from longer sections. I spent a lot of time on the bridge, but I think it was worth it. I bought the bridge first and assembled it before measuring and creating the terrain gap it spanned.
The strength of the bridge is entirely in the understructure. The girder work, which in real life would distribute and carry the weight on the bridge, is purely decorative on this one.
Central Valley says the 200-foot bridge is 28 inches long.
It takes an iron man to play with a toy iron horse.
Neptune48, I used a cabinet L-bracket, very common in DIY and hardware stores, inverted and screwed to two blocks at the ends of the gap (sliding French door affording access to the train room). The bridge, wooden frame in this case, had two 1/2" metal screws driven into the base so that they acted as 'shoes' for the bridge. Screws made them adjustable when the rails atop the wooden frame didn't line up every time.
The L-brackets had feeders from the buse wrapped around the threads of one of the mounting wood screws...affixing the brackets to the blocks. Same for the screws that were 'shoes'; feeders wrapped around their shanks, feeders reaching up through drilled holes and soldere to the bottoms of the bridge rails.
This was very simple, and it worked 100% effectively. It wasn't sophisticated, nor was it elegant, but it was like those T-34 Soviet tanks; they worked!
It's a poor image, sorry, but I think you'll catch on from what it shows:
Thanks for posting that information, Bear. I'm happy to learn anything useful about railroading. Being a fan of bridges in general, but rail bridges in particular, this is most interesting information.
Hello All,
As has been alluded to there is the cost of materials, which can be considerable if scratch building.
Then there is the "time budget" consideration.
How quickly do you need to complete this project?
Fast, Cheap, or Good?
The classic dilemma- -choose two.
A great scratch-built project could be the "Black Bear Bridge" which is outlined in the book Model Railroad Bridges & Trestles on pg. 106. Unfortunately, this book is out of print.
Another option would be to kit-bash a span using a commercial kit.
Faller produces such a kit and is available on eBay: Faller HO Scale Building/Structure Kit Single Long Steel Arched Railroad Bridge.
This kit would require adding extensions on each end to reach your span.
Scratch building these extensions would be less time-consuming than scratch building the entire span.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
CSX RobertIf you really want to get crazy, though not likely to see anything like it in the United States, the Najiehe Railway Bridge has a longest span of 1,155'.
While this is a little off topic, the Huey Long Bridge has double track and six lanes of car traffic: It's maintained by the New Orleans Public Belt Railway:
The widest clear span is 790 feet (240 m) long while each of the three additional spans are 530 feet (160 m) long, making the total river crossing about 2,400 feet (730 m) long.
York1 John
I was looking in the Micro-Mark catalog, I think they were Central Valley. Walthers catalog may have some others.
To make your piers you can carve them out of extruded foam. You can leave the surfaces smooth, a poured concrete or scribe in lines to look like random stone or stone blocks.
Greenwood Central PA I would like to have at least one and more so two to make the span. Worst part yet, I'd prefere it to be a curved bridge.
When I built my version of the wood trestle I referred to earlier, it was curved and on an incline. Not that difficult to do as long as neither aspect is too extreme.
Greenwood Central PAI need to span across about 29" from where my foam risers stop to where my next shelf level begins.
Similar to what Neptune suggested, I would do something like this:
-Photograph by Kevin Parson
The above example is actually a roadway bridge, but very similar to railroad bridges. I would not be surprised if it was a railroad bridge originally.
I would shorten the girder approaches and lengthen the center section to get the clearance you need beneath.
-Kevin
Living the dream.
Greenwood Central PA I think I can get over it with a long straight bridge/trestle. It's spanning over my Loco service shop so I can only have 2 maybe 3 supports for it.
The truss bridge from Central Valley....
...is 21" long. I'd suggest that you buy two kits, then after determining the best place for a single support, alter the bridge kits to make each one's length appropriate to span from both of the foam risers to the single support.The support could be built as stone or concrete, or done as structural steel.
I used scratchbuilt moulds to cast the supports for the bridge shown above, and for the one in the foreground below (the bridges members are from Atlas and Micro Engineering)...
...while the taller one in the background, from Micro Engineering, used all M.E. kit materials.
This one used mostly M.E. supports (modified to accommodate the terrain) and girders atop each tower, while the deck trusses are from Atlas...
...much of it now hidden...
Wayne