Hi everyone
I need to build a double track curved bridge about 30" long. The inner track will be 25.5" radius and the outer track will be 28" radius. I am modelling the late 50s so I am assuming that a steel structure would be more appropriate than a wood trestle. I am inclined towards a deck truss design or a Warren truss style. I am a little wary of a through truss design because of the difficulty of retrieving a derailed locomotive or car. I am willing to consider scratch building.
- Do you have any suggestions on how to approach this project?
- Are there bridge kits or components that would lend themselves to being kitbashed or which could be used for scratch building?
- If I do the bridge in three sections how wide would each section have to be assuming 2.5" track center spacing, 28" outer track radius and approximately 10" in length?
- How far out to lunch would I be if I had a wood trestle in the late 50s? (I think I already know the answer to that one.)
Thanks for your help.
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
Dave, given your era and what you want to do, Does Micro Engineering have anything you can use? The fact we're talking double tracked and curved doesn't leave you with much options: highly modified (Kit Bashed) from other bridge kits; or, scratch built. Although it would be highly likely no new wood trestles would have been built at this time, older existing wood trestles may still have been in use. So, if you would like a wood structure, I would just go ahead and build one.
NP 2626 "Northern Pacific, really terrific"
Northern Pacific Railway Historical Association: http://www.nprha.org/
Hi Mark
I have spent some time studying various offerings from several manufacturers who make steel bridges and components. So far I haven't seen too much other than plate girders and beams that could be used as individual components. The kits like Micro Engineering offers could be a good source of parts but they come at a cost. I am hoping that someone who has actually built a curved steel double track bridge would contribute to the thread.
Interestingly, the MR February 1958 issue that was the focus of the Digital Book Club thread this week has a very pertinant article on scratch building curved bridges.
As far as going with a wood trestle, I am really tempted. I love the look of the structures, and a recent thread by wickman showing his very impressive construction of a beautiful curved wooden trestle has me inspired. Here is his thread. Go to pages 3 and 4:
http://cs.trains.com/mrr/f/11/t/230924.aspx?page=4
To get the link to work, highlight it, then right click on it, then select "Open Link' or words to that effect from the drop down menu.
I am thinking the way to approach this would be to follow wikman's (Lynn) example by starting with the track curved to shape and then building the bridge around it. I may purchase a sample bridge so I can get a good look at how the structure is built.
ME girder sections work great for "mitering" to a curved template, however these are for a single track. For double track, there would be considerable kit bashing involved. Not only would you need the double track extension for width, but need to incorporate the track spacing of at least 2 1/4 to 2 1/2" for that radius. A ballasted deck (mitered plywood girders applied to sides) would be far easier to build, providing the side girders of 50 -70 ft girderspans and support piers will fit the era and look you want. Both side approaches could be constucted in this manner w/ a center bridge span of a kithbashed truss. Drwayne has a single track version of a bridge close to this, using that as a guide and modifying to dounble track may be the answer. If you were working w/ a greater radius the bridge construction would be far easier. Even the Wather's or other double track truss will need to be widened for clearances for that radius.
Modeling B&O- Chessie Bob K. www.ssmrc.org
hon30critterIf I do the bridge in three sections how wide would each section have to be assuming 2.5" track center spacing, 28" outer track radius and approximately 10" in length?
Here's a rough sketch of your dimensions:
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I have the right to remain silent. By posting here I have given up that right and accept that anything I say can and will be used as evidence to critique me.
The materials for such a bridge in the 50's would depend on the part of the country your RR is set. Out west, some RR's are still using small wood trestles even today. Anything that would be built new would be of steel. So you could get away with using wood and making it look old if your RR is west of the Mississippi.
Lay your project out full size on some kraft paper, starting with some track at the desired radius. Draw in the track placement, then draw in the sides of the bridge. That should give you the shape of the top deck. Then just fill in the girders as directly underneath the rails as you can and add the bracing. You just have to make it believeable to viewers. You don't have to replicate every brace or crossmember unless you are a rivet counter. At a minimum, every place where the girders join on the curve, you should have a support tower under it that goes to the ground. So if your bridge is in three sections, you should have two support towers of some kind.
This may be extreame, but if 'I' were building this 30 inch long bridge as an open deck type, and it was going to be a steel bridge, I would make my own girders from brass strips. I would start with a strip that would be the vertical piece and then solder on the top and bottom cap strips. Then I would solder each section together and add four solid braces from one side to the other. One at each end, and one at each joint between the ends. You would need two of these, one under each track. The two of them would also be spaced apart by brass spacers, but not at the same place as the others. The reason for that is not to un-solder the first braces.
This then would be my real structure for carrying the trains. From that point on, I would just add plastic details to the brass girders and plastic bracing between the girders with CA. Wash and paint the whole thing when done. Then add the wood ties or bridge track etc.
If your bridge will be toward the back of the layout, you can build it much simpler. Get a couple of sections of 3/4 inch square alumunum tubes. (Lowes or Home Depot usually carries them) You would put one under each track. Cut them at an angle to form the curve, and then cut two wood angle solid plugs to join each one together with. Glue them in with epoxy. Space the two tube section apart with wood sheet braces glued on. Then detail out the remaing bridge with plactic components. Paint the bridge your desired color, but then paint the tops of the tubes flat black. Then add your bridge track.
The long bridge seen here is using a 3/4 inch square aluminum tube as the main support for the track. Plastic girder sides will be glued onto it as work progresses and support towers will also be added.
Hope this helps.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
Wow, you even get people into drawing out potential solutions to your question!
A couple years ago I built a curved wood trestle for my layout. However, it was a single tracked trestle so really doesn't cover your particular situation. However, if you have an interest in a wood structure there is some useful information in the thread for you.
http://cs.trains.com/mrr/f/11/t/202778.aspx?page=1
To those who are interested, no, the cliff face in back of my trestle still has not been painted or sceniced.
I believe a through or deck girder would be your best bet.
Here is my former Micro Engineering 150' through and deck girder combo:
Otherwise, you'll be reaching into something like this to retrieve uncoupled or derailed items:
A wood trestle in the 1950's is not necessairly inappropriate.
The double track trestle on the Southern Pacific (now UP) main line across the Yolo Bypass (river overflow west of Sacramento, CA) was wood into the 1980's. The wood bents and structure under the track abd the bents were replaced by concrete over a number of years, not all at once.
The UP mainline through Marysville CA is on a low trestle that was wood into the 1990's. The structure under the track has since been replaced by concrete. The wood trestle bents are still there although now hidden. They are wraped in foam and a rough layer of concrete sprayed over them.
They are both low straight trestles.
I tried to sell my two cents worth, but no one would give me a plug nickel for it.
I don't have a leg to stand on.
This, I think, is the bridge to which Bob K. is referring:
As you can see, it's single track. I opted to place the girders (all Micro Engineering on the tall bridge) under the rails, theorising that such a bridge would be cheaper for the prototype to build than one on which the crossmembers support the load and transfer it to heavier longitudinal girders. My curve is a 34" radius, which permitted me to use some 50' girders where the terrain allowed. With a smaller radius, you'd probably be restricted to 30' spans if you chose to build a similar style of bridge.
Carl's drawing....
carl425
...looks pretty much like the bridge in Crandell's prototype photo:
selector I believe a through or deck girder would be your best bet.
...and would probably be the easiest solution. Depending on viewing angles for your bridge, you might get away with modelling only the visible side and the support structure, or you may need to model both sides fully and possibly, if the track is above eye-level, the structural details between the girders, too.The simplest solution would be to have your tracks on plywood subroadbed, with its edges cut as in Carl's diagram. Glue one-sided girders to the edge(s) of the plywood, add supports, either from M.E. or scratchbuilt, then ballast the deck and call it finished.Other options include a wooden trestle or a double bridge, similar in style to mine, as if one were built when the line was first laid, with the second added at a later date. It could be identical to the original or somewhat different, and it might also be at a slightly different elevation. Either of these (actually any, I suppose) would be a good opportunity to add superelevation, but I'd guess that the twin bridge option would really show it off nicely.
EDIT: Central Valley recently announced a double track version of their through truss bridge. The trusses can be lengthened using optional extensions, and the bridge superstructure is, like the original single-track version, removeable. You'd need to alter the ties, though, in order to have the rails curved.
Wayne
Anymore Pics? I'm having a similiar problem with Trestles and such and need some ideas and inspiration. Also need better under bridge clearance for a Over (single) and Under (double main Line)
http://www.trainboard.com/railimages/showgallery.php?cat=500&ppuser=5959
If one could roll back the hands of time... They would be waiting for the next train into the future. A. H. Francey 1921-2007
Thanks for all the responses and ideas!
Bob K - I agree that there will be some considerable kit bashing required, especially to get the width needed. I'm thinking that the best approach might be to use girders and towers from ME and scratch build the cross structure.
Carl245 - Thanks for taking the time to do the drawing. I will use my NMRA gauge to figure out clearances. The drawing has me concerned that a single steel structure won't look very realistic because of the tight radii and width required to accomodate double tracks. I'll have to do a mock up to get a feel for what it will look like.
Elmer - Great suggestions. Thanks. The bridge will be fairly close to the front of the layout so I want to have reasonable detail. I hadn't thought of using brass. I'm more inclined to use styrene but obviously it will have to be sturdy enough to support the weight of three locomotives (FP7 ABA consist).
Mark - Nice trestle. Thanks.
Crandell - I agree I don't want to have to reach in to a through truss bridge, but doctorwayne suggested that the superstructure could be made so it is removable.
DSchmitt - Thanks for the info about wood structures surviving into the 80s and 90s. My problem is that I want a fairly tall bridge (10" to 12") so that raises the question about how much of a stretch it would be to have a tall wooden trestle still in use in 1959.
Wayne - I didn't realize that the Central Valley through truss bridge superstructure could be removed. Simple solutions like that seem to avoid me. Your suggestion of twin bridges is actually what I had started with. However, I discovered a flaw in my track plan and the solution just happened to make the double track bridge a possibility. Two bridges might look better too.
My next step will be to go back to the track plan and see if I can re-arrange it to accomodate two bridges and still solve the track design flaw. Then I will make some detailed drawings of the possible options so I can mock them up.
Please don't hold your breath waiting to see a finished bridge. This is all pre-planning. The layout will be started in earnest in a few months.
One more question - chicken or egg? - can I build the bridge before the adjacent track is built, or should I lay the track first? I'm inclined to build the track including roadbed right through the bridge location and then cut out the space for the bridge. That way I can be reasonably sure that the curves on either end of the bridge will line up. No kinks!
Thanks again
hon30critter...One more question - chicken or egg? - can I build the bridge before the adjacent track is built, or should I lay the track first? I'm inclined to build the track including roadbed right through the bridge location and then cut out the space for the bridge. That way I can be reasonably sure that the curves on either end of the bridge will line up. No kinks!
For all of my bridges, I ran the 3/4" plywood subroadbed right through the areas where bridges would eventually be located. (The roadbed was cut out of the sheet, curves of the various radii needed, about 2" wide, and all supported on risers.) The track was installed, too, to verify that trains could handle both the curve and the grade. Once I had the bridge building materials on hand to verify their dimensions, I removed the piece which would be replaced by the bridge, flipped it upside down, then built the bridge, also upside down, right on the plywood, using the cut-out curve as a pattern. This ensured that the bridge would line up with the remaining roadbed once it was installed.
A reasonably skilled and methodical person could do it either way....the chicken first or the bridge it needs to cross first.
I have always laid my tracks first, particularly if the approach to the bridge is likely to be on a curve (how many layouts don't have a curved approach to a bridge?!?). I lay the track on the roadbed right across the part to be cut out and bridge inserted, and I remove only as much as I must to insert the bridge. Later, with the bridge in place and demonstrably meeting the grade of the roadbed on either end, I can safely re-lay the missing segment over the bridge. It makes it look engineered and realistic.
Not knowing the exact track plan or operations, but an interesting and unique way to accomplish this is a gauntlet track to carry over the basically single track bridge. MR about 6 mo ago had an article of this.
Wayne and Crandell
I concluded that I should do what you are suggesting. Build the layout without the bridge and then cut the bridge in. Even if I don't use the cutout roadbed as a base for the bridge it will provide a very accurate template.
Thanks
Bob
I remember the article on the gantlet track. It is an interesting idea. I'm a little leery because there will be a bit of traffic in the area but having to hold a train while another one clears the track is obviously quite prototypical.
Worth some thought.
Also came across a ME link showing many of the products and various uses. Many prototype pics of girder, bracing and bridge shoes. Drwayne and a few other notable bridges from layouts are even scattered here.
https://www.google.ca/search?q=MICRO+ENGINEERING+BRIDGE+SHOES&client=firefox-a&hs=AbC&rls=org.mozilla:en-GB:official&channel=sb&tbm=isch&tbo=u&source=univ&sa=X&ei=ISIeVITqIs6pyATmq4GIDw&ved=0CCUQsAQ&biw=1024&bih=635#imgdii=_&imgrc=eV2cEIIkEQB3aM%253A%3BknL_wgqYAshk4M%3Bhttp%253A%252F%252Fwww.railroad-line.com%252Fforum%252Fdata%252Fhvig%252F2007918234729_IMG_0054.JPG%3Bhttp%253A%252F%252Fwww.railroad-line.com%252Fforum%252Ftopic.asp%253FTOPIC_ID%253D17952%2526whichpage%253D2%3B768%3B576
Clicking on the pic/ tiles can take you yo many links
Thanks for the ME link. Lots of interesting material.
As far as a gantlet track, I realized it wouldn't work as soon as I looked at the track plan. One of the two tracks is actually a spur leading to a mine. That means that coal hoppers will be parked on the spur regularly. With a gantlet track they would fowl the main. However, that does make the two bridge option more attractive. With one bridge for the main and one bridge for the mine spur it would be logical that they would be two different construction styles. Could make for an interesting scene.
Moving the tracks so there is enough room for two separate bridges was easy so that is the way I will go. I managed to get about 6" separation between the two. I think I will do the mainline as a steel structure and the spur as a well aged wood trestle. It will look much better than one overly wide double track single bridge.
Thank you everyone for helping me think this thing through and giving me some construction options. Much appreciated!
For anyone interested, here is the track plan. The room is 23' x 10'. The two bridges are towards the left side of the layout. There will actually be a third single track bridge against the backdrop on the far left. Reach in is not a problem. There will be access to the outside of the layout on both sides and the bottom via folding doors.
Comments on the plan are encouraged.
Mark
I intend to read your thread over again as I get further into the design. Having different lengths is definately an option, however it would have to be the spur bridge that changes. The mainline bridge is trapped between two turnouts so it can't get any longer and I want it as long as possible.
I have come up with a plan for the mainline steel bridge but I need to clarify some dimensions to make sure the design will work.
I am basing the design on Micro Engineering's tall steel viaduct towers and 50' (Edited to use the proper description) deck girder bridges, not ballasted. I need to know how long the track is on the top of the towers themselves. I'm guessing at 30'. I also need to know how wide the bridge sections are. Based on my calculations I would need them to be a minimum of 14.5 scale feet - approx. 2".
Here is what the bridge would look like based on the above dimensions:
Will this work?
Thanks again for your help.
I don't think so, Dave. The tall viaduct is designed to be used with the deck girders, not the through ones. You might be able to widen the support towers, but it probably would use-up a second kit's worth of tower material.
The advantage of the deck girders is that they don't limit side clearance, especially important if your curves are fairly tight.Here's a view of another bridge on a curve which better shows the relationship between the tops of the towers and the bridges which they support.
I'm sorry, I didn't use the proper terms. I meant to use the deck girders. I'll correct my post.
Does that make it feasible? How wide are the deck girders?
The deck girders, once assembled, are the same width as the top of the towers - 8', while the M.E. bridge track is 10' over the tie-ends. You may have to use all 30' girders to accommodate the tighter curve (the towers are topped by 30'-ers) so you'd need 6 towers for your 210' bridge.Another thing to keep in mind is that the girders on the inside of the curve will need to be shortened, but not those which are atop the towers, as that would leave them unsupported.
Two types of bridges were not mentioned, both of which can be curved, a stone arch bridge and a concrete arch bridge.
Dave H. Painted side goes up. My website : wnbranch.com
I agree w/ Wayne. the 50' girder span could be used, but he tie overhang would be a bit excessive for your radius. If you could increase the radius, it would be a nice feature to at least have a 50' mid span between towers. Your radius is already allowing for some serious "mitering" of the open girder sections, where it needs to meet square tower support beams.