Track fiddler Here's a better view of the double Warren truss Bridge. I think this view will make a nice scene someday when it's finished. Don't you guys just love S curves.
Here's a better view of the double Warren truss Bridge. I think this view will make a nice scene someday when it's finished. Don't you guys just love S curves.
[quote user="maxman"]
Track fiddler Here's a better view of the double Warren truss Bridge. I think this view will make a nice scene someday when it's finished. Don't you guys just love S curves. I presume that you are going to put some sort of vertical support between the two spans and have just not got around to it yet, correct?
Track fiddlerI'm kind of learning maybe having a carpenter design a steel truss bridge is kind of like giving a monkey a hand grenade.
.
I repair heavy equipment, and I designed almost all the bridges on my model railroads.
In operation, my bridges have a 0% failure rate. If it holds up my models and looks decent, that is good enough for me.
I do work from photographs, and I have read a lot about bridges, but I am not too concerned if it would not work in the real world.
By the way... I love the pink foam concept. Please keep updating this thread with your progress.
-Kevin
Living the dream.
Thanks Kevin.
I will do that. I hope we're all patient though.
Steady Eddy. Slow as she goes.
Btw - My whole layout top is pink foam. I used Liquid Nails to glue down the track to the foam.
Another solution to the curved bridge:
Put a little space between the tracks below and put in pier(s) as able to fit. Then you can have 2 or 3 simple Pratt truss spans, or whatever you like.
John
Track fiddler I like to mock up cardstock to get a view of what things will look like before I start the build. The center rectangle will be a scratch-built bowstring truss Bridge. The parallelograms on either side will be kitbashed girder Bridges. The dotted line on the cork is how far I have to move the center line of the cork over to have outside radius clearance for my Bridge supports. I'm glad I used Alex plus caulk that was suggested before on this forum. It does release well if you change your mind. This bridge is going to take a while but I have nothing to do a lot of the time in the winter and all day to do it.
I like to mock up cardstock to get a view of what things will look like before I start the build.
Hey John how's it going ?
I realized that mistake a while ago and still haven't moved the cork. When I laid the cork under this future Bridge I didn't reference my template and put the cork to close together.
I dug up one of my posts earlier in this thread when I had realized what I did wrong.
I think now I'm going to wait until I get the model bridge built. After that, while the bridge is still removable I'll know exactly where to move the cork. I think that would be best. I would hate to have to move it twice.
Track fiddler
PRR8259 Btw - My whole layout top is pink foam. I used Liquid Nails to glue down the track to the foam. Another solution to the curved bridge: Put a little space between the tracks below and put in pier(s) as able to fit. Then you can have 2 or 3 simple Pratt truss spans, or whatever you like. John
Good sugestion. Railroads prefer simple straight spans. Long curved bridges would usually be made of a series straight spans with piers at each end of each span. They leave the fancy stuff to the Highway Dept.
Useful books
https://www.amazon.com/Model-Railroaders-Bridges-Trestles-Tunnels/dp/0890245967/ref=sr_1_sc_3?s=books&ie=UTF8&qid=1506468876&sr=1-3-spell&keywords=Railroad+bridge+deaign
https://www.amazon.com/Bridge-Trestle-Handbook-Paul-Mallery/dp/0911868798/ref=sr_1_2?s=books&ie=UTF8&qid=1506469037&sr=1-2&keywords=bridge+and+trestle+handbook
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.
Just wondering John.
Would you have an idea or example of a 3 Series connecting bridge structure that would work well in this area I'm working on.
I'm trying to create different varieties of bridges to keep things interesting.
I know prototypical railroads would span the most cost-effective Bridge structure.
I'm just trying to get away from girder bridges all over the place.
Thanks
Track fiddler Thanks Gary for the compliment. It put a smile on my face after A hard day's work. I do agree this bridge discussion is interesting, especially having an engineer involved in the discussion.
Thanks Gary for the compliment. It put a smile on my face after A hard day's work.
I do agree this bridge discussion is interesting, especially having an engineer involved in the discussion.
I tried to be funny with the Stonehenge comment by inserting Spinal Tap's "Stonehenge," but it wouldn't work. Even if it looks like Stonehenge, your risers and work are very well done.
Gary
garya Track fiddler Thanks Gary for the compliment. It put a smile on my face after A hard day's work. I do agree this bridge discussion is interesting, especially having an engineer involved in the discussion. I tried to be funny with the Stonehenge comment by inserting Spinal Tap's "Stonehenge," but it wouldn't work. Even if it looks like Stonehenge, your risers and work are very well done.
Now I gotcha.
Spinal tap....... yeah yeah. I do somewhat remember that one now. Wasn't that the one where the dude with the electric guitar was showing how the amp went up to 11 instead of 10 and that was way way better. Chuckle chuckle. I hope that was the one, I think I do remember that one now.
We're all good Gary.
Track fiddler Spinal tap....... yeah yeah. I do somewhat remember that one now. Wasn't that the one where the dude with the electric guitar was showing how the amp went up to 11 instead of 10 and that was way way better. Chuckle chuckle. I hope that was the one, I think I do remember that one now.
That's the one--I got it to insert now.
Your portals, you say you used the ballpoint pen trick--are they pink foam, too, and "engraved" with a pen? They look good.
John thanks for sharing your knowledge as it is appreciated.
I went back to the drawing board. I'm sure you can tell I paid attention.
Cosmetically similar to my other barn burner design, hopefully more realistic. I did still kind of mix things up a little bit, with a Camelback /Pratt and a Howe Truss on either end.
The only question can I mix a Howe with a pratt. And not be too far off in left field.
Sure hope so. I like how the Howe ( no pun intended) branches off from the Pratt.
The shape mimics a through truss bridge. I like it.
Cosmetically pleasing to my eye doesn't necessarily mean it is to another eye.
It would interest me what you have to say about this design.
Model railroading is all about the fun.
Respectfully, Track fiddler.
Edit. Usually blueprint image is better from a phone but I'll post this one too.
garya Track fiddler Your portals, you say you used the ballpoint pen trick--are they pink foam, too, and "engraved" with a pen? They look good.
I must have missed your post last night
Yup the portals were half inch pink foam. I cut a hole out with a inch and a quarter hole saw. Then I cut the tangents with a razor saw and drew the lines freehand with a ballpoint pen.
I learned early on you have to be careful not to get your paint too thick or you lose all the detail from the pen.
I put the paint on really thin and dried it with a hair dryer. It helped set the pigments.
SeeYou190 Track fiddler I'm kind of learning maybe having a carpenter design a steel truss bridge is kind of like giving a monkey a hand grenade. . I repair heavy equipment, and I designed almost all the bridges on my model railroads. . In operation, my bridges have a 0% failure rate. If it holds up my models and looks decent, that is good enough for me. . I do work from photographs, and I have read a lot about bridges, but I am not too concerned if it would not work in the real world. . By the way... I love the pink foam concept. Please keep updating this thread with your progress. . -Kevin .
Track fiddler I'm kind of learning maybe having a carpenter design a steel truss bridge is kind of like giving a monkey a hand grenade.
You know Kevin I think I might just join your way of thinking.
If a bridge looks good and serves its purpose, good enough.
I'm starting to think that trying to be completely prototypical every square inch of my layout can take some of the fun out of the hobby.
I think this will be the design.
I will start the build Sunday.
There are critical reasons I am doing this design and I will give them to you later.
You will notice one end member was changed. The end members never were a howe, my bad.
I was really tired that night when I made the drawing.
Now all three are Pratt. This is what I'm going with.
Camelback Pratt in the center. Pratts on either end.
I will elaborate on this later.
I don't like sideways pictures either this may be a little better
Thanks my fellow Forum members.
Don't sweat the small stuff.
Track Fiddler--
You can mix any bridge spans you want. A coworker showed me an image of P&LE bridge over the Ohio River, that is an historic, early, complex, continuous truss bridge (meaning the main truss is actually supported by multiple piers). However, due to pier spacing issues, etc. there is also a (different configuration) simply supported truss span at the one end.
With major river bridges, the Army Corps of Engineers and/or the US Coast Guard have a say in the pier locations, and it is desired, especially nowadays, to minimize the number of piers in the water, and any piers actually in the water are placed based upon where the shipping channel is, rather than by what looks good.
So all this basically means, on your layout you can space the piers however you want to or need to, and you can mix deck spans with truss spans, or vary the types of truss spans as desired.
After two tropical storms a few weeks apart destroyed the former Reading RR bridge at Montoursville, PA, (by pier washout) a couple years back, the current short-line owner replaced the Reading bridge with two new simple truss spans, and one deck girder or thru girder approach span.
Interesting info John.
I do remember hearing about that Montoursville PA bridge washout and seeing some footage of it on the news a while back.
Are you able to post a photo of that P&LE bridge over the Ohio River. Sounds interesting.
Hey John I seen the image I was asking you for came up on your thread.
I'm tired and it's late. I got to hit the rack as I got to work tomorrow.
Hopefully I can rattle your cage tomorrow night. I have a few questions and do greatly appreciate your knowledge.
You know I did start working on my bridge the Sunday I said I was going to. The bridge starts from the ground up. I had to start working on bridge supports as there is no room for piers.
I spent two Winters doing this layout design. There's no changing things. My grades are all 2% max. My radiuses 18 inches min.
The area where the forth bridge is going is written in stone with the underlying tracks unchangeable.
Instead of pears I need monopoint Steel columns on all four corners of the bridge where the Three Bridges come together.
Sometimes there's a trade-off when the most important thing is trouble free smooth running trains and a no derailment factor being most important on the list.
I built four of these. Small. A lot of pieces. Way more time-consuming then a bridge as far as I'm concerned.
So I decided to kitbash instead of scratch building on my fourth of the 8 bridges I need.
It went South. I cut up a Kato bridge. It was going good, than I cut the uprights too short, game over.
You know it's not the $14 Bridge that's the issue. It's my time. Now I got to start all over.
Sometimes that's just how it goes. Oh well I will get this.
Just believe me they are too short
PS Since I have to go back to the Hobby Store to get another Bridge. More tools are definitely on the list.
Last time I did kitbashing I wasn't dissecting parts and putting them back together.
Two exacto blades snapped and flew across the room. Kind of dangerous and I didn't find one. I can hardly wait till someone finds it in their foot. Ha ha that won't be good.
Track fiddler So I decided to kitbash instead of scratch building on my fourth of the 8 bridges I need. It went South. I cut up a Kato bridge. It was going good, than I cut the uprights too short, game over. You know it's not the $14 Bridge that's the issue. It's my time. Now I got to start all over. Sometimes that's just how it goes. Oh well I will get this. Track fiddler Just believe me they are too short PS Since I have to go back to the Hobby Store to get another Bridge. More tools are definitely on the list. Last time I did kitbashing I wasn't dissecting parts and putting them back together. Two exacto blades snapped and flew across the room. Kind of dangerous and I didn't find one. I can hardly wait till someone finds it in their foot. Ha ha that won't be good.
Can you replace the too short parts with comparable sized pieces of Evergreen styrene?
You might also check out Central Valley bridge kits. They have whole bridge kits, and additional parts kits.
Also MRVP just did a video series on kitbashing bridges for the Canadian (or Canadien if you prefer) Canyons layout.
I would get a miter saw of some kind.
Thanks for the leads I'll have to check that out.
I have a razor saw miter box. I need a razor saw on a stick type of thing to get into tight spots. I'm sure they make one, I've just never had a reason to look for one before now.
PS. It sure would make a lot of modelers life's easier if Micro Engineering or some company would make bridge gusset plates. How simple would that be?
PRR8259 Hello Track Fiddler-- I would like to comment about the bridge sketch shown just above. First of all, I totally understand the need to make compromises on a model railroad, and that sometimes visual "tricks" need to be employed. As a professional civil engineer, I would like to respectfully offer a couple comments regarding prototype truss bridge design: 1. Although you can conceivably build a "model" bridge that represents a chorded structure as you have shown, in real life a truss bridge is inherently a very rigid structure. During the days when these bridges were commonly built we did not have access to the computer programs of today that can analyze quickly all the (moving=live) load scenarios. They were designed often by graphical methods, where from a chart, for a given axle loading, certain "rules of thumb" were applied to arrive at the most economical members and configuration. In classical structural analysis, as employed for at least much of the 20th century, a truss can be analyzed by hand for a given, static (not moving) loading condition, but the analysis would have to be repeated a large number of times to find the worst condition for each member of the bridge, because the worst condition for each member would occur at different times, as the simulated load moved across the bridge. In the prototype condition, steel truss bridges, especially a more complex one such as the one illustrated in your sketch are almost always built in a straight line, tangent condition. To put kinks, or chords, or horizontal curvature into a truss bridge itself (track positions on bridges were allowed to vary) is almost unheard of in real life. Your sketch implies varying member dimensions that may result in a "normal" appearance when viewed from the side, but these dimensions would produce torsional (twisting) stresses in real life in what is otherwise a very rigid, "fracture critical" steel structure, which would not be recommended at all. It would have been strongly avoided. The Lehigh Valley and Reading Railroads did share one common truss bridge that had an unusual end configuration due to track curvature at one end. In that case a special truss arrangement of the end span may have been employed. That is the only case I am aware of. I saw photos, but it was years ago... 2. On a larger, more modern truss bridge composed of built-up steel shapes, where diagonals could take more than just tension forces, they would have been designed with thicker members to also take compression forces, as stresses may reverse as a moving load traverses the bridge. Due to the stress reversals, and to build some redundancy into the design, either the middle panel or the two adjacent middle panels of a main span would have had an "X" configuration rather than just a single diagonal in each panel. This guarantees that if one member failed (due to section loss from rusting), another diagonal can take the load, at least for awhile. 3. I understand that what I am saying would practically force you to change the horizontal curvature to get the bridge on a tangent. You can build the bridge as you have it sketched up, and I'm sure it will hold model trains and function adequately well. It just would look "odd" to anyone who practices civil engineering. It's your railroad. Have fun with the choices made. Respectfully submitted, John
Hello Track Fiddler--
I would like to comment about the bridge sketch shown just above. First of all, I totally understand the need to make compromises on a model railroad, and that sometimes visual "tricks" need to be employed. As a professional civil engineer, I would like to respectfully offer a couple comments regarding prototype truss bridge design:
1. Although you can conceivably build a "model" bridge that represents a chorded structure as you have shown, in real life a truss bridge is inherently a very rigid structure. During the days when these bridges were commonly built we did not have access to the computer programs of today that can analyze quickly all the (moving=live) load scenarios. They were designed often by graphical methods, where from a chart, for a given axle loading, certain "rules of thumb" were applied to arrive at the most economical members and configuration. In classical structural analysis, as employed for at least much of the 20th century, a truss can be analyzed by hand for a given, static (not moving) loading condition, but the analysis would have to be repeated a large number of times to find the worst condition for each member of the bridge, because the worst condition for each member would occur at different times, as the simulated load moved across the bridge.
In the prototype condition, steel truss bridges, especially a more complex one such as the one illustrated in your sketch are almost always built in a straight line, tangent condition. To put kinks, or chords, or horizontal curvature into a truss bridge itself (track positions on bridges were allowed to vary) is almost unheard of in real life. Your sketch implies varying member dimensions that may result in a "normal" appearance when viewed from the side, but these dimensions would produce torsional (twisting) stresses in real life in what is otherwise a very rigid, "fracture critical" steel structure, which would not be recommended at all.
It would have been strongly avoided.
The Lehigh Valley and Reading Railroads did share one common truss bridge that had an unusual end configuration due to track curvature at one end. In that case a special truss arrangement of the end span may have been employed. That is the only case I am aware of. I saw photos, but it was years ago...
2. On a larger, more modern truss bridge composed of built-up steel shapes, where diagonals could take more than just tension forces, they would have been designed with thicker members to also take compression forces, as stresses may reverse as a moving load traverses the bridge. Due to the stress reversals, and to build some redundancy into the design, either the middle panel or the two adjacent middle panels of a main span would have had an "X" configuration rather than just a single diagonal in each panel. This guarantees that if one member failed (due to section loss from rusting), another diagonal can take the load, at least for awhile.
3. I understand that what I am saying would practically force you to change the horizontal curvature to get the bridge on a tangent. You can build the bridge as you have it sketched up, and I'm sure it will hold model trains and function adequately well. It just would look "odd" to anyone who practices civil engineering.
It's your railroad. Have fun with the choices made.
Respectfully submitted,
Might I jog your memory.
Respectfully, TF
I did build it prototypically John
No hard feelings then, let's just go back to the river
TF
Well it is a cool bridge, and you certainly have patience to build that...more patience than me, for sure.
Thank you John.
From you that means a lot to me my friend.
Track Fiddler
Even though the bridge might not match prototype practice, it looks amazing and makes the layout work.
A+
Prototype practice what?
Just kidding
But really I'm not A+ Maybe B- Thanks