If anyone has the Walthers Cornerstone Arched Pratt Truss Bridge, eithter the single track or the double track version, can you tell me if the center segment is perfectly level flat on the top?
Being that it is an arched bridge, the remaining segments on either side slope a little, but is that center segment perfectly level on the top of the segment?
I ask because I am thinking about kitbashing this kit, so that middle segment needs to be level flat on top for the kitbash to work.
By the way, it will be either Item No. 933-4521 or Item No. 933-4522.
Thanks.
Rich
Alton Junction
is this what you are refering to http://bridgehunter.com/ky/mclean/bh47058/
j. c. is this what you are refering to http://bridgehunter.com/ky/mclean/bh47058/
Kit bashing a real bridge is beyond most of our budgets or expertise. I think he means this one.
Edit I misunderstood and thought Rich meant the piece connecting the left and right sections, but he means the the side piece over the X, which in the photo doesn't look flat.
I think that is an illusion of the photo. Foreshortening is the photographic word for it and is the result of a wide angle lens. The bridge is symmetrical but the impression is that everything to the right of that X in the bridge is longer. It wouldn't make any kind of sense to have a model that inaccurate that the segment would be curved or on an angle.
Henry
COB Potomac & Northern
Shenandoah Valley
The instructions are here:
https://www.walthers.com/143-single-track-railroad-arched-pratt-truss-bridge-kit
Left and right sections are 60/40 and 40/60. I believe the center section is level.
Walthers-archpratt by Edmund, on Flickr
Cheers, Ed
BigDaddy j. c. is this what you are refering to http://bridgehunter.com/ky/mclean/bh47058/ Kit bashing a real bridge is beyond most of our budgets or expertise. I think he means this one. Edit I misunderstood and thought Rich meant the piece connecting the left and right sections, but he means the the side piece over the X, which in the photo doesn't look flat. I think that is an illusion of the photo. Foreshortening is the photographic word for it and is the result of a wide angle lens. The bridge is symmetrical but the impression is that everything to the right of that X in the bridge is longer. It wouldn't make any kind of sense to have a model that inaccurate that the segment would be curved or on an angle.
was trying to find what truss he was refering to its called a Pennsylvania truss , there are several variations of the pratt truss .
BigDaddyEdit I misunderstood and thought Rich meant the piece connecting the left and right sections, but he means the the side piece over the X, which in the photo doesn't look flat.
gmpullman The instructions are here: https://www.walthers.com/143-single-track-railroad-arched-pratt-truss-bridge-kit Left and right sections are 60/40 and 40/60. I believe the center section is level. Walthers-archpratt by Edmund, on Flickr Cheers, Ed
By the way, how do you know that the left and right sections are 60/40 and 40/60?
The center section is level and perpendicular to the bottom, actually the main stress point of the entire bridge. That is why it has an ''X'' brace in the center. The others also are flat on top, but not perpendicular to the bottom. That is a riveted bridge, all the girders are straight, but angled when constructed. A welded bridge will have some pre-stressed curved girders.
Ed Pullman is just about correct in His assessment.
Electrical/Machine/Structural Design Draftsman......before I got drafted in 66'....
Take Care!
Frank
Frank, thanks for that reply. Very informative and much appreciated.
Check my PM that I just sent to you.
richhotrainBy the way, how do you know that the left and right sections are 60/40 and 40/60?
All I'm implying by that is that the joints of the side sections are offset.
4 panels + 3 on the right side (what I'm calling 60/40)
3 panels + 4 on the left side (what I'm calling 40/60) in order to off-set the joint.
W_prattruss by Edmund, on Flickr
Ahh, I see what you mean, Ed. Thanks.
http://pghbridges.com/basics.htm
This site has been in my 'favorites' since 'bout Day One.
selector http://pghbridges.com/basics.htm This site has been in my 'favorites' since 'bout Day One.
The bridge that I am thinking about modeling is the PRR vertical lift bridge in downtown Chicago. It is actually a Parker Through Truss which is a modified Pratt Truss. It is illustrated in the drawings from that link as a Parker "Camelback" (Pratt) Truss, which is the Walthers model.
rich is this the bridge your refering to ? http://bridgehunter.com/il/cook/bh50843/
j. c. rich is this the bridge your refering to ? http://bridgehunter.com/il/cook/bh50843/
rich is this the bridge your refering to ?
http://bridgehunter.com/il/cook/bh50843/
Here is the detailed look at the bridge.
https://historicbridges.org/bridges/browser/?bridgebrowser=illinois/sblift/
Rich, are you going to build it as a skewed bridge, like the prototype?
Wayne
doctorwayne Rich, are you going to build it as a skewed bridge, like the prototype? Wayne
gmpullman richhotrain By the way, how do you know that the left and right sections are 60/40 and 40/60? All I'm implying by that is that the joints of the side sections are offset. 4 panels + 3 on the right side (what I'm calling 60/40) 3 panels + 4 on the left side (what I'm calling 40/60) in order to off-set the joint. W_prattruss by Edmund, on Flickr Cheers, Ed
richhotrain By the way, how do you know that the left and right sections are 60/40 and 40/60?
The good news is that the center section with the X-bracing is perfectly rectangular, so it will be geometrically possible to add one or more additional center sections to increase the length of the bridge span.
What I fail to understand though is why the kit was designed with that 60/40 arrangement. That complicates the insertion of additional center sections. So, I need to further analyze how to pull this off. I invite all comments and suggestions in this regard.
richhotrainWhat I fail to understand though is why the kit was designed with that 60/40 arrangement. That complicates the insertion of additional center sections. So, I need to further analyze how to pull this off. I invite all comments and suggestions in this regard.
Rich,
Like I said in My PM.......The X sections are the main vertical stress part of the bridge. The 60/40 arrangement was to offset the stress on the X sections where the girders would meet, instead of having them directly over a joint, like in a hinge. Sort of like a reversing section on track where they tell you to stagger the joints......not directly across from one another.
What You would do, is add an X section to bridge part 4 and 2 or two X section per part. Then You would reinforce the bottom deck with full length I- beams for the deck as I also suggested in My PM. Don't over think this.....It's not that hard.
Did you say it came in a single and double track versions?If so which one are you doing?
Look forward to your progress.
Brian
My Layout Plan
Interesting new Plan Consideration
zstripe richhotrain What I fail to understand though is why the kit was designed with that 60/40 arrangement. That complicates the insertion of additional center sections. So, I need to further analyze how to pull this off. I invite all comments and suggestions in this regard. Rich, Like I said in My PM.......The X sections are the main vertical stress part of the bridge. The 60/40 arrangement was to offset the stress on the X sections where the girders would meet, instead of having them directly over a joint, like in a hinge. Sort of like a reversing section on track where they tell you to stagger the joints......not directly across from one another. What You would do, is add an X section to bridge part 4 and 2 or two X section per part. Then You would reinforce the bottom deck with full length I- beams for the deck as I also suggested in My PM. Don't over think this.....It's not that hard. Take Care! Frank
richhotrain What I fail to understand though is why the kit was designed with that 60/40 arrangement. That complicates the insertion of additional center sections. So, I need to further analyze how to pull this off. I invite all comments and suggestions in this regard.
I had considered what you pointed out about stress on the x-sections. That would certainly be true on a real bridge, but stress on an HO scale model???
zstripe richhotrain What I fail to understand though is why the kit was designed with that 60/40 arrangement. That complicates the insertion of additional center sections. So, I need to further analyze how to pull this off. I invite all comments and suggestions in this regard.
It is just that it will require a lot more careful cutting and sawing since the "mated" pieces will not exactly match. The X-bracing of both pieces to be mated will match, but the vertical end supports of each piece will not match since the overlapping pieces are of different widths, thanks to this 60/40 design.
It wouldn't matter if I settled for the length of the truss span (as is) out of the box, but I want to add two X-braced center sections to lengthen the bridge span, so that complicates matters.
railandsail Did you say it came in a single and double track versions?If so which one are you doing? Look forward to your progress.
richhotraint is just that it will require a lot more careful cutting and sawing since the "mated" pieces will not exactly match. The X-bracing of both pieces to be mated will match, but the vertical end supports of each piece will not match since the overlapping pieces are of different widths, thanks to this 60/40 design.
Whether the kit's design is 60/40 or 50/50, the mating surfaces of the two sections are a face-joint, with each side of those verticals representing half the thickness.To add the additional X-panel to each side, simply cut them from the donor bridge, then cut/file the just-cut vertical member to half of its original thickness. The mating edges of the bridge being lengthened are already half-thickness, so all that's needed it to lay the parts on a flat surface and cement them together.I would, however, use a continuous piece of strip styene, of suitable width and thickness, over the entire length on the top and bottom members of the lengthened bridge, before adding the upper and lower flange pieces (parts 6-7-8-9).
These two posts sorta confused me...
richhotrain...It wouldn't matter if I settled for the length of the truss span (as is) out of the box, but I want to add two X-braced center sections to lengthen the bridge span, so that complicates matters.
zstripeWhat You would do, is add an X section to bridge part 4 and 2 or two X section per part. Then You would reinforce the bottom deck with full length I- beams for the deck
I take it that the two X-braced sections to which you refer are not to lengthen the bridge by two panels, but rather one for each truss. Otherwise, you'll need to order a third kit.
I do agree with Frank's suggestion regarding the use of full-length I-beams for the deck, though.
Wayne, I do need to order a 3rd kit.
I attempted kitbashing a pratt bridge out of several kits thinking it would be quicker and easier than a scratch build. It was a painstaking experience. Very tedious, time-consuming and more expensive. I ended up scratching the project and starting all over scratch building. It was then I successfully completed the bridge.
Scratch building a bridge is really not that difficult with quarter inch foam board, a template, wax paper and T pins. I didn't have a template on my first build or any of them for that matter. Bridge design is not that difficult either. When you break it down it's just simple repeating geometry and really a lot of fun to scale out.
This was my first scratch built bridge. It is not a pratt but it easily could have been by changing only 4 members on either side. It is an N-Scale Bridge. HO would be much easier, not as tedious.
When I built this bridge, styrene was new to me. I didn't know how to pick it and I was not familiar with any of the members.
Had I done a little more research before the build, I could have done a lot better job. I am still waiting for a rainy day to replace the 12 angled members on the top of this bridge to thinner members.
Scratch built bridges as time-consuming, they are a lot of fun though. They are not that difficult.
Respectfully TF
Wayne, the point that I was trying to make in that passage that confused you is the the mating center x-braced sections are not an exact match. There is an overlap so when the two sections are mated they do match, but the actual dimensions of those two mated center x-braced sections are slightly different from one another, out of the box. All of the other sections are exact matches in dimensions.
Before I bought the Walthers kits, I downloaded the instructions and briefly reviewed the illustrations. I mistakenly thought that there were four sections to form both sides of the truss span, as seen below.
But, there are actually 8 parts involved. The previous illustration shows only one side of the truss span.
The photo below shows the actual four parts needed to form one side of the truss span. Notice the 60/40 split.
The next photo shows the parts joined to form one side of the truss span, as the kit is intended to be built.
But, I want to lengthen the span so I need to add two additional center x-braced sections, as shown in the drawing below:
I've been watching, could you alternate the sides, using the X pieces, to get the overall length the same? trying different combinations of X peices butted, one from one side, and one from the other side, to get the length?
Is scratch building the piece an option? instead of buying another kit?
Mike.
My You Tube