Bridges on e-bay!

[lionelsoni]

Generally speaking, the bending moment at the center of a reasonably shallow truss, uniformly loaded as with a train, is proportional to the square of the truss length; and the strength of the truss is proportional to its depth.  So, for example, doubling the length of the bridge without increasing the strength of the members requires that it be 4 times taller.

[3railguy]

Runtime, what I mean by that, is the designs are what you would see in real life and he shows you how to design your own bridges in layman terms like a CE would. If you were to follow his methods and cut shapes from cereal box cardboard, you could probably stand on the bridge. The modeling materials such as bristol board, plastic shapes, simulated rivets, glue, etc. would not be used in real life.

[runtime]

Thanks John! I'll look into it.

But I don't understand your last sentence:

3railguy

 

 With exception of modeling materials and methods, it is not a fairy tale design manual.

[3railguy]

runtime

Are there standard dimensions for the truss triangles, ie- they look like bisected equilateral triangles? What then governs height, other than clearance needs. I can intuit taller is stronger, but cannot remember the physics. Any CE's out there?

Yes, there are but the engineering standards, computations, and connection methods are outlined in huge volumes. There are several truss designs along with several reinforcement methods. An excellent  book is the "Bridge and Trestle Handbook" by Paul Mallery - Carstens.

 

 It has a reader's digest version of bridge engineering standards for designing your own scratch built models, canned bridge plans, and modeling techniques. With exception of modeling materials and methods, it is not a fairy tale design manual.

[runtime]

There is a relatively new 'double' truss RR bridge near Philadelphia (King of Prussia, spanning I76). By double, I mean there are two identical bridges end to end, spanning each half of the divided highway.

The proportions of these real bridges seem taller than the pictures suggest for those on the web site mentioned above. I've wanted to take a picture of these real ones for some time, as I find them  attractive,  but it's a very busy section of highway with various merges, and I'm usually the one driving.

Are there standard dimensions for the truss triangles, ie- they look like bisected equilateral triangles? What then governs height, other than clearance needs. I can intuit taller is stronger, but cannot remember the physics. Any CE's out there?

[3railguy]

runtime

TXT'

Thanks for the link! I'll save it for future reference.

Was wondering...do the truss bridges increase in truss height as the length expands, as I think it should?

 

When the length of a truss bridge grows beyond normal, the top chord is typically arched like the top chord on his hellgate. In real life, his six foot truss bridge would collapse. In real life, you don't see the height raised as the span grows very often due to cost of steel. This was done with earlier pre 1900 truss designs such as the Whipple Truss.

[runtime]

TXT'

Thanks for the link! I'll save it for future reference.

Was wondering...do the truss bridges increase in truss height as the length expands, as I think it should?

 

[wsdimenna]

 all his bridges are wood and cut using a CNC machine. They are plain without riviets etc. He also will build a custom length and style. Very reasonable.  If doing scale they most likely will not have the detailing. In my case I'm planning on using on of his bridges that will be about 15 ft from viewing area so high detail is not necessary. the  most important thing will be overall design and color. They are very well made and sturdy.

 

Bill D

www.truescene.com

[TXT]

I really like the different styles of bridges and I even think that the flat one could be used as a highway bridge!! They look really well made and I think they would hold up to the test of time! And his version of the Hellgate is smaller but for the guy like me who has to watch every nickel and dime its a good compromise! And the red colored under arch bridge is outstanding!! Im saving up to buy one!  

[3railguy]

His bridge construction standards look like prewar Lionel stamped steel and prewar Flyer wood, with a little postwar thrown in, all tossed in a bag. I think with cheery green and red colors they would be a good fit for a traditional pre or postwar themed layout. Something like an Atlas bridge that follows prototype engineered steel construction would look out of place in a tinplatish enviroment is. It's a matter of personal taste as well.

[lionelsoni]

I don't think he's misrepresenting his bridges, any more than Thomas the Tank Engine is a misrepresentation of a locomotive.  If I bought one, I would be getting just what he depicted and what I ordered, by all accounts built to a high standard of workmanship.

[ezmike]

I have not purchased one of his bridges so I cannot comment on thier quality but I have purchased several pairs of the PW 022 switches he refurbishes and sells on ebay and I have to tell you, the guy is great. IMHO, the switches look and work as good as the day the came out of the factory. The only problem I ever had was with a controller and he sent me a replacement and told me not to bother sending the other one back.

Not being an expert on bridge construction and the like I would expect that if there was a construction or design issue with one of them, he'd make it right. Again, just my opinion.

Mike

[TXT]

Buckeye, Thats why we play with Toy trains! so we can have curved truss bridges and sit back and at them . And by the way I always enjoy looking at your photos in the Sunday photo fun thread!!Have a great day!!

[lionelsoni]

Some of those other shapes also look improbable to me.  The arches appear to be closer to circular than to parabolic.  And the "extended arch" bridges seem seriously deficient in bending and particularly in shear at the ends.  It's too bad they couldn't have gotten some more plausibly prototypical designs, which would have been just as easy to build.

[3railguy]

The curved bridge is a good answer to those double oval over and under plans where you are cramped for space.

[Buckeye Riveter]

Thanks for the link.  This is the first time I had seen this line of bridges.  They all do look well built.  I am chuckling as I look at the curved truss bridge.  As far as I know, a curved truss bridge does not exist on the real railroads.  There are truss bridges on curves but the trusses are not curved.

[TXT]

I just thought I would let everyone know about these neat and affordable bridges on e-bay or at www.bridgeboss.com

 I just found these and they seem really well built with a nice paint job! If anyone has purchased one of these, I would like to hear how you like it !!!!!!!!!!!!! 

 

 

 e-bay store=     dada1043