The following image is of an HO scale arch bridge I designed and constructed back in the mid 90's. It's not necessairily prototypical but it was never meant to be.
Unfortunately, it was never entirely finished because the layout I had at the time was torn down shortly after it was built. Other than being a little dusty from 15 years of storage, I think it faired the test of time rather well.
Looks good ! I am planning on building a similar type bridge for my layout to bridge the gap between the east yard and the rest of the layout. My bridge will be built with an incline so that is going to provide me with a little more of a challenge.
Do you have any pics of the construction process?
Massey
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SMassey Looks good ! I am planning on building a similar type bridge for my layout to bridge the gap between the east yard and the rest of the layout. My bridge will be built with an incline so that is going to provide me with a little more of a challenge. Do you have any pics of the construction process? Massey
Unfortunately, I didn't take any pictures during it's construction. In fact, these are the first pictures I've ever taken of it.
Interesting design. This is the kind of weathering style I wish to apply to my Trestle project.
All it needs is some tension members and it would probably pass engineers inspection.
Cheers...
Chris from down under...
We're all here because we're not all there...
That is a nice looking bridge, but it seems completely unstable. It is held up by two arches made of 12x12 timbers (mayby 16x16) and they are held together by nails with no gussests or bolts anything. It is very attractive looking, but I would want some indication of the support and bracing that would make it stable.
It is an unusual design, but appealing. I worry about the diagonal braces under the deck that abut against the vertical posts partway along their lengths. That's quite a vector of force against a non-braced timber.
I also think you got the weather look done very well.
Crandell
ARTHILLThat is a nice looking bridge, but it seems completely unstable. It is held up by two arches made of 12x12 timbers (mayby 16x16) and they are held together by nails with no gussests or bolts anything. It is very attractive looking, but I would want some indication of the support and bracing that would make it stable.
As I mentioned previously, the bridge was never completed.
selector It is an unusual design, but appealing. I worry about the diagonal braces under the deck that abut against the vertical posts partway along their lengths. That's quite a vector of force against a non-braced timber. I also think you got the weather look done very well. Crandell
I agree, if it were a real bridge I would have never done it that way but since it was a model that would never have to support more than a pound or two at most, I exercised a little creative license because I liked the way it looked.
In the future, I plan to build another (newer) version of this bridge, only this time it will have a true curved arch that will be achieved by laminating thin strips of wood together.
Don't know much about bridge construction, but it seems to me that curved prototype bridges would not use curved elements, but short straight sections set together to make the curve.
Bob Boudreau
CANADA
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RailphotogDon't know much about bridge construction, but it seems to me that curved prototype bridges would not use curved elements, but short straight sections set together to make the curve.
There are exceptions to every rule.
Railphotog Don't know much about bridge construction, but it seems to me that curved prototype bridges would not use curved elements, but short straight sections set together to make the curve.
Real bridges use actual curved sections of metal to achieve the arch. Even with all of the new math and technology we have at our disposal the arch is still one of the strongest architectural structures ever invented. It does have it's limits as far as the length of the span is concerned and also the radii of the arch has a direct relation to its load bearing properties. Either way they can hold a massive amount of weight compared to the weight of materials used in construction.
Mainly what this bridge looks to be is a simple deck girder bridge with some diagonal bracing underneath. Whether these braces are actual load bearing and assisting in the way the bridge carries the load is unknown to me but it does look unique and cool. Many elements of architecture are not always structural but cosmetic in nature, and the diagonals on this could just be considered as such.
You're right! Mostly. Sort of.
When there are "elements" used in bridge construction (such as all those pieces that assemble up to make a steel truss bridge), it's more economical or efficient to use straight pieces, as you suggest. The various pieces of the bridge are variously in tension, compression, or are decorative/extraneous.
If a member is in tension and it is not straight, it will have to have extra mass to resist the malformation during tension. As an extreme example, how'd you like to try building a suspension bridge where all the vertical suspending "cables" had to maintain a curve.
If a member is in compression, it will also have to have extra mass to handle the tendency for the piece to fold sideways (not a good thing with bridges). Think of a straw on a table top with some weight on it. If the straw were bent a bit, would it hold the same weight? If you think it will, how about if I bend it a little more?
If a member is decorative/extraneous, then it just has to hold its own weight. And it can then be curved. But this adds to the price of the bridge.
That all said, you can build a bridge with curved elements. It just costs more. And some folks are willing to pay the difference so that the bridge is more attractive.
If anyone is going to suggest that a suspension bridge, such as the Golden Gate, has a curved main cable, any curve is there because it is so massive that it can't deflect to straight. A very light duty copy of the bridge will have all straight elements.
And, finally, a masonry arch bridge is a different animal than the one shown in the photos submitted by the OP. It does indeed typically have a curve to it. But that isn't like the one under discussion.
Ed