I'm building a covered bridge starting from the Garden Texture "Town Lattice Truss" plans. Garden Texture says
"Timber bridges were COVERED for one primary reason - to protect the costly timber structures from the elements. The sides and often large roof overhangs not only kept out the destructive weather, but also kept the bridge surfaces dry and kept the oiled timbers and decking used on bridges from getting slick. On roadway bridges originally used by horse and carriage, the bridge sides also made it easier to maneuver animals across a quickly moving stream below."
I found pictures of the Fisher Railroad Bridge in Wolcott, VT. In those pictures the decking appears to be solid supporting both narrow and standard gage rails. The Garden Texture plans call for a very open deck of three stringers supported by the column -beam frame bent units spaced 9' (4 1/2") on centers. I'm planning to make the deck solid so that it would support horse drawn wagons as well as 1930's vintage vehicles.
So now my question - how were the cross beams between the column bents attached to the lattice trusses to make the deck solid?
Thanks in advance for your help,
Rex
Rex, there are some pix of the covered bridge I made for my layout on my web page.
http://thescrr.com/ MOstly I winged it on making it how I thought it would work, so it is
NOT prototypical , I imagine.
Jerry
web site:
http://thescrr.com/
Jerry,
Very nice layout. The winter scenes are terrific. Your covered bridge looks like a deck truss design. I think I understand how the deck is supported on that one. The deck beams rest on top of the truss tension members with a spacing of every 2-3 feet for the stringers to span.
This "Town Lattice" design is a little different. The column bents attach to the lattice at each lattice crossing (five points) along the length of the column. The lattice actually rests on top of the cross beams which are butt connected to the columns. The bents are spaced every 9' (4 1/2") which is too much for the stringers to span. There must be some additional cross beams between the bents but I don't know how they were attached.
Of course I could take some liberties since this is only a model and attach some additional cross beams with non prototypical connectors but I'd like to know how it was really done.
Thanks for the pics,
Funny how you mention the Fisher Bridge....
I modeled my bridge to that one actually.
pics are here:
http://www.flickr.com/photos/13421463@N08/2526997008/
there are other angle shots too. The trestle bridge in the other pics, that was the basis for it, I finished it off.
I may not have made mine to exact scale to the Fisher, but I was going to overall appearance not exact scale relationships.
I didnt use any plans, just designed as i built, made changes as i went along to keep it looking the way i wanted it too. my wife likes it a lot and we are all happy with it.
Kevin
Kevin,
Nice bridge and layout. From your pictures your bridge appears to be a Howe Deck design. Take a closer look at the Fisher bridge internals and you'll see the Town Lattice truss is a bit different. Also the cupola is a smoke vent so it's actually open. I'm a firm believer that any design that works is great especially with our "10 ft rule". It's just the nagging engineer in me that would like to know how it was designed. Incidently the Fisher bridge's live load is now carried by a steel pier and 4 steel girders. The current timbers only carry the dead load of the truss, roof and snow load.
mine is not quite a Howe, nor is it quite a town lattice, but it is closer to a lattice than the howe as the howe has the wood beams crossing mid way, mine cross at the ends, mine would be a lattice if there were more cross beams. plus mine does not have any iron as the howe did. The Fisher is a Town-Pratt double Lattice. But I purchased my bridge as it appears in the pics, non covered. I dont have the time to build one from complete scratch. I took what I could get. They do look a bit different, but I figured that after its covered few would know the difference.
I have a side pic of the Fisher and the Cupola doesnt appear to be open, it looks vented just as I have in my model. I can dig up that pic if you want, its not on this computer, but I know I have it somewhere. I have a print out right in front of me but the file i would have to find.
I suggest you find a copy of "Covered Bridges of Vermont" by Ed Barna ISBN is 0-88150-373-8 My copy is old, its the first edition from when i worked at the Countryman Press, who at the time published the book. I only have the one copy, If i had more, I would loan one to you.
I was planning on driving up to the Fisher before I began, but my plans got changed on me. I was told there are sister birdges in Claremont-Newport Newhampshire, I went to those, but honestly they are not the same in my opinion. I can visit those much easier if you want me to take pics...infact I will be driving through Newport tomorrow on my way to a RR show in Manchester, NH. But for now, I need to get to bed as its 230am and we need to get up at 630 to head out.
night
oh, man, sorry, I just noticed that you were really focusing on the deck....my bad.
the deck of the fisher I believe is a planked, where as mine is open, thats only because I was too lazy to plank it. I should have, but was too lazy.
my book doesnt mention deck design, but from another pic I have, it does appear to be closed up and planked.
the bridge in Newport is closed up too.
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