I'm thinking about building one, but as far as I know, I've never encountered a real one. I'm assuming they were outlawed at some point. How late were wooden truss bridges still in use?
Henry
COB Potomac & Northern
Shenandoah Valley
I don't see why they would be 'outlawed'. If the wood, fasteners, supports, and engineering are sufficient for the loads, the railroads would ostensibly use them and continue to make money. If one had to worry about fire, then trestles would have been replaced earlier for the same reasons, but many of them are still in use...and burning. We lost a large one in Alberta a couple of years back.
The fact is that, where it made sense, the railroads' druther was to fill rather than to bridge. Where filling was possibly going to be iffy, say during spring runoff, they bridged. Where steel trusses made better sense due to increasing loads or local forest fires, then steel was put into service. This happened to the famous arch deck truss Stoney Creek bridge in the Canadian Rockes. The longest trestle in the world is the steel deck one over the Oldman River in southern Alberta, known locally as the High Level Bridge. It was built out of steel from the get-go.
You have to enjoy what you want on your layout. Everything is possible, including lack of funding to rebuild or to replace damaged and aging bridges. Even then, there's nothing stopping an enterprising railroad from constructing new bridging from materials they only have to acquire in the hillsides adjacent to the right of way.
A wood truss bridge (built 1936) on a coal mine branch in Canada. Bridge still exists. Don't know when last used by trains.
https://ogrforum.ogaugerr.com/topic/old-coal-mine-andamp-wooden-howe-truss-bridge?reply=18746738030440238#18746738030440238
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.
Paul Mallery's "Bridge and Trestle Handbook" should be on every modeler's bookshelf.
In it, he says:
"Modern timber bridges are built from treated timber, some even of redwood, and usually without cover [as in: covered bridge]. Modern timber truss and arch bridges would be found only in areas which presently or recently had good supplies of timber, such as the Pacific Northwest in the U.S. and throughout Canada. The Sioux Narrows bridge in Ontario, built just prior to World War II, has a 210' (64m) span.'
Timber bridges would be hand-built from local (more or less) timber, while steel bridges would be kits shipped in from factories. Whoever is specifying materials would run the costs and pick the winner. So, building a wood bridge in the middle of a desert would have limited appeal.
The span of 210' is 30" in HO. THET is a honkin' big bridge for a model railroad. It is, unfortunately, a highway bridge. Yuk!
There is also the matter of durability. There are steel trusses on the former SP&S mainline that are over 100 years old, and still being used.
Combine this with strength: what would a wood truss bridge capable of handling 100 ton coal gons at speed have looked like? That would have been the equivalent of the above mentioned SP&S bridges.
I also recommend reading (and saving) this discussion of wood and metal trusses:
https://www.tn.gov/assets/entities/tdot/attachments/chapter5.pdf
Ed
We were in Durango 2 years ago, I do not remember that bridge, but there was so much to see it still could be there.
One of the references above said they were still being made of wood as late as 1946, so that would fit into the transitions era. I may try shortening a CV truss bridge. It is what I "grew up with" on the East coast.
BigDaddy ...shortening a CV truss bridge.
...shortening a CV truss bridge.
THERE'S an adventure. I've got a CV bridge project tucked away, myself.
If you're talking anywhere after WWII, you've got some real explaining to have a wood truss bridge. I'm not agin 'em, mind you. I'm just talking reality. They were getting darn rare.
The CV bridge is a fantastic example of a lightly built steel truss bridge. Except that the SP&S bridges I mentioned earlier are almost exactly the same. And those are definitely main line.
I'd be a bit wary of shortening that bridge, though. How ya gonna do it? If you leave out panels, then the proportions might start looking really strange.
If you need a shorter bridge, you might think about a girder bridge. You can't get more railroady than that.
BigDaddyI'm assuming they were outlawed at some point. How late were wooden truss bridges still in use?
As far as I know they weren't outlawed. They just weren't built anymore and the old ones ...
The Spokane International/ Union Pacific had a Howe Truss bridge crossing the Kootanai River in Bonners Ferry Idaho:
http://www.moosecreek.ch/bilder/history-prototype-rallroads.html/history-howe-truss-bridge.pic/pic1.jpg
The bridge collapsed under a ballast train on December 6th 1985.
This website has a nice history of the bridge: http://www.moosecreek.ch/english/history-prototype-railroad.html
The website is translated from German to English.Regards, Volker
To add a bit to this: a potentially useful reference to wooden trusses is the Government handbook on covered bridges that Alexander Mitchell IV co-authored (the link is recent on RyPN but I can’t access it from here). The ’covering’ in a covered bridge protects underlying wood truss structure from environmental factors. A section in that handbook goes into why it’s unsurprising that even large diesels don’t overload such a bridge ... on the other hand a Howe truss is known for proceeding very quickly to catastrophic failure if “too overloaded” rather than gracefully degrading with plenty of warning...
In ‘the old days’ timber, even of great size and reasonable old-growth quality, was inexpensively available. So was even sophisticated joiners’ labor. But iron and fittings were expensive. Along the way these costs reversed, good welding technologies came along for fabrication and good equipment for placement, the ‘good roads’ and construction industries made structural concrete more available ... etc. And then comes the whole discussion of permissible preservatives and their likely effect on waterways and other ‘environmental’ areas of concern.
Overmod ... And then comes the whole discussion of permissible preservatives and their likely effect on waterways and other ‘environmental’ areas of concern.
... And then comes the whole discussion of permissible preservatives and their likely effect on waterways and other ‘environmental’ areas of concern.
True dat. Quite aside, my father left me a gallon of creosote oil in a metal tin a few years back. When I craft a wooden trestle, I paint its scale timbers with....go ahead...take a guess. Unfortunately, that unforgettable and so-pleasant smell doesn't last more than a few days, not for the teaspoon or so that it takes.
I have taken to soaking a paper towel in a few drops and hiding it away somewhere. Or splashing some on the back of a frame member where it won't be seen.
When the locally famous Kinsol Trestle was restored six or more years back, the stipulation was that the timbers could only be treated with modern preservatives, so they do stand out against the still-pretty-darned-heavily creosoted timbers in its central Howe Truss. With salmon populations under threat in the PNW, we do whatever it takes to ensure they continue to reproduce and to thrive in our streams, of which the Koksilah River is one. (Coke SIGH la)
Selector, creosote has been deemed a "carcinogen" to humans which means it causes cancer! I like your idea though of treating the wood bridges with it but I'd be careful spreading it around the layout just for the smell.
Steve
If everything seems under control, you're not going fast enough!
7j43k I'd be a bit wary of shortening that bridge, though. How ya gonna do it? If you leave out panels, then the proportions might start looking really strange.
I have no idea. In a recent Cascade Canyon video on MRVP where the constructed bridges from CV parts. Having never built a truss bridge I have no idea where to start with just parts
BigDaddyI have no idea. In a recent Cascade Canyon video on MRVP where the constructed bridges from CV parts. Having never built a truss bridge I have no idea where to start with just parts
Here are links to the Central Valley Instructions and building template
Instructions: http://www.cvmw.com/acrobat/1900_acrobat/1902_rev_2.pdfTemplate: http://www.cvmw.com/acrobat/1900_acrobat/1902_truss_diag.pdfPerhaps they help in your decission.
The bridge floor carries all loads with the help of steel strips. The trusses are for show in this model while in the Campbell Howe truss bridge the complete structure is load carrying.Regards, Volker
NWP SWP Selector, creosote has been deemed a "carcinogen" to humans which means it causes cancer! I like your idea though of treating the wood bridges with it but I'd be careful spreading it around the layout just for the smell.
Thanks for your thoughtful warning. It happens that I know this and take precautions to avoid contact with my skin assiduously. The odor, itself, is innocuous in the low exposure rate I enjoy....thankfully.
I may have sounded very enthusiastic about making sure I get a strong whiff of the stuff every time I enter my train room. The truth is that I only do this perhaps once a year, and just enough to get that slight sense of it for a couple of days. Then I forget about it until many months later. Also, the trestle I mentioned only gets the treatment each time I position it on a new layout.
Thanks, again, for taking the time to caution me.
Sure wish I still had my can of creosote, for similar odorous excursions.
In my motorcycling days, I remember reading in the mags where guys would put some Castrol in a frying pan on the stove while they listened to recordings of GP racing. This was a long time ago, before VHS tapes, even. Sometime in the last century. So the fun event was limited to aural and olfactory. It appears. And perhaps yakkin', if more than one weirdo was involved.
I have found that the shampoo T Gel has a smell extremely close to that of creosote, so it could be a possible olfactory substitute for the real thing.
VOLKER LANDWEHRHere are links to the Central Valley Instructions and building template
Thanks, they also have a collection of Youtube videos, which I have not had time to review.
Edit The written instructions use monofilament line for cross braces. The Youtube video I looked at uses brass rod.
BigDaddy Edit The written instructions use monofilament line for cross braces. The Youtube video I looked at uses brass rod.
I'm in long-term midbuild of a modified Central Valley bridge. The thing that bothers me about so many of the builds of this bridge that I've seen is that the tension rods aren't straight. Which they are, in reality.
I suppose the monofilament would end up being straight, but I would worry about the tension twisting the bridge. My thought was to use piano wire (being as it is quite good at staying straight) and glueing it only at one end of the rod. The other end would be in a slip fit hole. That would negate length change problems caused by temperature change.
Easy for me to say,as I haven't really done it.
BigDaddyEdit The written instructions use monofilament line for cross braces. The Youtube video I looked at uses brass rod. Tongue Tied
The design of the bridge comes to your aid. With the bridge floor as the models exclusive load bearing subassembly you can take for the rods what you like best.
I personally prefer a straight wire. Monofilament has to be kept under tension to stay streight. Plastics tend to creep (deflections grow under constant tension) with the result that the monofilament might not stay straight.Regards, Volker
I'm mildly surprised that monfilament would take paint.
I plan to use three Campbell wooden bridges, and one Central Valley steel truss, on my Northbound local turn route. Not mainline, light short trains. I hope it will be plausible for 1954.
.
-Kevin
Living the dream.
SeeYou190 I hope it will be plausible for 1954.
SeeYou190 one Central Valley steel truss,
Definitely plausible, which one?
SeeYou190 thee Campbell wooden bridges
That would depend on what you are running over it. 70ton cars, probably not.
I would look into protoype weight restrictions on the different types of bridges. 40 or 50ton cars, definite maybe.
That having been said, B&M had wood covered railroad bridges in service into the mid 1950s on some branchlines. There are color photos of a railfan trip in one of the B&M reference books with Alco S-(dont remember) switchers (a pair of them) pulling a raifan special across a wood covered railroad bridge. The bridge may or may not have had steel re-enforcement inside.
Edit: I forgot why I put 2-6-0 in here. Comparison I guess to the diesels that replaced it.
Here is the weight data:
http://steamlocomotive.com/locobase.php?country=USA&wheel=2-6-0&railroad=bm
GP7s by contrast weigh about 245,000lbs, over a shorter wheelbase, with a higher axle loading.
SW-1s weigh about 199,000lbs, have an even shorter wheelbase, but have a lower axle loading than the GP7. B&M had at least one bridge where the largest locomotive that was permitted was a SW-1, braking was not allowed on the bridge, and speed was restricted to 5 or 10mph.
There is a multi-span timber through truss at East Coulee over the Red Deer River in Alberta that was in use into the 1970s when the Atlas coal mine finally closed. Both CNR and CPR served the mine, although I am not certain which was the owner. Trains were hauled by GP9s, and the cars were typically 70 ton triple hoppers. CP would only run a single unit, but friends watched CN run across with a trio of GP9s.
In my first post in this thread I linked the former Spokana Internationat/Union Pacific Kootenay River bridge in Bonners ferry:
The photo shows a UP SD40-2 crossing the bridge in 1975, ten years before the bridge collapsed under a ballast train.
Here is a photo of four spans of the bridge which replaced one from 1905 in 1932:
https://scontent.ftxl1-1.fna.fbcdn.net/v/t31.0-8/14107718_1407057409311400_5919361048315271317_o.jpg?oh=f47fbb4bef6ff0b8551bad62b645de40&oe=5AACC040
So single wooden Howe truss briges were used by heavy trains into the 1980s.I would assume that there were speed limit and brake restrictions in place on that bridge.
Perhaps a poor railroad would build a river crossing with wooden truss bridges. But a navigation channel needed a larger span so a steel truss was used.
Remember the CV truss bridge follows an early prototype, the SP Piru, CA bridge built in 1902: https://scvhistory.com/scvhistory/lw2461a.htm
Regards, Volker
BMMECNYCDefinitely plausible, which one?
The original bridge kit they offered, I believe it is a 150 foot Pratt Truss bridge. I have owned this kit for around twenty years. Right after I saw an assembled one, I had to have it. It is a beautiful model.
Here's a bridge remarkably similar to the CV truss bridge:
There are 4 or 5 along the old SP&S line along the lower Columbia River. One or two have two more panels. They were installed around 1906. In 2015, when I was there last, they were still there, handling those trains of 100 ton coal cars at speed. Noting the rather intense lack of paint, I do believe they're all slated for replacement.
But.
They're still here. I think.
7j43k...My thought was to use piano wire (being as it is quite good at staying straight) and glueing it only at one end of the rod....
That's what I used for mine, although I simply bent the upper end of each wire and inserted those short protrusions into holes drilled through the sides of the upper members of the truss. The lower ends of the wire aren't fastened at all.
BigDaddy I'm mildly surprised that monfilament would take paint.
Wayne
I found a more "active" view of one of the old SP&S bridges I was talking about:
The main differences I see between this one and the CV bridge is that there are short diagonals in each end panel, and there are tension bars in the lower edge of each of the two center panels (pretty cool visually, I think).
If you look at the diagonal tension rods (the "piano wire"), you can see they stick out a long ways on each end.
What's slowed me down on my work on this bridge is that I now don't have any place to put it. Someday............