CVMV bridge prototype

The prototype for the CVMV truss bridge is in Piru, CA on the old SP branch from Montalvo (Ventura) to Saugus.  Having grown up in Ventura, I can state for a fact that SP occasionally ran Cab Forwards (4-8-8-2) on that route, with loco & tender at a bit over a million lbs..  So, I would expect sufficient capacity for your locos.

If you are modeling a

If you are modeling a specific prototype, then I would get photos of their bridges and try to mimic them.  If not, try replacing the central valley string with truss beams.  Look at Joe Fugate's bridge across the Wilamette river.  http://siskiyou-railfan.net/e107_plugins/coppermine_menu/displayimage.php?album=6&pos=1  A beefier bridge should look like his bridge.

The problem is, they are

The problem is, they are already assembled.  There are three of them! I don't want to just get rid of them.  I did not know they were such a "light weight" bridge.  For other similar bridges, I most likely will use the Walthers one.  But I need to find a place for to use them, and this is the "lightest duty" line that is in the plan.

Ken L.

Really an issue?

You have to decide for yourself what your tolerance is but this sounds like something that would fall into "modeler's license". The lighter bridges may enhance the overall effect of massive steam engines rolling along.

I pursue prototype modeling as I can too, but sometimes we have to work within our limitations, at least until an alternative presents itself!

The real question is.. would anyone notice?

I would also do some more research to test your assumption the bridge is too light. Compare it to bridges on your prototype of similar style.

Chris

It might be an issue....

As what I don't want is to be in the realm of implausiblity. 

I'm not a structural engineer, and i'm getting "mixed" replies on other discussion forums about this, The consensus on other forums has been this specific bridge design can not handle the load.  Though if what is reported in this specific thread is correct, and I have no reason to doubt it, it would seem the Mallet's and Alleghenies would be able to use this bridge since the SP used 4-8-8-2's on it.  Before this was known to me, I had concluded the bridge was insufficient and would be screaming out "IMPLAUSIBLE", which I am desperately trying to avoid.  I know the ol' model railroad saying that goes "it's your railroad, do what you want" and if I want a heavy modern diesel locomotive traverse a rickety wooden trestle, then go for it.  Now if that sort of thing doesn't bother others, that's ok, but to some it would, and to me, I want to stick as close to the prototype as I can.  Though I am proto-freelancing, I don't want to stray so far from the prototype that it becomes implausible. 

This is why I am asking around for ideas on how I might upgrade it after it is assembled.  But it seems I might not have too.  Hmmm... What to do????? Isn't Model Railroading just "fun".......

Ken L.

What you see vs what you read

I completely understand.. you want verisimilitude..

One thing to consider is the difference between people reading your post which introduces the issue in detail (predisposes them, if you will...) on the subject and coming up with an answer.. one that may or may not be rooted in any real knowledge vs people coming to your layout room and looking at the bridge and thinking "that can't be".

I would be careful about theoretical opinions..  much  more important to me would be the impression visitors get when they view the actual thing on your layout.. I bet nobody ever notices unless you say something..

I would look for pictures of your type of train crossing bridges and look at those and deciding if your bridge appears correct or what differences could be incorporated.. I would be wary of message board "experts" (lol.. like me..).

If you find an image of a 2-6-6-6 crossing a similar truss.. but it in your files.. and keep it handy if it ever comes up.

Chris

There is such a thing.......

......Between applying serious "real world" research/plausability to your freelanced layout, and over researching and thinking EVERY little last detail out. Same goes for prototype modelers, and I should know. I just cut in 5 new turnouts that I didn't REALLY need to make the layout operate any better than it already would have, but because I saw them in a photo, I went and added them in, making more work for me, more "mental anguish" in trying to retrofit them into the current plan, and costing more money to boot. OK, maybe not the same thing as your situation, but hopefully you get the point. Chris' suggestion is a good one - Just do it if it makes you "happy".

RAH

Slow order

Something else occured to me.. on some of the railroads I have researched there were older bridges that were not up to modern standards. Slow orders were in place for crossing the bridges. That might be another way to approach the issue.

Chris

Dangers of too much research/planning.

I know.  Some very well known model railroaders have advised me not to get so lost in research and planning that I loose sight of the real objective.  After spending almost a year developing the "back story" for the Pennsylvania & Allegheny, and how it interchanges with the Allegheny Midland, I finally decided enough was enough, and I had a sufficient enough "story" that I could let it be.  If I didn't stop myself, I could have gotten to a point where I was compiling a month by month history starting from the mid 1800s! 

I'm going to try to see if I can find a picture of the actual prototype bridge with one of those 4-8-8-2 units, that would be sufficient proof, and the issue hopefully will be settled.

Thanks all for the feedback and information! 

Ken L.

Central Valley Truss

Ken:

For what it's worth, the Central Valley Truss is a dead-ringer for the SP Siksiyou Line bridge just north of the town of Oakland on my layout.

Realize this was the SP main until 1927, and even after that, early cab forwards ran across this bridge, all the way up to SD70s a few times (tests by the SP to make sure the Siskiyou Line could be used as an alternate route to the Cascade Line in an emergency).

So I wouldn't use the bridge on a heavy traffic main line, but a secondary main or major branch line would be fine, even if the line had rather heavy locos on occassion.

Thanks Joe! I plan on using

Thanks Joe!

I plan on using it for a Coal Branchline, so including this info, I feel more comfortable using these assembled kits for it.  Thanks all again!

Ken L.

A bit more info

Ken,

It's friday night, so I had some time to dig into resources, so here is a bit more info in case you want to do structural calcs .

C&O 2-6-6-6 Allegheny: Loco weight = 724500 lbs., tender (2/3 load) = 341600 lbs.  Weight on drivers = 471000 lbs.

SP 4-8-8-2 Cab-forward  (as used over the CVMW's prototype): Loco weight = 657900 lbs.  Loco+ Tender = 100,050 lbs, so your 2-6-6-6 puts a bit more load on the bridge.

Interesting side notes:  The 2-6-6-6 had 67" drivers and a tractive effort of 110200 lbs.

                                        The 4-8-8-2 had 63" drivers and a tractive effort of 124300 lbs.

If I was going to chose a loco to get down and lug a load over mountains, the 4-8-8-2 is my hands down choice.  Plus, the engine crew gets to breathe fresh air.

Though I love the Cab

Though I love the Cab Forwards, that is most certainly an SP locomotive, i'm modeling in the Appalachian Mountains, so they would be a bit out of place.  So now with this new information, it looks like i'm back to rethinking how to modify this already assembled kits.  **SIGH** I must continue to remember Model Railroading is supposed to be fun! LOL

Thanks for the info.

Ken L.

How does it look?

Take your 2-6-6-2, put it on the bridge. How does it look? Take some pictures, how does it look in the pictures?

If you think it looks good then use the bridges as is.

Peter

Sorry, Ken

I'm sorry my rib-poking was a little too hard.  I just really love cab-forwards.

And I had read Paul Mallery's book on bridges in the distant past so, with the data on the locomotives, I am, of course,  now an expert on bridges. (NOT!)

I do find it interesting how the railroads selected their motive power.   I have read of some of the great debates that the coal haulers had regarding picking 2-8-8-2's, 2-6-6-4's, the 2-6-6-6, and others.  If I can find the book or article, I'll post the name and author.

I really like Peter's idea of putting the loco on the bridge and seeing how it looks, then seeing how it looks in photos..  There's where the fun is.  If it looks OK for a branch line (maybe with a speed restriction), then go for it.   It's that "good-enough" thinking, which leaves you with more time for other modeling.

I've got a couple of the CVMW bridges that I intend to use, somewhere, just because they look so doggone good.  The CVMW documents indicate that it was a standard bridge type, that was used nationwide.  The prototype was built in 1902, with the intent that they were used with the largest locos of the day, including the articulateds that were coming on -line about then.

And what happens....

And what happens when Master Model Railroader Jack Burgess comes to visit the railroad, and sees that the bridge in way under specs and shuts down the branch until the bridge is replaced with a more adequate one LOL!!! ??????

Ken L.

If Jack Burgess comes to visit you and complains

Then you tell Jack to get out of your studio and go back next door to the DYI Working on the railroad studio set  and finish his 8 part Special on the Woodland Scenics Foam core Kit that they are building and to leave your railroad alone!

Dan

In fairness to Jack....

He probably wouldn't do that.  He is very polite, gracious, and tactful.  If he ever did something like that , he would do so with a smile, laugh and after complimenting something about the layout! (hence theat the end of my previous post...we need a you tube channel for this forum so the sarcasm and jokes can be translated through where text fails miserably :-\). 

I'm just reminded of what happened during the LDSIG tour during the 1994 NMRA Convention at Joe Fugate's Siskiyou Lines.  I was helping with the tours, and I was standing next to Joe and Jack, and Jack was commenting on what an excellent job Joe did with the modeling the rust on Coos Bay bridge.  And he concluded by saying "oh by the way, I have to condemn the bridge because of potential structural failure caused by the rust" and we all laughed!!! 

But seriously, having others approval is very important to me.  I will get the most satisfaction when my proto-freelanced P&A will "pass muster" in terms of being plausible.  So even if I think it's "ok", if a majority think "that bridge is way undersized" then I will ahve failed a crucuial goal.  I know I won't satisfy everyone, there will be those who will totally scoff at me proto-freelancing so any attempt to get them to "approve" will fail.  But i would like to have a majority find the P&A more than acceptable.

Ken L.