RE: [CBQ] RE: Oregon, IL Truss Bridges

[GLEN HAUG <glenehaug@msn.com>]

Tom:

 

The truss spans in the bridge at Oregon are Pratt trusses, not Warren trusses.  I agree with the original responder to your post that the Central Valley 150' Pratt truss is a good starting point.  The trusses at Oregon were 132', but I wouldn't change the length of the panels if it were my bridge.

 

One thing you could do to make the CV model look almost identical to the spans in the Oregon bridge is to add reverse diagonals to all of the interior truss panels.  The CV model appears to have reverse diagonals in the two middle panels (3 and 4) only, whereas the prototype bridge had reverse diagonals in all four interior panels (2,3,4 and 5).  They were all eyebars, so they would probably be pretty easy to replicate with styrene.

 

The responder below evidently had a problem with the truss sagging.  I'm not familiar with how the CV model goes together, but you might experiment with trying to place some camber in the truss.  This is prototypically, and I would guess the trusses at Oregon originally had a couple of inches of camber.

 

Glen Haug
 

---

From: drsager2@yahoo.com
To: CBQ@yahoogroups.com
Date: Fri, 15 Nov 2013 08:23:34 -0800
Subject: [CBQ] RE: Oregon, IL Truss Bridges

 

 Tom,


I cannot speak to the accuracy of the Walthers vs. Central Valley designs other than to say Wikipedia is your friend (search for truss bridge).  


What I can say is that the CV bridge kit offers a lot of flexibility as far as length and design.  I actually bought 2 of the CV kits to span a duck-under (and significantly shorter) version of the IC bridge over the Mississippi.  From a construction standpoint, the CV bridge kit allows you to get pretty close to your target length without a lot of effort as the kit comes in (4"-6"?) sections that are assembled to length.  To provide structural strength the kit includes a strip of (spring?) steel that slides into a groove under the bridge (between the side floor beams and directly under the track) to make a "T" design (or more accurately |+|).  I made the mistake of not firmly attaching my 2 pieces of steel together prior to installation, so my bridge tends to sag a bit when running a group of F units across it (it's a bit difficult / impossible to get epoxy between them now and CA glue just doesn't seem to hold them together).  I suppose if I actually had the prototypical bridge supports it would be fine, and I might yet do that (as the bridge by itself does not seem to be enough of a deterrent to have people actually duck under it - perhaps a 1 x 12 will! ^-^).


Something to keep in mind is that you will need a fair amount of space when building the model (IIRC they suggest 2' plus).  The other thing is that you can contact CV for support and they actually respond.  

Just my .02

- Dave Sager

Union, IL 

---In cbq@yahoogroups.com, <thommack@...> wrote:

Anyone have any suggestions as to the best HO scale stand-in for the truss bridges over the Rock River in Oregon, IL?
 
Tom Mack
Cincinnati, OH

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