Advice on bridge building

I think your best bet for this would be some kind of stone or concrete viaduct, as that would allow you to have the solid, finished deck. Virtually all other types of bridges have see-through, or open, decks.

The other option is a plate girder bridge, which I believe also has a solid deck. Stay away from truss-type bridges, as they were all open as far as I know.

 

Paul. I agree with Corey. you need a solid structure. That way you won't haved to mess things up by cutting out the wood under the tracks.

 

Colonel, you really got yourself a challenge there!

A vaiduct will be nice because you do have that turn in it. Maybe two viaducts with a plate girdersp[annint the straigt middle section. I have seen Plate girders with the roadbed built up way above them. I wish I had pictures, but if going with that, cut a plat girder in half, glue it to the bottoms of each sid of the tracks, but leave enough room for a natural steep slope upto the mailline level. And then the Viaduct supports each end of that.

I notice you have FIVE tracks going under that area, you might consider the plate girder of the span over the Four tracks (the kind of straight part, and a concrete portal on the single track(like on the Grand Cnyon Line Near Williams, Arizona...Boy do I wish I had the pictures!)

You might also be able to dresas it up like a modern bridge...and there is a modern example of a plate girder bridge in Pheonix where the Grand Avenue Tracks cross I-17, Last real bridge until the I-10 YEs, I really wish I had a Picture!.

You have a very interesting ball of string, but give us some time, I am sure we will untangle it!!!

Viaduct seems most feesible.

[ 02 December 2001: Message edited by: Benny ]</p>

 

May I add? A Atlas cantilever or suspension type bridge would work wonders in that specific locoation with a little TLC to cut and install the bridge in sections for the curve and then to have it all ballasted and or a deck girder bridge like used in viaducts would work perfectly. You then would need a long section of 1 by 1 inch square metal tubing to cut and fit to the curve and length and also to fit the 2 sections together on a bent that spaned 2 tracks with one rail going through the center, kind of like a tunnel portal and then to rest the tubing on it. To bad I can't take a picture in my mind and put it online! I got a great way that would work with real metal tubing and a little enginuity and some patients! You could do that in a manner to set the bent(s) one on each side of one set of tracks below (in the yard) to hold up the middle of the 2 sections of metal tubing. The tubing could be peices from a metal pourch post that holds up pourch roofs! This would work great! Then work on detailing it to look like deck girder type briges and do 2 sets for each set of tracks going over head.. Man Benny I have to side with you I could do that project in the matter of 3 hours give or take. And turn out like a kit built deck girder and noone would ever notice that it was actually steel pourch posts! To bad I can't take a thought from my head and put it in a picture and then put it online!!!!!!!!

[ 03 December 2001: Message edited by: 7600EM_1 ]</p>

 

I'd say, those are great ideas, but wouldn't it be nicer if you added a cut hillside to that? And just add a bridge where the tracks cross under! If anyone out there has any better ideas tell Colonel quick!!

 

Consider redoing the upper level trackwork's roadbed, starting the curve sooner so that the length over the yard tracks is straight. Then you can model a ballasted deck girder by simply buying Atlas girder bridges (cheap) sawing off the sides (discard the track section) and epoxy them to the side of the plywood subroadbed. Five tracks wide would require bridge supports about 10" apart, or about 70', which I think is reasonable.

Gary

 

I agree with Gary. Get a straight run through if at all possible. Plate girders are good for up to about 150 ft span (1:1) and the depth of the girder should always be about 1/10th the span (ie. for 10 inch span, 1 inch depth (height if you like)). Skewed spans are no problem with plate girders.

You might consider putting a central girder in between the tracks as well, or even cutting out a slot between the tracks to make separate single tracks with slightly different (older and newer) bridge girder styles.

 

Oh, I forgot this. For pictures go to Google (the search engine - www.google.com ) and choose the Images tab. Put plate girder bridge in the field and hit "Google search". The results aren't all PG bridges, but it'll get you started .

 

Hey guys, if he moves the subroadbed, he has to take up the track, and this is what he doesn't want to do. Using the existing configuration, what would you do?

I would still go back to the cuved stone single-arch viaduct. The engineering is there for it, but you may have to play with clearances some.

 

No problem, just tryin to help!

 

Corey, "Using the current configuration, what would you do?" I wouldn't. Don't mean to sound like a smart ass, just my humor. The biggest problem is the curve which appears to start right over the first track. No way I can see to span 5 tracks with a viaduct which also has to curve at one end prior to reaching room for a support. There is no ballast yet, I would think less than 1 hour is required to remove track, cut out roadbed and replace with new, lay track, done. Problem resolved. Certainly the result will be more plausible. I've found over the years that reluctance to re-do work usually leads to disappointment. Just my 2 cents.

Gary

 

Hi Paul, After reading your reply and taking another look at the photo, a couple questions come to mind. The five yard tracks appear to curve to the right after passing beneath the upper level tracks in question. From the photo, it would appear these yard tracks would become hidden about that point. Is that right? If so, what is your plan to have them disappear from sight? Also, and unrelated to our topic, do they continue on for some distance as 5 tracks? I'm just wondering if you have turnouts back there, they sure would be hard to access. Anyway, could you post another photo from the vantage point of the 5 tracks passing beneath the others? A head on view with the upper tracks running from left to right over the yard tracks? Also, what is in your plans for the area in front of the upper level tracks? As far as your concerns about radius, I hadn't considered that. A suggestion: Make a couple templates of the minimum radius you feel you can live with out of cardboard (I have a set of the templates made years ago by Arbour, they sure do come in handy). Cut out a straight section to represent the bridge, tape these together, and see how it looks sitting in place. My feeling is you will have to lose a portion of that open space I asked about. Good luck and have fun, that's what it's all about!

Gary

 

In Kansas City one of the local railroads got together and built a structure much like the one you have so that they could avoid existing yards. They built it with a viaduct much like what you would see with American highway overpasses. Regardless of the bridge type, the concept is a viable one.

 

Paul, I was wondering what you decided to do about the bridge. Any progress?

Gary