I'm about to create bridge track for a wooden truss bridge by cutting the spacers between Atlas Code 100 flex and positioning the ties closer together, as others have suggested in this forum.
How far apart should the bridge-track ties be? The best estimate I've been able to find is from Chuck in a 10/2008 thread, who said "A yard of flex and a little work will yield about 24 inches of bridge track and a couple of lengths of spare rail to use elsewhere." That says half-again as many ties, or about 2 mm separation.
Does that sound about right, or am I being too anal? Come to think of it, can anyone be too anal?
Thanks.
Rick Krall
I thought google would answer this pretty quickly, but alas, no luck. The best I could find was the separation "appears to be" one tie width.
-Tom
Chuck's approximation is a very good one Rick. I did it a similar way, spacing a tiny bit less than a tie width. (8-10 real inches perhaps). What I didn't completely like was that bridge ties are often longer than regular ties so I restricted the flextrack trick to my rear trestles. I used commercial bridge track in the fore and mid-ground.
Karl
The mind is like a parachute. It works better when it's open. www.stremy.net
Thanks, Tom and Karl,
I'll go with flextrack and your consistent suggestions.
Thanks, too, for your quick responses.
This is a piece of home-made, Atlas Code 100 bridge track on an older Atlas chord bridge model. I found that it took almost a full 3-foot section of flex track to make this 18-inch span, so that's a compression factor of 2 to 1. Here, the Atlas bridge is designed for standard-width Atlas ties, so tie length was not an issue.
This is on a short, home-made trestle. Again, it was close to 2 to 1 for putting the ties together. This gives a better idea of what it looks like without the bridge in the way.
In both pictures, I added guard rails. Ideally, I think it would be better to use Code 83 rail, but I didn't have any. What I did have was old, old brass flex track, which I used as the "donor" track for the ties, so that rail was available. It actually worked out fine.
It takes an iron man to play with a toy iron horse.
fkrall I'm about to create bridge track for a wooden truss bridge by cutting the spacers between Atlas Code 100 flex and positioning the ties closer together, as others have suggested in this forum. How far apart should the bridge-track ties be? The best estimate I've been able to find is from Chuck in a 10/2008 thread, who said "A yard of flex and a little work will yield about 24 inches of bridge track and a couple of lengths of spare rail to use elsewhere." That says half-again as many ties, or about 2 mm separation. Does that sound about right, or am I being too anal? Come to think of it, can anyone be too anal? Thanks. Rick Krall
Howdy, Rick,
"Wooden truss bridge" suggests that you are modeling pre-USRA, since most such had been replaced with metal (or masonry) by the first decade of the 20th century. At that time, there were no common standards for bridge tie spacing or size, either cross-section or length. Length varied all over the lot, from standard (Atlas flex has eight foot ties) to humongously long (the ties on the truss spans of the Georgetown Loop bridge run all the way across the top of the entire structure.)
In scanning a quick attempt to find ANY info, I noted a reference to 9 foot tie length in a FRA document, and a note that the rails on a Civil War-era bridge were, "Spiked through the ties into the stringers." In the latter case, either the ties were remarkably thin or the spikes were remarkably long!
A photo of my own prototype reveals that the ties on a long, tall deck girder bridge were standard length but deeper than standard. The spacing was about equal to the tie width. No edge timbers, just a strip of flat steel about 50mm wide (apparently meant to keep the ties from moving around.) The guard rails were something like mine cart rail, Code 40 or less in HO, spiked to every fifth tie. This was heavy-duty construction - in the 1960-era photo there were triple-headed D51 class 2-8-2s crossing that bridge.
One sneaky trick - insert a long tie every fifth tie or so, and use it to support walkway planks between the rails and the trusses. Then run a heavy timber along the inner edge of the walkway, just overlapping the ties. Unless someone inverts the bridge to look, no one is likely to notice that that 6x6 is supported by air, and it will add the missing foot to the tie length.
Just a few thoughts from someone with a LOT of bridges (and bridge ties) in his future.
Chuck (Modeling Central Japan in September, 1964)
There are two examples of open floor bridge decks in the Bridge and Trestle Handbook by Paul Mallery.
The first is 1909 vintage Harriman System and shows 8 inch wide ties with a 4 inch spacing. The second is 1915 vintage Northern Pacific and Shows 9 inch wide ties, also with 4 inch spacing.
More great input; thanks. Lots of knowledge and beautiful bridge work on this forum.
4" works out to 1.16 mm, so I'll tighten my 2 mm a bit.
BTW, my method is simply to turn the track over, trim the Atlas spacers to the target length, and slide the ties together. I'm saving the cut-out sections in case I need to CA them into the openings to square the ties to the rail.
Some more information is given at this link: http://books.google.com/books?id=WFRDAAAAIAAJ&pg=PA73&lpg=PA73&dq=bridge+tie+sizes&source=bl&ots=O0nau330yn&sig=0TUCvRyI2puWXhdGhVOYsgNpJqM&hl=en&ei=itLdS7_VCZDO8wSs25HKBw&sa=X&oi=book_result&ct=result&resnum=8&ved=0CCkQ6AEwBw#v=onepage&q&f=false.
Note that they give the spacing as center to center of the ties. Also, from what I can determine, the height of a bridge tie is equal to or greater than the width.
If you want to buy some pre-made bridge track that probably is close to the proper dimensions, there is always Micro Engineering. They have some bridge track shown at the Walthers website: http://www.walthers.com/exec/productinfo/255-11101
Oh, and I'm sorry if the first link causes this post to be overwide. I don't know how to make a link wrap if it chooses not to.