I am building a curved trestle on my N scale layout. It it almost finished, except for the ties atop the stringers. What is the best way to align the ties so they follow a nice smooth curve? Any help would be much appreciated.
Thanks,
Scott
Assuming the ties are all quite uniform in length, which was almost always the case on trestles, make their centerlines conform to the centerline on the bridge deck, and orient the ties’ longitudinal axes with a radius running to the pivot point, or center of the curve. You’ll need a marking cord, snap string kind of set-up, but without resorting to snapping all the chalk lines. Just place a pivot of some kind, and then have another anchor for the black thread, or whatever you use to indicate the radius, outside the curve. Personally, you should be able to get very close just using the Mark 1 eyeball. On the inner side of the curved deck, place the ties a smidgen closer together.
Ties on a trestle are spaced closer than regular ties.
Railroads don’t use “ties” on timber or even steel trestles unless it’s a ballasted deck. They use “bridge timbers” which are much larger than ties in all three planes, depth, width and length.
I know this will be taking the easy way out, but if this is your first trestle you might want to think about using bridge flex track. I know it’s not the same as wood, but once you get the timbers on it you still need to put the rail on, and the guard rails too. The advantage to using bridge flex track is that the track work will be easy to do and it will be level and smooth. The disadvantage is that it won’t look quite as good as with real wood ties. It all depends on your skill level.
I suppose some would say that I cheated on my curved trestle… I simply used flex track and called it close enough. It’s been in place for better than four years and I don’t recall anyone saying anything about it. [:)]
If you really wanted to be more precise, a “T” square should do what you want. The ends of the arms of the T would ride on the inside of the curve and the leg of the T would indicate how to line up your ties / bridge timbers.
Hope this helps…
dlm
Roger, I don’t know if that is even true as a generalization. As the link below suggests, ties is indeed what they are called often, and their dimensions are dependent upon the loads and speeds on the trestle. Note that the dimensions given in the first two sections of the table here do not indicate a large difference.
http://www.blackbearcc.com/ties.htm
-Crandell
I made a jig and it worked wonders
Great photos and information, it seems with trestles the ideas are wide open, such a variety of construction, the idea of using 2 or 3 types of bridge elements on one trestle is intriguing, guess this is why I like logging railways, it fits into the “anything goes” category (sorry, you purists) this is a great post.
I would like to thank all of you for your input. You have all given me a lot of ideas to tackle this project. Now I just have to put them to good use.
Scott
They call them “Bridge Ties” but “Bridge Timbers” is more correct. Google “bridge ties” and you get sites about marriage, Google “bridge timbers” and you get, bridge timbers. If you notice in your link, the scale size quoted is 8 x 8 x 10. Pretty small bridge timbers. Besides, it’s a hobby store site, hardly a reliable source. 
I’ve tried Googling “bridge timbers” but cannot seem to find a source for bridge timber sizes yet the ones I’ve handled were typically 8 to 10 inches wide, 12 to 15 or so feet long and at least 15 to 16 inches, or more, deep. The wooden derail guards were typically 8 x 8s lag bolted to the bridge timbers.
According to
“57 Plans”
“Compiled in the Office of Chief Engineer”
Maintenance of Way
for the
Pennsylvania Railroad
Ties were 8" x 10"x 9’ with 16" centres.
Where as the Model Railroad Bridges & Trestles uses 7 3/4" x 7 3/4" x 8’ Ties on their Standard Trestle.
I think size is a matter of a Railroad’s Chief Engineer and other engineering minimum standards.
Fergie
Fergie,
Southern Pacific common standard plan for E-50 live load open deck wooden trestles dated April 22, 1958 also showed ties 7.75" square and 8’ long. Tie spacing appears to be two-times tie width.
I note that ties for open deck steel bridges used large ties, placed closer together. I’m looking at SP’s common standard plans for open deck steel bridges, revised Oct. 3, 1961. Ten-inch wide ties were used on heavy traffic lines, and eight-inch for light traffic lines. Thickness of ties was dependent upon the center-to-center distance between the girders/stringers. Examples: 6’6" centers needed a tie 9.5" thick and 9’ long, 10’ centers needed a tie 13.5" thick and 12’ long, and 12’ centers needed a tie 15.5" thick and 14’ long. I don’t see dimensions given for tie spacing, but from the plans it appears to be about 1.5 times the width of the tie. On curves, superelevation was obtained by using a beveled tie, with the slope in the 6’4" of the tie center. Also, curved track may need longer ties than on straight track. Further, bridge ties were slightly notched where they rested on the girders/stringers.
Edit – It seems to me that ballasted deck bridges/trestles have become much more common than open deck types in recent decades. I note 1920s SP common standard plans included those for ballasted decks. I presume ballasted bridges/trestles use standard ties and spacing.
Mark
Thanks for the updated info everyone.