I am looking to build a trestle bridge of my own and I need some detailed picturs so if you could help it out it would be a big help. I am looking to build a trestle bridge that has a 1.5% grade on it and is a 25" curve radius. The pictures would help a lot thanks.
You have seen my trestles. The plastic kit could be built as a curve. The wood one can be built anyway you please. Again I suggest Kalmbach’s Bridge and Trestle book. It will tell you everything you need to build any thing you like. They have lots of pictures and directions.
Hey Challenger - this is the third post you’ve made on the same subject sonce 530pm today!!! Relax a bit & wait for the answers!![sigh]
Yes. Wait. It is very good to have pactience.
Just the other day, I posted a question on one of the threads here & it didn’t take for some reason. I tried two more times at posting before the 3rd finally was posted. I don’t know where the 1st two went, so perhaps he was having the same problem & couldn’t find them to delete… I dunno.
Sorry…I don’t have a grade nor a curve on my trestle, but I do have a scratch-built trestle.
And, BTW,…Patience is a virtue!! And one of life’s lessons that is most needed in today’s FAST world!
For the most part, building with strip wood can achieve any grade and curve. It’s just a matter of making EVERYTHING very gradual.
First, set a standard for the bents (spacing and angles) and build them for the height needed at each of the eluviations for the trackage through the sceene.Then tie each bent to the other with a consistent radii (use a section of curved track or a template made with card stock) with short pieces of strip wood for the beams and decking.
Sorry if that sounds too simple…But it really is, if you think it through first!
Nice looking model selector!
But I was wondering…do you have a prototype pic?
From a basic engineering standpoint, the diagonal braces on the near side is braced left to right. The far side right to left. I would think that’s a good opportunity for a lateral collapse. I would think it should be “X” braced on both sides.
But…they did do scary stuff back in the days. [?]
Rotor
Art is on target, a good bridge book is better then a picture
Front bridge 30 in rad scrach built, back bridge is 26 rad, kit, both on 2.76 grade…John
Are you referring to a “trestle” ? and is it an incline and curved?
Rotoranch, this trestle is freelanced and has a curved deck. All trestles have girts and batten to keep the bents from moving in the two major axes, and the diagonal bracing helps I suppose to keep spacing between the bents. Although not evident from my image, I placed girts faithfully, and I used the 18 deg batten on the outer pylons.
The sway braces are oversized, but it was all I had on hand. I was in a hurry to get a running layout, so I held my nose and used them. I agree that they are long and probably not strictly oriented according to sound engineering practices. Perhaps in another life I’ll take engineering and know better. [:)]
Thank-you for your kind praise.
-Crandell
Challenger–
Though not a wood trestle, this is a photo of the steel viaduct I built from 2 Micro Engineering tall trestle kits. It’s on a 36" radius and a 2% grade. These photos were made just after I installed it, last year, so the scenery’s not in.
the last photo shows it with some scenery installed.
Tom
Building a trestle on a graded curve is a royal pain in the butt. Can be done but you have to watch and make sure your curve stays constant as does your grade… I have a lot of slides that I’ve never scanned of the actual constuction but I’ll tell you you’re looking at about 2 months of work here.
This particular trestle bridge is at about 32" radius and 20" tall at it’s tallest and about a 2% grade. It is also about to be dismantled for a layout rebuild.
Another photo
Good luck…
Horizontal bracing, used by itself on some trestles, ties the middle of tall vertical members back to the abutments, so they can’t sway or deflect. The vertical members can only support their rated loads as long as they stay straight. The problem with using only horizontal bracing, is that all of the lateral support is dependant on the entire length of the horizontal bracing. If one piece of a multi-member horizontal brace fails, the rest are no longer connected to a solid anchor (where a free span, like over the river, interrupts the horizontal bracing scheme).
Further, once a horizontal brace reaches the length of the vertical members, it can bow just as easily as the verticals, and isn’t much use in reducing axial sway and deflection.
Some trestles would then add a vertical anti-sway tower at specified intervals, where two adjacent bents were X-braced from grade level at the bottom all the way to deck level at the top.
Even with well fixed horizontal braces, whether anchored to ground or an X-braced tower, a square or rectangle is not a stable shape. The corners can pivot to create parallelograms, which won’t support vertical compression loads, so the bents in between X
I took templates from Kalmbach’s book on bridges and came up with this:
I was able to figure out the curve by taking a piece of wrapping paper, putting it over the track and then embossing it onto the paper. The Imprint was aperfect template.
Total time to construct was about 20 hrs
Fergie
Thank-you for your explanation, jeffers_mz. I’ll try to be more careful in my eye-hand execution for my next trestle. [:)]
-Crandell