wooden trestle climbing a grade?

Discussion in 'Scratchin' & Bashin'' started by cookster, Sep 28, 2005.

  1. cookster

    cookster New Member

    Has anybody built a wooden trestle on an incline? I've got a 3% grade across the span for the bridge. I had two identical bents made when it dawned on me, the top of each bent needed to be at a different height. But this doesn't seem right. All bent tops should be in plane (level) and copies of each other, right? My original thought was to attach each bent cap to the stringers (as you would on a level trestle), but then I realized this would cause the girts, etc to be on an incline as well. That wouldn't look right, would it?

    I could build a level trestle, then add small risers to each bent to build the grade, but would this be correct? How would the prototype do this?

    Thanks in advance,
  2. sumpter250

    sumpter250 multiscale modelbuilder

    The most used application of timber trestles, was to span long areas like valleys, or wetlands, and were usually level. I have seen pile bents used for an incline, but really didn't pay much attention to how the stringers sat on the bent caps.
  3. nachoman

    nachoman Guest

    well, i built one. It is on an incline of about 4.5% and on a curve about 14". I didn't build the trestle at the same time as the benchwork. When I got around to building the trestle, I cut out the section of track and subroadbed, built the deck of the trestle at the workbench to a pattern I had drawn up on paper, and then glued the deck in place on the layout at each end. I then custom measured and built each bent by measuring the distance from the deck to the scenery below. Mine is only for HOn3 and only about a foot long, so it did not need to be especailly strong. If you have no scenery underneath this time, I would reccomend a sturdy wooden base, then add risers from the wood up to the level where the scenery will go, and place the bents on top of the risers. That way, the risers will be resting on something secure, and you can then build scenery around them.

  4. jim currie

    jim currie Active Member

    see if you can find any photo's of the trestle on the Angle's Flight incline .
  5. doctorwayne

    doctorwayne Active Member

    You're right, the top of each bent needs to be at a different height. The difference, however, is added at the bottom. This way, the bents will rise with the grade and the top ends of them will appear similar, while the bottom of each successive bent will extend lower (from track level at least, assuming the ground that you're building on is level) and of course, as the bent height increases, the width at the base of the bent also increases. To keep the bents perpendicular to the ground rather than to the track you'll need to either sand the top surface of the bent cap to the proper angle or notch the underside of the stringers carrying the track: in my opinion, sanding the cap would be easier. I hope this is the information that you're looking for. I haven't built a wooden trestle on a grade, but I've done a couple of Micro Engineering tall steel viaducts on grades (and curves too) and ended up building them from the top down. Not very prototypical, and the matter was complicated by the fact that the terrain at the base was very irregular.
  6. Doc Holliday

    Doc Holliday Member

    Here's a pic of a trestle I built on a 2% grade. The right end also goes into a 18" radius curve. The trestle will ultimately go over water so I built each trestle bent the same size and varied the lengths of the wooden piles to match the incline. I glued the trestle bents at 2% off a right angle to the trestle beams so the bents would be vertical. The angle was so slight there was no need to sand anything.
  7. cookster

    cookster New Member

    Ok Doc, so if I understand correctly, the lateral braces (beams, girts, whatever we call them) that normally are level running acrross the trestle from end to end, on your trestle actually follow a 2% grade. The bents of course are still plumb (vertical). I thought of that, but wasn't sure if it would look correct. I guess I can put the bottoms of the bents at various heights, with an uneven ground surface, and that would disguise the fact that the beams aren't level. Plus, I was considering adding a bridge in the middle of the trestle span, which will also break up the appearance of the girts on an angle. Guys, thanks for all the ideas.
  8. Doc Holliday

    Doc Holliday Member

    Cookster, that's exactly what I mean. Even at a 2% grade, the bents looked funny if they were at a right angle to the rail rather than being truly vertical. I actually built and installed the entire trestle, including the bents, but without the piles and pile caps. I then measured and cut the correct length for each set of piles and slide and glued them in under the bents.

    Here's another pic showing three of my bridges/trestles. The front two will be over a lake. The large trestle in the back will be mostly over ground with maybe a stream in the center. If you look closely at the pic, you can see the bottom of the large trestle's bents where they rest on uniform stryofoam "steps". Personally, I think this uniformity looks kind of strange and would not likely be found in the real world without a whole bunch of dirt moving. Seems more likely that the trestle bents would be built to the varying lengths needed to reach the uneven native terrain. I plan on adding to some of the steps to achieve this effect (if I ever get to it) and will probably add some type of foundation under each timber as well.
  9. Papa Bear

    Papa Bear Member

    Nice looking trestles, Doc! :thumb:

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