trestle instructions

Model Railroader Layouts and layout building
1

Hi everyone

Would someone have a photo or information on size of lumber is to be used in a curved or straight trestle for the area I have marked in red? My jvmodels 2016 kit instructions has no instructions for this option. I will be installing two bents to support the upper area where the centre bent is shorter.

Thanks

Lynn

2

I would use lumber that simply looked right and not worry about if the lumber was to engineering specs. Also, most of the trestles I’ve seen, have double bents at the ends where the bridge portion is supported. One bent goes all the way up and supports the stringers and track and the inner bent supports the bridge portion as in your photo. The two bents are tied to gether with short girts to keep them in position. I have to admitt that these trestles I’ve seen, are on model Railroads and not in real life. However, I suspect they’re desingn is based on good engineering practices, as seen in photos of real trestles.

3

I guess I should have been more specific, lumber size is not so much the issue but how to lay it out as any photos I’ve come across just aren’t clear enough. I realize I will have to make a single short bent for the Centre but its more how is that area all tied together?

Thanks

Lynn

4

Did you get your answer from what I added to your question?

5

Lynn, that central “short bent” isn’t a bent. It’s called a Howe Truss, named after the engineer that designed that system of spanning between bents, often over a river or over a track passing under the bridge at that location.

As Jim has suggested, the materials available locally, or that can be shipped reasonably economically from other locations, determine the engineering plan for a given structure. Bent frame timbers, whether round pilings or milled lumber, were typically never longer, without being capped and another tier added atop them, than about 30’. The taller the bents, the more ancillary timbers had to be added to control swaying and buffeting forces. This added to the cost and weight of the structure. However, certainly bent frames rising much more than about 15’ would have sway braces in two planes and girts in some cases (girts are large timbers that run along the axis of the bridge between bents to help stiffen the bridge. They would sit atop any caps and run from cap to cap). The Howe Truss is a stiff boxed frame that sits on its own bent frames abutted tightly to the bents on either side of the obstacle being bridged. It has many components, the chief remarkable feature being a maze of diagonal braces in several planes.

6

Wickman,

A handy scale lumber chart for Your references:

http://www.cardstone.com.au/basswood/railroad.htm

Take Care! [:D]

Frank

7

Thanks guys,I’ll have to see if I can find a better picture for reference, picture is worth a thousand words at this point.

8

Thanks guys I found a better picture off the campbell site that shows much clearer. It apears there are at least 4 beams sitting on the top of the right hand bent and crossing over to the top of the left hand bent then the short bent is sitting centre.

9

I took the Campbell’s Straight trestle kit and put a curve in it as I just had no use for a straigt one.