Large Scale Central

Long Trestle Project

This post is the beginning of a build log for a new trestle on the layout. It will be 560 scale feet long in 1:20.3 scale. That’s nearly 28 actual feet. The entire trestle is on a 2½% grade. I’m building it with five consecutive 112 scale foot long segments (about 5½ actual feet.) This length is convenient for working at my 6 foot long workbench.

The first segment is a slight (60 foot diameter) curve to the left. The next two segments are tangent (straight.) The final two segments are a slightly tighter curve (36 foot diameter) to the right. Basically it is a very long bridge on a very gentle S-curve.

There are 36 bents spaced 16 scale feet on centers. The bents are made from 12” x 12” posts and sills, with 12” x 14” caps. Diagonal bracing is 3” x 10” boards. Stringers are 8” x 18” timbers cut to 16 scale foot and 32 scale foot lengths. Three stringers make up each beam. Two beams are spaced ½ actual inch apart to support the ties. 1/8” x ¾” aluminum strips are sandwiched between the stringers on the tangent segments.

There are seven different heights for the bents, ranging between 4 and 14 inches tall. Most are single story, although there are a few two story bents near the center of the bridge. Here are the range of heights.

Here is the completed stack of bents.

All of the joints on the bents were made with Titebond III wood glue and various length pins with a pneumatic Grex 23 gauge pin nailer. On the two story bents, the posts of the second story are connected to the intermediate sill with staples. You can see the staples in the following photo.

Here is the pile of 8" x 18" stringers.

Here is a pile of 6 foot long 1/8" x 3/4" aluminum strips to be used for strengthening the tangent segments and keeping them perfectly straight.

Here is how I sandwich the aluminum strips between the wood stringers. I use “Gorilla” brand construction adhesive in a caulking gun and clamp the glued-up stringers between a couple of 1" x 2" boards until the glue sets. Clamps are like locomotives … you can never have too many.

In the next installment, I will tackle the curved segments and start building-up the deck.

More to follow,

Bob

Watching with interest Bob. Always love your projects and I like the way you do bridges. I will be stealing your techniques.

A question though. I like the way you use the aluminum splines to strengthen things. I have seen you do this before. Here you mention them only on hte tangents. Are you planning on using them in the curves as well? If not, why not?

Devon

This will be a nice project to watch… Nice, Bob…

I take it that you will use proper length bridge ties, hand layed rail, with proper guard rails. If you are going to the trouble of building a good looking trestle, it will be worth the extra effort to do it correctly. You will be glad you did in the end…and have a model that you can be truly proud of.

So far you seem to be doing a fine job of it…

Oh gee, just like…

Skip it.

Andy Clarke said:

This will be a nice project to watch… Nice, Bob…

i’ll say… (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)

Go Bob Go!

I have a number of trestles in my future. I’ll be watching your progress intently.

Looks like you have another fine build in the works Bob.

Chris

Here is an update to the build log. I forgot to show you in the first installment how I will join the five segments together. Here is a photo showing the joint between segments #2 and #3 (the two tangent segments.) You can see how I offset the aluminum strips running between the stringers by two inches at each end.

I did not laminate the aluminum strips between the stringers on the curved segments for a couple of reasons. First, the curved segments of the trestle deck are not actually curved. Rather, they are a series of seven pie-shaped straight sections with a slight angle between each section. I needed to cut the ends of each section to the proper angle. Secondly, my curves are not fixed radius. They are free-form with built-in spiral transitions. Because of this, each section along the curve has a slightly different angle from the preceding section.

I decided to make each section using 1/8” thick spacers between the stringers. I made each spacer from two ¼” zinc plated steel washers. The washers are attached to each other and to the stringers with construction adhesive. I glued two ½” thick wood spacers between the innermost stringers to maintain the proper distance between the beams. Here is what each section looked like before the angles were cut on each end. There are twenty-one sections like this; seven for each of the three curved segments.

I shaped the proper angle on each end with a 6” disk sander. The angles are very small; they vary from about ½ degree to about 1½ degrees. Each angle was cut to fit.

I should explain how I did this. Initially, when I laid the track, I ran ladder roadbed everywhere. Even across the gaps where I knew I would come back later and build bridges. I simply laid flex track on the ladder roadbed and just imagined that there was a bridge there. When I was ready to build the bridge (like now), I simply removed the flex track, cut-out the section of ladder roadbed, and used it as a template to build the bridge.

Here is where I cut out the roadbed for segment #1.

Here is that piece of removed ladder roadbed on the workbench with the new segment #1 beside it.

I did the same thing for the two other curved segments.

Each of the seven pie-shaped sections that make up each curved segment are joined together with 1” long pieces of 1/8” thick wood glued between the stringers.

After I glued-up all of the pie-shaped pieces, I cut and stained the 561 bridge ties I will need to populate the trestle deck. Each tie is 8” x 8” x 9’.

While I’m waiting for the glue to cure and the stain to dry, I ordered some N-B-W castings from Ozark Miniatures to dress up the stringers. There will be 280 in total.

Don’t expect another update for a couple of days – I need to take a break and pig out on some turkey and fixings. Happy Thanksgiving all … more to follow soon.

Bob

Wow Bob, Top notch work. That’s really going to look nice. I’d say you earned the right to pig out.

561 ties! 280 NBW’s! A bridge builders equivalent of a rivet counter…(http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)

i certainly will keep watching this thread!

that project sounds very interesting.

This is a great thread!

We all know it will be finished as Bob , doesn’t do Devoning ! ( couldn’t resist Devon!)

Wow you need a hobby Bob! (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)

Great project. I will follow with interest . . . . (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-smile.gif)

Sean McGillicuddy said:

This is a great thread!

We all know it will be finished as Bob , doesn’t do Devoning ! ( couldn’t resist Devon!)

Wow you need a hobby Bob! (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)

Hey now. . .Well Bob does get things accomplished

Had a chance to get back in the shop today after the holiday break. Didn’t get a lot accomplished, but I did get the ties installed on the first three segments. Thought you might like to see how they go down.

The only tools you need besides a pin nailer are a 4” x 8” spacer block and a tie alignment jig. The spacer block is simply a piece of 4” x 8” timber. The tie alignment jig is a piece of wood cut to the same length as a tie, with a cross piece glued perpendicular to it. The cross piece fits against the outside edge of the stringer. The cross piece is glued such that an equidistant portion of the long piece hangs over either edge of the stringers.

Place the spacer block against the last tie laid and spread a bead of wood glue on the stringers.

Place a tie on the glue and hold it against the spacer block. Use the tie alignment jig to center the tie on the stringers and keep it perpendicular to them.

Nail the tie to the stringers. I generally use four pin nails per tie and vary the pattern.

Here is the pattern I use to hold everything together.

Tomorrow I’ll finish placing the ties on the last two segments and hopefully start spiking rail.

More to follow,

Bob

Great work Bob. I enjoy the in-depth pics and explanations(http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-cool.gif)

Just a quick update on how the deck is coming along with a few more photos. I drilled holes in the aluminum strips that extend out from the first segment. This end will mount to the existing PVC ladder roadbed at the end of the bridge.

Here is how the rails line up on the deck directly above the center stringer in each beam.

I like to use Split-Jaw rail joiners on the layout, but they didn’t fit between the ties at the ends of the segments. Instead, I took a few Code 250 aluminum slip-on rail joiners and filed them down to fit the web of my code 215 rail. I cut notches in the end ties to fit around the joiners.

For the curved segments, I pre-bent the rails with a rail bender slightly tighter than the desired curves.

I spiked the pre-painted rails to the ties using eight spikes per tie.

I removed the paint from the rail tops with a sanding block. Only the running rails will have shiny rail tops. I will leave the paint on the tops of the guard rails.

I spiked the guard rails eight inches OUTSIDE of the running rails, using eight spikes every fourth tie. NOTE: I model the Rio Grande Southern Railroad and this is how they did it.

Today I spiked the rails on segments #1 and #2. Tomorrow, I will add the guard timbers at the tie ends and move on to segment #3.

More to follow,

Bob

Very cool! should be very solid. and realistic.

Great job. And a great thread. I’m curious whose spikes and what do you use to insert the spikes?