How to build a custom bridge

I build bridges and trestles using basswood. This would certainly work for your 18-inch length but it would not have the fine detail of plastic. The bridge geometries in your photos are complex and would require a lot of careful work to design and cut the pieces. Also, your 18-inch length corresponds to 72 feet full scale. The bridge in your first photo is several times longer. Therefore, the proportions of an 18-inch bridge in 1:48 would need to be different than in your photo. For your model and layout terrain, what would the height from the footings to the bridge deck have to be?

MELGAR

Condensing that bridge to 18" would require changing to a much smaller scale.

In the mean time to just fill in the space with your intended project just print out an 18"  full front on photo and mount it on a poster board  cutout  until you get around to a stick built model. 

When it gets to actual construction,  consider just capturing the essence of the bridge shape with a silhouette of bass wood construction w/ rattle can painted rust.

I've actually done the Diablo Canyon bridge (the top picture). I made two of them out of plexiglass, and for years left them unpainted. They were real conversation pieces. When I opened enterTRAINment, I modified one to be double track, and painted one black and the other green. Right now, they're stashed up in the rafters. They're each 6' long. They don't have a lot of structural detail, but they do make a point. If you are interested, I would be willing to sell one or maybe both. 

I've used the method of printed side view to desired scale on cork board with transparent wax paper on top to guide gluing sticks of wood for beams held in place with push pins.  You can make intricate truss patterns quickly and repeatably.  Use card stock paper for gussets if you want the plate effect at joints. I used sticks of pine ripped on a portable table saw.  The model was for an architectural class.  It was incredibly strong and ended up being the professors go to for an example of how a project could be done.

You're right, @MELGAR, I would have to simply the bridge for such a short span.  It is about 24" from the bottom of the canyon to the deck of my phantom bridge!  Your bridges look great!  If those are bass wood, how did you create I-beam look and gussets with rivets?

I'm not sure what your budget is for what you desire.  This is a nice Plastruct O Scale truss bridge which I built before they offered it in O scale.  (Took HO plans, had them enlarged, then bought the equivalent pieces; very strong).  It's 30" in length but can easily be shortened or lengthened.  List is $39.95:

https://plastruct.com/shop/tra...-kits/3002-kit-3002/

You can phone them and they will mail you the plans and bill of materials.

Thanks @Pingman

Another option may be to use a LIONEL (or other mfg. bridge that uses a sheetmetal base, and use the molded plastic pieces, but use Plastruct or other meterial to supply the actual track support.  Plate girder sides in plastic are available to attach to plywood or other road bed to simulate a prototype bridge.   You could do the same with a LIONEL bridge, for example a 6-2122:

Remove the sheet metal base and create your own boxed truss structure while retaining the fine detail of the molded plastic.  Just a thought.

Kitbasher posted:

You're right, @MELGAR, I would have to simply the bridge for such a short span.  It is about 24" from the bottom of the canyon to the deck of my phantom bridge!  Your bridges look great!  If those are bass wood, how did you create I-beam look and gussets with rivets?

The bridges above were built from kits which included basswood with i-beam cross sections and metal gusset plates. For my recent bridges I use conventional basswood strips for beams and 1/32-inch sheet for gusset plates - no rivets but not necessary either in my opinion. An under-construction example shown below. Length 24 inches.

MELGAR

Looking at your original photos, LIONEL's PW and contemporary "arch under bridge" would be a close facsimile; you'd simply need to supply the bridge decking.

Thanks so much for all the ideas guys.  This forum is way better than Google!  And just about as fast!

KITBASHER,

The length-to-height ratio of the bridge for your layout is 18-inches/24-inches = 0.75. The bridge in your first picture has a ratio (eyeball estimate) of about 4.0. Therefore, a curved arch with your geometry would look very different and might not be feasible unless you build tall stone piers up from the valley floor. A through-truss bridge with a length of 18 inches (72 feet) would be realistic.

MELGAR

If you are building a bridge 18 inches long, you should be able to get the materials from plastruct for 50 to 100 dollars. If this bridge is going to be a focal point on your layout, use the plastruct materials. They are the most realistic and simplest materials to use for realistic results for steel bridge construction.

you can find a few previous threads where I showed many pictures of construction of this type of bridge here on the forum.

kitbasher, a quick search for Alan's truss bridge work instantly gave this thread at the top of the list:

https://ogrforum.com/...roject-truss-bridges

Great info.

Big_Boy_4005 posted:

I've actually done the Diablo Canyon bridge (the top picture). I made two of them out of plexiglass, and for years left them unpainted. They were real conversation pieces. When I opened enterTRAINment, I modified one to be double track, and painted one black and the other green. Right now, they're stashed up in the rafters. They're each 6' long. They don't have a lot of structural detail, but they do make a point. If you are interested, I would be willing to sell one or maybe both. 

Hi, Do you still have these bridges for sale ?

Send him an email; Big Boy is pretty easy going ...

or try..

. @big boy4014 

it likely sends him an alert notice (if on) 

Just a note of information, scale rivets are available, and can be used in any type of construction. I built an open deck girder bridge using steel. I was fortunate to have access to a host of sheet metal tools and materials. The rivets were hand punched, and all components were soldered. 

Properly assembled Plastruct is very strong. 18" inches is very short. You still need to have clearance for all of the rolling stock and locos, so you can't skimp on the height all that much. It might be easier to make a deck truss rather than through truss. It requires significantly less material because it only has to be as wide as the track sitting on top of it, whereas a through truss must have a hole that's wide enough to handle the 11 foot loading gauge of a train (2.75" minimum). As a result you could build the deck truss for less money.

Deck truss lets you approach on a curve since any engine overhang will not ram into the bridge posts. 

I took Plastruct's Bridge kits and converted them to decks for the reason given above (curves on approaches) and saved enough material to build a third deck plate bridge and a big tower to hold it up.

This is my drawing of the deck truss. I modified the Plastruct drawing. You can see how much narrower it is.

The walkway was balsa that I strip cut from a large sheet. If I were to do that again, I would have used basswood strips (even coffee stirrers. The balsa was just a bit too fragile. The 'hairpin' rail stanchions are Bowser white metal which were much less expensive than investment cast brass. Today, I'd maybe 3D print them and cast them out of resin. The real bridge abutments are solid wood behind the faux concrete foam ones. Kiel Line bridge shoes are used on the one end of each bridge. The other end is the "sliding end" to compensate for the expansion of all that structural steel.

And here's the deck plate bridge I built with the leftover pieces. I simulated the rivets on the ABS gusset plates using MicroMark (Archer) rivet details. They work pretty well and are an alternative to pressing in rivets using a NWSL riveter or a star wheel.

Very nice work TRAINMAN2001.  I think the Loch Ness monster has migrated to your layout. 

rail posted:

Just a note of information, scale rivets are available, and can be used in any type of construction. I built an open deck girder bridge using steel. I was fortunate to have access to a host of sheet metal tools and materials. The rivets were hand punched, and all components were soldered. 

Rail,

Where would one get rivets or rivet plates? I need to do a very large truss bridge.

Dave

luvindemtrains posted:

rail posted:

Just a note of information, scale rivets are available, and can be used in any type of construction. I built an open deck girder bridge using steel. I was fortunate to have access to a host of sheet metal tools and materials. The rivets were hand punched, and all components were soldered. 

Rail,

Where would one get rivets or rivet plates? I need to do a very large truss bridge.

Dave

A quick search led me here. There are probably other sites as well.

https://www.tichytraingroup.co...x?SearchValue=rivets

NWSL. (North West Short Line)  Riveter.    Requires Sensi-Press and the attached Riveter+ table. 

Turntable bridge. 

Not as precise as the rivet machine, but I used a masonry nail with a sharpened point, and a hammer. I do like the machine, and if I ever build another bridge, I would consider getting one. Would this work on light gauge steel, or just brass?

Should work with light gauge steel.  

Thanks for the information Rail!

luvindemtrains posted:

Thanks for the information Rail!

You're welcome.

I have made a number of bridges from 1/4"x1/4" and 1/4"x1/2" pine. I used a table saw to rip the pieces from 1/4"x2" pieces. The bridge is very strong (you can stand on it) and will hold the weight of the train no problem. I got my bridge designs from the model train book "bridges & tressles". I drew the bridge (side view) on brown wrapping paper (comes in a roll), then hand cut the various wood pieces sized to the drawing. I then used the drawing as the template to assemble the bridge. 

the pictures show my model of the Stoney Creek Bridge (CPR in the Rocky Mountains), which is a similar design to the bridge you shown in your pictures. You can compress the design, or remove some of the spans, whatever you need to do to fit the space. 

This project was very fun and cost very little. I used small orange crates (the kind that is often sold at Christmas time) and stir sticks for the fine girders and gusset plates. 

y You need an exact-o style knife, a fine wood file and a small wood saw or dremel tool (to cut the wood). I used small pieces of plastic sheets (the window plastic of train boxes or other toys) under the glued joints, so the glue would not stick to the brown paper template I created.

The look is not quite as good as using plastic beams, however the cost is much less and after painting, it looks pretty good (in my opinion).

Good luck with your bridge project: