Scratchbuilt plate girder bridge

[Ray Dunakin]

I've just posted some pics of the plate girder bridge I built, beginning with this shot of the unpainted bridge:

http://albums.photo.epson.com/j/ViewPhoto?u=3009006&a=32116967&p=74300644

From there you can scroll through the rest of the photos.

The main structural components of the bridge are two sheets of of 1/8" thick G10 fiberglass, measuring 2.5" x 22". You can get G10 from plastics dealers. It's a very strong, rigid material which is often used in modern composite aircraft, among other things.

The ribs and flanges are made from styrene angles, which I bought from Plastruct.

To simulate rivets, I dabbed on spots of thick acrylic craft paint, using the tip of a nail. The thick paint dried into small hard bumps. They aren't raised as much as a real rivet would be, but they still look good.

To make the "feet" (or pedestals) of the bridge, I built one master out of stripwood, styrene angles, and nut/bolt/washer castings. Then I made a silicone rubber mold of the master, and cast the feet out of plastic resin. You could just build all four of the feet, but since I will be needing more of them for future bridges it was worth it to me to make a mold.

The finished bridge was painted with red primer, then a coat of black primer. I used Rustall weather it. The ties are stained Western red cedar. I obtained miniature tie plates and spikes from Micro Engineering. The tie plates were glued to the bottoms of the rails, then the rails were painted to look rusty. Afterwards, the tie plates (with rails attached) were glued to the ties with urethane glued, and spiked.

The result is a very realistic looking bridge which is strong and durable.

[gabbyhayes]

Ray

Very nicely done. It looks really good in it's setting. What is the idea of the beams along the outside of the rails

Gabby hayes

[Ray Dunakin]

Thanks. The wooden beams along the outside of the rails are called guard timbers. On a prototype bridge or trestle, they are used to keep the tie plates aligned.

I forgot to mention a couple things... On this model, I didn't bother trying to replicate the interior structure since it could only be seen from directly underneath. The two sides of the bridge are connected by four pieces of G10, 2" wide.

[gabbyhayes]

ray

I would have thought that there would have been rails along the inside - hence the beams question. Especially like the way you did the rivet detail. again nicely done

Gabby

[Ray Dunakin]

I thought about putting in the guard rails. I think they're supposed to keep the train on the bridge in the event of a derail. However, some bridges don't have them, and it would have been kind of a pain to do it prototypically because they extend quite a ways down the track on either side of the bridge. So for now I'm leaving them out.

[rpc7271]

Very nice. You obviously did your resaerch for this bridge. Nice weathering. Now if there was a train crossing it it would be perfect!

[ttrigg]

[Anonymous]

Ray,

That is an awesome looking deck bridge! The rivet detail is incredible as well. I hadn't heard of this G-10 fiberglass material before. Do you think it would be possible to do a curved deck bridge with it? Also, what kind of adhessive did you use?

I also want to tip my hat to your GRR construction efforts. A large undertaking which is really coming together very nicely indeed. My own track plan will probably be very similar to yours for the same reasons. I'm somewhat luckier in that my 'slope' is nowhere near the grade of yours. Best of luck and keep the pictures coming. [:)]

[Ray Dunakin]

QUOTE: Originally posted by Bob Zajicek
That is an awesome looking deck bridge! The rivet detail is incredible as well. I hadn't heard of this G-10 fiberglass material before. Do you think it would be possible to do a curved deck bridge with it?

Thanks! G10 is a laminate made of layers of fiberglass cloth and epoxy. If I remember correctly it is compressed under vacuum to remove trapped air. Once formed, it is extremely rigid. The thicker the sheet, the less it bends. So if you wanted to create a curved shape with it, you'd have to use something quite a bit thinner than the 1/8" thick stuff I used. I'm not sure what thickness you'd need -- that would depend largely on how sharp a curve you want. Curving the horizontal styrene angles for the flanges to match might also be a problem.

BTW, I've been thinking of writing a brief article for GR on using G10 to build bridges.

QUOTE: Also, what kind of adhessive did you use?

Epoxy would be the best choice, however I mostly used thick CA since I am somewhat sensitive to epoxy fumes. What you use, be sure to lightly sand the G10 first.

QUOTE: I also want to tip my hat to your GRR construction efforts. A large undertaking which is really coming together very nicely indeed. My own track plan will probably be very similar to yours for the same reasons. I'm somewhat luckier in that my 'slope' is nowhere near the grade of yours. Best of luck and keep the pictures coming. [:)]

Thanks, and good luck with your layout.

[Ray Dunakin]

I've finished assembling the 44" long bridge. All that's left is to put on the simulated rivets, then paint and weather it. Doing the rivets will be a real test of my patience. Not only is this bridge twice as long as the first one, but it's also detailed on both sides. The first one is only detailed on one side because it is positioned close enough to the cliff that the "back" will never be visible.

[Anonymous]

hate rivets - so time consuming but always do mine with styrene punchings from a leather punch - varying thickness and diameter gives a good choice - just sand after gluing to a rounded profile. I will try to post some of my railway gun models made with this method of rivetting

[Anonymous]

btw the bridge is stunning - my thoughts on a similar project were to sheath an aluminium square section in styrene - yours is a good deal easy tho . time for a rethink here.

[fsm1000]

Very good, and I like your rivet method. Cool [:)]

[Ray Dunakin]

Thanks. I finished the rivets on the long bridge last night. It wasn't too bad, just did it a little at a time over several evenings. I started painting it this evening.

BTW, I had considered using styrene on metal but some folks here pointed out that the different expansion rates of the metal and plastic (due to temperature changes) might cause the styrene to debond.

[Ray Dunakin]

Finished putting the ties on the long bridge. Next up will be installing the tie plates and rails. Most of the weathering is done too, but I still want to tweak it a bit. Need to get more Rust-All first.

I also finished the concrete bridge pier and abutment today. The pier turned out really nice. It's cemented to a concrete foundation that was poured in place with forms cut to fit the shape of the stone "bedrock".

Sorry, no pics yet on this stuff.

Now I need to build the curved portion of the viaduct. It'll be a 6' diameter curve. On a real plate girder viaduct, the girders are not curved. Instead, straight segments are connected at an angle. I need to figure out how long I can make these segments and still have it look right on such a tight curve.