Curved Stone Arch Bridge Project (New Pics 2/14/15)

I have been on that bridge several times, most recently biking across it.  That is one AWESOME bridge!  Wise choice.

 

I began by building a wooden framework out of Masonite.  I had a fair amount of trouble getting the arches the way I wanted.  I drew them out in PowerPoint on my computer until I was happy with their basic shape.  After that I had to decide if I wanted to vary the shape of each arch or change the width of the legs to accommodate the curvature of the bridge.  I decided to vary the legs and keep the arch shape uniform across the bridge.  I cut the outside walls first and that was a mistake as I misjudged the correct width differences in the legs.  I then cut the inside walls with leg widths of 2" and the outside legs had to be 5" wide.

 

 

 

The next issue was how to surface the under arches.  After trying different materials, I decided on Strathmore construction board that I got at Hobby Lobby.  It was flexible enough but still strong enough for my base.  I screwed small one inch pieces of wood in 5 places under the arches as a support for the Strathmore board.

 

 

 

  

For the finish surface I was hoping to use real stone.  I had looked at all the local building supply stores and wasn't happy with any of them.  So I decided to try to find a flexible, thin Styrofoam that I could carve my stones in and then paint them to look like a limestone bridge.  I found a 1/4" thick foam that is used for insulation under metal siding.

 

I will post pictures of that portion of the journey on my next post.

 

Art

 

While I was building the bridge I had my double-track mainline out of service for some time.  When I got the framework completed, I had to stop and play a little. 

   

 

 

 

The structure passed all the critics and was approved for the stone carving to start.  We will start with the best stone mason we could find on the next post.  Actually it was the only stone mason we could find that would work for free.

 

Art

Its looking good Art. Can't wait till Sunday and see how things have changed since I saw it last.

 

          Scot

WOW, WOW, WOW, this is going to be a spectacular addition to your wonderful layout. Can't wait to see your progress.

 

We have talked about this project for a long time and it is nice to see it move ahead. You are correct, this is your "signature piece" for the layout.

As someone from the Minneapolis area, it's one of my favorite spots in the city and I recommend any visitors to make their way down there.  From the bridge you view the Mississippi as it spills over a hydroelectric dam, watch boats go through locks, have a good view of the University of Minnesota campus, view ruins of the old flour mills that dominated this area, view the famous Guthrie theater, and have a breathtaking view of the downtown skyline.  On a summer evening, there is really no better view in the city.

 

Great choice and I agree that it will be the centerpiece to your layout.  Can't wait to see how it progresses.

 

Really nice start with the bridge, Art!  I like the use of the construction board.  When I built my straight stone arch bridge from 2" thick sheets of styrofoam sandwiched together, none of the arches I cut matched perfectly, so I used drywall compound to smooth them out underneath and spray painted them black to hide the imperfections.

 

For brickwork, maybe you can try using a straight edge and a Dremel tool to cut the bricks into the masonite.  It'll be tedious and take a little time but it'll look good.  I used a straight edge and a Hotwire foam knife to make mine.

 

Art,  WOW!!!!!!!!!!!!!!!!!!! absolutely awesome.

 

 

 

Very interesting thread.  I too built a curved stone arch bridge which I finished in 2000 and is the most difficult modeling project I ever attempted.  I built it over the course of a year.  Its the geometry that makes it tough.  It was cast in place, and required 153 pounds of hydrocal plaster.

 

 

 

Art, this is a great project!  You commented you were going to face the masonite with 1/4in insulation used under siding.  This is normally styrofoam and hard to form stone or blocks.

Lowes carries extruded polystyrene in .52 and .25 widths.  This is the thinner version of what our club used to make our arch bridge.

It looks like you're off to a great start and this will be wonderful addition to your layout.

Art Wonderful addition to your layout.

Brian,

Very impressive job!  Thank you for the how to photos.

gorgeous!!

really nice job!!

Andre.

Great start, Art. I believe you have captured the proportions and esthetic of the prototype perfectly, a daunting task in itself. No doubt it will be a fun project and wonderful when completed. Can't wait for updates.

 

  

Art,

To couple on what John wrote, I was just at Lowes yesterday buying dome wood for a shelf in my wife's laundry room.  I went past the foam insulation and took notice it looked different from what I have seen.  Dummy me, I should have taken a photo, because I knew you were planning to use 1/4 inch.  I saw two types, both grayish green.  One was 2 inch thick, the other was folded sheets of the 1/4 inch.  Instead of having a smooth surface as I am used to, both had lots of random depressions like the foam doesn't fill completely in when it is being formed.  For normal base or scenery work this would be fine, but the depressions are a bit deep for carving stone or block.

 

Like I said, I should have taken a photo; big dummy.  Now I can't remember the name of it.  It seemed that was all Lowes was selling except for the white bead stuff that isn't as useful around the layout.  Has anyone seen this?

Both are WONDERFUL projects, really GREAT WORK……..

Man Art, that is some bridge! Fantastic job.

You have captured the verisimilitude of the prototype--great job!

 

Carl

Brian & Neal - You two have served as inspiration to me as I contemplated this project.  You both have used different materials and created bridge masterpieces.  If mine turns out half as good as yours I will be very happy.

 

Thanks for all the favorable comments and encouragement. 

 

Art

I tried carving the stones in the foam and was pleased with the results so far.  The good news is that it is easy to work with common tools.  The bad news is that it is very time consuming and tedious work.  The first under arch took 3 hours and the first side wall took 5 hours.  With 7 arches that comes to about 90 hours of carving!

 

 

I used a blunt regular lead pencil to make the mortar lines and a metal dental tool to shape the stones.  My hand got a little sore as it was not used to doing this and for such long periods of time.

 

Art

 

There was an interesting stone chimney application for a doll house kit that I did for one of the Granddaughters.  There was a sticky-back stencil paper applied, then a white glue paste mix applied.  Before the paste mix dried, the stencil was removed. The chimney was painted brown for the mortar lines before the application.

Red brick was the same application.

Art,

 

That looks fantastic!  This is something that would fill your time on a snowy day.  I'm sure you get a few of those in the Chicago area.

Art, the carving looks great!  The time will be well worth it once you see the end results!

As I started painting the foam I must have done everything wrong.  I went to Home Depot with a close-up picture of the stone work on the real bridge.  A very nice young lady tried to help me.  I even went back to the kitchen remodeling area and brought a sample of real tile that looked like limestone for her to look at.  She said she could not use the tile in her color matching machine but she knew what I wanted.  After spending an hour, we picked a color and I headed home with a quart.  I showed it to my wife and she said it was too yellow.

 

The next day she went with me and we spent another hour looking at every paint sample in HD.  We finally picked out a light base color and two accent colors.  Got home, painted it on the foam and she said it wasn't right yet.

 

So my son-in-law is a contractor, carpenter, and master faux painter.  I asked him if he could stop over on the way home and help me.  He looked at all my colors and started painting and blending colors and it started looking like limestone to me.

 

Armed with my new confidence I forged ahead and tried his technics.

 

 Art

 

At this point I was dying to see what it would look like on the framework.  So after I painted the new wall section that I did yesterday and finished 3 under arches, I went down and placed the panels.

 

 

The sections have to be glued in place to close the gaps, but I started getting excited that this might work.  My next step is to determine the right glue.  I can't use a contact type cement as I don't trust my being able to place it in exactly the right place the first and every time.  I don't dare use anything that will attack the foam.  Any suggestions are very much appreciated.

 

Art

 

Sorry Art, I have never worked with form….

Art i'm not really sure you should be posting this build. to save yourself further embarrassment stop posting pics, get to work finishing it and then let me know where to send the ups pickup order. i can't wait to see the finished bridge to say the least you are off to a terrific start. when you finish this one you can do one for me.

Art, I have had the best luck using Latex Acrylic Caulk to bond the foam together.  Liquid Nails makes an adhesive explicitly for foam insulation board also.  

 

The caulk take some time to fully cure, but it remains just flexible enough that it wont' break loose.   I have used plain old wood glue out of the bottle as well.   One nice feature of the caulk is what squeezes out of the joints can be smoothed over to hide any seams.   While I am waiting for caulk to cure/dry,  I have set it under weights with plywood to even the load, or on verticals and odd shapes I have used large rubber bans, bungee cords bought at the discount stores to hold everything in place.  Hope that helps. 

Art, ditto on Chris's suggestion of using Liquid Nails Projects & Foamboard Adhesive.  I have used it extensively to glue my plaster rock castings onto closed bead foamboard, and also to glue down Woodland Scenics foam roadbed.  It grasps the items your gluing quite nicely, but stills leaves ample time for adjustment.

This is a great thread.  I have at least one bridge to build and it helps a lot.  Nice bridges, guys.  Thank you, this will help me a lot. 

Hey Art, man the carving of the stone is really fantastic and the SIZE of the Bridge is overwhelming. I feel sorry for the Turkey on Thanksgiving with the way you use a carving knife. LOL

Very impressive project!  Stunning work, Art.  Thanks for sharing.

 

David

Art, absolutely fantastic. What amazing craftsmanship. I look forward to the finished product.

Art that look's good, it is amazing what you can do with foam board and paint and a lot of time .

 

Guy

I too have been to see this bridge and Art, you have done a great job so far and can't wait to see the results.

 

One question, it seems that in one of the pictures above, it seems like the bridge is lit from under the arch, have you given any thought to lighting this centerpiece before you get too far along in the construction? If so, can I assume LED's? Not sure how I would light this, but it does deserve some kind of attention...just a thought.

 

Charlie

That is an interesting suggestion, Charlie.  I plan to add spotlights in the ceiling on a dimmer, but haven't thought of lights on the structure.  There maybe lights on the real bridge now, but I don't think that there were any when it was a railroad bridge.  If anyone knows more about it, please join the discussion.

 

Art

Hello Art:

 

I agree that I was probably not lit as originally built, but it was just more of a comment to think about before it was too late.

 

Spot lights will be nice as you will have a place to take "roster" shots of your trains in the future.

 

Charlie

WOW,  Very nice work and the amount of time to carve each block.  1 question, how thick is the foam you carved the blocks into and where did you get the foam, from Hobby Lobby as with the curved undersides.  Thanks for showing the how-to's on this project.  It will be the first thing people will comment on when they see your layout, like a big trophy in a cabinet or deer head on the wall.  Nick