Saturday, November 26, 2016

Des Plaines River Crossing Part II

More work has been completed on the Des Plaines River crossing between Maywood and River Forest.  To transition from the roadbed to the bridge, abutments were constructed for both ends of the bridge.  The abutments are assembled from .080 sheet styrene.  The concrete that the bridge rests on is made from three strips glued together with liquid cement and sanded on all sides.  It was a bit tricky to get the correct distance from the cement to the top of the roadbed so that there is a level transition from roadbed to bridge.  Luckily, the liquid cement gives a little bit of time to make adjustments for a perfect fit.

With the abutments in place, I moved on to install the four piers.  When I formed the piers out of plaster, I made each one taller than needed by about an 1/8 of an inch.  To get the piers exactly the right height for a level bridge, I sanded the bottom of each pier on a sheet of 80 grit sand paper until it was the correct height for each location.  I used a 24" level and a lot of trial and error in the process.

Once the piers were all the correct height, I glued them and place.  The steel girder spans were place on the piers and then the track was put back in place so that trains can use the bridge to cross the N scale Des Plaines River.   The steel girder spans are Micro Engineering kits.  I did not glue the steel girders and track in place since they will need to be removed in order to do the scenery. 

Here's the bridge so far.  As you can see from the prototype photos, the bridge still needs walkways between the tracks and on each side of the tracks.  Also there is a lot of piping that will need to be added.   These will steps won't ne taken until the scenery is installed.

Looks even better with trains!

Tuesday, November 15, 2016

Des Plaines River Crossing Part I

I have begun construction of the Des Plaines River crossing located in Maywood, IL which is just east of the Proviso Yard.  The bridges used for this crossing are a series of steel girder spans supported by four very long cement piers.  The four piers are much longer than needed to support the steel girder spans.  I'm guessing they were built this way for possible future expansion, but I am not certain.  Below are a couple of pictures of the prototype.

   Since there are no commercially available piers that match the prototype, I decide to mold my own piers with a scratch built styrene mold and poured plaster.  I came up with the dimensions of the piers using measurements from google maps.  I also used measurement from the actual location on the layout as I needed the height of the piers to match the existing track alignment.  Styrene sheets were cut and then glued together for the mold.   The mold does not have a top or bottom which allowed me to slide the hardened piers out without breaking the mold.

   I used liquid cement to join the joints of the mold.  After giving the liquid cement 30 minutes to dry, I mixed up some plaster to the consistency of a chocolate shake and poured it into the mold.  The plaster I used was "Smooth It" from Woodland Scenics.  I think just about any plaster would do fine.  I choose this product only because it was what I had on hand.  It worked quite well with the resulting pier being heavy and dense.  The wet plaster was too much for the thin styrene walls of the mold.  So, I used a couple of weights to keep the walls of the mold straight.  After about 10 minutes, the plaster was firm enough for me to use a small piece of styrene to clear off the top of the plaster.  After a few hours, the plaster was hard enough to remove from the mold.  The plaster was completely hard and dry overnight.

   Here are the four piers placed where they will located for the crossing.  I'll post more as I continue with the project.