EUGENE TURNTABLE - 2 - TURNTABLE BRIDGE

Construction of my turntable and associated track and service facilities continues as a long-term, many-step process.  I previously reported the preparation of the turntable pit:

https://espeecascades.blogspot.com/2019/11/eugene-turntable-1-pit-preparation.html

The next step was construction of the turntable bridge.  

An important reason for my selection of a Diamond Scale turntable was that product most closely matched the Eugene, Oregon turntable.  The prototype turntable still exists and sees limited use in spite of the down-sizing and almost elimination of that once large yard and locomotive service base.  In particular, the Eugene turntable featured a deck girder bridge with a rounded-top turntable arch.  The arch served to convey power to the electric motors for the table.  In the model form, that same arch will serve as part of the track power circuit.

The Diamond Scale turntable bridge is built up around a rotating core consisting of a shaft held by two bearings and a center block.  The primary bridge structure consists of wood girders that straddle the center block and end pieces which serve as mounting points for the turntable drive dolly models.  Bridge ties are glued to the wood bridge girders.  A pair of brass strips are attached near the center of the bridge to support the bridge arch.  One of my project delays involved getting appropriate 00-90 screws to affix the straps with.  In hindsight, I could have substituted pins.  A cosmetic plastic girder set is fixed to the exterior of the wood girders.

Turntable bridge girder built up and mounted on the center block and shaft assembly.  The green wire will bring track power up through the shaft in parallel to a similar circuit using the bridge arch.  Two brass straps straddle the center of the bridge.  These will support the bridge arch.

The turntable bridge ties were laid out on double-stick tape on the template provided by Diamond Scale.

The turntable ties were glued to the bridge girders and weight applied while the glue set.

The bridge dollies have been built up and are awaiting installation.  Note the wire dangling near the center of the turntable bridge at the top of the photo.  That wire is soldered to both of the near-center brass straps to convey power from the bridge arch to one of the bridge rails.  The other rail will receive power from the bridge dollies, including the Tomar wiper seen here.

Bridge dolly mounted on the end of the bridge.  A wire is attached to the wiper at each end and through a mounting screw to the dolly.  These wires feed the "right hand" rail on the bridge when looking toward the control cab.

Aligning the rail on the turntable bridge proved an interesting challenge.  For my first attempt, I carefully measured to find the center of the end blocks.  I then laid the rails using these locations (both ends).  When I tested the bridge, I found turning the bridge 180 degrees did not align with the pair of tracks (approach and roundhouse exit) that I tested with.  This was undesirable.  

The first three roundhouse tracks at Eugene aligned with three approach tracks allowing locomotives to run straight through the turntable into those roundhouse tracks which then exited into the back shop.  Although I do not have space for the back shop, I still wanted to be able to run locomotives straight through over the turntable into the first three roundhouse tracks, regardless of which end of the table faced the roundhouse.

The solution was to use my four feet long straight edge to align the turntable center, ends and the extended tracks.  I was able to get very close, with a slight bit of tolerance created by chamfering the ends of the turntable bridge rails as called for in Diamond Scale's instructions.

Aligning approach and roundhouse tracks with the turntable bridge.  Use of the four-feet straight edge provided center marks that could be used to lay the rail on the turntable bridge.

Once the rails were on the turntable bridge, I could complete its assembly.  This included bridge handrails, walkways, the control cab, and the bridge arch.  I chose to paint the handrails white to match photos of the Eugene roundhouse and turntable shot in the mid to late 1950s.  Before that time, the handrails likely were basic wood, perhaps with some treatment.  By the 1960s, the handrails appear to have weathered and had pieces replaced such that they take on the same grungy appearance as early photos.  Even later, the wood handrails were replaced by pipe stanchions and cable.  The interim period with white handrails was quite striking and fit well with my prime modeling year focus for this area--about 1958 when the new diesel sand facility was built.  Photos taken at the end of steam locomotive operation also show the white handrails.

The turntable arch was built up from a number of white metal castings.  This proved a tedious task, as the various geometric elements precluded laying it over a template for assembly.  I needed to glue each joint with CA and let that joint set before moving on to the next joint.  The couple of days it took me to assemble the bridge arch seemed to summarize my entire experience with the turntable bridge assembly--not difficult, but tedious.  The turntable arch was mounted by soldering it to the underside of the pair of near-center brass straps.  I also soldered the end of the thick magnet wire that completes the center arch circuit from the feed tube at the top of the arch to one of the brass straps.

Mounting the bridge arch by soldering tabs at the base of the arch supports to the undersides of the near-center brass straps.  The magnet wire connected to the feed tube at the top of the arch has been soldered to the strap in the upper right position in this photo.

After a tedious construction effort, the turntable bridge has been installed!

Completed turntable bridge installed.

LET THERE BE LIGHT!

One immediate impact of my recent terrain-forming effort at Cascade Summit was the elimination of the light paths filtering down through the still-open bench-work at that upper level to illuminate the scene below which climbs up out of Oakridge to McCredie Springs.  I had always planned to provide additional lighting for this "land down under," but had never gotten to it. 

The "land down under" without lighting now that the Cascade Summit Terrain has been formed in the scene overhead.

When I began construction in 2012, I thought I might use single-tube florescent fixtures, but did not pursue that seriously as other work always had a higher priority--at least as long as that light continued to filter down to the scene.  With the terrain above now blocking the light, I needed to do something--now!  Fortunately, LED lighting has come a long way since 2012, with affordable solutions readily available.  I considered modern tube-style LED fixtures, but their cross-section size, mounting concerns, and relatively higher cost scored against them.  LED strips seemed the way to go.  

I looked at several supply sources for LED lighting strips.  I ended up selecting the strips from MicroMark.  A big factor in this choice was the recommendation of a fellow model railroad friend of mine in Virginia, Paul M.  Paul had used the MicroMark system to light the lower deck of his two-deck railroad.  I have since found a fellow model RR owner locally who has also used the MicroMark system, but it was Paul's recommendation that drove me.  I liked that the MicroMark system was well-engineered and had UL-tested components. 

I still delayed, as I needed to select a color temperature to match the 5000 deg-K lighting used in the rest of my railroad space.  MicroMark has three LED light temperature ranges, two of which bracket, but do not match my desired color.  The need to solve the lighting problem--now!--drove me past that hurdle to place an order.  I selected the 6000-6500 deg-K strips rather than the warmer 4000-4500 deg-K strips also available from MicroMark.  I previously experienced "warmer" (lower color temperature) florescent tubes in some new fixtures added after initial construction--tubes with a similar 4000 deg-K rating.  They were noticeably warmer (and quickly replaced with the correct tubes!), so I shied away from the warmer lighting for the current LED project and selected the bright-cool 6000-6500 deg-K strips.

The area beneath Cascade Summit now lit with 6000 deg-K LED light strips.  Note the color difference in this picture between the overhead warmer-lit scene and the bright-cool lighting below.

As illustrated in the photo above, the color temperature does make a difference, at least in photographs.  In person, the difference is barely noticeable.  Far more important is that there is light on the scene below the Cascade Summit overhang.

I mounted the LED strips to pieces of 1x2 lumber with a 3/4-inch cove molding on the edge forming a roughly 45 degree angle.  If I were to do this over again, I would simplify this to ripping a 1x4 using a 45 degree saw blade angle--no need for the complexity of the cove molding.  Indeed, the self-adhesive on the back of the LED strips does not attach to the cove molding, so I hold the strips in place with wire ties.

LED strips mounted on 1x2 lumber with cove molding edges. 

The LED strips provide needed lighting and are safely out of the way overhead.  I have a few minor adjustments to make at the ends and I may fill the molded cove with adhesive caulk to provide a flatter surface for the LED strips.  I may also need to provide a small amount of valence for the lighting, though that did not seem to be a distraction in the first operational test during the February 1 operating session.  For now, I am happy to have light on the Montieth Rock scene and the climb up out of Oakridge.

Mike L. guides Amtrak Number 11 past Montieth Rock in this now well-lit scene underneath Cascade Summit.