Wednesday, February 17, 2016

CORRECTING A HUMP AND A SAG


As my railroad settles in, I have found a couple of roadbed issues that demanded attention.  The first was a hump in the roadbed and track in the middle of my Cruzatte location.  This one developed because I fit a modest width plywood roadbed piece between two eight-feet long pieces without proper (e.g., full width and beyond) splice plates underneath.  As I set the grade through Cruzatte, I allowed this filler piece to form a vertical kink—a hump.


Cruzatte roadbed hump.  Short filler roadbed section is on the right.

The hump became very obvious once I built the mountain operator platform and we began walking along this stretch of railroad.  I built the roadbed through this area using ladders and stools—not the best spots from which to observe something like this hump. 

The correction of the hump was straight-forward.  I removed the track.  Since I lay track using Dap 230 adhesive caulk, I have found I can flood such an area with alcohol and then easily pry up the track using a putty knife.  Once the track was removed and the area dried overnight, I used my belt sander to sand down the cork roadbed.  Final trimming was done with a Stanley Surform® and a sanding block. Relaying the track and re-installing the track feeders completed this job.



Cruzatte roadbed shaved down to remove the hump.


Cruzatte roadbed hump corrected. 

The second roadbed problem was at the RR-West end of the Salmon Creek mainline bridge.  Here, a dip or sag had developed.  I am not quite sure how I built this sag into the roadbed, though the fact that the roadbed splines that pass through the middle of the bridge (concealed by the cosmetic bridge girders) at less than standard roadbed height is the likely culprit.  See my posts on this bridge construction at:  http://espeecascades.blogspot.com/2014/04/salmon-creek-mainline-bridge-1.html  and http://espeecascades.blogspot.com/2014/06/salmon-creek-mainline-bridge-2.html 


Salmon Creek roadbed dip at the RR-West end of the bridge.

Correcting this dip required removing a couple of pieces of track, including half the track on the bridge.  That took some care to avoid damaging the bridge handrails.  In the end, the piece of track from the bridge needed to be replaced, as the ties broke away from the rails in several places.  

As it happened I also had a section of track lifted up from the roadbed just up the line from this area, so another section of track was removed.  The track had bowed up because the roadbed shrunk a bit over the past month, likely due to the dehumidifier in the basement as part of the house maintenance issue cited in the last post.  I could work on both problems (the bridge dip and the track lifting) at the same time.


Track hump caused by roadbed shrinkage.

With the track removed, I started filling the roadbed dip with balsa sheet glued on top of the cork roadbed.  The balsa lends itself well to shaping with hand tools and is plenty strong enough to support the track.  I needed to install about a quarter inch of filler material at the deepest point of the dip.  The top layer was a relatively smooth section of 1/32 inch thick balsa sheet.



Roadbed dip filled with balsa and sanded to fair back into the existing roadbed.


Salmon Creek mainline ready for service.

As noted above, I had a couple of instances of track popping up off the roadbed, likely due to roadbed shrinkage with the dehumidifier used in the layout space as part of the house maintenance issue.  I had quite a track bow at Wicopee.  In  the end, I needed to remove close to 1/8 inch of rail from one piece of track to refit the track. 


Track bowed up at Wicopee.

Adjustments to the roadbed are known issues for new track.  Both the full-size railroads and model railroads go through these adjustments.  Indeed, the prototype Cascade Line was not cleared for passenger train service for at least six months after line completion as the roadbed and track settled in.  For my model railroad, it will be good to just run the current railroad with only modest scenery efforts for a year or more so I can more easily spot and correct any more roadbed settling issues.

1 comment:

  1. Nice to see you getting back to the railroad. I hope your house issues will clear up. I enjoy watching your progress and getting ideas as I build my benchwork.

    Thanks,

    Dan

    ReplyDelete