Saturday, October 31, 2015

Helix progress

Work has been progressing on the helix.  This photo shows the helix as it currently is.  Both yards are tied in now with the outer loop from the upper yard climbing a little more than one turn and the inner loop from the lower yard climbing two full turns.

The inner loop from the lower yard and the outer loop from the upper yard each have there own power district.  Each turn of each loop will have a feeder.

I picked up a roll of 16 gauge paired wire from to use as the main bus that will connect the inputs of all the PSX modules in the layout to the DCC system.  That is the black and red wire shown in this photo.  The outputs from the PSX power district modules are 18 gauge.

One of the reasons I am using the threaded rod design is to have the ability to experiment with the performance of equipment in pulling a given train up the grades and make adjustments if needed.  The last layout had 4 % grades which worked fine but those were short and the trains I ran on that layout were normally only 8 or 9 cars long.  I knew the grade would have to be less than that on the helix.

I started out with a rise between turns on the helix of 3 inches.  This calculated out to being 2.5 % on the outer loop and 2.8 % on the inner loop.  Then I began to run trains up the helix with various types of cars and locomotive.  I plan to run locomotives in pairs on most trains and most of the sidings will hold about 20 or so fifty foot cars.  With the 3 inch rise the 6 axle units did fine but the 4 axle units would start to loose traction about the time the full train was on the grade.  So I began to adjust the levels of the helix downward.

What I settled on was 2 - 3/4 inches between the levels.  That 1/4 inch seem to make a big difference.  Both 4 and 6 axle pairs of  locomotives can now pull trains longer than the staging sidings up the helix.  With 1/2 inch thickness of the decks, there is 2 - 1/4 inch of clearance which is plenty for the highest cars and my small hands still easily reach between for cleaning track for re-railing a car.  So far, with all my testing not a single car or loco has derailed within the helix.  So the final grade on the helix is going to be 2.3 % on the outer loop and 2.5 % on the inner loop.

Once I decided on the space between levels, I cut a piece of scrap material to use as a height gauge.  Adding the 1/2 inch thickness of the plywood structure to the 2-1/4 inch space make each turn lift 2 - 3/4 inches.

Another tool I made was a double ended guide with a stop that rest at the inner edge of the deck and lengths for the inner and outer loops.  Once the lines are drawn, the installation of the cork road bed and track goes easily, two sections for half a loop at a time.

I have noticed that the helix sections seem to have a little twist in them after being installed which makes the spacing vary a bit between some levels.  While this does not seem to affect the operation in any way I would still like to keep the spacing consistent so I may add some thin spacers between the threaded rods.

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