Sunday, March 14, 2010

Layout Progress Report #9 as of 03/14/2010

The fun has begun....the helix, that is.  As previously shown, my layout is 2 levels, the upper scenicked level connected to the lower staging level with a single track helix.  The design specifications for the helix are as follows:

  • Single track 
  • 17 inch radius
  • 2.5" rise per loop
  • 6.5 loop total

Using nominal 1/2" plywood with cork and Peco 55 track this yields a height clearance of almost 1-7/8", with a grade of 2.34%.  This is more than the NMRA recommended clearance of 1.65"

If you do a search on the internet you will find many different techniques for building one, including purchasing some kits to make the helix build simple.  I decided to make the components and build it myself, as it is the most cost effective solution.  Keeping with the cost effective theme meant that cutting the helix loops as semi-circles out of plywood would also not work as it leaves a lot of wasted wood.  I decided to use a technique of making a circle out of 12 straight pieces of wood, with each end of the wood cut at a 15 degree angle.  Here is a CADRail drawing of what it will look like:

With a table saw and miter saw it will be rather straight forward to cut these pieces to size.  I will be able to cut all the wood needed for the helix using one piece of 4x8 plywood.  To join the pieces of wood to make the helix I will cut an 1/8" slot into the edge of the wood and connect them with some 1/8" thick masonite pieces.  The same masonite pieces will be used as supports using threaded rod risers.

I started working on it Saturday morning after a trip to Lowes for the remaining hardware.  First thing was to rip the plywood to 3" wide strips, and then cut them down to the appropriate length with the miter saw.  Here you see the pile of wood strips cut to length:

Here you can better see how the wood pieces will work together:

Now is time to cut slots into the ends of the wood strips.  To  do this I am using my router table and a slot-cutting bit.

Here you can see the business end of the slot-cutting bit with a guide bearing on top.  It will make short work of cutting the slots.

After some serious sawdust the wood strips are slotted.

Then I cut the 1/8" masonite slot pieces with the table saw and miter saw, and drilled some holes for the threaded rods.   Here is the whole pile of parts that will make the helix.

First I made a jig to mark the track centerline on each piece out of a couple pieces of wood.  Doing this before assembly will make things easier.  Once again I will use a punch to mark the line.

Next it is time to grab one circle of pieces and lay it out on the base to see how it will fit.  I also marked where to drill the holes for the threaded rod risers.

The next close-up will give you a better idea of how the helix will be put together.

Once everything is laid out and marked, it was time to remove some of the base where the helix will start.  I calculated that after 3 sections the helix will rise above the base, so I cut a hole with a jigsaw for that.  I also drilled the holes for the threaded rod risers and started putting them into place.

All the threaded rods are in place, secured in place with nuts, washers and loctite threadlocker.

Here you see the first three pieces in place.  The first piece is spliced to the base, with the remaining pieces supported by risers under the base until the first masonite tongue piece is used.

So the helix construction has begun, next time I will continue to chronicle the building of the helix....

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