Awesome photos, all! Love
Awesome photos, all! Love seeing all the Great Northern action in particular.
Thanks for the interest, Brian, Jim and Neil! I hope folks don't mind me replying directly here, but I am happy to shift this into another thread if we want to just keep this one for photos.
Brian, my original staging yard schematic looked like this (apologies for the roughness of the drawing):
The yard was joint for both ends of the railroad, accessed by a common track off the helix. To use the yard, a train goes head-first into the arrival track, and then backs around the reversing loop into a storage track. This looked fine on paper, but didn't work well for two main reasons:
1) The reversing loop: Backing around the reversing loop and into a stall was very prone to derailment, as the slack action on long trains going around 3 S-curves and nearly 360 degrees of arc led to frequent accordions and stringlines ... despite my having laid the track very carefully. When it worked, it took a long time, and it's not very fun to slowly, and with some anxiety, back up your train for so long.
2) Less important: the single common access track for trains into staging sort of harms the illusion of "opposite ends of the railroad". Train crews who shouldn't really be interacting (because they're many miles apart in the real world) needed to coordinate, and frequently so.
The one good decision I made with this design was putting the turnouts along the aisle, rather than deep in the back, even though it cost me some staging track length. Maintenance has been much easier for that fact.
I have an idea for your staging yard which I'll share over in that thread 
.
Jim, the cork without track provided the original connection from Snohomish down to the joint staging yard (see my previous post for background: mrhmag.com/node/42576#comment-474042). Here's a photo of what got ripped out:
This diagram below shows what the railroad will look like after the renovation. Before the renovation, the mainline ended at Summit before descending the full helix into joint staging. The extension will add the Tunnel District, Apple Valley, and Great Interior.
I came up with a way to use the helix to almost double the mainline length, while making it part of the modeled road rather than just a way to get to staging, and I hope to share more about that in the future (it'll be easier to explain after at least the subroadbed is complete ... but if anyone thinks such an idea will be useful for their own design, I'd be happy to try to show it sooner):
For how I built the helix:
In general, I think there are two choices to be made when building a helix: 1) continuous-laminated vs. cookie-cutter, and 2) threaded-rod vs. wooden-spacer.
1) I chose the continuous-laminated approach, which uses wood very efficiently. I cut 1/4" plywood sheet into trapezoidal pieces which approximate the curvature of the helix. I created two layers of trapezoidal shapes, staggering one layer by ½ length of a trapezoid, and then laminated the layers together with wood glue and screws to provide a continuous helix (the picture above shows what this ends up looking like). By the way, I’d recommend using ⅜” sheet instead, because the minimum size screw which makes sense for lamination is #4 x ½”, and they’re actually a bit longer than ½”. This approach worked well and saved wood, but was A LOT of effort. If I was doing it over, I’d probably just cut the helix out of ½” or ¾” lumber cookie-cutter style.
2) I used threaded rods to separate the decks, but I think using wood block spacers is also perfectly good. Threaded rods provide a clean look. 8 rods of 5/16" diameter is good enough to hold it up nicely. Some people prefer wood block spacers because they find the rods, nuts and washers are a real pain to install, but I didn't feel that way. I just cut some temporary wooden spacers to separate the levels, slipped the nuts into each level as I dropped the rods in, and then adjusted them one by one.
I don’t remember where I originally got the idea for this overall design, but the helix in this link has a very similar design:
https://siliconvalleylines.com/benchwork/the-helix/
This thread has some good discussion of the tradeoffs between threaded-rod and wooden-spacer:
https://model-railroad-hobbyist.com/node/3455.
Despite my having done continuous lamination + threaded rods, let me throw in one more reason to go for cookie-cutter-and-wooden-spacer. Once you build a helix for a certain direction of ascent (clockwise vs counterclockwise), it’s rather difficult to flip the direction for a future plan … and the orientation of my helix has constrained a number of future layout design options. However, flipping a cookie cutter with wooden spacers would be substantially easier than flipping a continuous laminated helix with metal rods.
Siddharth
