Re: The Helix
Posted by Jim Courtney on Nov 05, 2017; 7:02pm
URL: http://c-sng-discussion-forum.254.s1.nabble.com/The-Helix-tp9915p9972.html
Well, Keith . . . after the Mies van der Rohe reference, I will now forever think of your helix as the "Bauhaus Helix".
Having designed a helix into my aborted layout project and having only built the first loop, I would caution you to carefully consider vertical clearances.
Sn3 locomotives, especially our favorite C&S locomotives with the tall extended Ridgeway spark arrestors, are significantly taller than even large HO scale standard gauge locomotives. I figure minimal vertical clearance from rail top to be at least 3 inches. Add in the track and 1/2 inch homasote roadbed and your talking about 5/8 to 3/4 inch extra before you get down to the rising base of the helix. I planned for 4 inches of absolute vertical clearance, taking into account all obstacles.
Then you have to decide how thick of a material for the climbing helix loops -- I had planned to use 1/2 inch 7-ply cabinet plywood, but wonder how much warpage might occur between supports. Would 3/4 inch plywood be better? Would sealing both sides of the material (varnish say) prevent this?
Finally, with 30" radius loops, I couldn't figure out how to cut more than half circles out of a 4'x8' sheet of plywood, and with a lot of wastage, at that.
The more segments of helix base per circle, the more joints are required:
How will you join each segment? A half-inch plywood splice, under each joint, will further cut into the vertical clearance at the top of the loop below. I figured that I'd need 4.5 to 4.75 inches of vertical clearance, from the top of the helix sub-roadbed of loop (n) to the bottom of the helix sub-roadbed of loop (n+1). With a 30" radius helix loop, this increased the grade to about 2.6% as I recall.
How many Sn3 cars will an Overland 2-8-0 pull up a steady 2.6% grade on a constant curve? I feared I might build the thing only to find out I had a helix for light engines or caboose hops!!
How would one go about milling the joints of the circle segments, removing the top half off one piece and bottom half off the next piece, so the joints would overlap without lower reinforcement? And do it squarely at the end of a circular piece? Surely there is a tool for this!
I'm not trying to discourage you . . . I simply got scared off by the complexity of the wood working.
I look forward to seeing how you solve all these problems, so I make fewer unforeseen mistakes, if I ever attempt my helix.
URL: http://c-sng-discussion-forum.254.s1.nabble.com/The-Helix-tp9915p9972.html
Well, Keith . . . after the Mies van der Rohe reference, I will now forever think of your helix as the "Bauhaus Helix".
Having designed a helix into my aborted layout project and having only built the first loop, I would caution you to carefully consider vertical clearances.
Sn3 locomotives, especially our favorite C&S locomotives with the tall extended Ridgeway spark arrestors, are significantly taller than even large HO scale standard gauge locomotives. I figure minimal vertical clearance from rail top to be at least 3 inches. Add in the track and 1/2 inch homasote roadbed and your talking about 5/8 to 3/4 inch extra before you get down to the rising base of the helix. I planned for 4 inches of absolute vertical clearance, taking into account all obstacles.
Then you have to decide how thick of a material for the climbing helix loops -- I had planned to use 1/2 inch 7-ply cabinet plywood, but wonder how much warpage might occur between supports. Would 3/4 inch plywood be better? Would sealing both sides of the material (varnish say) prevent this?
Finally, with 30" radius loops, I couldn't figure out how to cut more than half circles out of a 4'x8' sheet of plywood, and with a lot of wastage, at that.
The more segments of helix base per circle, the more joints are required:
How will you join each segment? A half-inch plywood splice, under each joint, will further cut into the vertical clearance at the top of the loop below. I figured that I'd need 4.5 to 4.75 inches of vertical clearance, from the top of the helix sub-roadbed of loop (n) to the bottom of the helix sub-roadbed of loop (n+1). With a 30" radius helix loop, this increased the grade to about 2.6% as I recall.
How many Sn3 cars will an Overland 2-8-0 pull up a steady 2.6% grade on a constant curve? I feared I might build the thing only to find out I had a helix for light engines or caboose hops!!
How would one go about milling the joints of the circle segments, removing the top half off one piece and bottom half off the next piece, so the joints would overlap without lower reinforcement? And do it squarely at the end of a circular piece? Surely there is a tool for this!
I'm not trying to discourage you . . . I simply got scared off by the complexity of the wood working.
I look forward to seeing how you solve all these problems, so I make fewer unforeseen mistakes, if I ever attempt my helix.
Jim Courtney
Poulsbo, WA
Poulsbo, WA
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