I am seeking help with a bit of a construction issue. I am building a 2 level layout, and with out scrapping the top and lowering the main level to add a 3rd level to get me to the top, and an issue with the no-lix that i wanted to do with a 2.5% grade, and run that along one 14ft wall and have it hit the second level around the other top, which now I don’t think will work, with out up-ing the grade, it seems I am left to choice to go a helix route at this time.
I would like to see if I can do one with a radius of 28" and am wondering how much realestate that would take up, and I am going to have to put it into the wifes area, and will have to bargin some lease issues lol. I did want to orginally put in a 1.5x8’ yard in the orginal area, but if the wifes agrees, then do a helix with a smaller yard just for staging. I am wanting just a single track, and have never built a helix before.
I am looking for help and options at this time please…space is limited. I was using WS risers to do the grade with, but I am HO scale, and seeking help on this one pleae
28" radius is 56" diameter, and you’ll need some space around the edges, you’ll need a few inches all around, so about 5 1/2 feet, you might be able to squeak it down a little more but you need room on the outside of the curves for overhang and then the supports. So you will need a space about 66" x 66" to fit a 29" radius helix.
lets see 28 + 28 = 56 " dia. @ track center ,add min. clearance from track center to edge 1 1/4 " + 1 1/4" = 2 1/2"( MAY NEED MORE FOR BIG STEAM), SO 56" + 2 1/2" =ABOUT 58 1/2" ADD A 1/8" MASONITE WRAPPER 59" could do it ( the wrapper is the out side support ,screwed on …ask me How I know mines 29 1/2 " radius 61 3/4" x 73" oblong to keep the rise @ 2% ,I run diesels and 85’ Walther’s pass. cars no problem ,works great BUT YOU GOT TO KNOW a helix can kill the length a train do to the added drag of a tite radius ,so add 1 to 2 % to your grade depending on the radius ,ex. my 2% helix is really @ 2 1/2% +grade on my train because of the 29" radius,and you well notice it …Jerry …perfect bench work and track work a must ,and testing as you build
Randy was more generous than I would be - I figure that a 28 inch radius would occupy an octagonal footprint five feet across flats. That assumes that you want it fully enclosed (with thin Masonite) except for a narrow viewing window so you can keep track of where your train is during the LONG time it will be on the grade.
On the upper level, the space above the helix will be (mostly) useable real estate. The same cannot be said for the lower level. You will want to keep the center of the helix accessible so you can get in to clean up if anything untoward happens.
My own helices are built inside segments of steel stud, which provides me with built-in guardrails as well as an extremely thin roadbed structure. The main supports are threaded rods, located at the points where there is adequate clearance - the inside centers and outside angles of the straight segments. They are also a lot smaller, since they are only used by short trains of short cars - 350mm radius, 3.7% grade.
Well I figured 5’ would not be enough because that only gives you 2" outside of the centerline of the track for clearance - car/loco width and overhang PLUS the supports for the next layer. Depends on the method used to support each layer I guess - somethign liek the threaded rod method could get away with less clearance. I was thinking more on the idea of Jim Hediger’s simplefied method of realizing that the length of the support blocks is exactly the same around the whole circle on all but the bottom level. Although this lends itself to using an outside the roadbed support system as well, with evenly spaced brackets of some sort going under to support the roadbed. Depending on the thickness of these supports, it would only be an inch or two over 5’ and still allow plenty of clearance on the outside of the track.
On top, but not inside it. 30" radius is 5’ diameter - to the CENTER of the track. So the outside edge of the track is more than 60" in diameter, overhanging the 5’ frame. Plus you need to see how much your longest locos overhang - even on 30" radius the nose of a Big Boy is goign to stick out pretty far. If you only run smaller locos, then you might eb able tto skimp on clearances a bit. But test before building an entire helix and then finding a few of your trains can’t negotiate it. You can probably get away with 29" radius inside a 5’ frame assuming the 5’ measurement is inside width of the frame, not the outside. If it’s 5’ across the outside, then you have to subtract the thickness of the frame members and see what you cna really fit inside.
Remember, curve radius is to the center of the track. Diameter (a full circle, like a helix) is twice the radius – to the center of the track.
So with 30" curves you’re at 5 feet diameter even before allowing for distance to the outside edge of the track, plus clearance to the outer helix supports, plus the supports themselves. Depending on your helix construction method, the overall width for a 30" radius helix is probably at least in the 66"-72" range at the widest points (where the outside supports are located).
If you’ve not built a layout with grades formed by bending the subroadbed before, a helix might be a bit of a construction challenge.
This is where the time-tested concept of “Givens & Druthers” come into play.
For Example: If your “Given” is an outside subroadbed radius of 30" (5’ = 60") – Then your “Druther” must be reduced to no less than 28" on-center (or less) for the track-center. This assumption is a bit optimistic before taking into account bracing benchwork.
Question: Is that “Druther” acceptable for the “Given?”
Note: Cuyama’s sage advice above is even more realistic for the “Given.”