Yesterday I went up to Pinetop and did a 4' x 4' grid survey (240 measurements) with some help from a friend and a rented Home Depot transit. My initial estimate that I would need a 3' helix is now more like a 2.5' helix. It's better to redesign now than get the helix built and find that it's too high.
I'll try and get some pictures posted.
Rex
To answer some questions:
This is a single track helix that's 15.91' in diameter thus making it a 50' circumference. It has 4 turns to raise 36" @ about a 1.5% grade.
There is an R5 sectional track on my old LGB track layout template. It says R5 = 231.82 cm and if my conversion factor is correct I believe that works out to 7.6' which is close to what I want. Of course the template may be out of date and no one offers R5 anymore???
Anyway I'm looking at bending some SS track so I don't have to polish it as often.
I've finished the third prototype and have not added any superelevation per advice here. Are there any other things I need to consider with this helix?
If this is a single or double helix with a relatively low ascent (say 2% or less), I would say that superelevation would be a frustrating waste of time. If your grade is steep and there will be many loops, say 4% and four loops or more, it might not be a bad idea to give it maybe 1/2 bubble super-elevation. This will help to ensure that, in the event of a decoupling and subsequent runaway, the car(s) will come out at the bottom relatively unscathed. Otherwise, they might build up enough momentum to be thrown off the tracks by centrifugal force.
BTW, I don't know what the diameter/radius of R5 curves is, or how many tracks you have on the helix to give you any better advice than that.
Mark
Thanks! I hope I don't get into rollercoaster speeds on the downhill runs. I'm on my third prototype of the helix section. The first one only had 1' between trusses which wasn't enough to get a car out the side in the event I had to. The second prototype had 2' between trusses but didn't account for the inside being 3" less than the outside. I figured that I better account for superelevation if it was required before building the 3rd prototype. Hopfully it will be the one I build the jigs from.
Unless you roll your trains at (real) rollercoaster speeds, superelevation (curve banking) for anything smaller than really large scale live steam is purely cosmetic. Since you specified, "Inside a helix," I presume the train is unlikely to be clearly visible. If that is the case, superelevation would be more of a nuisance than an asset.
When superelevating visible curves, less is more. Just enough 'tilt' to be easily noticed is more than enough. Models don't transfer their weight to the outside wheels on a curve to anything like the extent that full scale trains do, and on ordinary lines (not used for Acela, TGV and equivalents) the real railroads only superelevate a few inches.
Just my . Other opinions may differ.
Chuck (modeling Central Japan in September, 1964)
Should I bank 200' of R5 curves inside a helix? If so how much?
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