# A helix



## Guest (Apr 19, 2011)

I'm gonna make a double track helix using 18" and 22" radius curves at 4 % incline to connect to the 26" and 28" radius mainlines on the upper level, I think like a three level spiral, a helix ? Does anyone have one ? Some positive experience ? I guess it's the only way to connect the two independent levels with some 30 - 40 cm height difference. How does this sound ?


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## gunrunnerjohn (Nov 10, 2010)

Well, I'm currently working on a design of a helix to connect the layout with a ceiling track, it's the only way I could see doing it.


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## sstlaure (Oct 12, 2010)

[email protected] 18" radius you're looking at about 3.5% grade to maintain 4" spacing between levels of the track (NMRA recommended minimum) That grade on that tight of a curve will require some decent pulling power depending on the length of trains you're going to run.


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## Guest (Apr 19, 2011)

Hmm, how many freight cars, or Amtrak phase 3, or Pullman, or double decker Regio passenger cars can be pulled up or down if I add 2 or 3 9" straights to make it more of an oval for "easing" the grade ? Will Conrail #6087 GE Dash 8-40CW, Bachmann, make it on 18" radius ? And how about Union Pacific #6900 DD40AX Diesel, Bachmann, they say 22" radius is minimum for this one ? They will be the two tracks, 18 and 22, one train "downhill", the other "uphill", that's the idea ? !


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## Guest (Apr 19, 2011)

Because there will be 26 and 28" radius mainlines.


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## sstlaure (Oct 12, 2010)

18" R will be tough with the longer passenger cars. I try to maintain 24" R as they will handle just about anything.

With 18" R - If you add straights on each side:
9" straight - 3.1%, 
18" straight - 2.7% 
27" straight - 2.4%. 

(I've got an Excel spreadsheet set-up for figuring this out.)

If you went 24" and 27" radius on the helix you'd accommodate any kind of rolling stock/engines and you'd be looking at 2.7% & 2.4% grades with a 4" rise between layers.


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## Guest (Apr 19, 2011)

so with 27" straights on sides I should be fine even with the longest passenger cars ?


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## sstlaure (Oct 12, 2010)

Your problem isn't the straights - it's the radius of the turns. You'll definitely have a more manageable grade with 27" straights on each side. If you've got truck mounted couplers they are a bit more forgiving on the radius of the curve.

I like LONG trains and want to have ~20 car trains so I'm limiting my rise to 2.4%. I've planned a 4 track wide helix with the innermost at 27"R and the outermost at 36"R


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## Guest (Apr 19, 2011)

sstlaure said:


> 18" R will be tough with the longer passenger cars. I try to maintain 24" R as they will handle just about anything.
> 
> With 18" R - If you add straights on each side:
> 9" straight - 3.1%,
> ...


I want to fit this independent helix (18, 22) to the 26,28 mainlines, though the 22 oval must be connected via turnout to 26, right ?


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## sstlaure (Oct 12, 2010)

holava said:


> I want to fit this independent helix (18, 22) to the 26,28 mainlines, though the 22 oval must be connected via turnout to 26, right ?


All depends on your track plans. Do you have a sketch of what you're looking at? Is this a single mainline or double? Point to point or continuous running?


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## Guest (Apr 19, 2011)

When I'm talking about long passenger cars, I mean 3-5, with freight cars, I mean 10-15. Acela can make the 22" radius without a problem, right ?


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## Guest (Apr 19, 2011)

In that helix section I have only 160 cm of width, and I need to fit there the 26 and 28 double continuous mainline.


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## sstlaure (Oct 12, 2010)

holava said:


> When I'm talking about long passenger cars, I mean 3-5, with freight cars, I mean 10-15. Acela can make the 22" radius without a problem, right ?


With those length trains you'd probably be fine around 3% or so (guessing) Acela is a fairly short engine so I wouldn't think there would be any problem on 22"R curves.

I like the big 80+ foot modern cars and longer engines (6 axle) so I wanted to make sure they all run reliably. That's why I've gone with 24"R minimum.


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## sstlaure (Oct 12, 2010)

holava said:


> In that helix section I have only 160 cm of width, and I need to fit there the 26 and 28 double continuous mainline.


160cm is ~ 63" so you could to 24/27" R and still have room on the outside for clearance.

Take a look at my build thread Post #76 and you can see how/where I've placed my helix. I've drawn this thing dozens of times to get it all worked out. It will be tucked underneath a staircase in a mostly useless area of my basement.


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## Guest (Apr 19, 2011)

You've got space, pal, but I don't, and I just want the helix, like 1/5 or 1/6 of the whole layout to connect to the upper level, that's why I'm looking for "kind of reliable" solutions based on what I'm willing to sacrifice on the helix, no showoff definitely, yours sounds luxury, 4 tracks and that radius, man !


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## sstlaure (Oct 12, 2010)

I'm also planning on building it over the next 20 or so years 

If space is at a premium - you may want to look at a train elevator (run shorter trains) or even have 2 separate levels that don't necessarily connect to each other (run independently.)

Helixes take up a ton of space.

What's your total layout space? (length x width)


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## Guest (Apr 19, 2011)

sstlaure said:


> I'm also planning on building it over the next 20 or so years
> 
> If space is at a premium - you may want to look at a train elevator (run shorter trains) or even have 2 separate levels that don't necessarily connect to each other (run independently.)
> 
> ...


It's 18/11, somewhere 12 feet, but where I want to place the helix it's 160 by 210 cm. What's the train elevator ? I can't find your post #76 !!! I'm buying almost all at once when I "kind of" figure it all out, hopefully in a month or so. That's funny, I don't plan to work on it for 20 years, wanna finish in 6 months top. The upper level will be only a double oval on some improvised structure with thin legs, with a lot of bridges so that there's a very clear view on the lower level.


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## sstlaure (Oct 12, 2010)

holava said:


> It's 18/11, somewhere 12 feet, but where I want to place the helix it's 160 by 210 cm. What's the train elevator ? I can't find your post #76 !!! I'm buying almost all at once when I "kind of" figure it all out, hopefully in a month or so. That's funny, I don't plan to work on it for 20 years, wanna finish in 6 months top. The upper level will be only a double oval on some improvised structure with thin legs, with a lot of bridges so that there's a very clear view on the lower level.


Here's the link to the main level (there will be a total of 3 levels when I'm "done")

http://www.modeltrainforum.com/showpost.php?p=68147&postcount=76

Here's a really cool example of a train elevator - fast-forward to about 1:03 in to see it in action. Most that I have see are straight - this one incorporated the entire corner.

http://video.search.yahoo.com/search/video?p=model+train+elevator


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## Guest (Apr 19, 2011)

Wow, your layout is wonderland, and how about some easements, half 18" curve plus 3" straight, etc. and half 22" curve plus 3" straight, etc. Would that help with Amtrak or modern Regio cars ? Or could that be the "perfect" solution for just getting to the upper level ?


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## sstlaure (Oct 12, 2010)

With 18 x 11 feet you should have plenty of space to put a helix. 

@ 160cm diameter you're looking ~63" diameter, that's 31.5" radius max at the outermost edge. If you've got a couple mainlines running around the outside of the helix figure taking about 5" off of that (room for 2 tracks and clearance along the edges) so you're looking at 25" or so for your outer track. Space the tracks about 3" apart around the curve and you should be able to fit 22"R/25"R on your helix which should be adequate for all but the longest cars (think 86 foot boxcars, car haulers with end couplers.)

Try to fit as big of a radius as you can for reliability. Not saying 18" won't work at all, but it won't work as well as something larger, that's for sure. 99% of the derailments on my current layout happen in the one corner where I went tighter on the radius to fit the curve (It's maybe 20"R)

FYI...I use flextrack for maximum flexibility in design rather than EZ-track. You limit what you can do if you're planning on using EZ-track (and EZ-track is more expensive as well.)


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