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Question about Layout Design Assessment Formulas and Helixes Dream and design
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Regular poster 197 posts Onewolf Regular poster 197 posts
Onewolf

I have a single track mainline that uses a helix to connect the lower level to the middle level.  The helix is a double track and I plan to use the outside helix track for upward bound traffic and the inner track for downward traffic.  It will also function as a (VERY LONG) passing track.  The helix is 4 times longer than the 'normal' passing tracks.

My question is how to account for the double track helix?  I am currently counting the outside track as mainline and the inside track as a passing track, but for the sake of the operational formulas I am saying the helix passing track is the length of the longest 'normal' passing track in order to not skew the average passing track length value.  Is that reasonable?

Thanks.

- My layout build thread -
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DKRickman Prolific poster 3,069 posts
DKRickman

Good idea, but does it matter?

My first thought is that "average passing track length" seems like an utterly pointless bit of data, unless you can average your trains across the layout.  More important is the shortest passing track length.  Longer tracks just don't matter when it comes to figuring out how long a train you can run across the railroad.

With that said, I like the idea of designating the helix as the same functional length as the rest of the sidings.  You certainly don't gain anything by it being longer, and you don't lose anything by designating it as the same as the longest modeled siding.

If you want additional capacity, you could consider putting one or more crossovers in the middle of the helix.  That would convert it into two or more consecutive sidings.  The trackwork would have to be excellent to be reliable, but it could be done if needed.  Or, since the tracks are directional, consider adding signaling of some sort, or automatic block control so that you can stack multiple trains in, one behind the other.  That would also convert the single helical siding into a series of shorter sidings, in a sense.

Ken Rickman

Danville & Western HO modeler and web historian

http://southern-railway.railfan.net/dw/
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Chris VanderHeide cv_acr Super User 2,354 posts
Chris VanderHeide cv_acr

Hidden crossovers

Quote:

If you want additional capacity, you could consider putting one or more crossovers in the middle of the helix.  That would convert it into two or more consecutive sidings.  The trackwork would have to be excellent to be reliable, but it could be done if needed.

That's something I'd be skittish about. Even if the trackwork is bulletproof, don't like the possibility of driving trains into each other or through a reversed switch in hidden areas.

At our club we have a lot of hidden track and helices (some if it doing some complicated contortions behind the scenes), but no hidden crossings or switches (except in the staging yards themselves - not in connecting trackage).

Chris van der Heide

My Algoma Central Modelling Blog

Canadian Freight Car Gallery

CPR Sudbury Division (Waterloo Region Model Railway Club)
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ctxmf74 Super User 15,990 posts
ctxmf74

"If you want additional

Quote:

"If you want additional capacity, you could consider putting one or more crossovers in the middle of the helix.  That would convert it into two or more consecutive sidings.  The trackwork would have to be excellent to be reliable, but it could be done if needed."

to avoid access problems the helix could be split into two parts with the crossovers exposed on a hillside scene......DaveB 

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joef MRH Founder 17,571 posts
joef

If all else fails, make it connecting track

The rule of thumb on track you aren't sure how to classify is to make it connecting track. I'd make one route through the helix mainline and try making the other connecting track. Connecting track helps you move trains, and that's what the second helix track does. But your concern about using the second helix track as a passing siding skewing your stats brings up an important point - a "passing siding" that long is something of a waste - you need a crossover in the middle of it to split it up - and then it won't skew your number so badly. The stats also suggest improvements, like it does in this case. I also see the complaint that the average passing siding length is meaningless - hey, it's a stat, alright? Statistics are just that - numbers that give you some idea of what's going on, but the stats themselves never give you the complete picture - and in some cases stats can give you the wrong idea. That's why there's books about how to lie with statistics, and why politicians have refined the art of spin doctoring with stats to such a fine art. Always take stats with a grain of salt. They're not the whole picture and it's always best to remember that. But they also give good insight as long as you don't make the stats into some kind of magical numbers that you never go beyond.

Joe Fugate​
Publisher, Model Railroad Hobbyist magazine

[siskiyouBtn]

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Onewolf Regular poster 197 posts
Onewolf

Thanks...

Thanks for all the responses.  I'm quite happy with the operational design assessment stats of my current layout design.  Since I'm happy with the current operational assessment numbers and my building layout will provide enough challenges I will forego adding any crossovers in the helix.

Here are the numbers for my current design based upon 7" car length (instead of 6" car length). My goal has been to run maximum of 30-35 car trains and the design will allow that.

Using 7” car length

Room Area (sq ft)

912

Layout Area (sq ft)

???

Number of Turnouts

82

Total Track (ft/cars)

1540/2640

Mainline Track (cars)

1086

Passing Track (cars)

180

Storage Track (cars)

364

Staging Track (cars)

358

Service Track (cars)

137

Connecting Track (cars)

515

Passing Sidings (number of)

3 +Helix

Passing Sidings length (cars)

36,34,52,52 (Helix)

Passing train length (cars long/avg/short)

55,45,34

Staging Tracks (number of)

10

Staging Track lengths (cars)

38,38,37,36,36,36,35,35,34,33

Staging Train length (cars long/avg/short)

38,35,33

Operational Stats

Maximum number of cars = 649

(80% * (storage + staging + passing/2) = .8 * (364+358+180/2)

Maximum cars to Maximum Mainline Ratio = 649/1086 = 59.8%

Number of cars moved = 531

(40% of (staging x 2 + passing + connecting)) = .4 * (358*2 + 180 + 431)

Trains (531/34) = 15

Dispatching Threshold = 41

(3 x shortest passing siding + 2 x average passing siding + longest passing siding) / 6) = (3 * 34 + 2 * 45 + 55) / 6

Staging Tracks

Lower Loop (38, 37, 36, 36, 35)

Upper Loop (38, 36, 35, 34, 33)

Passing tracks (Upper: 36, Middle: 34, Lower: 52, Helix: 154 (52))

- My layout build thread -
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