# Helix Clearance?



## Tabooma County Railway (Aug 12, 2012)

Hello,

Long time HO modeler (40 plus years) now planning an outdoor layout, and am wondering if there is a "rule of thumb" or something regarding vertical clearance for G scale in general? Such as for a helix - I have the space to add a helix under my house (huge, deep crawlspace) to perhaps have the railroad gain elevation to the front yard level. I know in HO, there is an NMRA guage to make sure you allow enough clearance, but haven't figured out what it might be for G scale. 

Thanks,

Al Carter
Mount Vernon, WA


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## steam5 (Jun 22, 2008)

Al 

Have a look at this thread, may give you some ideas 

http://www.mylargescale.com/tabid/56/afv/topic/aff/9/aft/111280/Default.aspx 

Alan


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## Greg Elmassian (Jan 3, 2008)

If you have a lot of space, and can make the helix broad, then go 12", if not, then you need to start considering if you will run 1:20.3 or 1:29 or 1:32 locos... the smokstack on a Bachmann shay is pretty tall. 

Greg


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## Tabooma County Railway (Aug 12, 2012)

Thanks for the replies. Haven't decided on a scale, but will be mostly, if not all, diesel power (sorry, you steam fans...). I like 1/29th stuff, but I also like 1/24th vehicles and buildings.... 

Al Carter


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## toddalin (Jan 4, 2008)

Assuming that we want the helix to be a reasonable size, if you use a 10'-diameter circle and allow for 10" of clearance, you end up with a 2.65% grade. Recognizing that you are pulling the cars through a continual arc, I would not go any steeper than this.


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## mickey (Jan 28, 2009)

Depending on the final height, thats also a lot of track. Ready for the cost?


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## Greg Elmassian (Jan 3, 2008)

Todd, in your calculations, how much thickness are you giving to the rails and ties and support underneath as a total? When I did this, the grade was a bit more. 

greg


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## Tabooma County Railway (Aug 12, 2012)

Mickey,

Ha! No, I'm afraid to even think about the cost. Of course, building a garden railroad isn't cheap, anyway you look at it...

Al Carter


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## toddalin (Jan 4, 2008)

Posted By Greg Elmassian on 13 Aug 2012 10:02 PM 
Todd, in your calculations, how much thickness are you giving to the rails and ties and support underneath as a total? When I did this, the grade was a bit more. 

greg 

The 10" of "clearance" includes clearance for the trains and thickness of the rail on lattice-work. The actual clearance for the tops of the trains is a bit over 9" and is plenty for 1:29 scale. I have a 10" diameter PVC tunnel and obviously the rail doesn't sit at the very bottom. At one end, the peak has less than 8-1/2" clearance, but everything I have (including my 1:20.3 Shay) clears fine.


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## Greg Elmassian (Jan 3, 2008)

OK, so there's really a bit over 9" from rail head. That's more in line with my measurements of grade when I was considering a helix. 

I swear my old shay with the diamond stack was 10.5" but all that matters is measuring the rolling stock that is desired. 

Al, in 1:29 the tallest thing I think you will encounter is the container cars from USA Trains.That's what I used for clearance measurements.


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## mickey (Jan 28, 2009)

Posted By Tabooma County Railway on 14 Aug 2012 09:23 AM 
Mickey,
 
Ha!  No, I'm afraid to even think about the cost.  Of course, building a garden railroad isn't cheap, anyway you look at it...
 
Al Carter 


You got that right. I can attest to that personally.


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