# The Helix



## Shifty1 (Apr 2, 2015)

I have my helix planned out. Dimesions are below.

Diameter: 36"
Radius: 18"
Run: 113"

Outer Track Radius: 16.5"
Outer track run: 103.62"
Grade: 2.1%

Inner track radius: 15"
Inner track run: 75.26"
Grade: 2.95%

Outside track spacing: 1.25"
Inside track spacing: 1.5" on center
Spacing between levels: 2.25"

Platform width: 8.5"



Bracing/spacers: 4 outside, 1/4" into platform. 4 inside 1/4" into platform.


Number of levels: 23 total climb is 46"

Outside track will be "inbound" or uphill climb to shelf level.
Inside track will be "downhill" or line from shelf to table, or main layout level. I chose the higher grade for the downhill in hopes that gravity will help negate some of the "push in..." (can't think of the name for it when train cars lay in towards center on tight turns).

One of the gents from caboose hobbies, in denver... the only one outside of the forum that said gofer it... made a valid point... Runaways. Having dabbled in the r/c airplane hobby some. I am thinking of using opto sensors, servos, and foam padded doors at the main layout side of the helix to prevent that... or... keep the runaways from blasting through the table side of the layout...

Which leads me to questions for you guys that have experience with the helix... 

First question... I'm going to stage pushers at the table side for the climb up for long trains.

Being uphill is a 2.1% grade, it doesn't worry me too much.

The downhill... close to 3% grade... would a trailing pair of locos help slow the descent? 

Lastly...

Not a single online article or youtube vid on helix', covers the way the levels are spaced. Being that im using 4 inside and 4 outside braces.. do I divide the run by 4 yo determine that? Or?


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## DonR (Oct 18, 2012)

You should hear from several members who actually do have a Helix.

I know nothing about them, but I do note that you are planning a 16.5 
inch radius on it. Do you have only small 4 axle diesel locos to run
on it? The combination of the 2" + slope and the extra friction from
the tight radius make make helper locos necessary to get up it it
would seem to me.

Don


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## Shifty1 (Apr 2, 2015)

The radius' won't be the issue. I can run big boys and dd40's up and down, according to mfr's specs and recommendations. The uphill, yes might need pushers. Im just wondering if the downhill side. 3% grade. Will the lead locos on a very slow throttle, will have enough resistance to hold the rolling stock back, or if it needs helpers at the back.

Also, of course how to space the helix


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## DonR (Oct 18, 2012)

Keep in mind that the motor drives the truck gear train through
a worm gear. This will be an automatic brake on any downhill
runs you make, I feel certain. Pull back on the throttle and it should
be safe.

Are we talking about an HO radius of 16.5" being able to accomodate
a Big Boy? I don't have one but from what I've read in posts by
guys who do, they want a radius of 22" + for those huge locos.

Don


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## cv_acr (Oct 28, 2011)

I'm assuming this is an N scale helix?

Those numbers will *NOT* work in HO.


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## Shifty1 (Apr 2, 2015)

Yes, this is n scale


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## DonR (Oct 18, 2012)

Never mind.

Don


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## Shifty1 (Apr 2, 2015)

I just need help with the top and bottom approaches. On the bottom, especially. How do I "ramp up to the 2.25" spacing? Thats the part that really have me stumped


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## traction fan (Oct 5, 2014)

*Helix level spacing*

Shifty1;

The amount of spacing between adjacent levels should be determined by the overall height gained; in the entire helix, divided into the overall length of track in the entire run up the helix. This is what you presumably used to get your percent of grade figures. Then divide by the number of levels to get the spacing between levels. It is very important that this distance be equal for all levels; to maintain the same percent of grade throughout the helix. Also, on a pragmatic level, the spacing must be high enough to more than clear your tallest raillcar, or loco.
A handy tool for maintaining a given grade is a small (2"-4") level. These are sold as, "line levels" at Home Depot, Lowes, Etc. (They are sometimes hung from a tightly stretched string or "line" on construction sites).
The reason we model railroaders want them is simply for the short length. Set the level on a separate piece of straight track. Now raise one end of the track to get your exact desired percent of grade. At the downhill end of the level, shim it up until it reads dead center level.
Now attach the shim* to the level. You have just created a tool. When set on your helix track, with the shim end downhill, you can check the grade percentage. It should read dead level, if your track gradient is correct. By sliding the level along the track, you can (and should) check the grade of every inch of the helix.
On your runaway question; Don R is correct that the worm gearing of the loco at the front end of a descending train will hold the train back; no rear helpers needed. The precautions you mentioned (foam-padded walls between the train and a disastrous fall to the floor) are wise. Things happen. Cars come uncoupled and roll back down, Etc. 
On the approaches, simply use a lower percentage of grade (1%-1.5%) to ease the train into the steeper grade. This is called a vertical "easement", and is common on both full-sized, and model, railroads 

* you can substitute an adjustable, screw leg for the shim. This allows the level to be set to more than one grade. You can also mount the level,with shim downhill, on a flat car for convenient movement along the track

Hope that answers your Questions; 

Traction Fan


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## MtRR75 (Nov 27, 2013)

traction fan said:


> You can also mount the level,with shim downhill, on a flat car for convenient movement along the track


Good idea, but test the flat car on a level track and make sure that the bed of the flat car is level with the track first.


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## Shifty1 (Apr 2, 2015)

That is a huge help! Thank you very much!

The way I figured my grades was dividing the runs from track centerlines by the spacing which is 2.25 inches.

As far as the climb up... I'm just going to make an audible call on that.. mandatory pushers going uphill..


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## fcwilt (Sep 27, 2013)

I did this diagram about vertical easments for a friend.

It is generic enough that you should be able to apply it to the ends of your helix.


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