# Helix



## skatewake (Feb 18, 2008)

Okay, here is another question.

I need to build a helix. I have to elevate around 27" which at 2.5% grade roughly comes out to a 11'-6" circle x 2.5 times at around 11" rail head to rail head. I would like to go with a 10' diam. circ, but to get the height between rails it would need to be around 3% grade. would that be to much of a grade? I am going to have inter model and passenger cars rolling through this up and down. Any thoughts?

Thanks again,

Charles


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## Guest (Dec 31, 2008)

depends, what locos you use, and how many cars you plan. 
if you don't want to tow more than 12 aixles, 3% on straights is no problem.


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## CLRRNG (Sep 26, 2008)

*Hello Charles,* 

*I have had similar dilemas with what your are scratching your head about. I alway reverted back to actual field testing.*

*If you have the track already I would make a mock-up of a complete circle with the 3% grade. Choose your heaviest train (good idea to add 10% in additional cars) and run it up the "test" helix and see what your loco's are capable of pulling/pushing up that grade. *
*What ever the result is I would pay close attention to not maxing out your loco's ability to do its job. Heavy loads on grades stress the loco's gearing. The loco will also draw more power to tackle the task you put on it. This will effect battery run time if you run battery power. Or, if you are on track power will increase the amp draw to the power supply. *

*Hope this helps* 
*Glen*


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## Greg Elmassian (Jan 3, 2008)

I was going to put in a helix at my place, slightly smaller in diameter but close in dimensions to what you are planning. I was surprised how steep an incline I could go up. 

I mocked up the helix enough to run a few trains up and down. 












First going up is much tougher than down. No so much because of the grade, but the tendency of stringlining cars.

You have to limit train length severely.


Second, the track has to be absolutely flat to avoid pulling cars off. 

Long cars will be a problem even with these precautions, the grade required will put angles and stresses on your couplers that are not pretty.


Long cars can also have clearance problems entering and exiting the loop unless you provide significant vertical grade transitions at the beginning and end of the helix, which I found to be impractical in my case.

Going down is easier, but the weight of the cars will try to push the cars behind the loco off the track also.


This is my experience, hope it helps.

Regards, Greg


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## Joe Mascitti (Oct 30, 2008)

I've been trying to get RJ to build a helix for over a year now.....


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## Greg Elmassian (Jan 3, 2008)

Me too! He'll cave in eventually... just about the time you go DCC! ha ha! 

Greg


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## Joe Mascitti (Oct 30, 2008)

He's got the perfect spot for a one at least 25ft diameter....no problems with long trains on that...


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## aceinspp (Jan 2, 2008)

Yep I could build one but I wonder why Greg changed his mind. Joe you also could have built one to get up the grade you had just for a change. HeHe. Later RJD


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## Greg Elmassian (Jan 3, 2008)

I changed my mind because the loop was too tight for long trains, and a very smart guy came over my place, and in 5 minutes figured out a superior solution. You should meet this guy. 

Anyway, I made a longer hairpin loop down that wall in the picture and am still testing longest reliable length of trains. Got a 5 car USAT streamliner running perfectly headed up by 2 E8's so it's getting there. 

Regards, Greg


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## NavyTech (Aug 2, 2008)

How do you figure out a 3% grade? Too clarify my question how many inches can I rise up in a 10 foot span?


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## Truthman (Dec 13, 2008)

A 3.6 inch rise is a 3 percent grade over ten feet. 10 feet x 12 inches = 120 inches x .03 = 3.6 inches. 3.6 inches is just about 3 inches and 19/32. 

nate


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## Dwight Ennis (Jan 2, 2008)

In addition to coupler problems and stresses, grades on curves, in practice, seem steeper than the same percentage grade on a straight due to increased friction on the outer wheels. I'm not sure what the compensation factor is (I'm not sure if there IS a calculated compensation factor), but a 3.6% grade on a curve is going to seem steeper to the equipment trying to climb it. The sharper the curve, the steeper it will seem. Greg's suggestion of doing a mock up is a good one.


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## Semper Vaporo (Jan 2, 2008)

I vaguely remember an HO setup that had two levels with a helix at each end to move trains from one level to the other.


They had to make one helix for UP only and the other for DOWN only. The DOWN helix had a positive elevation (super-elevation - tracks tipped toward the center, or inner rail slightly lower than the outer rail); But the UP helix had negative elevation (supra-elevation - tracks tipped outward, or the inner rail slightly higher than the outer rail). 

If the train stopped on either helix the cars would fall off due to the amount of super- or supra- elevation that was needed to keep the train on the tracks while underway.


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## Greg Elmassian (Jan 3, 2008)

When I mocked that helix up, I noticed some things I did not anticipate, the grade was so severe that the undersides of the heavyweights hit the rails at the top. 

Regards, Greg


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## Trains West (Oct 4, 2008)

greg it looks like the wall is about 2 ft tall or more ..... if so your helix should have one more loop around on the way down ........ also what dia is it ....... most of the time to go over the same track in a loop you need like 12 foot dia for about 10 inch clearence


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## Greg Elmassian (Jan 3, 2008)

21 inches high, diameter about 8 foot, slightly under by about 2 inches. 

The grade itself was not as rough as the grade transitions into and out of it, and the vector forces that would encourage stringlining on long trains. 

Regards, Greg


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## aceinspp (Jan 2, 2008)

Why one would put reverse elevation in a helix curve is beyond me. In the world of RR this is a no no. No wonder then had problems. Later RJD


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## Semper Vaporo (Jan 2, 2008)

When pulling the train UP the hill there is a pull to "string line" the train (pull it towards the middle. By supra-elevating the helix the stringlining is negated by the outward tip of the cars.


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## Guest (Jan 9, 2009)

years ago for my last layout i made a lot of trials. 

first point: make a transition on upper and lower end of grade. the length depends on the lengths of your longest cars/wagons. 
either by bending track up- or downwards, or by using a couple of short pieces of track. length of longest car/loco = length of transition. 
(if you go really steep, longer transition is needed) 

second point: by trial and error, i found a ratio, that R1 curves (2' radius/4' diameter) can be mastered by trains at two thirds of the elevation, than straights can (if all other factors are the same) 

third point: count the driven aixles of your locos. the bachmann 4-6-0 i got, is my weakest loco. it manages 12 aixles at 3% o straights. (mind: four aixles on the tender alone!) (light cars about two thirds of a pound per aixle) 
if you need a real "mountain goat", that is not a rack aided, use a LGB Stainz (old model). 
Stainz dragging 12 aixles - 5% 
Stainz dragging 12 aixles plus 1 pound of additional leadweight - 6% 
Stainz dragging 0 to 8 aixles - 7% 
Stainz dragging 0 to 8 aixles plus 1 pound of additional leadweight - 8% 
i found just one way to get to 9% of grade. sanding the rails sideways with coarse sandingpaper. but that helps just for three or four passings, then slip sets in again. - the trains just come back down... 

for my upcoming new layout i am planning 10 aixles and 5% elevation on straights with locos that have two driven aixles. (and not using the weak bachmann 4-6-0) 

steep grades seem to be no option, neither for long trains nor for modern trains with big cars.


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## Greg Elmassian (Jan 3, 2008)

I experimented, with a helix the size I am showing, super-elevation just lifts half the wheels off the rails. Just too tight, it's hard enough to transit from level to a 5% grade, you also would need to transition the superelevation too. 

Regards, Greg


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