# HO Helix



## 05Slowbalt (Dec 19, 2011)

So I need some help here. I don't expect anyone to answer it for me but if you would like to explain how to come up with the answer that would be great lol. 

Here is the brake down:

In the picture the two circles are the helix I would like to make under the table to run two tracks the whole table but under to a staging area. Now I want to drop down about 8 inches. So how big and how many inches apart or what I am trying to guess is how do I build the helix. I know how to make it just don't know how to get the right grade and everything so it works. I hope you guys understand my question. I know what I am trying to ask but I keep confusing myself lol. Oh the curves will be either 56" to 60" for a half circle.


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## tjcruiser (Jan 10, 2010)

56 to 60" _diameter_ ??? Seems big. Or do you mean 56 to 60 half-circumference, for the half circle?

Assuming the latter ...

Circumf. of a circle is pi x Diam (pi = 3.14). Your full circle is, say, 116" circumf, so diam = 36" ... 18" radius. Typical, so that seems ok.

Now, what elevation rise do you need per loop, to provide adequate clearance for the loop below? I'm gonna speculate 3.5". So, now look at grade ... 3.5" rise / 116" circumf = a grade of 3.0% ... doable, I think.

For a 8" rise, you need a little over 2 full loops ... so if you enter down below running West (for example), you'll rise through about 2-1/4 loops, exitting at the top going North (assuming a clockwise loop direction).

Does that help?

TJ


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## 05Slowbalt (Dec 19, 2011)

Yea it helps. My half circle comes to 60" or 30" for 1/4 of the curve. So my total circle would be 5 feet by 5 feet (right?). Now what you did it made the grade a 3.5%. I want to run trains about 15 to 20 cars. Is that to much of a grade to run trains on.


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## tjcruiser (Jan 10, 2010)

5 x 5 ?

You're not being clear ... if you have 60" circumf of the half-circle (or 120" circumf of the full circle), then your track diameter is about 38" ... that's just over a 3' x 3' footpring ... NOT 5' x 5'.

I said 3% grade and a 3.5" rise per loop. Don't confuse the two.

3% is common, but the question of optimal grade is never easily answered. Train pulling power / traction will be limited, especially with the continuous turns (more friction, more slippage).

How strong of a puller is your loco? If I were you, I'd build some temporary functional mockups and test things out, before you commit to the full , detailed construction.

TJ


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## 05Slowbalt (Dec 19, 2011)

Sorry you did say 3%. Now I put in one more picture because I am having a hard time explaining the 5'X5' thing. Thanks so far TJ for your help. Thats why I joined this forum.


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## broox (Apr 13, 2012)

At a quick back of the napkin calc that makes about a 22-24" radius (24 would be better if possible)

It might be a bit tight to rise 3.5" in a loop with a reasonable grade. (again this is all in my head, not real maths)

one thing you can do to make the grade a bit more betterer, would be to add a couple of straights in to make it more of an oval instead of a circle helix. every inch makes a difference! (thats what she said, huh )


I'll think about it a bit more and might post again when I get home tonight.


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## broox (Apr 13, 2012)

So, do I see right, you want 2 helixes?


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## 05Slowbalt (Dec 19, 2011)

broox said:


> So, do I see right, you want 2 helixes?


Yes you will enter the staging yard under the main table on one side of the table. Then travel the whole table under the main layout to come back out the other side.


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## hoscale37 (Nov 20, 2011)

Building two helix is going to be a lot of work. Just throwing this out there- why not just build one helix so that you can reverse the trains and use it to go up and down from the bottom lower staging yard to the upper part of the layout? 

Just looking at it from a cost perspective- it may be less expensive to start off with one helix and on the lower staging area have a 3 way Wye or a switching area that allows you loop around the yard- Meaning that you could have a train enter from the above layout, go down the helix to the staging area- then in your staging area a second train would be put together and would exit on the opposite side of your staging area to make it's way back up the Helix and back onto the upper part of your layout.


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## tjcruiser (Jan 10, 2010)

OK ... so you're talking 60" DIAMETER ... distance across the circle. The radius, of course, is simply half that ... 30". Will you be using flex track for that???

Now, let's rerun the math. (My earlier assumptions were for 60" half circumference.)

Distance (or circumf.) around a full 360-deg loop = pi x diameter = 3.14 x 60 = 188".

If we still need to rise 3.5" per loop (for overhead clearance), our grade is 3.5 / 188 = 1.8% ... very moderate, by nearly any standard. Even if your rise per loop were bumped up to 4" (with two full loops to get your target 8" rise), the grade would be 4 / 188 = 2.1% ... not steep at all.

TJ


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## joed2323 (Oct 17, 2010)

If i was you i would look over scotts build thread, it shows he he built his helix.
Each loop rises 4 inches by using a 1x4 for the spacing of each revolution.

http://www.modeltrainforum.com/showthread.php?t=8241&highlight=helix

Scotts the man with helix questions, hopefully he will join this conversation soon

The idea of building a helix, is a easy one, when a person can basically double the mainline run by having another level above or below or even both on there existing layout


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## sawgunner (Mar 3, 2012)

hey TJ want to come visit me for a weekend and build 2 helixes? LOL


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## NIMT (Jan 6, 2011)

When figuring in the height you also have to figure in the base material too.
3 1/2 clearance requirement, and 1/2 for the 1/2 plywood base and if you want to get nitpicky you will need to figure in the cork and ties and rails to get a completely accurate and workable grade.


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## sstlaure (Oct 12, 2010)

I've got lots of pics of my helix build in my build thread. Page 4 is the start of the helix coming out of staging.

Use a 1x4 on it's dimensional side and that sets the perfect height for clearance of the tallest cars + track and cork roadbed. If you're going 30" radius you'll be golden. Mine is around 27" and works just fine. Single engine can pull a full train with 24 Walthers goldline Ore cars no problem.

I cut my wood sub-roadbed about 6" wide and used 1/2" thick plyboard.

I can send or post other pics if there is something specific you'd like to see.


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## 05Slowbalt (Dec 19, 2011)

Thanks everyone for the advice! And thanks TJ its like math class all over lol. And yes I want to do 2 helix. I am on a budget but I want it built right and how I would like it the first go around. And sstaure I will be for sure checking out your build! Thanks guys.


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## norgale (Apr 4, 2011)

I'd say three loops with three inches between the loops and that includes the cork roadbed. Make it any diameter you want but the larger the diameter the lower the grade % will be. 3% is pretty steep for a helix. IMHO! Pete
OOPS! Forgot about double stacks and triple car carriers. Guess you will need more than three inches clearance. Pete


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## 05Slowbalt (Dec 19, 2011)

*Helix Frame*

So I started to build my new layout bench work. This is the two 5' by 5' squards that will have the helix under the table to go to the lower staging yard. I just thought I would share.


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## tjcruiser (Jan 10, 2010)

Looks like things are looking up ... literally!

TJ


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## sstlaure (Oct 12, 2010)

An 8" drop would be (2) complete 360 degree loops with a 4" total drop/level (3.5" clearance + 1/2" plyboard) See how I inserted the 1x4 inside the loop to support the sub-roadbed of the level above without needing any extra head space..


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## norgale (Apr 4, 2011)

That's really nice SST. Looking for what comes next. pete


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## sstlaure (Oct 12, 2010)

When bow season is over I'll probably get back to work on it. Spending a ton of time in the woods trying to trick a deer onto my dinner plate and it's not working so far.....


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## 05Slowbalt (Dec 19, 2011)

sstlaure said:


> When bow season is over I'll probably get back to work on it. Spending a ton of time in the woods trying to trick a deer onto my dinner plate and it's not working so far.....


To bad your so far away. For the help I would trade off that you could hunt on my land. I do not hunt but all my friends and father inlaw dose and they all got both a Doe and Buck! Thanks for the pictures I can use them as reference.


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## sstlaure (Oct 12, 2010)

I've got plenty of deer on my property, just none that will cooperate and walk through my shooting lane. I'm seeing 4-8 every day. It's just a matter of time though before the stars line up. Not sure what a non-resident tag in NY costs, but deer tags here in MI are only $15 for residents, so it's cheap entertainment and I hunt right on my own land so I can go from freezing my butt off hunting outside to inside having a warm shower and a meal in 5 minutes flat..


Seriously - building a helix isn't that tough to do if you plan it out. Give me a jingle if you have any questions or want some more detailed pics. My helix is contained inside the benchwork (under mountains, etc) but I can still access the inside of it to get any detail pics you may need for reference.


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