The Big Helix: Designing a Helix (252)

Building a helix is a complex procedure that requires some fairly complex planning up front so as to avoid mistakes along the way. In this video we'll start by making some critical measurements and then use them to calculate the sizes of our loops, length of the helix, amount of track required, the slope of the loops, and the angle of the roadbed. Once we have all that figured out we'll be ready to move on in subsequent videos to build a stable base for the helix, install the loops, lay some track and get'er done!

[corker]

I wish my some of my math teachers explained geometry, trig, etc., as easy as you do. I actually understand it!

[peterjhillier]

Thanks Larry, what an excellent Video working from first Principles, you make it so easy to follow. Best wishes.

[bernardc]

Grateful for the educational tips & tricks, Larry

[rjl]

thank you for the great full detailed video

[jhoodfysh]

That was a great video Larry. I am looking forward to watching the series.

[mikejames]

Hello Larry
Great video as usual.
Most helix designs all seem to be circles, but don't forget the good old oval. This gives the potential of greater travel distance between curves, allowing more distance to rise, also helps reduce train drag, it may allow you to reduce the helix diameter if that's a construction issue, but of course you cant go to tight, certainly should be same as or larger than the tightest bend your train types/lengths can handle without derailing.

Just thought this would be a good idea for those of us with a tighter area.

I based mine around the calculations shown woodland scenic's slope = 4" rise requires 16ft distance to give a 2% slope ( I used just the calculation not the polystyrene product on my helix)

Mike

[jimsmoter]

Great video. Who would have thought math would come in handy in building a helix for a layout? looking forward to the helix build.

[andrewstevenson]

Great video, Larry. I think I must have been doodling impossible trackplans or just plain asleep in school for the maths lesson when we did negative tans! I am a fan of using set track on helixes to eliminate any tracklaying issues.
After building helixes using timber supports, I've sworn that if I build another I'll go with a method I've seen in German railway modelling magazines, which uses threaded steel rods, and then you use nuts to support the trackbed, and of course you can adjust the nuts minutely to get get the gradient absolutely perfect.

[thomasgrassi]

Larry Great info. I have a heix on my Layout and presently adding a third level which mean I need to extend my helix. I bought my helix kit from TrackSideScenery The product is very light and easy to work with Looking forward to seeing the progress on your helix.

[dundasjunctionmodelr.r-jam]

Larry looks very interesting. I have not used trig since high school, plan to build a similar helix and staging yard on my new helix. Next week more progress

[dkaustin]

That was interesting. I tried the app on my iPhone previously and found supporting the phone to be a pain to deal with while making adjustments. So, I bought a digital torpedo level from Amazon that is 6 inches long and will fit between the levels of a helix and not fall over as it has a base a little wider than the HO track. I have seen 10” torpedo levels too. It works a lot better. You mentioned building the helix out from the corner and later moving it into place. If the floor is level under there, have you considered building a base on lockable casters? Build it so you can roll it out for maintenance, removing derailments, etc. Then roll it back in, lock down the casters, insert two pieces of rerailer tracks to join it to the levels. Helixes do eat up a lot of track. Imagine if you were building it double tracked? You might see if Tracksetta has a curved gauge to fit your needs and get one to help lay out the curved flex track. Joey at Trackside Scenery has a helix kit cut to your requirements using I think Gator Board. You should take a look at it before you start cutting up sheets of plywood. It is all black in color. Just another option. Don’t you have Avnet articulated steam engine? A Y6B? Will that be okay on your helix design?

[j.mcq.]

I was going to say I get a different answer for the inverse tan of 0.0186 but I realized I had my calculator set for rads, not degrees!

[randygates]

I’ve built two helix’s (helii?). On the first one I used flex track. Soldering all those joints around curves was a major headache. On the second one I used curved track soldered together (Kato). It went together so much better. Mine are both double track which makes it more difficult. I’m anxious to see yours come together!

[marioangols]

Hi Larry, very nice video.
I want to add my sand grain, for the construction of the helix you will use plywood 12mm that it's ok, when you cut the helix from the plywood sheet there are a few different approaches, I saw a video where they use the octagonal principle for the helix base, this makes the cuts to be straight, easier to cut, joint the segments and less waste. each segment of the octagon is a trapeze that overlaps with the next section. I used to make a small helix and work very well. The circle is into the octagon.

[FunWithHOScaleStuff]

Curious thing, I was just reading that exact same book. I'm also rereading the "Realistic Operation For All Scales, How to Operate our model railroad" by Bruce Chubb.

[mapruitt]

Interesting video, Larry. Pretty good explanation of the grades and their calculations, with one glaring omission - you didn't talk at all about compensated grades. Your grade may be 1.86 percent, but with compensation for the grade on the curve, you're actually closer to an effective grade of 2.79%, using the LDSIG-modified John Allen formula of CG = G + 28 / R, where CG is Compensated Grade, G is actual grade, and R is the curve radius.
The load a loco may be able to pull might be rather disappointing if compensated grade isn't taken into account.

[Mr._Darby]

You lost me at the first mathematic equation! I will still be following along with you.

[kennethoriel]

Really great explanation of how to figure the loops. However, I might suggest that when determining the distance between levels one should first determine how high the highest piece of rolling stock running on it will be. Then allow some extra "headroom" above that. Next, and this is a little different from what you said, take the thickness of the plywood or what ever you are using to support the track, PLUS any cork roadbed AND the thickness of the track itself. I think this will help avoid getting the levels too close together.

[crashj]

The inverse function(-1) can be read as "the angle whose tangent is . . . " and of course it also works for other functions as well.

[fredlotte]

Larry, instead of struggling to measure the angle, just measure the height between layers. It's much easier to measure it accurately just as you measured the total required rise. You can use math or a simple graphical method to figure the height of the bottom layer above the (presumed level) foundation bench work. Once you complete the first turn, make each additional layer the constant separation height above the one below it.

Have you considered the reduction in headroom at roadbed splices? If you follow the normal splice practice your headroom will be 2.5" at the splice plus there will be a nasty edge to dig into the back of your hands when you do track maintenance.

Linn Wescott suggested an overlapping type roadbed construction in Ch 7 of his book _How to Build Model Railroad Benchwork_ probably available at Kalmback.

A friend of mine is building a 3 track helix that I designed using that method. Tracks are 34, 36.5 and 39" radius with a total rise of about 21". It connects 4 different layers of his RR. We are using curved segments cut from 3/8" plywood and overlapped like bricks to form a continuous 0.75" thick roadbed about 4.75 turns long. It has 4.5" rail to rail separation or about 3.75" (minus track height) between layers. We are using threaded rods with nuts & washers to support the layers which makes for easy adjustment of height.