The helixes (climbing spirals)

(Starting construction: October '01)

An article on this subject is published in Modelspoormagazine 59.
A cut-down version can be seen below.

In total I have three helixes on my layout:

A first helix is situated under the fiddle-yard and the left hand side entrance of freight station "Duvelle". It connects to this station on one side, to the other side it connects to the hidden track triangle. Using two levels, it gains a height difference of 7 inches. It was finished in November '01. Part of it can be seen on the picture below-left.

The second spiral is a lot larger: 4 levels make a difference of 11 inches. This spiral is situated on the central peninsula, under the castle on the hill, and connects the lower left entrance of "Boulroie" to its upper left one (the 'dam'-bridge). On the upper right picture you can see the nearly finished helix. It was finished in December '01.

The third helix sits under the city part of the layout, on the far right hand side of the layout. It connects the main staging yards to the upper part of "Boulroie". The height difference is 14 inch, making it the largest climbing spiral on the layout. The lower layer was built in March '02, the upper layers in February '03. The pictures below show the helix during construction.


Helix construction:

This subject was published - more thoroughly - in Modelspoormagazine 59.

Hardly known with the real railroads, but quite commen in model railroading, a climbing helix is used to taccle height differences towards a higher track or towards a sub-level fiddleyard. Designing and building one isn't obvious

One of the main design-fase issues is maximum slope a train can handle. This climbing percentage depends on train length, hauling power and the presence of (tight) curves in the layout. Generally, on an (almost) staright track a model enigine can pull a long haul about 2,5%. When dealing with curves this slope is reduced to 2cm per meter.
Each non-level crossing needs a minimum height difference. When we take subroad material into account, this should be 10cm in H0, as we want to be able to handle trains "in distress" in the helix. This means we need at least a 4 meter length to climb one helix level. The radius of a spiral is therefore in H0-scale at least 65cm.
Most helixes have more than one track, typically one climbing and one descending. Always try to plan the climbing track at the outside, as this is always a bit wider.
One should always be able to reach the tracks. therefore, the helix should be accesable from below towards the inside of it. Supports of the helix should tehrefore be placed only at the outside of the roadbed, allowing us to handle trains or tracks if necessary. These supports of course shouldn't interfere with the traffic.
Catenaries are planned in the helix, too, be it merely to protect pantographs from being damaged by the subroadbed structure. These catenaries don't have to look "nice" however. Some pieces of brass wire will do fine.

Choosing the right subroadbed materials is a balance between weight, flexibility, solidness, construction ease and costs. My choice is described here.
Another thing: this article is illustrated with virtual-reality rendered pictures, as my helixes were arlready built before writing this, and I hardly took any construction-illustrating photo's during build-up.

An open-frame support is an obvious choice for this type of construction. Corner supports are added to a solid, perfectly horizontal 130 x 130 cm frame. On these wooden basis, 10cm wide supports are mounted at the correct height.
De helix curves consist of several uniformly shaped pieces. We draw a cardboard mould, wich we use to draw the shapes to a wooden panel. This way, hardly any material is lost when jig-sawing our plywood.

The upper wooden parts get 8 drilled holes near the corners of each half. Four small wood screws connect each piece to one below while the glue sets. Build three quarters of a circle at once.
Further wood construction is paused now, as we now are still able to mount our rails and subroadbed without being bothered with a higher helix level. A 4mm layer of cork is glued, as are our first pieces of flextrack. It's a good idea to solder the electrical connections at this time.

We use large bolts, rods actually, to support the upper helix decks. Using nuts and washers, these are mounted in O-shaped wood screws. To prevent any bending of the lower helix part, place these wood screws were the wooden supports are located.
Using other nuts and woodscrews, the pre-mounted higher helix level can now be placed. the exact height can be trimmed by fine-tuning the position of the nuts.

To place the catenaries at the exact position, we drill pairs of holes along the track center lines, about 20cm apart. A 25cm long brass wire is bend to shape and pulled through these holes. This way we construct a continuous, well-aligned catenary.
At the helix start point, we need a porch to support the catenary. This is made from the same steel rod as used to support the upper deck levels. Using nuts and washers, their height can be adjusted. Make a smooth entry point, so pantographs can lower themselves easily.

After placing the catenaries, the higher helix level can get its cork subroadbed and wired flextrack. Look at the pictures to see the catenary and bolts constrcution. Continue the next levels the same way.

That's it! This example shows a three-level helix, climbing 30cm (one foot) up. Of course you can make yoorself even larger ones using the same method.

©2007 Gerolf Peeters - updated 05.05.2007 See: Frame - Track support - Plans