Large Scale Central

A different type of helix

I am thinking of building a helix to make the indoor part my new layout double level and am wondering if the diameters of each level of the helix have to be the same or could I tighten the radii of each level eg start out at 900mm (approx. 3ft) radius and finish with 750mm (approx. 2.5ft) at the top.
The idea is to make scenery of a train climbing the side of mountain (1:20.3 Shay and Connie mostly) which has a slope. It will then run across the back of the shed and down on similar helix on the other side.  For the run across the back I want to do scenery between the two levels and really want to have some depth perspective.
Thoughts and suggestions most welcome.

it is probable, that you even have to work with different radii.

depending on your chosen size/scale, you need to have 220 to 260mm height between above rail to any structure above.

if you go with a 4% grade (40mm per meter, even for Stainzes with few cars near the maximum on R1 curves) you gain about 12mm height per 300mm/1’ piece of curved track.

as 12 pieces of this track are a circle, you have to take 12mm height times 12 pieces of track. so, the full circle gave you 144mm height… about half of what you need for a helix, where allcircles have the same radius.

but a mining loco with flatcars might fit in…

on my layout i have two 11 meter(sic!) long 6% grades, plus graded curves at each end to gain the 700mm difference between the two levels.

edit: at re reading i noted, you have a connie…

the big hauler from a starterpack, that i got, is extinct, since i expected it to tow it’s own tender up the 6% grade.

The area I am trying to do this in is 4.5M Wide x 6M Long and about 2M high.

I am looking at a long run across the 6M length with 2 helixes in the 4.5M width.

I have a suggestion of adding straight lengths to take the level up sort of an oval shape.

Again all thoughts welcome.

The whole plan is that the lower level will have a very large shunting yard plus a single track running through a town scene which will be in the back corners.

I’ll see if I can draw it out.

Do you actually have to get up and over the lower track or could you have it just raised and set back? A full 360+ degree spiral may not be needed

With my old layout (alas no pics) I played around with something similar to what you are describing: a double oval of mostly R2 curves and a few straights that climbed 19 inches with a 4% grade (my inspiration came from ‘The Polar Express.’ The table for that section was 6 by 8 feet (give or take a couple inches)

Issues were -

the transition grades at the top and bottom of the slope (I never was fully satisfied with the top transition). It takes a good six feet or so to go from ‘flat’ to ‘4%’ You have to start with a gentler slope and work your way up to it. Same for the top, to avoid a ‘ski-jump’ type effect.

‘Reach.’ As the table was set against a wall - though thankfully not in a corner - accessing the wall side was a pain.

Obscure track. The upper loop crossed the lower loop in a couple places. What with the back wall, this forced putting about half the ‘Climb’ inside tunnels or otherwise out of sight. This did not become apparent until I began construction. Likewise, clearances both vertical and horizontal were tight. Pretty much mere inches side to side (hence the tunnels in places) and maybe half an inch vertical on the one crossover.

I did run most of my loco’s up (and down) the helix, though my roster was (and is) unimpressive.

The Bachmann Annie (4-6-0) did best: it could make it to the top towing three cars plus the tender easy. Four cars was a bit iffy, wheels sometimes slid a bit near the top.

The Lionel 0-4-0 could pull three cars; four if the last one was smallish.

Hartland Mack could manage maybe two cars. Then again, four cars on a flat surface was pretty much its limit.

Weirdly, what I think of as the ‘Christmas Locomotive’ (0-6-0 that came from a Lionel ? Holidaze set I picked up dirt cheap on EBAY) could also manage three cars.

I abandoned the helix because of the above issues with the revamped layout. Instead, I have long straight climbs and a couple curves. Grade on the new version is about 3.8%.

Graeme Price said:

The area I am trying to do this in is 4.5M Wide x 6M Long and about 2M high.

I am looking at a long run across the 6M length with 2 helixes in the 4.5M width.

it all depends, what you want.

if the lower deck shall be just a storage, two full circles give the necessary height. if both decks shall be “playable” and visible, you need four full circles to gain height.

that would mean a 105cm radius for the lowest circle on each helix. are you prepared to have two mountains of four square meters each on your layout?

lengthwise you could squeeze a passing siding between the mountains. that would be just long enough for a loco and two one-foot-cars (if you use short turnouts)

why don’t you make a provisional structure for a helix, to try it out?

Korm Kormsen said:

Graeme Price said:

The area I am trying to do this in is 4.5M Wide x 6M Long and about 2M high.

I am looking at a long run across the 6M length with 2 helixes in the 4.5M width.

it all depends, what you want.

if the lower deck shall be just a storage, two full circles give the necessary height. if both decks shall be “playable” and visible, you need four full circles to gain height.

that would mean a 105cm radius for the lowest circle on each helix. are you prepared to have two mountains of four square meters each on your layout?

lengthwise you could squeeze a passing siding between the mountains. that would be just long enough for a loco and two one-foot-cars (if you use short turnouts)

why don’t you make a provisional structure for a helix, to try it out?

The lower part in the main will be for parking trains with a scenery backdrop just to add interest. I really would like to run a line right round the shed so that I can run in wet weather, my problem is that I need to get into the middle of the layout and don’t really want to duck under, I suppose I could use a lift up part but would prefer not to.

I am now thinking of maybe spiral loop instead of a helix with the rise staring part way down the a side and rising over the track around the same point then running across the length and repeating it on the other side.

I suppose I can run across both length sides to get extra room, now that is a thought worth pursuing.

Thanks for the suggestions.

Graeme Price said:

The area I am trying to do this in is 4.5M Wide x 6M Long and about 2M high.

I am looking at a long run across the 6M length with 2 helixes in the 4.5M width.

I have a suggestion of adding straight lengths to take the level up sort of an oval shape.

Again all thoughts welcome.

The whole plan is that the lower level will have a very large shunting yard plus a single track running through a town scene which will be in the back corners.

I’ll see if I can draw it out.

Graeme Price said:

The area I am trying to do this in is 4.5M Wide x 6M Long and about 2M high.

I am looking at a long run across the 6M length with 2 helixes in the 4.5M width.

I have a suggestion of adding straight lengths to take the level up sort of an oval shape.

Again all thoughts welcome.

The whole plan is that the lower level will have a very large shunting yard plus a single track running through a town scene which will be in the back corners.

I’ll see if I can draw it out.

This is a sketch of what I am thinking.