The Story of the Helixes

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As this was going to be double track throughout, I would need two helixes, inside the mountains, one either side of the layout. This would give me the opportunity for a grand high level bridge from one peak to the other. The bridge I decided on was one that features on the BLS railway, although not actually over the stretch of track that I had originally intended modelling (one of those 'influences you might say).


The one thing I discovered straight away was that this project wasn't going to be inexpensive. To buy helixes 'off the shelf' would be costly, although the idea of building them from scratch filled me with dread. However, I concluded that it could be fun!! So I went ahead with a scratch build. In the design of these spirals you have to balance track radii as well as track length, and most important of all gradient. Most model locomotives will really struggle with gradients over 3%, but then you've got to consider what space you have again, and frankly how much of Mum's garage I could steal. I decided on the tightest radius possible and make it for downward  travel only (the inside spiral). This type of working, I decided, would help as the inside track gradient on my helixes was around 4%, really rather too steep for a heavy train of several coaches. The outer track of the spiral softened this gradient down to about 3.5%  as the track length is obviously longer. It didn't take a railway engineer to conclude trains would be better travelling up by the outer track. The actual height I needed to achieve from baseboard to Bietschal bridge was about 16 inches, not really scaled to the 400 metres that the real BLS prototypes achieve, but then I felt it was enough to give the idea!


Continental H0
On visits to railway society meets and so on, I had always been surprised at how large track curves/radii had to be, and in starting this project I soon realised just how many problems that one element was going to be. In the early trials of the helixes a number of long coaches that say they could manage a 358 mm radius without derailing... couldn't, and frankly it is something which really worries me about my layout, as inevitably I have had to rely on this type of curve. My good friend and railway advisor Gerald, has suggested looking at the carriage couplings, which I will do once I am nearer actually running some trains. H0 was the scale of choice, as the availability of rolling stock seemed really good. Now you know my naievity at this modelling business, so more about the problems with rolling stock later, suffice to say that, at times, I have had thoughts that N or even Z gauge would have been a better choice.


Whether I went about it the right way or not, the helixes seem to work OK. I used 6mm ply for the spirals supported off a 9mm ply base by threaded M6 rods with nuts. Don't tell me I didn't warn you! A bit of simple arithmetic set the heights at each rod, and hey presto hours and hours and hours later.. two helixes. Actually I've given them names... I know, this is where you start to question my sanity... but they are known as Felix 1 and Felix 2...maybe I shouldn't have told you that bit! They were the first bit of construction even ahead of the baseboard, and here too I've been making it up as I go along... Instead of a full baseboard I've arranged a series of legs that support 75mm x 25mm bearers set at 500mm intervals, and strengthened by that word! I thought this would help me get access to the underside of the hills and mountains, and also get into the middle of the helixes. As friend Gerald pointed out though, how was I to get to the back of the layout incase of problems on the bridge..Good point Gerald...I'm working on it.
So two helixes.. time to join them up!

Next - Joining up the Helixes

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