Building a Helix - Part 2 A few lessons learnt - Updated

Well, it wasn't quite a 'golden spike moment' or the completion of the transcontinental railway or Adelaide to Darwin link but last week, I finished the helix linking the lower and upper levels of Philip Creek. To mark the occasion, 4856, the oldest locomotive on the roster, collected a few wagons from the upper level and moved them to the lower level.

The concept of using an octagon shape to support the helix worked. I found it easy to cut and shape 540 x 125mm rectangles. Sure, the mitre saw got a serious workout but it was better than cutting circular strips. Originally, I intended to use 100mm wide strips but I found it needed to be wider at the octagon nodes. I wasn't too worried about getting the octagon geometry exactly correct. It was more important to get the circle within it laid out in preparation of the track laying. 

I did spend a fair bit of time getting the grade correct using a combination of spacers and a modified spirit level. This was all part of the build, check and test approach I used throughout the construction process.

I had to revise my exit arrangements from the spiral to the upper level of the layout. I had made a slight error in the measurement of the height difference between the upper and lower levels to the extent that the exit level had to be reduced from 5.3 turns to 5.1. The mis-close became obvious as I was setting out the fifth level and so the actual spiral finished around the 4.7 point and the remaining height is gained in the climb between the exit and the destination, the coal mine module. The photo to the right gives a birds eye view of the exit. The turnout will be the start of the Kingston Plains branch line.

As I was setting the height of each node, nuts were only finger tightened. I thought this would be sufficient but over the past few weeks, I have noticed some nuts required further tightening. I may have to revisit the whole structure with a spanner. 

Because of the long run of track in the helix (about 21m), I provided an electrical feed to each level of the spiral.

I used Peco track in the spiral and this track now includes provision for pinning on one side only. It's probably in literature somewhere suggesting that track should be pinned on the inside rather than outside of a curve. But I missed it and for ease of access, I pinned the outside of the curve. However, after a few days, the inner side of the track began to lift. I was able to correct this with staples pushed over the sleepers on the inside of the curve. See photos opposite.

Update

I had included a short Peco point (turnout) with a nominal radius of 650mm to provide access to the Mount Windeatt branch line. I hadn't noted any problems with the slight difference in radius between the helix (610mm) and the point when initially installed but over the past few weeks problems started to emerge particularly for the four driving axle steam locomotives. Maybe it was the changing climate or perhaps bumping the area during the adjoining bridge constructions, I just don't know. To overcome this, I increased the radius of the lower loop slightly where it joins the point and gradually transitioned this back to the nominal  radius over about half a lap of the helix. It was a bit of a pain to work on the lowest level of the helix with the upper levels in place, particularly having to insert a short additional length of track to facilitate the increase in radius. For me, the lesson is to keep points out of the helix.

And so the helix is now operational and the sequence below shows 4856's descent through the helix and exit onto the Yellow Rock module.

 

 

 

With the two levels of the layout now joined, attention has turned to the construction of the upper level staging area which represents Muswellbrook, Werris Creek and locations further north. With the helix  in place, I can also look forward to connecting the two branch lines, Mount Windeatt and Kingston Plains. These links will have to involve the creation of two lift up bridges, another challenging task. But it will give me the opportunity to run a few trains to actual destinations while I complete the rebuild of the Philip's Creek township.