Progress Report 24 - The Copper Mine Loop

With sunshine forecast coinciding with a day's leave it was time for a little more civil engineering. To improve operational realism I had decided a loop was needed to enable trains from the copper mine to pass through Bulkeley station (see How the Line will be Developed and Planning an extra loop).

The site for the new loop

The route was first surveyed, using a couple of R3 points to decide the best places to link the loop into the existing track formation, then the trackbed was dug out.

From previous experience (see below) I made sure the underlying ground was firmed-up well before the breeze blocks were positioned and levelled. Actually there needed to be a gentle 1/60 gradient which was determined by making sure the bubble of the spirit level was just touching the mark at one end.

Digging out the trackbed foundations

After checking, and double-checking for 'level', the gaps between the blocks were filled with a 4:1 (sand:cement) mix of concrete using my usual 'manual' method (see Peckforton Station comes to Life).

The blocks in place before concreting

Normally I would leave the concrete several days to harden but the forecast for the next few days was bad and my leave was of finite duration, so after a couple of hours I laid the track. This was fixed to the blocks using a hammer-drill, rawlplugs and screws. I was using-up odd pieces of track I've accumulated and so you may notice that this loop includes one 2m length of brass Tenmille track, one 2m length of brass Aristocraft track and two 60 cm lengths of LGB stainless steel track. I've not used the latter before and so will be interested to see how it fares and whether it will take solder (I suspect not!). Note: I use LGB track joiners (fishplates) throughout, finding they join the different types of track together with no problem (see Peckforton Station comes to Life)

The new loop

When the weather improves (it's pouring down today), I will bond the rail joints with solder and wire jumpers. After a suitable period of testing, it will be properly landscaped and ballasted. The points will be controlled remotely using a point decoder. Incidentally, the kink in the track in the cutting is deliberate. Apart from finding the alignment of the mainline was improved if I repositioned the leading point, I though the kink gave the loop a more 'industrial' look. I'll see how it works out in practice.

Dealing with sunken blocks
In my rush to lay the first lengths of track back ion 2005, I did not spend enough time firming-up the ground underlying some of the breeze block trackbed. As a consequence a small number of blocks (around eight in total) have sunk. In a couple of cases, this has been by less than a centimetre but I found there was one stretch where three blocks had subsided by around 2.5 cm. This was particularly significant as these blocks were in the middle of a gradient, so rather than there being a uniform 1:40 slope, there was a slip dip, followed by a short 1:20 rise.

Rather than removing the blocks, firming-up the ground and replacing them, I decided to adopt a different approach. In the past, where I have relaid the blocks, the ground subsided again and so I had to repeat the process. This time, I left the blocks where they were and raised the track above them until it was in the correct line.

This entailed removing the original screws and replacing them with longer (2") ones. This approach allowed me to adjust the height of the track quite precisely.

Once I was happy with the alignment, I packed wet concrete (a 1:4 cement:sand mix) into the gap between the track and the blocks with my usual rubber-glove protected fingers approach, finishing off with a 1.5" paintbrush. A mixture of small stones and sand was sprinkled over the wet cement and the whole lot left to harden off.

The new 'raised' track, loose ballasted

I've now used this approach on two other sections and so far, am very happy with the outcome. I will let you know how it works-out.