Shed loop and tunnel

After a break in construction of 3 years, I decided to add a balloon loop at the engine shed end of the line. The existing line was out and back via a loop which meant that every alternate run was driven backwards with the loco pushing the wagons. As more and more children were using the line, running backwards was becoming increasingly unsafe, so the addition of a second loop would provide a continuous run. The return semicircle of track is exactly half the radius (3.18m) of the previous curves, with each panel being 45°. I built a wooden template for these in the same way as the previous ones to ensure very precise curves. I had obtained a large quantity of second hand track for the extension. The sleepers were carefully removed, and the rail bent with a rail bender to either straights or curves for the track panels.
I also obtained a point with the secondhand track. I completely rebuilt this as a 6.37m radius point for the junction off the loop to the turntable and engine shed. Since this would be kept set to the loop except when getting out or putting away the rolling stop, I fitted a brass bolt to lock the tie bar into either position. This is just visible in the picture.
I had to remove around 3m of concrete edging slabs which marked the path border so that the rail could cross from the path to the narrow passageway behind the shed. The slabs were extremely well concreted in place, and it took a good morning's work with a 7lb sledgehammer to remove these!
After clearing the area between the shed and fence, I compacted the earth and covered this with terram to prevent the weeds coming through. I then spread 10mm limestone ballast on top of this.
I surveyed the ground using the technique described on the balloon loop extension and ground surveying page and found I could get an acceptable gradient of 1 in 60 from the point up to the shed. I laid the track on the grass and marked out the trackbed to be dug out with white paint.
I dug out the turf and fitted the concrete edging. The trench was lined with terram and filled with the 10mm ballast as described on the ground preparation and tracklaying page.
I constucted a new 6.37m radius point. This was where the track divided to loop behind the shed.
I decided that I wanted the trains to run anticlockwise around the shed loop only. This was because with the very limited visibility I didn't want two trains to try to go round either way with children on and crash! The point lever from Ride on Railways was ideal for this as a locking pin can be fitted to ensure that the point can only be set one way. When the train passes through on the way back it pushes the rails, but these return to the set position when it has passed.
I ran a number of fully loaded trains to help pack the ballast. The 10mm ballast seems to give a much better foundation for the aluminium sleepers than the 17mm stone I used previously, and in due course as further settling occurs, I will top the old ballast on the original line with this.
The completed loop has really made the railway so much more fun to operate. No longer do alternate runs have to be done backwards, and it is now very easy to have two or three trains running at the same time. In due course I plan to put tunnel mouths at either end of the passageway behind the shed.
The extension was finally completed and opened by my son on his fourth birthday, 6th June 2006.