The deep-level tubes

The Bakerloo, Central, Jubilee, Northern, Piccadilly, Victoria and Waterloo & City lines are deep-level tubes, with smaller trains that run in two circular tunnels with a diameter of about 11 feet 8 inches (3.56 m), lined with cast-iron or precast concrete rings, which were bored using a tunnelling shield. It is these that were the tube lines, although since the 1950s the term "tube" has come to be used to refer to the whole London Underground system. Many of the central London deep-tube line stations, such as the Central and Piccadilly lines, are higher than the running lines to assist deceleration when arriving and acceleration when departing.^] The deep-tube lines generally have the exclusive use of a pair of tracks, except for the Piccadilly line, which shares track with the District line between Acton Town and North Ealing and with the Metropolitan line between Rayners Lane and Uxbridge, and the Bakerloo line, which shares track with London Overground services north of Queen's Park.

C Stock,

The C Stock, consisting of C69 stock, it was a class of rolling stock used on London Underground's Circle, Hammersmith & City and District line between 28 September 1970 and 29 June 2014. The class was maintained at Hammersmith Depot. The fleet's lifespan was just under 44 years.

The C69 stock was constructed using the then-standard form of a load-bearing aluminum under frame with a non-load-bearing body of riveted panels on aluminum framing. The high-density nature of the Circle line service meant that loading times were important; consequently all cars were fitted with four double sets of air-operated sliding doors per side. Seating was mainly transverse, and total seating capacity was 32 per car. The 106 DM cars (Nos 5501-5606) were each coupled to one of 106 T (Nos 6501-6606) forming semi-permanent two-car units, with an automatic coupler at each end. Three such units were then marshalled as six-car trains for normal service. The DM cars were slightly longer to accommodate the drivers' cabs, the saloon dimensions in all other respects being the same

This is my second attempt at rolling stock and this is deficiently any improvement from my  first. However if you don't try you will  never improve.

I now taken the D stock back to the yard for a total rebuild and already I'm happy with the improvement I'm doing.