UPDATE SHEET 01 Understanding Track Engineering APRIL 2016 The following two sheets have been omitted from: This book is an essential introduction to the theory and practice of railway track engineering in the UK. ChapterIt gives the 9 reader Switches the historical perspective & of how Crossings railway track developed and new forms were designed following Section extensive9.2 researchCrossing and practical experience. Design & The book is aimed at people new to the rail industry and also a guide for the more experienced track engineers who need to Manufacturerefresh their knowledge. The PWI is the professional body in the UK and internationally that is solely dedicated to the advancement of the knowledge of railway infrastructure and promoting the sharing of best In the editionspractice worldwide.of: UPDATE SHEET 01 Understanding Track Engineering Understanding Track Engineering first published in 2014, including APRIL 2016 the e-book, reference PWI 20150414. These pages have been formatted to A5 and are to follow page 330. www.thepwi.org WWW.THEPWI.ORG PWI Knowledge Advice Support Education UPDATE SHEET 01 Understanding Track Engineering - APRIL 2016 Page 1 of 2 UPDATE SHEET 01 Understanding Track Engineering - APRIL 2016 Page 2 of 2 vertical S&C is the need to provide twist rails at each leg of the junction, normally one sleeper bed long. Some layouts occur so frequently that they have acquired their own names. Probably the commonest of these is the CROSSOVER, in which two turnouts are laid crossing Fig 9.3 (a) to crossing in adjoining tracks to enable trains to change tracks, as in Figure 9.3(a). Fig 9.3 (d) This is one of the commonest layouts and in former days it was often referred to as a “LEAD”. This name led to the use of the term “half lead” to describe a turnout. If two crossovers are laid across one another as in Figure 9.3(b), the layout becomes a Fig 9.3 (b) SCISSORS CROSSOVER. In this layout there are four turnouts and one diamond. Fig 9.3 (e) In a DOUBLE JUNCTION two tracks diverge from a double track through line, as in Figure 9.3(c). This layout consists of two turnouts and one diamond. An OUTSIDE SLIP consists of two turnouts and a diamond, arranged as in Figure 9.3(d) so that in addition to travelling along either of the two straight tracks, trains Fig 9.3 (c) Fig 9.3 (f) can transfer from one to the other. The addition of two more turnouts on the opposite side of the diamond makes it into a DOUBLE OUTSIDE SLIP. In such layouts the Figure 9.3 S&C Configurations commonly in use route from turnout to turnout is called a slip road or track. An INSIDE SLIP serves the same function as the preceding layout but the slip roads are contained within the diamond, thus saving space. The components of a single A crossing enables a wheel travelling along a given rail to pass through the rail of a inside slip, shown in Figure 9.3(e), are a diamond and two pairs of switches without track which crosses its path. Refer now to Figure 9.4(a). This shows two tracks crossings. The addition of two more pairs of switches makes it a double inside slip, crossing one another at right angles. In each of the four corners of this square is a sometimes called a compound or double compound. CROSSING. It will be seen that there are basically four identical L-shaped pieces and four identical short lengths of rail. The gaps between the short lengths of rail and The final example of a layout is the TANDEM, shown in Figure 9.3(f). Here, two the L-shaped pieces are necessary to allow the wheel flanges on one track to turnouts are laid one after the other in series. In the type of tandem shown, the toes of the switches are separated by a distance somewhat greater than the length of the switch rail from toe to heel. If the toes of the switches are placed as close together as possible the layout becomes a threethrow; this type of layout is restricted to sidings where space is very restricted, as gauge variations are unavoidable. Turnouts and diamonds are themselves composed of two elements: • Crossings • Switches This chapter will first describe the parts of crossings, how they are designed, and how they are made. Then turnouts and switches will be dealt with in the same way. The geometrical design of S&C work will be described, starting from the simplest form of turnout and working up towards the more complex layouts. 330a 330b.