3 Point Wiring - Gauge 0 Guild

1 Part 8 Section 3. ELECTRICAL. Issue Date September 1993. 3 point wiring operating at a time. A single power supply connec- tion to the layout ensures that all the track is Two Rail Turnouts energised, which is fine if the layout design is sim- ple. However, to ensure good electrical contact Commercial turnouts are wired in one of two ways, between the locomotive and the rail it is preferable through wired or self isolating. Through wired to use live crossings but this requires the crossing turnouts, like the Lima version shown in Figure 3- polarity to change when the Point changes. 1a, are generally associated with commercial set- Figures 3-1b and 3-1c show two alternative meth- track used for small layouts having one locomotive ods adopted by commercial track builders.

2 Note: The dotted lines in the following drawings show the location of the gaps required if copperclad sleepers are used. F Dead frog unit in plastic F. R. Bonding wires taken R around frog a) Set-track points , rails permanently energised. (Lima etc.). R F. F Narrow insulation Gaps in copperclad gap sleepers F. R. R Blade contact provides current path Polarity determined by blade position b) Self isolating Point with live frog using blade contact. (Marcway etc.). R R. F Tie-bar Closure rail linked switch to adjacent stock rail F. Isolating gap in Insulated closure rails sleepers R. R. Polarity determined by tie-bar switch position c) Self isolating Point with live frog using tiebar switch.

3 (Peco). R R. FIGURE 3-1. Commercial Point construction methods. Compiled by K. Sheale. Photo T. Hughes 8-3-1. There are advantages and disadvantages with each ties as the Point movement may appear to be satis- method, for example the blade contact method (Fig- factory, and rolling stock pushed through it moves ure 3-1b) does not require any moving parts, apart freely, while a locomotive comes to a dead stop. A. from the Point blades themselves that is, whereas further problem that can occur with blade contact the tiebar switch (Figure 3-1c) gradually suffers type points , especially if the clearances are tight, is from wear and erratic contact.

4 On the other hand, arcing between the open blade and the back of the with the blade contact type a small piece of ballast wheel running on the adjacent rail. or a film of corrosion on the blade can prevent good When using hand built points , energising the electrical contact. This can sometimes cause difficul- crossing through a change-over switch is to be pre- Note: The dotted lines in the following drawings show the location of the gaps required if copperclad sleepers are used. F. R. Tie-bar operated micro-switch FIGURE 3-2. Basic self-isolating 2-rail Point . F. P1 P2 X2. X1. R. Tie-bar operated Gaps in copperclad micro-switches sleepers FIGURE 3-3.

5 Standard three way 2-rail Point . 8-3-2. Part 8 Section 3. ELECTRICAL. Issue Date September 1993. ferred to ensure positive electrical contact. Figures The only three rail turnouts produced commer- 3-2 and 3-3 show the rail breaks and switch Wiring cially are those specially prepared for tinplate collec- for a simple turnout and a three-way turnout. On tors. In those points the centre-third rail is bonded manually operated points one of the most popular across the gaps into a single electrical unit. These types of change-over switch is the button points do not normally have section switches mount- microswitch operated by the tiebar. An alternative is ed on them.

6 The slider switch which can double as a simple Point points for three-rail use can either be commercial lever. Some suggested methods of Point operation two rail points adapted or hand built. The usual and switching are shown in Section practice is to bond the running rails throughout the layout to form the common return path and divide Three Rail Turnouts the third rail into sections. Examples of an isolating Point and a three way Point are shown in Figures 3- (These include centre-third, outside-third and stud 4 and 3-5. contact). R. Outside 3rd rail Running rails P1 bonded together F. Tie-bar micro-switch FIGURE 3-4. Basic self-isolating 3-rail Point .

7 Outside third shown but connections are similar for inside third and stud contact collection systems. R. P1 P2. F. Tie-bar micro-switches FIGURE 3-5. Standard three way 3-rail Point . Outside third shown but connections are similar for inside third and stud contact collection systems. 8-3-3. Self Isolating points New insulating gaps Wire bond in copperclad sleepering {. New insulating breaks }. Wire bond Button micro-switch FIGURE 3-6. Self isolating Point with tiebar switch. The rail breaks, new gaps in the copperclad sleepering and wire bonds show how a blade contact Point can be converted. Pointwork having live crossings requires a change- rails are soldered to copperclad sleepering, cutting over switch to alter the crossing polarity when the additional insulation gaps.

8 (Figure 3-6) Note that Point reverses. One of the simplest and most reliable the three wires involved are local to the Point and do methods is the button micro-switch operated by the not necessarily form part of the power supply to the Point tiebar as shown in Figure 3-6. The blade con- track. Also note that there are several designs of tact versions (Figure 3-1b) are difficult to keep elec- micro-switch available so check which terminal is trically clean and it is recommended that they be which before connecting up. converted to switch operation when being laid. This Where Point movement is controlled by a Point entails cutting insulation breaks in the closure rails motor, there is usually at least one auxiliary change- just before the crossing, bonding the switch and clo- over switch mounted on the Point motor body which sure rails to their adjacent stock rails and, if the can be used to change the crossing polarity.

9 PHOTO From the left, button, lever and roller micro switches suitable for changing the polarity of the Point crossing. The slider switch, if fitted with a Point operating rod, makes a useful local Point control. 8-3-4. Part 8 Section 3. ELECTRICAL. Issue Date September 1993. Multiple sidings track power feed and return connections (F and R on the drawing) is to show them at the toe of the Figure 3-7 shows a fan of four dead end sidings. Each Point (s). However, they could equally be made at the of the three Point crossings (X1, X2 and X3) is wired positions marked F1 and R1 as the outer rails of the locally' and, as a result, only one siding can be made fan do not have any breaks.

10 Useful if the control live from the track feed and return connections. position happens to be at the far end of the sidings. Handy Hint: The usual convention when sketching F1. Main feed rail Siding 1. X2. Siding 2. F P2. X1. P1 P3 Siding 3. X3. R. Siding 4. Tie-bar micro-switch Main return rail FIGURE 3-7 R1. Siding fan showing only one road energised via the self isolating points . Loops Where self isolating points lead to a loop, additional breaks can be varied but a useful position is one and insulation breaks are needed. Figure 3-8a shows a a half locomotive lengths from the fouling Point . loop with both points set to the straight route result- Should a locomotive be accidentally driven beyond ing in a short circuit.