Basic introduction to Points Page 1 of 12 Uncontrolled document for information only – see disclaimer** on last page

Points are used to enable trains to switch tracks from one to another or into a station or siding etc. They are operated by electric powered point machines, hydraulically power clamplocks, torsion operated systems, air powered machines, mechanically operated points or train

operated point machines (either by hydraulic type or spring).

They also come in many different types of ‘turnouts’, these are as follows:

Not all configurations are shown.

Rail type:

The track in the UK comes in various types, this is either Flat bottomed vertical, Flat bottomed inclined, Bull-head or UIC60 (European adopted rail).

Bull head and UIC are disguisable by the way they look, but vertical and inclined look exactly the same. The only way to tell is by looking on the slide chairs it is mounted on.

Either a ‘V’ will be stamped on the chair for Vertical Rail, or ‘X’ for Inclined. Vertical & Inclined rail are actually the same, it’s the chairs it is mounted on that make it

vertical or inclined.

LH & RH Turnouts (LH SHOWN) Known as

‘Plain Leads’

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Basic layout of point equipment (track):

Types of Rail:

Switch length:

The length of switch rails is determined by at what speed the train is to cross over to another track, the lengths are A,B,C,D,E,F,G,SG (small switch ‘G’),H.

The smallest switch is ‘A’ for very slow speeds and up to ‘H’ for very fast speeds. The length of switch will also determine how many stretchers should be fitted (minimum is

two) and how long the backdrive will be.

The switch length letter is found on the gauge blocks at the rear of the switch which hold the switch and stock together.

Fastenings:

The switch rail rests on slide chairs, some points are fitted with Austro or Schwihag rollers, the Austro rollers are becoming more obsolete as these take a full day to fit and are non-

adjustable. The switch rail is only fixed at the rear to the stock rail by bolts and clips. The clips are either pandrol or fastclip type on modern points.

Stretcher

bars

Flat bottom and rare bull-head type rail UIC 54B type switch with UIC60 stock rail

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The slide chairs (also known as ‘slide base plates’):

The track at each end is either welded together or fixed together by fishplates (left hand picture) or insulated block joints (‘IBJs’) (right hand picture), if the track circuit voltage needs to be separated.

Pandrol type ‘E’ clip New modern ‘fastclip’ type

Normal conventional non roller slide chair ‘Schwihag’ type roller baseplate (modern)

Austro-roller (becoming more obsolete)

‘AS’ type chair screw used to secure the slide chairs to

wooden sleepers only. ‘M’ screws which are wider in

diameter are used if ‘AS’ screws no longer grip. Or Hilti

coils are used instead (these are like large wall plugs).

Sometimes six hole insulated block joints are used which are insulated by glue and not plastic.

Page 4 of 12 Track bed:

The points are mounted on mostly wooden timbers and on more modern layouts on concrete

reinforced sleepers. On concrete sleepers different track components are used to secure the rails and to stop lateral

movement. The track bed is made up of large stones known as ballast, this is compacted by hand using

kango machines or a S&C (switch and crossing) tamping machine. The track is either level or has a ‘cant’, where it is on a bend and has to lean either left of right to enable trains to go around

the bend at higher speeds. Points are usually sited on level parts of the railway away from bends. The ‘cant’ is measured using a track gauge with ‘super-elevation’ gauge fitted (pictured

below).

The track gauge:

The distance between both rails has to be maintained within a pre-determined distance known as the track gauge. This depends on the type of rail installed. The track gauge pictured above also measures this distance.

The tolerances are; for flat bottomed VERTICAL rail it is 1430-1438mm, for INCLINED, BULL HEAD & UIC60 rail it is 1433-1441mm.

S&T equipment:

Conventional fixed Stretchers:

The switch rails are independent of one another but are fixed together by stretcher bars. The new type of reinforced stretcher bar is coloured yellow and have the manufacturers name

and date marks on them.

The new yellow stretchers are secured to the rail by stretcher shoes, these are also coloured yellow and are fixed together by using the new type hardlock bolts. The nuts used are male and

female and lock together using a torque wrench set to 250Nm.

Insulated ‘swan neck’ (to

stop the track circuit rail

voltage shorting).

Super-elevation gauge

Stretcher shoe

The points ID number, should

always be on the normally

closed side and readable from

the facing direction.

The soleplate. By law

all points must have

one to hold the gauge

at the front.

Facing direction (arrowed).

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Before yellow stretchers were introduced, they were black and were secured using either

square headed black bolts or hexagon black bolts with spring washers. The stretchers and bolts are still widely used on many points, but if a fault (ie crack is detected)

they should then be changed to yellow.

These type of stretchers are known as fixed, this is because they are drilled and cannot be altered once bolted.

The stretchers come in two formats (on plain leads only); these are either long or short. The long ones are only used at the front position (at the toe), and all the rest are the short type. The long stretcher is basically longer because it has what is known as a kicking strap which

protrudes through both sides of the points to stop the switch rail from possible lifting although very rare.

On switch diamonds (machine operated) the stretchers are the same but use coloured angled shoes (these are used to make sure the stretchers are straight and do not bend because of the

extreme angles of the switch rails).

On switch diamonds that are operated by clamplocks, the stretchers are installed with the insulation in the middle and also use coloured shoes.

On double slip layouts, there are four different coloured shoes used; black, grey, green & red.

Adjustable stretchers:

Modern point layouts rebuilt on concrete sleepers will more than likely have adjustable stretchers, these are not fixed and can be adjusted at anytime to alter the FWC or switch

openings. The brackets which they are fixed to are totally different to the shoes mentioned above. The

stretchers have no swan neck insulations but have rubber insulations at both ends where they are fixed to the brackets.

They are held in place by either half-lock nut type nuts or hardlock nuts. Both configurations require different maintenance techniques.

Adjustable stretchers can only, at the moment, be fitted to UIC type rail. There are also less fitted; a ‘C’ type switch UIC54B rail for instance will only have two stretchers fitted as

opposed to three on vertical and inclined points. Also modern points are fitted with an additional detector at mid position to double check

the points are fitting up along the entire length.

Switch diamonds with yellow stretchers, coloured shoes

(grey & white) and insulations set in the middle.

Old style fixed black stretchers using hexagon black

bolts (plain lead set shown).

Page 6 of 12 Backdrives:

Pictured above is a LH backdrive fitted to a ‘C’ switch.

All Vertical track points over a ‘C’ switch MUST have a backdrive fitted and all Inclined track points over ‘D’ switch MUST also have one fitted.

The backdrive is used to push up the rear of the points and hold them there by using cranks

and rodding.

They help maintain the RSO and FWC and prevent FBC.

RSO (residual switch opening): the small closed gap that should be between 1.5-2mm. FWC (free-wheel clearance): the other open gap in which the train wheel flange runs through

mentioned later. FBC (flange back contact): if the FWC & RSO are incorrect and track gauge is wide, the train

wheel may hit the back of the switch rail and cause the stretchers to break.

The backdrives come in many many different configurations, they can be fitted to the left, right or in the centre (known as a four foot backdrive), these are used in limited clearance areas where normal (six foot) backdrives cannot be installed, such as stations or cuttings.

Backdrives now come as a kit and are installed on plates instead of bolted through the

sleeper. The price of a typical kit can start at around £2000.

The operating equipment:

Pictured above is a HW point machine on points fitted with adjustable stretchers.

‘RSO’ on closed

side ‘FWC’ on open side

Lock fender

‘Four foot’

backdrive

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Above is a mechanically operated set of points by lever in signalbox.

HW point machine basic layout:

Drive rod, this drives

the points normal or

reverse.

The lock rod, connects

to the lock blades.

Short detection rod. This

detects the nearest to

machine switch rail.

The long detection rod. This

detects furthest switch rail

from machine.

Lock fender, this

connects both switch

rails as a connection

point for the lock rod.

This with the lock rod,

locks the points either

normal or reverse.

Clamplock operated basic plain lead layout:

Hydraulic actuators,

these drive the

points normal or

reverse.

Lock body.

Lock arm, this locks

the switch blade to

the stock rail via brass

locking piece.

Adjustable tie-bar,

holds drive lock

slides together.

Drive lock slide,

this pushes lock

arm in and up to

lock switch

blade.

Switch rail bracket, lock

arm’s are fixed to this. Brass locking

piece. Centre thrust bracket, the

hydraulic actuators are fixed

here.

HW1000/2000

machine

Inside the body,

two microswitches

‘copy’ the fixed

and adjustable

cams to detect the

points closed and

locked.

Clamp used to secure

points out of use. 998 type detector

used to detect

points N or R