Rolling stock and load outlines

Every clearance starts with the vehicle. Before anyone can say how much room a train needs, someone must say how big the train may be, and that is the job of a rolling stock outline: a cross-section, drawn about the track centreline and rail level, that no part of a vehicle or its load may extend beyond when the vehicle stands on level, straight track. Rolling stock is designed and registered to fit within an approved outline; loads on wagons must fit within a loading outline; and the transit space of each corridor is built around the outlines approved for it.

This chapter explains how an outline is drawn and read, compares the families of outlines approved for the NSW network in the ARTC standards, shows why a vehicle’s length and bogie centres matter as much as its width, and checks a load against its outline, using the running case’s traffic.

Reading an outline

An outline is drawn as a half-width at each height above rail level, symmetrical about the track centreline. Near the rail it is narrow, because the wheels, bogies and underframe must clear platforms, check rails and equipment beside the track. It widens above platform height to the full width of the body, and narrows again towards the roof, where the body’s corners are rounded or chamfered. The shape matters as much as the maximum width: a structure that clears the outline at shoulder height may still strike it lower down, at the step or the bogie, or higher up, at the cantrail.

Figure 1How a rolling stock outline varies with height

	Typical shape	What it must clear
Near rail level	narrow; wheels, bogie frames, brake gear	check rails, guard rails, platform edges, trackside equipment
Platform and step height	steps, doors, footboards	platform copings and their faces
Body side	full body width	walls, piers, masts, adjacent trains
Cantrail and roof corner	rounded or chamfered	tunnel walls, bridge soffits, signal heads
Roof and fittings	roof, vents, pantographs on electric stock	bridge decks, overhead wiring, loading chutes

The approved outlines

ARTC’s Transit Space Standards, BDS 11, in its 2005 issue, listed the rolling stock outlines approved for the NSW network: an outline for non-electric vehicles, which included the approved loading profile, outlines for narrow, medium width, extended medium width and wide electric vehicles, and an ANZR ultimate vehicle outline. It also referred to the national Railways of Australia vehicle outlines for interstate stock, and provided special load gauges for loads larger than the standard loading profile, which Chapter 9 covers.

Each outline has its own half-width at each height. ARTC’s Application of Kinematic Envelope, BDS 13, gave typical body half-widths used in its worked envelopes: 1,485 mm for non and narrow electric stock, and 1,600 mm for wide electric stock, among others. Those are the starting points from which the kinematic envelope is built, as Chapter 5 shows.

Figure 2Typical body half-widths used in BDS 13's worked kinematic envelopes

Non and narrow electric1,485 mm from track centreline, straight track

Medium electric, at shoulder1,485 mm from track centreline, straight track

Medium electric, at waist1,525 mm from track centreline, straight track

Passenger stock with doors open1,579 mm from track centreline, straight track

Wide electric1,600 mm from track centreline, straight track

The differences look small: 115 mm in half-width between narrow and wide stock. But a structure designed for narrow stock and then passed by wide stock has lost 115 mm from a margin that may be only 200 mm. That is why a corridor’s approved outlines must be known before any structure is designed, and why changing a corridor to accept wider stock means checking every structure on it.

Length and bogie centres

Width is not the only dimension that matters. A rail vehicle rides on two bogies, or on fixed axles, and on a curve its body forms a chord across the curve: the middle of the body swings inside the track centreline and the ends swing outside it. The amount depends on the distance between the bogie centres, which controls the inward swing at the middle, and on the body’s overall length, which controls the outward swing at the ends. A long vehicle with widely spaced bogies swings much further on a curve than a short one of the same width.

So a vehicle’s outline is incomplete without its length over body, its bogie centres and its overhang beyond the bogies. Two vehicles that fit the same static outline can need quite different space on a curve. Chapter 3 calculates the swing, called centre throw and end throw, for the running case’s vehicles.

Figure 3The running case's design vehicle

overhang at each end = (length over body − bogie centres) ÷ 2

Length over body

17,000 mm

Bogie centres

12,500 mm

Body half-width

1,500 mm at the widest point

1. overhang at each end = (17,000 − 12,500) ÷ 2 = 2,250 mm
2. the middle of the body lies 6,250 mm from each bogie centre
3. Chapter 3 uses these to calculate how far the middle and ends swing on the 400 m curve

Height

Vehicle height matters for bridges, tunnels, loading structures and overhead wiring. Freight vehicles carrying containers, especially double-stacked containers on corridors built for them, can be much taller than passenger stock. Electric vehicles carry pantographs that rise to the contact wire, and their outlines include the pantograph envelope. The approved outline for a corridor sets the maximum height, and vertical clearances are built up from it, as Chapter 6 shows.

Vehicles that move relative to their outline

A vehicle that fits its outline when new and standing still may not fit it in service. Worn wheels lower the body; worn suspension lets it roll further; doors that open outwards, such as plug doors on passenger stock, change the outline while the train is moving slowly at platforms; and loads can shift. Outlines and kinematic calculations allow for some of these effects, as the doors-open half-width in BDS 13 shows, but only if the vehicles are maintained to the standards assumed.

Loads and loading outlines

Open wagons, flat wagons and well wagons carry loads that are not part of the vehicle, and those loads must fit a loading outline, usually smaller than or equal to the vehicle outline. The load’s position on the wagon matters: a load placed off-centre, or one that is long and overhangs the wagon’s ends, behaves on a curve like a longer vehicle. The load’s securing must stop it shifting, because a shift of a few tens of millimetres can take a load that just fits its outline outside it.

Loads are checked by measuring their width, height and position on the wagon, and comparing each critical point with the loading outline. For long loads, the length and the position of the load relative to the wagon’s bogies are recorded, because they decide how far the load swings on curves.

Figure 4Checking a load against its loading outline

• Avoid: Identify the outlinewhich loading outline applies on every corridor of the route
• Avoid: Measure the loadwidth and height at each critical point, and its length
• Avoid: Measure its positionoffset from the wagon centreline, height above rail, distance from bogie centres
• Avoid: Compareevery critical point inside the outline, with the wagon's own dimensions included
• Avoid: Securingload restrained so it cannot shift laterally, longitudinally or vertically
• Do: ? Out of gaugeany point outside the outline referred for special load approval before the move

Tare, loaded and worn

A vehicle sits at different heights depending on its load and the wear of its wheels and springs. Empty, its springs are extended and its body rides high; loaded, the springs compress and the body drops; with worn wheels, which have a smaller diameter, the whole vehicle sits lower. The height of the roof, the height of the steps and the half-width at a given height above rail all change with these. An outline is defined for a stated condition, and the kinematic envelope adds allowances for the movement from it. Clearances near platforms, where a step that drops into the coping is as dangerous as a body that strikes a wall, are especially sensitive to vehicle height, and Chapter 8 returns to them.

Things that stick out

Mirrors, handrails, steps, ladders, door handles, hose connections and lamps all project from a vehicle’s body, and every one must be inside the outline. They are easy to overlook when a vehicle is modified or a fitting is replaced with a larger one. On passenger stock, outward-opening or plug doors move outside the closed-door outline as they open, which is why BDS 13 gave a separate doors-open half-width for one passenger fleet. Operators who add equipment to vehicles check its effect on the outline before the vehicle runs.

Gauge and the outline

The track gauge, the distance between the running edges of the rails, sets where the wheels run, but it is not the same as the outline or the clearance. Australia’s interstate network runs on standard gauge, 1,435 mm, with broad gauge and narrow gauge lines elsewhere, and dual gauge track where two gauges share a line. On dual gauge track, the track centreline of each gauge is in a different place, so vehicles of each gauge are offset from each other, and clearances must be checked for each. The running case’s line is standard gauge only, which keeps its centreline simple.

Outline drawings and their datum

An outline drawing is only useful if its datum is clear. Most are drawn about the track centreline and from the top of rail on level track, but some vehicle drawings use the vehicle’s own centreline and the top of the underframe, and some older diagrams use imperial dimensions. When a vehicle or load is compared with an outline, both must be referred to the same datum, at the same condition of load and wear, or the comparison is meaningless.

The running case: the corridor’s traffic

This is an illustration. The rail infrastructure manager told the overbridge consultancy that the corridor carried locomotives and freight wagons within the national interstate vehicle outlines, some long container wagons, and occasional passenger trains, and that the bridge must allow for future double-stacked containers and for electrification, which was not yet planned but must not be ruled out. The consultancy took its design vehicle from the longest wagon on the line: 17.0 m over the body, bogie centres 12.5 m, half-width 1.5 m. It noted that a vehicle of the same width but with bogie centres of 14 m, if one were ever registered for the line, would swing further at its middle on the curve, and asked the infrastructure manager to confirm the longest bogie centres to allow for.

Why the outline is the operator’s promise

An approved outline is a promise from the operator to the infrastructure manager: every vehicle and load we run will fit within this shape. The infrastructure manager builds and maintains the transit space on that promise. A load that exceeds its outline without approval breaks the promise silently, and the first sign may be contact with a structure. That is why loading checks and the out-of-gauge procedures of Chapter 9 matter as much as structure design.

Interstate and local outlines

Australia’s railways grew up as separate systems with different gauges, outlines and structure gauges, and the interstate network carries vehicles built to national outlines across lines originally built to state standards. A line may therefore have more than one set of outlines in use, and the critical vehicle at one structure may differ from the critical vehicle at the next: a wide passenger train at a platform, a tall container train under a bridge, a long wagon on a sharp curve. Clearance checks consider every outline approved for the corridor, as BDS 13 required when different types of rolling stock operate over the same section.

Measuring a vehicle

Registered rolling stock comes with drawings that show its outline, but vehicles are sometimes measured, to confirm a modification, to check a vehicle whose drawings are uncertain, or to investigate a strike. A vehicle is measured standing on level, straight track, with its suspension at its normal loaded or tare condition as required, by taking the half-width at a series of heights on each side and the height at a series of offsets, from the track centreline and rail level. Its length over body, bogie centres and overhangs are measured too. The results are drawn over the approved outline, and any point outside it is a matter for the infrastructure manager.

A failure: the modified wagon

This is an illustration. An operator fitted a group of flat wagons with new side stanchions to carry steel coil, and the stanchions, mounted on the wagon’s outer edge, stood about 40 mm outside the approved outline at their top. Nobody checked the modified wagons against the outline. On their first trip, one stanchion struck a signal post on a tight curve near a yard, bending the stanchion and damaging the post.

The modification had changed the vehicle’s outline, and every modification that changes a vehicle’s outline must be checked and approved. The stanchions were moved inboard, the wagons remeasured and re-approved, and the operator added an outline check to its modification procedure.

Exercise: two vehicles, one outline

Two wagons fit the same static outline, with a half-width of 1,500 mm. Wagon A is 15.0 m over body with bogie centres of 10.5 m; wagon B is 18.0 m over body with bogie centres of 13.0 m. Calculate each wagon’s overhang beyond its bogie centres. Which will swing further inside the curve at its middle, and which further outside at its ends? Do not calculate the swing yet; Chapter 3 does.

Wagon A’s overhang is (15.0 − 10.5) ÷ 2 = 2.25 m at each end; wagon B’s is (18.0 − 13.0) ÷ 2 = 2.5 m.

The inward swing at the middle depends on the bogie centres, so wagon B, with 13.0 m against 10.5 m, swings further inside. The outward swing at the ends depends on both the overall length and the bogie centres, and wagon B, being longer overall, also swings further outside. This is an illustration: identical static outlines say nothing about the space each wagon needs on a curve, which is why a corridor’s clearance checks use the critical vehicle’s length and bogie centres as well as its width.