BS AU 241:1991 pdf free download.Specification for Mechanical coupling between tractors and semi-trailers : interchangeability.
1 Scope
BS AU 241 specifies the various elements and dimensions of a tractor vehicle and a coupled semi-trailer which together constitute an articulated vehicle, in order to ensure interchangeability.
It specifies certain interchangeability dimensions of the gooseneck contour and operating dimensions relating to some angle values.
The requirements of BS AU 241 permit use of the same semi-trailer with two-axle or three-axle tractors.
NOTE The dimensions of the 50 mm and 90 mm fifth-wheel coupling pins are specified in ISO 337[IJ and ISO 4086121 respectively. Mounting zones for pneumatic braking couplings are specified in ISO 1728[31.
The articulated vehicles are intended for commercial transport of cargo of the greatest possible variety: BS AU 241 does not necessarily cover special combination types (e.g. high-cube vehicles, low-bed vehicles, tipper vehicles).
Limitations of maximum gross mass and overall dimensions are generally laid down by legislative requirements.
2 Interchangeability dimensions
2.1 Height of fifth wheel of laden tractor The height of the fifth wheel of a laden tractor above
GRP, h (see Figure 1), in millimetres, shall be 1 200 mm mm.
To establish conformity, the height of the fifth wheel of the laden tractor, h, in millimetres, may be determined according to the following formula (see Figure 1, Figure 2 and Figure 3):
r h0,137l1+0,095b+r+r1—143,5 where
1 is the distance between the coupling axis and
the axis of the rearmost axle of the tractor;
b is the total width of the tyres at the rearmost
axle of the tractor;
r is the radius of the tyres. unladen;
r is the radius of the tyres, laden.
2.2 Height of fifth wheel of unladen tractor The height of the fifth wheel of an unladen tractor above GRP, h (see Figure 1) shall be 1 400 mm max.
2.3 Forward clearance zone radius of semi-trailer
The forward clearance zone radius of the semi-trailer, d (see Figure 4), shall be 2 040 mm max.
2.4 Gooseneck contour
The gooseneck shall be located on the outside of the surface of revolution generated about the vehicle
coupling vertical axis, as shown in Figure 5 and described below.
The generator is constituted as follows:
— a part AB of length ‘2, situated in the
horizontal plane of the centre of the coupling and in the median longitudinal plane of the
semi-trailer;
— a part BC situated in the same median plane making an angle y with the horizontal plane;
— an arc of a circle of radius r2, tangential on one hand to the portion BC previously defined and on the other hand to a vertical portion DE situated in the median at a distance and radius r: from the coupling axis.
During the rotation of the generator, AB describes a horizontal plane, BC describes a conical surface of revolution, the arc of the circle describes a portion of a torus, and the vertical axis DE describes a portion of the surface of a cylinder of revolution.
The values adopted for these elements of the generator are as follows:
12 = 750 mm
y=4°
r2 = 450 mm
r32 300mm
3.3 Angle of articulation
The angle of articulation, q (see Figure 4), is the projection of the angle between the longitudinal axes of the tractor and semi-trailer in the horizontal plane.
3.3.1 The articulation of the vehicle shall be such that no contact is made between the semi-trailer and the tyres of the tractor, taking into account the maximum value (09 = 7° for all angles q up to 25°, for both two-axle and three-axle tractors.
3.3.2 Under manoeuvring conditions, the angle of articulation q’ shall be able to reach 900 and the angle of inclination o vary from 70 to 3° as the angle p varies from 25° to 90°.
3.4 Free space between tractor and semi-trailer
The free space between the tractor and semi-trailer is measured as follows (see Figure 4).
3.4.1 13 is the distance between two cylinders of revolution, both having the kingpin axis as their axis. One of these cylinders has radius r3 (lower part of the gooseneck) and the other is the cylinder of smallest radius within which all points of the rear part of the tractor are located:
l 100 mm mm.
3.4.2 14 is the clearance between the surface of the cylinder of revolution having as its axis the axis of the fifth wheel coupling, and of radius d, and a conical surface of revolution having the same axis. This conical surface is generated by a line making an angle of 6° from the vertical towards the front of the tractor. A point X of this surface is positioned on the plane of symmetry of the semi-trailer at a height of 250 mm above the fifth-wheel coupling face.
At this point. 14 = 80 mm mm.