AS 3711.3:2015 pdf free.Freight containers Part 3: Corner fittings (ISO 1161:1984, MOD).
C. 1.2 A typical twistlock assembly usually consists of the following components:
a) a horizontal load-bearing surface, capable of supporting the bottom corner fitting of a fully loaded container under dynamic conditions;
b) a fixed collar, designed to project upwards into the bottom hole of a bottom corner fitting to a height no lower than the level of the inner surface of fitting Ihaving due regard to the way(s) in which different containers may be carried on the vehicle, i.e. whether the containers are supported by their four corner fittings or by their base structurel;
c) a rotatable head (the twistlock proper), the head of which shall project into the corner fitting, i.e. above the load-bearing surface;
dl an arrangement for rotating the head and securing it in the desired position (and in some cases, an arrangement whereby the rotatable head may be pulled or screwed down until it exerts a clamping force on the inner surface of a corner fitting, as well as acting to restrain the corner fitting against lift off).
C.1.3 The twistlock assembly may be
a) rigidly attached to the vehicle;
b) arranged so that the fixed collar and the rotatable head can be withdrawn below the level of the load-bearing surface (e.g. on a multipurpose vehicle);
c) hinged or otherwise arranged so that the entire assembly may be withdrawn (e.g. to allow the removal of the assemblies at intermediate points along the length of a 40 ft chassis, to eliminate the possibility of interference between the bottom side rails of a 40 ft container and the surfaces provided to support the corner fittings of shorter containers).
C.2 Dimensions for arrangements involving four twistlocks for securing containers to vehicles
C.2.1 For the four twistlock system, it is assumed that the load-bearing areas of the four twistlocks of the container-carrying vehicle chassis or a container railway car are in the same horizontal plane. With the exception of the twistlock collar and rotatable head, no part of the vehicle chassis or railway car may protrude above this horizontal plane. (See also annex B of ISO 1496/1.)
C.2.2 A theoretical approach to the determination of the dimensions and tolerances required to define the centre positions of tie-down twistlocks of a particular size to ensure engagement with the bottom corner fittings of series 1 containers is given in clause C.4.
C.2.3 This theoretical approach is based on a strict interpretation of ISO 668 and this International Standard.
C.2.4 It assumes that the four twistlock collars are rigidly mounted on the vehicle (but for retractable types which inevitably involve a certain amount of “slop” or “play” — see C.2.1O).
C.2.5 It assumes that metal-to-metal contact (i.e. an interference fit) between the fixed collars and the container corner fittings can only be envisaged in the most extreme case, e.g. when a container, built to maximum permitted tolerances and allowable difference between diagonals and which is parallelogrammed in one sense, is to be placed on a chassis the twistlock collars of which are positioned with the minimum permitted tolerances and allowable difference between diagonals and which are parallelogrammed in the opposite sense.
C.2.6 The probability of encountering this theoretical “worst case” is very difficult to estimate, but it is likely to be extremely small. Hence, in practice, tolerances may be used which are a little less “tight” than the theory would suggest (see C.2.11).
C.2.7 For the series 1 containers, the nominal centre-to-centre distances for the positioning of twistlock collars (defined in such a way that the positive and negative tolerances on these dimensions will have the same numerical value) will be identical to the corresponding dimensions measured between the centre points of the bottom holes in the bottom corner fittings of containers, and are given in table 1 (using the nomenclature defined in clause C.4).AS 3711.3 pdf download.