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THE opening months of the last war were conducted in a very leisurely fashion because the expected disasters had not befallen us. Not until our armies were rescued from the beaches of Dunkirk did the stark realities of the situation percolate into the public mind. Once the facts were understood the whole country was galvanised into activity.

Tracked hydraulic excavators are versatile and ubiquitous items of off-highway plant and machinery that are utilised throughout the construction industry. Each year, a significant number of excavators overturn whilst conducting a lifting operation, causing damage to property, personnel injury or even fatality. The reasons for the overturn are myriad, including: operational or environmental conditions; machine operator acts or omissions; and/or inadequate site supervision. Furthermore, the safe working load (SWL) figure obtained from manufacturer guidance and utilised in lift plans is based upon undertaking a static load only. The purpose of this paper is to determine whether the SWL is still safe to be used in a lift plan when slewing a freely suspended (dynamic) load, and, if not, whether this may be a further contributory factor to overturn incidents.

Previous research has developed a number of machine stability test regimes but these were largely subjective, impractical to replicate and failed to accurately measure the “dynamic” horizontal centrifugal force resulting from slewing the load. This research contributes towards resolving the stability problem by critically evaluating existing governing standards and legislation, investigating case studies of excavator overturn and simulating the dynamic effects of an excavator when slewing a freely suspended load at high rotations per minute (rpm). To achieve this, both the static load and horizontal centrifugal force from slewing this load were calculated for six randomly selected cases of an excavator, with different arm geometry configurations.

The results from the six cases are presented and a worked example of one is detailed to demonstrate how the results were derived. The findings reveal that the SWL quoted on an excavator’s lift rating chart considerably underestimates the extra forces experienced by the machine when an additional dynamic load is added to the static load whilst lifting and slewing a freely suspended load.

This work presents the first attempt to accurately model excavator stability by taking consideration of the dynamic forces caused by slewing a freely suspended load and will lead to changes in the way that industry develops and manages lift plans. Future research proposes to vary the weight of load, arm geometry and rpm to predict machine stability characteristics under various operational conditions, and exploit these modelling data to populate pre-programmed sensor-based technology to monitor stability in real time and automatically restrict lift mode operations.

One of the common law duties owed by the employer is his duty to take reasonable care for the safety of his employee. This common law duty is an implied term in the contract of employment and is therefore contractual in nature. Because of the difficulties which may arise in bringing an action in contract for breach of the employer's duty of care, the employee who has sustained injuries during the course of his employment (although he may sue either in contract of tort will normally bring a tort action.

The Secretary of State in exercise of powers conferred by sections 138(1) and 180(3) of the Factories Act 1961 and now vested in him and of all other powers enabling him in that behalf, hereby makes the following Order:—

THE luncheon given by the Lord Mayor, Sir Ralph Perring, to more than 700 guests at Guildhall on November 14, officially launched the country on National Productivity Year. Apart from representatives of the 120 local committees these were people from trade and employers' associations, trades unions, professional bodies and research organisations. It was, in effect, a token mobilisation of Britain's industrial might, because behind it stands a large army devoted to the task of increasing the country's output.

TO check the suitability of a given strut cross‐section, for a given length and safe concentric working load, is a simple matter provided that a working stress curve or formula is available, but the reverse process of obtaining a suitable cross‐section, for a given length and load is under normal circumstances a tedious trial and error task, unless comprehensive tables of the properties of the required section arc available. The author's method permits a very close first approximation to be obtained, which is frequently sufficiently accurate to enable the required cross‐section to be laid out without further trial.

THAT WAS A BRAVE and surprising report that Prof. Elie Kedourie sent in to the Centre for Policy Studies, the more so because the professor is himself working at London University.

The Minister of Labour by virtue of the powers conferred on him by sections 138(1) and 180(3) of the Factories Act 1961(a) and of all other powers enabling him in that behalf, hereby makes the following Order:—

Mutual Investigation. There seems to be a refreshing, open breeze blowing through the ranks of time and motion study technicians these days. Gone are the ponderous exponents of the mystic art and, instead, we find the experts vying with each other, almost, in telling their audiences how easy time and motion study really is if you only sit down and think about it.