Metric news for building trades

projects using time-scale bar charts are known, but if the methods of C.P.A. are used, combined with activity-onnode symbolism, all these objections can be overcome. These and the other reasons add up to a fair case and, by implication, establish a target to be achieved for both simplicity and clarity in the new method proposed and in its exposition. The author has achieved both, and is therefore much to be commended. Moreover, the importance of many other aspects for practical and successful planning, apart from the method as such, is properly emphasised. For instance, no method, however good, can be better than the quality of the time estimates for completion of the various jobs in a project. This, and the usefulness of network methods in providing detailed past records for future guidance, is duly noted. But the training value to the individual of making time estimates and networks, and then comparing the final results with the estimates, as a means of improving his estimating ability, could be given greater emphasis. Sometimes the difficulty of carrying out some of the practical procedures is not mentioned, but that does not diminish the value of the practical advice, although occasionally the succinctness may hide the importance from the reader. The brevity here is admirable but a three-line whip is needed in the margin: It is fatal to impose times on the men responsible for a job. In all cases the job duration should be discussed and agreed with the people who will be carrying it out. Failure to do this will certainly generate resistance. In practice, this often means seeking advice from people quite junior in the management structure, but it is foolish to ignore the vast amount of knowledge that exists at these junior levels. In short, find out who knows most about the technicalities of the job and ask them. With regard to time estimates, perhaps a small suggestion could be offered to the author for possible future usage. In his analysis, the jobs to be done are enclosed in a box with a small section of the box, at the left hand end, containing a number in it which is the job time, ie the duration required to complete the job. These boxes are later extended on a bar chart to a correct scale according to the durations. Now, for certain jobs the duration depends on the number of men allocated, and the author rules that the time estimate given is that for the 'normal' level of the resource being used, ie the 'normal' number of men put on that job. It might perhaps be advantageous to show the number of men assumed to be allocated, on the basis of which the time estimate has been made, by placing another number, perhaps inside a small circle, within the segment at the left hand end of the job box. This addition, where appropriate, would avoid the only possibility of ambiguity or error due to memory failure, an important source of ergonomic difficulty, which the reviewer has been able to detect. It can reasonably be argued that this new method, like other network techniques, involves no more than a form of logical thinking, together with a formalised way of recording decisions and estimates, so as to overcome the memory problem for large numbers of items during the planning stage and to display the results to others. This is largely true, but the advantages of a simple and agreed

method for showing the logical decisions should not be dismissed lightly. At the least, as has been suggested before for network techniques, this method should be of value for people inside the organisation or project hierarchy to get managers and directors, or professors, to make their decisions in adequate time for everything else to be done. B.S.

Mechanical handling safety 'Safety in Mechanical Handling' is the title of a new booklet, price 5s, in the Department of Employment and Productivity's Health and Safety at Work series. It is illustrated and deals, in simple terms, with the principal dangers in the mechanical transport of goods and materials in industry. The subject is treated broadly in two parts: movement of goods and materials by vehicles; and other mechanical means. The range and complexity of handling equipment in use today makes it almost impossible to deal with every type of equipment. But the safeguards and procedures to eliminate risk described in the booklet will prove useful in application to appliances not specifically mentioned. Safety precautions dealt with in detail are those relating to mechanised conveyors and elevators of various types, fork lift trucks and stacking equipment. The use of road transport vehicles and their safe operation within factory areas is also discussed.

Metric news for building trades Metric versions of three BSI publications of great importance to the building industry are now available: CP 204 'In-situ floor finishes': Part 2 'Metric units' 23s; CP 299:1970 'Sprayed asbestos insulation' 12s; BS 402 'Clay plain roofing tiles and fittings' Part 2 'Metric units' 14s. CP 204 Part 2 deals with the application of all types of floor finishes, and the recommended thicknesses for screeds. The contents includes bases, concrete finishes, terrazzo, mastic asphalt, pitch-mastic, cement rubber-latex and magnesium oxychloride, with appropriate sub-sections dealing with work on site, inspection, testing and maintenance. The imperial version of this code is retained as Part 1. CP 299:1970 replaces the 1968 imperial version. The technical content is unaltered. BS 402 Part 2 specifies requirements for plain roofing tiles and fittings and vertical hanging tiles of clay or marl when manufactured to metric sizes. The work sizes are in accordance with the recommendations for the coordination of dimensions in building. The imperial version of the standard is retained as Part 1.

BSI address Copies of various British Standards may be obtained from: BSI Sales Branch, 101/113 Pentonville Road, London N1 9ND.

Applied Ergonomics December

1970

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