NATURE 



THURSDAY, JANUARY 14, 1909. 



^ OBSTRUCTION AND USE OF CRANES. 

 Cranes: Ihcir Constniclion, Mechanical Equipment, 

 and Working. By Anton Boltcher. Translated and 

 supplemented with English, American, and Conti- 

 nental Practice by A. Tolhausen. Pp. xvii + 510. 

 (London : A. Constable and Co., Ltd., 1908.) Price 

 42s. net. 



MODERN developments of means of transit, 

 especially in the direction of the transhipment 

 of he;ivy goods, have made it necessary that rapid and 

 powerful lifting gear should be devised, and pari passu 

 with the developments of heavy engines and wagons, 

 heavy ordnance and large ocean liners, there has been 

 an equallv interesting and important advance in the 

 construction of rapid and heavy cranes. 



The book before us has for one of its aims the 

 presentation of the progress that has been made, and 

 with this end in view many types of cranes are de- 

 scribed and discussed in detail, and illustrated by 

 photographic views of general arrangements, together 

 with dimensioned drawings of more than seventy 

 particular examples. 



The book is, however, by no means simply a de- 

 scriptive work, as all parts of cranes that lend them- 

 selves to theoretical treatment are dealt with in a 

 sound manner. The first part of the book deals with 

 first principles in crane-building practice, and to those 

 who have had a preliminary training in the elements 

 of applied mechanics should be of interest and of great 

 value in showing their applications to definite design 

 problems, as well as for the immediate object in view. 

 For example, the use of the funicular polygon in the 

 resolution and composition of forces is illustrated, and 

 the laws of motion are used to determine the time 

 of motion, and the forces required to give momentum 

 to the travelling portions of various forms of 

 cranes. It also includes an interesting paragraph on 

 " efficiencies," and, along with other valuable tables, 

 one giving the efficiencies of crane parts. In the 

 paragraph on struts only Euler's formulae are given. 

 This is to be regretted, as it is generally agreed in 

 this country that more trustworthy results are obtained 

 bv such formulae as Rankine's or Tetmajer's. Part ii. 

 is devoted to the general arrangements of cranes, and 

 opens. -with a concise summary of the local influences 

 which decide the character of cranes in different 

 circumstances, followed by general descriptions of 

 many types, from the old-time hand winches to the 

 most modern electric-driven travelling cranes. 



Part iii. deals with crane-driving principles; driving 

 by hand, shafting, steam, water and electricitv are 

 treated, and the principles involved in the determina- 

 tion of the power required to lift a given load at a 

 given speed, and the gear ratios are dealt with in 

 detail. The subject-matter of the hydraulic and elec- 

 trical sections is particularly good, but the translation 

 is not all that could be desired, as the meaning is at 

 times somewhat obscure, especially in the electrical 

 section, which, we fear, will liardly be intelligible 

 NO. 2046, VOL. 7(j] 



except to those verv familiar with the theory and 

 practice of motors. The translation is surely not 

 happy when, in the hydraulic .section, a sentence is 

 rendered as " the rams beget larger diameters with 

 equal lifts." In one or two cases the obscurity is in- 

 tensified by slips in proof-reading, as, e.g., on p. 102; 

 the velocity of the water through the valve is propor- 

 tional to the difference of pressure in the valve box 

 and cylinder, so that in the formula, />„ should be 

 replaced by pQ — pi- We were some time before we 

 could put a meaning to the following, w'hich opens 

 the paragraph on speeding up electric motors : — " The 

 current curves represented in Fig. 257 — corresponding 

 with full cut-off initial resistance to the inscribed circum- 

 ferential moment — are independent," &c., and even 

 now we are in doubt as to the author's meaning. It 

 is also, we think, not usual to speak of the back 

 E.M.F. of a continuous-current motor causing current 

 lagging. In the paragraph on " running down " we 

 were rather held up for the moment by " To hold the 

 load in a fixed position the simple running down \\\\\ 

 suffice in many cases," until we realised that the 

 translator meant that the switch is in the running- 

 down position, and the mechanical friction of the 

 gearing, &c., is sufficient to prevent the load running 

 down. 



We do not remember in English works to have met 

 with the method used by the author of determining 

 the ratio of the areas of the lifting rams and the valve 

 openings of hydraulic cranes, by consideration of the 

 difference between the velocity of lifting and lowering. 

 The method, though simple and well known to some 

 English designers, has not received the attention it 

 deserves, and is well worth careful study by those 

 engaged in this branch of designing. 



Part iv. considers in a very complete manner crane 

 parts and accessories, and designers of all classes of 

 machinery will find the information given valuable. 

 This is followed by a section devoted to the design 

 and calculation of crane girders. The designs of 

 riveted joints and of various forms of girders are 

 considered in a very practical manner, and where 

 theory fails current practice is referred to. .\ number 

 of sound hints are given, as, for example, when the 

 author is dealing with the stiffening of traveUing 

 girders, he remarks : — 



" As practice alone can guide us in this respect, 

 it is advisable, when such exigencies can be drawn 

 upon to draft the design in such a manner that 

 eventual stiffening may be resorted to if found to be 

 requisite in testing or working." 



The determination of the maximum stresses that 

 can occur in the members of a lattice girder, due to 

 the crab moving over the girders, is dealt with in a 

 way that should appeal to those who are familiar 

 only with the ordinary stress diagrams, the influence 

 line being deduced from a number of diagrams drawn 

 from a single load fixed at a different point for earl- 

 of the diagrams. It is, we think, unfortunate that 

 the very simple method of influence lines is not 

 better known, as without the labour involved in 

 drawing stress diagrams the unit load diagram or 

 " influence line," for any member, in the top boom, 



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