332 



NATURE 



[August 6, 1S91 



THE INSTITUTION OF MECHANICAL 

 ENGINEERS. 



nPHE summer meeting of the Institution of Mechanical Engi- 

 ■^ neers was held at Liverpool last week, commencing on 

 Tuesday, the 28th ult., and concluding on Friday, the 31st ult. 

 The President of the Institution, Mr. Joseph Tomlinson, pre- 

 sided throughout, and the meeting was highly successful, the 

 long and varied programme being carried out with regularity 

 and precision. The sittings for reading papers were held on 

 the mornings of Tuesday and Wednesday ; the afternoons of 

 those days and also the Thursday and Friday being devoted to 

 excursions. We will first deal with the papers and discussions. 

 The sittings were held in the concert-room of St. George's 

 Hall, and the following list of papers was on the agenda : — A 

 review of marine engineering during the past decade, by Alfred 

 Blechynden, of Bairow-in-Furness ; description of the ware- 

 house and machinery for the storage and transit of grain at the 

 Alexandra Dock, Liverpool, by William Shapton, of London ; 

 on the experimental engine and the alternative testing machine 

 in the Walker Engineering Laboratories of University College, 

 Liverpool, by Prof. H. S. Hele Shaw, of Liverpool ; on the 

 mechanical appliances employed in the construction of the 

 Manchester Ship Canal, by E. Leader Williams, Engineer-in- 

 Chief to the Canal Company. There was also a paper on the 

 Liverpool water-works, but this was adjourned to the next 

 meeting. 



The Institution having been welcomed to Liverpool by the 

 Mayor, Mr. J. B. Morgan, and the formal business having been 

 transacted, Mr. Blechynden's paper was read. Mr. Blechynden 

 has taken up the work commenced by Sir Frederick Bramwell 

 at the Liverpool meeting of 1872, when the latter presented an 

 historical paper giving a review of marine engineering up to that 

 time. In 1881, the Institution met at Newcastle, when Mr. F. 

 C. Marshall, a well-known Tyneside engineer, read a paper 

 which consisted of a retrospect of the nine years since Sir 

 Frederick Bramwell's paper had been read. We now have 

 Mr. Blechynden carrying on the work. These periodical re- 

 views are instructive. They cause the engineer to take stock of 

 progress made, and enable him to see the lines upon which im- 

 provement may be expected to travel in the immediate future. 

 Mr. Blechynden has been fortunate in the period which has 

 fallen to his lot to review, for during the ten years past 

 the triple compound engine has been developed. When 

 Mr. Marshall read his paper, the ordinary compound engine 

 with two cylinders was all but universal for steamships. Boiler 

 pressures averaged 77 '45 pounds per square inch, the average 

 piston speed was 467 feet per minute, and the heating surface 

 per indicated horse-power was 3 '99 square feet. The consump- 

 tion of coal per indicated horse-power was i '828 pounds per hour. 

 As a contrast to this, Mr. Blechynden tells us that at the present 

 time the three-stage expansion engine has become the rule, 

 and the boiler pressure has been increased to 160 pounds, 

 and even as high as 200 pounds per square inch. Four- 

 stage expansion engines of various forms have also 

 been adopted. Forced draught has come to the front — 

 largely, it would seem for the purpose of being abused — tbe 

 pision speed has risen to 529 feet per minute, the heating 

 surface per indicated horse-power is 3 '274 square feet, and the 

 coal consumption per indicated horse-power per hour is i'522 

 pounds. By these figures it will be seen that during the last ten years 

 the working pressure has about doubled, and that fuel economy 

 has been improved by about 20 per cent. We may say 

 that we do not always place full reliance in the details given 

 with regard to fuel economy in connection with mercantile 

 marine engines. We think that the power is apt to be taken on 

 the best performance of the engines, so that they are credited 

 with a duty they cannot maintain continuously throughout a 

 voyage. Probably, however, the figures given by the author are 

 accurate for comparative purposes, and they are not, as are 

 some results claimed by marine engineers, altogether too good 

 to be true. We would here draw attention to the author's 

 expressions "three-stage " and " four-stage " compound engines. 

 Engineers have been in the habit of referring to these types as 

 triple expansion and quadruple expansion engines. This no- 

 menclature is inaccurate and misleading for an ordinary two- 

 cylinder compound, and even the simple non-compound engine 

 expands the steam more than three or four times. Some engi- 

 neers, recognizing this, have used the terms "triple compound" 

 or "quadruple compound," but Mr. Blechynden's expression has 



the merit of greater accuracy and simplicity. We hope that en- 

 gineers, who are apt to be somewhat loose in the naming of objects, 

 will adopt Mr. Blechynden's terms. Added to the paper are 

 tables giving details of construction and performance of repre- 

 sentative steamers of the present day. A long discussion followed 

 the reading of this paper. It turned chiefly upon the question 

 of forced draught, corrugated flues, and the rules with regard to 

 boiler testing which Mr. Sennett introduced when he was at the 

 Admiralty. With regard to the forced draught question, the 

 very sensible opinion seemed to have been arrived at that forced 

 draught, though a good thing in itself, may prove a great ill 

 if overdone. It is in the Navy chiefly that forced draught has 

 gained an evil reputation, and naval officers are largely to 

 blame for this, although the engineers must take their share of 

 the responsibility. When it was found how great an accession 

 of power could be obtained by forcing combustion with a 

 fan, naval officers thought they had a royal road to speed. 

 Boilers which had been designed on principles that had grown 

 up under a simple chimney draught regime, were urged by fan- 

 blast to duties beyond their powers of endurance ; and then, 

 when tube plates buckled and tubes leaked, forced draught was 

 said by gallant admirals to be "the invention of the Evil One." 

 The engineers, as we have said, were also to blame. The 

 boiler has always been the Ishmael of the machinery- 

 designer, nearly all the attention having been lavished on the 

 engine. As a consequence boiler construction has been a 

 matter of rule of thumb, and, when the empirical rules upon 

 which it was based have no longer applied, the engineer has 

 been nonplussed through want of a basis of scientific knowledge 

 upon which to build anew. The torpedo-boat builders have no 

 trouble with forced draught, though they blow far harder than 

 in any other vessels ; but then the torpedo-boat builders are 

 good engineers — not mere blind followers of "practice" — 

 as was proved by the paper read last spring on this subject 

 by Mr. Yarrow before the Institution of Naval Architects. 

 In speaking upon corrugated flues Mr. Macfarlane Gray made 

 a remark on the subject which might have received more 

 attention. It has long been claimed by the makers of this type 

 of furnace that additional heating surface, and that of a most 

 valuable kind, was obtained by the corrugations. This Mr. 

 Gray said was a fallacy, for the heat from the furnace proceeded 

 only in radial lines, and therefore no greater effective area of 

 heating surface could be obtained than that due to a plain 

 cylinder. 



Mr. Shapton's paper was an interesting description of 

 the building and machinery referred to in the title, by 

 which grain is transported and stored. The warehouse in 

 question consists chiefly of a vast cellular structure which might 

 be described as a brick and mortar honeycomb, filled with grain 

 in place of honey. There are 250 hexagonal bins or silos, each 

 measuring 12 feet across the angles and 80 feet deep. The 

 storage capacity is 2,240,000 bushels. The grain is lifted from 

 vessels by elevators, and carried to the top of the building, from 

 whence vertical movement is supplied by gravity. Horizontal 

 travel is carried on by continuous moving belts or bands which 

 run over wheel pulleys. The way in which streams of grain can 

 be diverted into any required direction is very curious to watch. 

 A good part of th« discussion on the paper turned on the 

 best form of bin or silo. At first one would think that the 

 bin designer could not do better than follow the bee, but 

 it was shown that cylindrical chambers made of sheet 

 iron would give a large saving of space over the hexagonal 

 brick bins. The advantage is due of course to the thinner walls 

 of sheet iron, the cylinder being a form by which advantage can 

 best be taken of the high tensile strength of iron. In America, 

 where the silo system was in common use long before it made 

 its appearance in this country, the bins are made wholly of wood, 

 but this is subject to rot, and harbours weevils. Sheet-iron 

 rusts and brick retains moisture, so that with brick the grain 

 heats unless well looked after and ventilated. On the whole, 

 however, brick has the preference in this country. Sir James 

 Douglass made a suggestion which will, we should think, receive 

 attention at the hands of future silo designers. The represen- 

 tation of the Eddystone Lighthouse at the Royal Naval Exhibition 

 is a building not altogether dissimilar from a silo. It has very 

 thin walls, which are constructed of expanded sheet steel, or 

 sheared lattice work, which forms the bond for a crust of Port- 

 land cement. The result is a wall of great tenacity and rigidity, 

 and one which would not have the same defect as brickwork with 

 regard to harbouring damp. The problem of ventilating grain is 



NO. II 36. VOL. 44] 



