1819. 1 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



317 



the side-pipes F G, are common to every engine of this description; 

 the internal construction of the steam-chests, valves, and the mode 

 of worlving, arepeculiar and constitute the chief merit of the in- 

 vention. 



In the construction of a steam-engine, two important considera- 

 tions present themselves, the attainment of a maximum of force, 

 and the minimum in the consumption of fuel; to acquire the first 

 it is requisite to form such an arrangement of the working parts, 

 as to obtain the closest approximation to a perfect vacuum under 

 and above the piston, and the other is accom])lished by having as 

 small an expenditure of steam as possible. These desiderata are 

 to a great degree attained by the principle upon which these valves 

 are constructed, and the way in which they are worked. Referring 

 to the engraving, which is a section of one set of valves, it will be 

 seen that each set contains two double-beat valves S, T, also the 

 shut-oif valve R, and the throttle- valve Q; these valves constitute 

 the whole of the openings by which the steam is admitted and re- 

 turned from the cylinder; the valves S, next to the steam-pipe E, 

 are the valves by which the steam is admitted to the cylinder; and 

 the valves T, are the exhaust, or the valves by which the steam 

 escapes from the cylinder to the condenser. All the four valves 

 are of the same area and dimensions, but the steam-valves are 

 not lifted up so high as the exhaust-valves, for the reasons 

 which are afterwards given. The direction of the arrows ex- 

 hibit the passage of the steam in its ingress to the cylinder, and 

 its ultimate escape to the condensei-. The double-beat valves 

 of this construction have certain proportionate areas, the upper 

 portion being larger than the bottom, in the ratio of 1*158 to I'OOO. 

 The object of this enlargement of the upper part of the valve being 

 to give a preponderance to the pressure of the steam on the top 

 side, in order to overcome the pressure of the packing in the 

 stuffing-box which embraces the spindle, and to assist the gravi- 

 tating force of the valve in its descent when liberated from the 

 cams P. 



The mode of working the valves is by the shafts I, and wheels; 

 they derive their motion from the crank-shaft and revolve at 

 the same speed; the vertical spindle I, upon which the two 

 circular discs P, are fixed, passes through the steam-chests C, 

 and by its rotary motion the cams which are fixed uyon the 

 discs P, raise the valves as they pass under the rollers N, N, 

 which are connected to the valve-spindles by the cross-heads M, 

 M, *d by these means the valves are raised and retained open or 

 shut for any definite period. The rollers N, N, are steadied by 

 the cross-heads M, M, sliding upon the vertical guide-rods O, O, 

 at their outer ends, and sliding at their inner ends in vertical 

 grooves in the centre boss U, which is supported by the guide- 

 arms O, O. 



To work this engine economically much depends upon the pres- 

 sure of the steam and the amount of expansion given to the valves; 

 the usual practice is to work with steam at 15 lb. on the square 

 inch, and cut off at one-half the stroke, and expand the other 

 half; but in other cases, when the engines and boilers are calcu- 

 lated to bear a high pressure of steam, say from 30 to 40 lb. on the 

 inch, the cams are formed so as to cut off the steam at one-third 

 or one-fourth of the stroke. As is shown at P, there are 



generally three and sometimes four cams upon each of the 

 discs, so as to cut off the steam at one-half, one-third, or one- 

 fourth, or at any other point corresponding with the force of the 

 steam and the load respectively. 



To obtain this range of expansion the rollers N, N, which work 

 the steam-valves, are movealde, by brass strips which slide in the 

 grooves in the cross-heads iM, M, so as to bring the roller over 

 any one of the cams that may he required; and the fixed pointers 

 V, show by a graduated scale on each brass slide, the exact 

 point of the cylinder at which the steam is cut off, and by these 

 means the extent of expansion is regulated and brought under the 

 eve of the engineer. 



' It has already been stated that the steam-valves are not lifted 

 so high as the exhaust-valves, and the reason of this is, that as the 

 e.xhaust-valves are not variable in their action, and always require 

 full openings into the condenser, it is desiralile to retain them open 

 throughout the whole length of the stroke. This process is ef- 

 fected with a greater degree of certainty than by any other 

 description of valve; the exhaust-valves are raised suddenly by 

 the short inclined planes of the cams, and having allowed time for 

 the escape of the steam from the cylinder through a wide passage 

 into the condenser, they suddenly fall by gravitation, and thus a 

 more complete vacuum is formed under the piston than is probably 

 attained by any other process. 



The working of these valves is effected with a degi-ee of cer- 

 tainty and simplicity which renders them very satisfactory both as 

 regards their efficiency in conducing to the economy of steam, and 

 the perfect ease with which they are worked. 



Remarks made at the Meeting after tlie reading of the foregoingPaper. 



The Chairman observed that the principal part of the improvement 

 described in the paper, appeared to consist in the arrangement for effecting 

 the expansion action by cams revolving horizontally. 



Mr. W. Smith said he had seen several engines working with this expan- 

 sion gear, and could testify as to the superiority of their action ; the expansion 

 gear was very simple and worked exceedingly well ; he had taken indicator 

 diagrams from the engines. He was not acquainted with any cases where 

 this plan had been at work for a long time, and be had some doubts as to 

 the lasting of the parts. 



Mr. McCoNNELL remarked that was a matter on which they could scarcely 

 express an opinion unless furnished with accurate data respecting the work- 

 ing. The Cornish engine reports were very complete as to the performance 

 of the eneines and the consumption of fuel; and if they had such informa- 

 tion with "reference to the working of the invention in question, it would be 

 highly important as regards the improvement of the engine and in economi- 

 cal results. 



Mr. CowpER suggested the desirability of making a collection of indicator 

 diagrams in the Institution, and expressed his willingness to co-operate with 

 other members in supplying some. 



Mr. W. Smith said it was his intention at an early meeting to lay before 

 the Institution several hundred indicator diagrams which he had taken fruru 

 engines in Staffordshire and the surrounding district. 



Mr. McCoNNELL observed that the meetings of the Institution would 

 afford parties connected with large manufacturing establishments an excellent 

 opportunity for comparing the working results of engines in full action, not 

 only in Staffordshire, but in Lancashire and other districts; and it was desir- 

 able that this class of information should be as perfect as possible. 



Mr. Slate thought the diagrams referred to would read an important 

 lesson to the parties employing steam-engines, and induce them to look after 

 tlieir own interests and not waste their power. He had seen a number of 

 Mr. Smith's indicator diagrams, and the results of them would surprise 

 many ; most of them showed a very inferior action, and some showed only 

 5 lb. per inch of vacuum with 13 lb. per inch of steam ; but there were a, 

 few good diagrams amongst them. 



Mr. Gibbons remarked that one important thing they would have to at- 

 tend to was the description of fuel used, which varied so greatly in Stafford- 

 shire as to render it a matter of great difficulty to collect accurate data. 



Mr. W. Smith thought it very desirable to know the description of fuel and 

 thg consumption, wherever it was practicable; but all that he proposed at 

 present was to lay before the Institution diagrams exhibiting the economy of 

 the engine, and not the consumption of fuel. 



Mr. McCoNNELL suggested that they should not confine themselves to 

 the relative economy of the different constructions of engines, hut they 

 should also take into consideration the different constructions of boilers and 

 the relative consumption of fuel for the power produced, as well as the kind 

 of fuel employed. He saw no reason why the reports of engine performance 

 should be confined to Cornwall, for it would be highly important to have 

 them for the various other districts, more especially Staffordshire, Lancashire, 

 and Newcastle. 



Mr. Gibbons remarked that this would be extremely difficult to obtain iu 

 Staffordshire, because the quality of fuel varied to an extraordinary extent. 

 In that district they had a considerable boiler surface, and in many cases 

 ustd only coal-slack for fuel, which was good for nothing else; but in Corn- 



