ists. 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



183 



heat contained in Ihe water required by such boilers, would give but 

 3,000 cubic feet of steam at 20 lb. pressure. The boiler under cunsiiiera- 

 tion is equally successful in diminishing the risk fron) ex[)Iosion, arising 

 from the rending strain due to the pressure of the steam — as. on a com- 

 parison with the common boiler, in which we suppose the steam at only 

 Z6 lb. pressure, the rending force in such common boiler is 5,400 lb ; whilst 

 in the tubular, even with 100 lb. pressure, the rending force amounts only 

 to 900 lb., or but one-sixth of that given in the instance of the common 

 boiler. The most obvious and certain conclusion to which such well- 

 established principles lead, cannot fail to show how ill-grounded and 

 unscientific must be the objections raised against high-pressure steam, 

 when generated in such boilers. 



4. The laws relating to the expansive action of steam plainly indicate 

 the importance of the two leading features of the matter before the meeting 

 — viz. : that of removing the atmospheric pressure from the exhaust side 

 of the piston on the one hand, and. on the other, enabling us to ujake use 

 of high-pressure sleam with safety ; as by the removal of Ihe atmosphere 

 in non-condensing engines, an economy is produced by this cause alone 

 equal to 38 per cent. ; and, by increasing the pressure of the steam at the 

 commencement, can be obtained a further increased economy upon the 

 Cornish system, equal to 40 per cent. 



[Mr. Craddock here described, by means of plans, his boiler and con- 

 denser.] 



Considerable discussion ensued upon the reading of this paper; the 

 principal objections to the conclusion said to be arrived at were tliose 

 raised by Mr. M'Connell. It was asked by him, if any trial had been 

 made with the engine in actual work ? ftlr. Craddocic replied, that the 

 tiial he deemed most proper to submit to the meeting was that made at 

 the London Works (Smethwick), because it must be free from all suspi- 

 cion ; and that to the authenticity of the indicator figures taken olf the 

 engine when there, he had no doubt Mr. Cowper would satisfy the meet- 

 ing. 



Mr. CovvPER said, he had taken some indicator figures off the engine, and 

 that it was then doing 20-horse power — that is, indicator horse-power ; the 

 condenser then took l^-horse power to work il. 



Mr. M'CoNNtLL then raised an objection, that the engine was not tested 

 with the other engines working at the London Works. 



Mr. Craddock replied, that he had always expiessed a wish that it 

 should be so tested, but the firm nut intimating its assent, it was not fur 

 him (Mr. C.) to insist upon anything of the kind. 



Mr. Stephenson, Mi-. M'Connell, and Mr. BiCKLEsaid, that the test of 

 pumping water, or some such work, was the best test of power. 



Mr. Craddock replied, that he was a little surprised that Mr, Buckle, 

 the representative of an ancient and eminent firm, should object to the in- 

 dicator as a fair test of the power of the engine, when it was well known 

 that the indicator was the instrument used by them to test the power of 

 their own engines. 



It was argued by Mr. Crampton, that the only advantages the double- 

 cylinder engine possessed over the single one was greater steadiness of 

 motion ; but this did not compensate for the loss of power, whiih, he con- 

 sidered, arose from the use of two cylinders, in the steam passing from the 

 one piston to the other. Some time ago, he had made some elaborate ex- 

 periments upon that very subject, and his conclusions then, were, that the 

 loss amounted to 14 per cent. 



Mr. Craddock replied to Mr. Crampton, by admitting a loss in the ex- 

 pansion, which took place between the two pistons ; but, in the small 

 engine before the meeiing, it was obvious that this was reduced to the 

 smallest possible amount: he further called l\Ir. Crampion's attention to 

 the great irregularity of motion that would result by currying the expan- 

 sive principle to a great extent into one cylinder. Mr. Craddock here 

 referred to an expeiiment made on the previous evening with the small 

 engine before the meeting ; it v\as scarcely necessary for him to remind tlie 

 meeting, that in so small an engine, when first started, the friction was con- 

 siderable; yet it had worked up to its speed, with the sleam cut off at 

 l-60th of the stroke. 



Mr. Crampton replied, that the steam would lose all its power before 

 expanding to such an extent. 



Mr. Craddock said, if Mr. Crampton would favour him with a call at 

 the Works, he would show him the fact expei-imentally. He wished fur- 

 ther to remind the meeting that, from his own experiments, he was con- 

 vinced that, by admitting high-pressure steam direct fiom the boiler into 

 one cylinder, much of it was condensed by the compaiatively cold metal 

 of such cylinder ; and that the water resulting therefrom, being in contact 

 with the metal of the cylinder, did, when placed in conununication 

 with the condensei-, again assume the form of steam, thereby uselessly car- 

 rying much heat from the boiler to the condenser, without producing me- 

 chanical effect. But as he had stated his views upon this sulject else- 

 where, and as it may appear to the meeting a somewhat abstruse subject, 

 if not an hypoihetical one, he would not trespass upon the meeting by any 

 further remarks upon it. 



Mr. M'Connell said, that he was somewhat surprised that after the 

 length of time which Mr. Craddock had devoted to the subject under dis- 

 cusion, he had not arrived at some more accurate data, and had not made 

 up his mind as to the real capability and comparative advantages of his 

 boiler, 



Mr, Craddock replied, that although he had certainly devoted much 

 time to the practical consideration of the subject, he had not directly 

 deduced such accurate data as would justify him in stating definitely the 



comparative merits as to economy of coals in the generation of a given 

 weight of steam ; but, nevertheless, if Mr. MConnell would favour him 

 with a call at the Works, he had no doubt he should he able to show him 

 he hiid not been idle, but he had been driving after great points, knowing 

 full well ihat on these depended the economy. 



Mr. M'Connell said, that it appeared to him that the condenser was most 

 valuable for marine purposes. 



Mr. Craddock replied, that its advantages for such purpose may be 

 staled in a lew words, as the condenser would ensure waler, fi'ee from de- 

 posit, for the use of the boiler, thereby rendering tubular boilers pi'actica- 

 ble, they enabling us to generate high-pressure steam with safely ; and 

 thus, by carrying out the expansive principle, with other consequent ad- 

 vantages, a saving of £2,000,000 sterling per annum may be effected in 

 our steam navy. 



Mr. Jackson proposed, that in order to test the relative value of the 

 single and double cylinder engine, and set that question at rest — at least 

 so far as that Society was concerned — Mr, Crampton he requested to pre- 

 pare a paper and diagrams on the subject, to be laid before ihe members at 

 a subsequent meeting, 



Mr, Craddock suggested, that a more conclusive test would he that of 

 an engine having two cylinders, one of which could be readily thrown out 

 of action ; its being connected with ihe same boiler, expaiuliiig the sleani 

 to the same extent, and performing the same work — the steam and coal re- 

 quired, in both cases, being accurately weighed — would give the most 

 salia'actory solution. 



The request to Mr. Crampton being carried unanimously, he (Mr. 

 Craddock) couseuted to comply wiih such request. 



HYDRAULIC STARTING APPAR.\TUS. 



Mr. FoTHERGiLL read a paper, descriptive of " A Hydraulic Apparatus, 

 for Connecting Heavy Machinery, and Disengaging the sa^ie from the Prime 

 Mover, without producing those Sudden Shocks ivhich the use of Ordinary 

 Clutches occasion." J3y Mr. Jackson, 



A level pinion is supposed to he connected wiih the engine, or other prime 

 mover, and gears into a bevil wheel, to which is cast a rim, which is turned 

 internally. The wheel turns loose upon a shaft, being lined with a brass 

 bush ; the shaft, however, is provided with four projections, through each of 

 which a hole is bored — the centre lines of these holes lying in one horizontal 

 plane, and meeting in one common central chamber. In these holes four 

 rams, which are respectively cast of one piece, with blocks, are fitted, the 

 blocks being lined with copper, and turned, so as to fit the internal surface 

 of the rim. Supposing that the machinery, which is assumed to be con- 

 nected with the shaft, required to be started, hydraulic pressure is applied 

 to the under rams, by pressing the ram which is in the shaft down upon a 

 column of water, also contained in the shaft and the common central cham- 

 ber, by means of a fly-wheel, which, with its nut and a screw, forms one 

 piece with the ram — this ram, the nut, and screw, being guided and sup- 

 ported by a lirass box, which is screwed into the upper end of the shaft. It 

 is evident, that on the ram in the shaft being thus pressed down, the under 

 rams will gradually and simultaneously press the segments against the inter, 

 nal surface of the rim, with a power proportionate to the force applied at the 

 circumference of the fly-wheel, until the friction produced by such pressure 

 shall be equal to the resistance of the machine to be set iu motion. The 

 machine will, therefore, gradually assume the velocity, which, according to 

 the speed of the driving-shaft, it ought to have; at the same time, that any 

 extraordinary momentary resistance, such as might be supposed to occur 

 occasionally in rolling-mills, or other machinery of a similar nature, instead 

 of causing the wheel to break, will have a tendency to make the rim to slip 

 on the segment until the obstacle be removed, or overcome. In order, how- 

 ever, that too great a pressure may not be applied to the lower rams, the 

 upper one and the screw are perforated with a small opening, the extremity 

 of which is closed by a valve, acted upon by a spiral spring, encased in the 

 brass box — so that if, at any time, the pressure exerted upon the rams 

 should exceed that to which tne spring is regulated, the water would lift the 

 valve, and escape through it into the box, and through an opening in the lid 

 of the latter into the atmosphere, until the balance of the pressure was again 

 established. 



Mr. M'Connell wished to know, whether there was any other means 

 than that supplied by the safety-valve, if he might so call it, whereby the 

 maximum of pressure could he ascertained. 



Mr. FoTHERGiLL remarked that, in fact, the machine was a self-acting 

 regulator. A certain amount of resistance was required to make the rams 

 work, and whenever the resistance became too great, the spring and the 

 valve carried off the superfluous power. — It was resolved by several of the 

 members, that the cone seemed to answer every purpose which this machine 

 was intended for ; but it was argued by Mr. Fothergill, that Mr. Jackson's 

 machine removed the greatest objection to the use of the cone — viz., the 

 backward pressure. By the present invention, the pressure was confined 

 altogether to the direction in which it was wanted. Several other members 

 expressed themselves highly pleased wiih the machine ; and after a vote of 

 thanks had been passed to Mr. Jackson, it was resolved to print the com- 

 munication, and lithograph the diagram, for the use of the members. 



