1850.J 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



275 



condenser, B the eduction pipe, C the air pump, D the cold water 

 cistern in wliicli tliey are immersed; E is the injection valve, a 

 conical valve risin;; a little above the bottom of the condenser, with 

 a perforated cap below in the cold water cistern : this valve is 

 lifted by the screwed rod F, and the admission of the injection 

 water can be regulated with the greatest accuracy by the screw. 



FIj. 5. 



The water enters the condenser in a fine sheet all round the valve, 

 which strikes the sides of the condenser and fills the whole space 

 with a fine spray ; he had ascertained this by tryina: the valve in a 

 box similar to the condenser, but partially open, with a column of 

 water of the same pressure as the injection, and he found the dis- 

 tribution of the water was so perfect as to fill the box with a com- 

 plete spray or fof;:. There was also a different construction in the 

 air-pump uliich he considered advantag^eous; the bottom dropped 

 into a well G G, in the bottom of the condenser, and the water rose 

 up the space G G, when the air-pump bucket dipped into it, form- 

 ing a water-valve instead of the ordinary foot-valve, and giving 

 pressure enough to ensure the bucket-valve opening if there was 

 any obstruction. An indicator figure, taken from the engine when 

 in full work, at 24 revolutions per minute, driving shafting and 

 two fans, indicated 72j-horse power. By an indicator figure of 

 the same engine when part of the work was thrown off, it amounted 

 to 38i|-horse power; and by another indicator figure for the engine 

 and four lines of shafting alone, without any work, amounted to 

 l-t horse-power, at the same speed of 24 revolutions per minute. 

 The engine is high-pressure, expansive and condensing, and is one 

 of a pair working coupled together; there was originally in their 

 place, a pair of high-pressure engines, non-expansive and non- 

 condensing, and the comparative economy of power effected by the 

 present engines is so great, that although the same boilers only 

 are used, there is 2j to 2,j times the power obtained. The indi- 

 cator figures exhibited by Mr. Cowper to the meeting, were drawn 

 to the scale of 20 inches length of stroke, and i-inch for each lb. 

 of pressure; and he begged to suggest that scale as a convenient 

 one to be adhered to, for indicator figures intended to be exliibited 

 to the Institution. 



Mr. Slate thought the plan of injection proposed by Mr. Cow- 

 per, was a very eligible one. AVith reference to tlie alternate 

 injection of the water, he had experienced the difficulty in marine 

 engines, of too much water being admitted by the injection cock, 

 whenever the engines were working slowly, causing the injection 

 water to clioke up the ('ondenser, and even get up into tlie cylinder, 

 and he had adoj)ted a slide valve in the injection pipe, admitting 

 only water enough at each stroke of the enyine for the condensa- 

 tion of t!ie steam; the jet of water was thiown against a perfo- 

 rated distributing plate. 



Mr. M'Co.xNELL remarked that, there would be a tendency in 

 the rose of the injection pipe, as adopted by Mr. Smith, to become 

 choked up. 



Mr. Cowper observed that in the plan he had described, that 

 difficulty was quite obviated, as in the case of the circular valve 

 becoming ehokeil, they had only to lift it up an inch or two by 

 the screw handle, and then screw it down again, and the rush of 

 water would effectually wash out any obstruction. 



Mr. M'CoNNELL considered that a great advantage, as it would 



prevent any stoppage of the engine. He thought the members 

 of the Institution were much indebted to Mr. Smith for his 

 researches, but their obligaticuis were small compared with those 

 of the iron manufacturers of the district, with whom he had 

 been more immediately brouglit in contact, as the saving proved 

 to have been effected l)y tlie improvement of the engines, formed 

 so serious a proportion to the whole expense of working them. 

 It was important that this subject should occupy the attention 

 of the iron masters, because their material must bear a proportion 

 in its price to the management bestowed in its manufacture. He 

 hoped Mr. Smith would not lose sight of the subject, but keep 

 it prominently before, not only the iron manufacturers of 

 South Staffordshire, but the ownei-s of steam-engines throughout 

 the country; and he thought this Institution was an excellent 

 vehicle for the purpose, because it was only by such an Institu- 

 tion that information could be collected in a practical foi'ni, and 

 the results be duly investigated and considered. In conclusion, 

 he proposed a vote of tiiauks to Mr. Smith, which was passed. 



BLOWING ENGINES. 



{With Engravings, Plate X.) 



On a Blowing Engine working at High Velocities. By Abchi- 

 UALD Slate, of Dudley. — (Paper read at the Institution of Me- 

 chanical Engineers). 



Mr. Slate directed attention to the various changes through 

 w-hich this description of engine has passed, the better to elucidate 

 the difficulties to be overcome, and the advantages to be derived 

 from the further change now proposed. 



The first records he has been able to collect show the blowing 

 cylinders to be single-acting, or having the power of propelling 

 the blast when the piston was moving in one direction only ; three 

 or more of these blowing cylinders appear to have been attached 

 to one crank-sliaft, worked by a water wheel, and thus a tolerably 

 steady pressure of air has been obtained. When the gradual im- 

 provements of the steam-engine and the demand for increased 

 means of manufacture caused it almost entirely to supersede all 

 other power, the blowing apparatus appears to have been accom- 

 modated as much as possible to tlie steam-engine, so as to afford 

 the character of engine for the time being, the fullest development 

 of its power. 



In pursuance of this object, the single-acting atmospheric engine 

 of Newcomen was attaciied to a blowing cylinder, which pro- 

 pelled the air from the ujiper side of the piston only, and in addi- 

 tion to the water regulator, which appears to have been known at 

 an earlier date, there was attached a cylinder, now known as the 

 regiilating-tub, which was equal to or larger in diameter than the 

 blowing cylinder. In this was fitted a piston with a rod moving 

 in a guide fixed on the open top of the regulating tub, the bottom 

 of the latter being close, and having an open connection to the 

 main from the blowing cylinder. The piston in the tub was 

 loaded to the pressure of blast required, and in the intervals be- 

 tween the discharges of the blowing cylinder, the descent of the 

 piston in the tub kept up the discharge of air into the water regu- 

 lator, which intervened between it and the furnace; thus in effect, 

 as far as possible, making the engine double-acting. To prevent 

 the piston being blown out of the regulating tub, a large safety- 

 valve was attaciied to the top of the rod by a sti-ap, long enough 

 to allow the desired jilay of the jiiston, and short enougli to lift 

 the safety-valve, or snorter, as it is usually termed, if the piston 

 at any time exceeded its limits; .and the number of strokes of the 

 engine were also regulated by the tub piston, as to it the cataracts 

 were attached. 



W hen tlie double-acting engines of Watt were introduced, the 

 regulating tub was still retainedTthough not nearly so essential a 

 part of the machine as in the forii'ier instance. 



The next change that took place was the general abandonment 

 of the water regulator (though some of these are still at work, or 

 have been within a few yeais); the reason for this change was the 

 discovery that the air in summer, already surcharged with mois- 

 ture, took up an additional quantity from passing over the surface 

 of the water in the regulator, and that this was prejudicial to the 

 working of the furnaces. 



W'hen the large area of the water regulator was shut off, it was 

 then found that the tub was by no means such a perfect regulator 

 as it was supposed to be, as the momentum of the engine passed 

 too sudden into the heavy piston of the tub, and throwing it up 



37* 



