1847.] 



THE CIVIL ENGINEER AND ARCHITECrS JOURNAL. 



39 



Indicated, or gross H.P., of the cylinder engine, , . 22-86. 



Effective H P., as per brealc .. .. .. lo'70. 



Kxliiiiiting: a loss of about 31*32 per cent. 



Effective H. P., from the rotary engine, as per breal£ .. fi'OO. 



Water evaporated per hour .. .. -. lyuolb. 



Giving (or indicated H.P.. per horse per hour .. 7H-74 lb. 



Ciiving lor effective H. P., per liorse per hour .. lUii.'ilb. 



Giviuf for combined effective H.P., per horse per hour, 86tl9 lb. 



The (Jioiensions of the cylinder engine were : 



Diameter of cylinder .. .. IDi inches. 



Length of strolie .. .. .. 3 feet. 



Speed of piston, per minute .. 263 feet. 



lilean pressure per indicator .. 10*1 lb. per sq. in. 



The dimensions of the rotary engine were : 



Diameter of wheel, 7 feet inches. 

 Number ot vanes, 3!>. 



Size of vane 4i inches wide, by 5 inches deep. 

 Two steam jets 2^ inches diameter each. 



The useful fact developed by these last experiment?, is the recovery of five 

 horses effective pnwer, in addition to 15*7 horses power from the same ori- 

 ginal steam, that is to say, steam which would otherwise have passed use- 

 lessly into the condenser, and been annihilated. It is, therefore, manifest 

 that nearly one-third more power may be obtained from any cylinder eiif;ine 

 by combining with it this rotary engine, without the use of additional fuel, 

 boiler, or apparatus of any kind.* 



With the view of proving that the auxiliary or supplemental wheel engine, 

 as combined witli the condensing engine, did not diminish the performance 

 of the latter, the indicator and break were applied to it when working alone, 

 the connexion witli the wheel engine having been shut off, and the waste 

 steam suffered to pass through its usual pipe to the condenser. Under these 

 circumstances the effective power of the Condensing Engine came out 15*637 

 horses, and the water expended as steam 115*1 lb. per horse per hour; thus 

 demonstrating that no diminution of its original power, nor increased con- 

 sumption, were occasion by its combination with the Rotary Engine. 



In order to prove that no opposition to the passage of the waste steam 

 from the cylinder to tlie condenser is occasioned by the interposed wheel 

 and case, the indicator was applied on the connecting pipe immediately in 

 front of the jet holes, and the vacuum exhibited by it was in close accord- 

 ance with the vacuum in tlie cylinder as ascertained by the same instrument. 

 The wheel-case is, in fact, a virtual enlargement of the condenser, and the 

 value of tlie vacuum in the cylinder suffers no depreciation from its inter- 

 position. The power recovered and given off by the wheel is simply due to 

 the steam's momentum — low as is its elastic force — acting by impact on the 

 wheel vanes in transitu helwecn the cylinder and condenser ; — the wheel 

 working m vacuo, and therefore, unresisted, or resisted only to the extent of 

 imperfection of such vacuum. The more perfect the vacuum maintained 

 throughout the case, the greater will be tlie useful effect obtained from the 

 wheel. 



In respect of the practical economyof your rotary engine, as regards steam 

 and fuel, and as compared with the ordinary unexpansive cylinder engines, 

 we know that the latter are not worked with less than 70 lb. of water per 

 horse per hour, and they much oftener reach or exceed 80 lb. , deduction 

 being made of friction only when the engine is unloaded, which is very 

 small. It appears, however, from the foregoing dynamometric and break ex- 

 periments, tliat fully 30 per cent, should be deducted from the gross indi- 

 cated power of the cylinder engine, as the value of its friction when loaded ; 

 or, in other words, that we realise less than 70 per cent, of the gross power ; 

 and the loss of effect when speed has to be quickly got up, as in the case of 

 marine engines working screw propellers, most probably considerably exceeds 

 30 per cent. The consumption, therefore, of 100 lb. of water as steam per 

 horse power, per himr, by your engine, maybe considered, in respect of 

 economy, as placing it on au equally advantageous footing with the class of 

 engines alluded to." 



The errors of calculation here exliibited appear to be just tlie same 

 as before, and destroy all contidence in the results. The question of 

 the expediency of employing the revolving steam-wheel resolves it- 

 self simply into this — is more power gained from the impinging force 

 of the steam than is lost by obstructing its passage from the cylinder 

 to the condenser ? The assertion that no force is lost by thus imped- 

 ing the passage of the steam is manifestly absurd ; for it is equiva- 

 lent to saying that the efficiency of the condenser is just the same, 

 whether the steam-ways be large or small. Mr. Parkes alleges, in 

 proof of his assertion, a circumstance which does not bear on the case 

 in the slightest degree. Premising that the power of the condensing 

 engine in both cases " came out" nearly the same (by his calculations), 

 he adds, when the rotary engine was at work, the vacuum in the cy- 

 linder and condenser was nearly the same. But the obvious wav of 



* By reference to the coal account, during the last eighteen months, 1 tind that a sav- 

 ing of 100 tons of coals has been effected within that period, by worliing the wheel in 

 connection with the cylinder engine, whilst the power recovered from the cylinder engine 

 has been more than equal to the duty performed by a separate engine, previously employ- 

 ed tor that purpose only. And 1 also understand that the Rotary has not cost 5s. in re- 

 pairs during that time; that the packing, in the stuffing boxes of the v\heel-axle, lias 

 been but once renewed j and that nothing has occurred to require the case to he opened. 

 —J. P. 



testing his assertion was to try whether the vacuum in the cylinder 

 was the same when the rotary engine was connected, and when it 

 was disconnected — that is, to ascertain whether the resistance to the 

 motion of the piston from imperfect condensation was not increased 

 by the interposition of the steam-wheel. 



We by no means take on ourselves to decide absolutely against the 

 merits of Messrs. Cordes and Locke's invention. On the contrary, so 

 little is known of the iinpinging force of steam that the question is 

 still fairly arguable whether more be not gained by employing that 

 force than is lost by obstructing the passage to the condenser. The 

 circumstance stated in the foot-note, of 100 tons of coal being ?aved 

 in 18 months, seems of itself an unmistakable fact — a vote defait, as 

 the French call it — in favour of tlie invention. At all events, the in- 

 ventors deserve the credit of calling attention to a very interesting 

 subject, and it may be hoped that for the sake of science they will con- 

 tinue their investigation. The foregoing remarks refer exclusively to 

 the erroneous methods of calculation adopted in the report sent by 

 them, and will, we hope, direct — not repress — their efforts. 



DECIMAL METAL GAGES. 



We wish to direct the attention of our readers to Mr. Iloltzapffel's pro- 

 posal for assimilating the Gages of Metals, by adopting a universal decimal 

 system, as set fortli in the annexed Table. 



Values of Gages /or Wire and Sheet Metals in general use, ex'jiressed in 

 decimal parts of the inch. 



