1839.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



J 99 



BUNNETT AND CORPES CONCENTRIC STEAM-ENGINE. 



Fif! 1. Elcvnlioii iifa Hii,'li-pres»iii'e Engine 



Fig. 2. A Longitnilinal Section 

 talten tliroiigh the centre of llie Engine. 



Fig. 3. Transverse Ssction 

 takeo tlirougU tlie ceutro of the Ens;ine. 



'^- ,!-.i^»1 



The letters of reference are the same in both sections. 

 A — Is thefi.Ned slialt in tlie centre of the engine, on which llie connecting 



arms supporting" tlie piston rod, and carrying a cro.ss liead oi piu for tlie 



connecting rod to oscillate freely upon. 

 B — Sleani chamber in which the piston reciproe.ites. 

 C — Piston. 

 D — Circular piston rod, which is made of stquare steel, admitting of metallic 



packing to the stutling bo.xes. 

 E — Blockings against which the outside covers of the cylinder are bolted, 



and also carrying the metallic .slutting boxes. 

 FF — The slide valves shewn at one-third of the stroke. 

 G — The Exhaust. 



HH — The pipes conveying the steam to the slide valves. 

 II — The connecting arms oscillating on the fixed centre shaft, and carrying 



the weight of the piston, piston rod, Sec. 

 KK — Are the steam ports. 



BUNNETT AND CORPE'S NEW PATENT CONCENTRIC 

 STEAM-ENGINE. 



Messrs. Bunnett and Corpe, of Deptford, tlie patentees and inventors 

 of the im[)roved iron sat'ety-slmtter, now In such liigli estimation and 

 extensive use, have lately taken out letters patent for a concentric 

 steam-engine, drawings of which we have given above. We shall tiist 

 state the action of the engine, as we saw it at work in the paten- 

 tees' manufactory, and then proceed to point out its advantages. It will 

 be seen, tliat in appearance it is similar to a rotatory engine, but its- 

 action is of a decidedly diH'eieiit character. The circular case, as shown 

 in lignres I and 2, forms in the lower part the steam-chamber, in 

 which is accurately (itted a sipiare piston, with Barton's patent 

 metallic packing. Through the centre of the piston, and attached to it, 

 is a concentric or ring-liUe piston-rod, which at a point opposite to 

 it (the piston) is lirinly embraced and supported abovi; by two con- 

 necting arms, liaving a double bearing upon a fixed shaft in the 

 centre of the engine ; on which they oscillate sufficient to allow the 

 piston to reciprocate freely. The piston-rod is made of square steel, 

 and works through two metallic-stuffing boxes in the top of the steam- 

 chamber ; and from the side ol'one of the arms above mentioned projects a 

 pin, to which is attached the coiuiecting-rod transferring the power of the 

 engine to the crank of tlie fly-wheel and gear. On each side of the steani- 

 chamber are two distinct slide-valves, worthy of particular notice: they take 

 their motion from an eccentric on the crank shaft, and have two slide- 

 boxes or covers, by which means no steain is lost by exhaustion in tlie 

 passages, as in the single slide, the exhaust is also fully open at the 

 No. 21 — Vol. 11.— June, 1839.' 



commencement of the stroke, and remains so to any subsequent part of 

 it that may he desired. By this arrangement of the valves, the steam 

 can he worked expansively or not without cams, tappet, or gear of any 

 kind, the slides of themselves cutting oH" the steam at any part of the 

 stroke. Having thus explained the structure of the engine, we will now 

 proceed to show its mode of operation. The steam-valve being opened, 

 and the exhaust-valve closed on one side, and the contrary on the 

 opposite side, tiie steam is admitted, and propels the pistoii forward to 

 the opposite side, when the steam-valves ch.ange their position, and the 

 steam is admitted on the opposite side, which again propels the piston 

 back to its original position,— and thus, by the backward arid forward 

 motion of the piston, it passes through two arcs of a circle, similar to a 

 pendulum, and carries with it the annular piston-rod and the arms at- 

 tached to it, thereby sets in motion the connecting-rod ; the piston being 

 entirely carried or suspended by the arms attached to the fixed centre 

 shaft, is relieved from all tendency to wear irregulaily, there being in 

 fact, no pressure upon it beyond that of the springs necessary to keep 

 the segments in their places. 



By the simple arrangement and working of the engine the connect- 

 ing rod has a direct action, without the intervention of guide rods or 

 parallel motion of any kind, and during the time that the greatest 

 force is required upon the crank, it never forms an angle of more than 

 live to ten degrees ; its reciprocating motion describing an arc of 

 a circle, which so nearly assimilates to the rotatory action of the crank, 

 the changes of motion are effected with surprising ease and rapidity; 

 and whether it be from the direct application of the force upon the crank 

 alone, or the absence of parallel motion, or from tlie power bi'ing- com- 

 municated as it were, upon an inclined plane, direct to the connecting- 

 rod, or by a combination of all these, very great power is most cer- 

 tainly gained. 



The patentees have made several experiments, some of which we 

 witnessed, proving the advantai;es of the position of their connecting 

 rod and crank motion over the methods now in use in locomotive 

 and other engines, we have annexed a table of these experiments. By 

 these it will be seen that in some positions of the crank, it having just 

 pas.sed its centre, nearly double the power is obtained, and taking- the 

 average of a whole revolution of the crank an advantage of more than 

 one-third is gained ; the experimental engine was set in motion in our 

 presenee, and with a piston of 24 inches snperlices and a pressure ot 

 'JDlbs. only on the square inch, it exhibited great power, driving 

 several lathes, drilling machines, &c., while without any load 

 crank performed upwards of iJliO revolutions in a minute. It is 



the 

 the 



