10 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[January, 



commodation is for 1120 sitters, of whom 3 j may, hereafter, have to make 

 ■way for an orgau. The clear internal dimensions of the church are, from 

 «ast to west, 87 feet, and from north to south G8 feet." 



ON THE CHANGE OF OSCILLATORY INTO ROTATORY 

 MOTION. 



By F. Uashfop.tii, B.A., Fellow of St. Johu's College, Cambridge. 



Notwithstanding all the disputes respecting the crank, it appears that 

 no better substitute has been or probably can be found. In fact, the beau- 

 tiful adaptation of the velocity of the end of the connecting rod to the re- 

 quirements of the piston is such as cannot be surpassed. Still there ap- 

 pears to be a great objection to the present method of employing it in 

 locomotives and some of the steamers, as the Great Britain. The piston 

 rod and the connecting rod are inclined at a considerable angle during the 

 most important part of the stroke, and this gives rise to very considerable 

 friction. 



In the beam engine, and where there is room for its application, the 

 parallel motion of Watt has been found to answer completely every pur- 

 pose, but in locomotives, &c. there is not the necessary space. For this 

 purpose it is proposed to make use of the well-know property, that if a 

 circle of radius r roll in the interior of a circle 2 r, any point in the cir- 

 cumference of the former will constantly describe the same diameter of 

 the latter. This geometrical principle has been already applied in me- 

 chanics, but never, it is believed, in the manner about to be explained. 



In figs. 1 and 2, H K represents an arc of a circle, having equal cylin- 



Fig. 1. 



/ 



V 



/ 





Fig. J. 



drical studs fixed at equal distances in the pitch circle of radius 2t,c 

 being its centre. These are fixed firmly to the frame. The bar c E, re- 

 presented by the dotted line, is capable of moving about the fixed centre c, 

 Hind at E carries the centre of the segment F G of radius r ; e E = r C D 

 is the piston rod, and during its oscillations C F is compelled to roll oa 

 H K, and C will describe a perfectly straight line. The piTot Ehad belter 

 be rigidly connected with the arm c F. The figures represent a projec- 



ion on a plane perpendicular to the axis, which is turned by the crank; 

 The diameter of K H must not be less than the length of the stroke of the 

 piston. The figures represent the necessary sines of the several parts to 

 ensure a stroke C 15, the whole of the guarding machinery being on one 

 side of the i i-ton rod. 



Figs. 3 and l represent two differnet states of the same contrivance for 



Fig. 3. Fig. 4. 



communicating motion directly to the crank, without the employment of 

 any connecting rod, and so that the axis to be turned may be placed at 

 little more than half the length of the stroke from the end of the piston. 

 The letters refer to the same parts as before, the pitch circles alone being 

 represented. 



In this arrangement the cranks must be at the end of the axis to be 

 turned. This, however, would not be of great importance in its appli- 

 cation to the screw propeller, or to locomotives, where the connecting rod 

 acts outside the wheels. It is evident, from an inspection of the figure, 

 that the velocity of C is greatest when passing c, and that it is gradually 

 brought to rest at each end of the stroke, although e E may be revolving 

 all the time. 



In order, however, to render these suggestions of any practical utility, it 

 will be necessary to point out the method of rendering the motion extremely 

 easy and durable. The studs should be made sufficiently strong to with- 

 stand the forces to be applied, and covered by short triblet-drawn brass 

 tubes, and left at liberty to revolve. These could easily be changed in a 

 short time, if they should become bruised or worn, and would save from 

 injury the constant parts of the machinery. 



It is well known, that by the geometric chuck almost perfect epicy - 

 cloids and hypocycloids can be traced with ease and rapidity. Now, 

 hese are the curves required wherever pin wheels are used. Suppose 

 t hat we have a large chuck, and that we replace the tracing point by a 

 circular drill or cutter kept constantly revohiig with its centre in the 

 place of the point, as the chuck, on which the wheel to be cut is mounted, 

 is caused to move slowly, the exact form of the teeth will be given. The 

 teeth ought to be cast sufliciently large to bear shaping by the revolving 

 tool. On account of the certainty with which almost perfect forms can be 

 given to the teeth of such wheels by ordinary workmen, it appears that 

 this method of changing angular velocity would be useful where strength 

 and freedom of motion are required, whether for turret clocks, or for in- 

 creasing the angular velocity of the screw propeller. 



The methods of forming the teeth of spur wheels in common use appea 

 to be very defective. There are so many chances of error in the setting 

 out and cutting of patterns, and afterwards in the alteration caused by 

 unequal construction of metals, that it appears desirable that 90m^ im - 

 rovenient should be made ; and I am in hopes of being able to point out a 

 method by which teeth of any pitch may be formed without any change 

 of cutter, and approximating very nearly to the forms recommended by 

 Professor Willis. 



THE RAILWAY SUSPENSION BRIDGE. 

 Patented by Mb. H. H. Rcssell. 



(With an Engraring, Plate II.) 

 The accompanying illustrations (Plate II.) exhibit the constrnclion of a 

 recently patented suspension bridge, which the inventors propose to apply 

 to the purposes of railway trafiic. We have been favoured by Mr- 

 Lapidge, the county surveyor for Surrey, at whose expense the patent 

 was secured," with a description of this invention, written with a mo- 



* A model of the bridge, upon a large icat«, may be seen at Mr. l.aptdge*s offices, 

 Derby-8tr«et, Westminster, 



