A Manual of the Mechanics of Engineering and of the Construction of Machines Volume 3, PT. 1; Designed as a Text-Book for Technical Schools and Colleges, and for the Use of Engineers, Architects, Etc

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1883 Excerpt: ...is very troublesome in the shafts of centrifugal machines, which with their extraordinary velocity (about 1,000 revolutions per minute) soon begin to run unsteadily, and as this evil is increased by the high speed, serious accidents sometimes result. In this respect the use of a double mechanism, such as is shown in Fig. 167, may be regarded as a decided improvement. Here two flat disks A and A'are placed upon two shafts CD and CD ' which run with equal velocity but in opposite directions. The flat disks are pressed against See Zeitschrift deutsch. Ing. 1874, p. 531. the disk E so that the shaft G F is subjected to no lateral pressure whatever. The belt pulleys H and H' are of course driven by means of a crossed and an open belt. In order to effect the transmission of great forces by friction wheels, without employing too great a pressure, the arrangement shown in Fig. 168 may be employed, an end Fio. 167. Fio. i63. view DAD being given of one wheel and a section through the rim BAB of the other. Here the surfaces of the wheels consist of a number of V grooves so arranged that the projections on one wheel enter the grooves of the other. That this will cause an increase of friction is evident from the theory of the wedge, the force R which presses the wheels together being resolved into two components, the relation between R and N being given by: a representing the angle included between the sides of the groove. As in former examples (§11 and § 31), we determine the friction which resists the sliding of the surfaces of the wheels on each other to be: For this case, also, some text-books give F =?--; the remarks of § 31 are therefore here applicable. Fig. 170. Theoretically the number of grooves employed is immaterial, but practically several g...