Problems in Machine Design (Paperback)

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. 1899 Excerpt: ...to CM, . Suppose the lap increased to C M2, then the least velocity of cut-off is reduced and is proportional to G3 N2; but, on the other hand, the latest cut-off possible is at C H. In fig. 105 is shown the effect of reducing the angle KCE. This reduces C G3, and therefore the least velocity of cut-off; but if the latest cut-off is fixed, this reduction lessens C Go. Suppose E C K and the lap fjxed, then an increase of the angle of advance of the distribution eccentric increases C G E, without any corresponding advantage, so that the angle of advance of C E should be small. In order to obtain this, we may make cut-off by the distribution valve take place at about 8 of the stroke. In fig. 107 this has been done, and the expansion valve so designed that cut-off can take place anywhere from the commencement to six-tenths of the stroke. The angle of advance of C K is 60 deg., and Fio. 107. E G is drawn parallel to C K; from G on the circle G m2 is drawn perpendicular to Ch, giving the negative lap. Cg is perpendicular to E G, and when the half travel of the expansion valve is Egr the cut-off takes place with least velocity, the crank being at C;if CI is the outside lap, I being on CH, then the velocity of cut-off of the distribution valve is proportional to El, and of the expansion valve, which is double-ported, to twice g It will be found on measuring the figure that 2gmx = El, so that these velocities are equal. It must be possible to reduce the half travel of valve to En, Mra being perpendicular to AB, if cut-off is to take place at the commencement of the stroke; if its least value U greater, the earliest cut-off will be only a trifle later. The greatest relative travel of the two valves has been made equal to that of the distribution valve, and its greatest.