1846.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 29 



a: . , \± s 



pinion at d, and if a vacuum be formed by pumping out, or exhausting the 

 air from the front of the piston in the usual and well known manner by air 

 pumps worked Iiy steam engines or otherwise, the pressure of the natural 

 atmosplierc will urge tlii« piston onwards towards the vacuum, if permitted 

 to do so, and conseijuently the rack with it, and that being in gear with the 

 pinions, cannot advance without turning them as it passes, and also there- 

 fore that portion of them which is outside, the tube, as at q, q, Fig. 1. There 

 may be pinions on each side of the tube, opposite eacli other, as shown in the 

 enlarged section fig. 9, if advisable, wliich wil) render it necessary that the 

 " rack " should be double, or cogged on both edges as shown ; and hereafter 

 I shall describe and consider this to be the case throughout the following 

 deicriptiou, as being the most comprehensive form, although si7ig!e " racks " 

 and " pinions" may be found generally the better plan in practice, when the 

 difference is merely the use of one pinion instead of two, as before described, 

 and the " racks" being cogged only on one side, the " carriage rack " in such 

 case must have a guide to keep it to the pinion, which guide may be a plain 

 upright, or a plain or uncogged pinion, in the place of the pinion so removed. 

 To the under part of a railway carriage, in any convenient manner will be 

 attached a limilar "ratk " to the " piston rack," (but without the piston or 

 plain part as at o, o, in fig. 3,) which is called the " carriage rack," such a 

 rack is shown in the annexed figure, fig. b, the front end is tapered or pointed 

 to render easy its entrance between the pinions, and fig. 7, a front view, and 

 fig. 8 a sidt view ; s, is one of the places where it is attached to the carriage. 

 The rack is made precisely to correspond with the internal or " piston-rack," 

 and will be the exact width the pinions arc apart, so as to be in gear like the 

 "piston rack," with the two opposite pinions at one and the same time ; 

 this rack also is the length of the other, so that it may reach two or more of 

 the pinions or pairs of pinions at once. Fig. 9 is a transverse section of the 

 tube, with opposite pinions, showing also a section of the carriage rack t, t, 

 and a section of the " piston-rack" at ti , both racks being in gear respec- 

 tively with the pinions v,v,v.v. The boxes or projections, ic, which contain 

 *he lower part of the pinions, will have a hollow or chamber, to permit the 

 said pinion to revolve freely, but to be made and put on to the tube air-tight, 

 having but one opening into the inner part or chamber, viz. alj. (Figs. 2 and 

 9) through which the spindle of the pinion passes. To admit of the pinion 

 being put into its place, the box must be made to separate and go together at 

 a vertical joint abova j, and by bolts ?/. and air-tight. To make the passage 

 of the spindle from the exterior to the interior of the tulx' air-tight, to be 

 so, upon the spindle of the pinion (l«low the upper cogged part) is a flat 

 sliuulder, era conical or bevelled one, at an angle of about 10°, as shown at k, 



(Fig. 2) and the upper edge of the passage through which the spindle passes, 

 .7. is also bevelled, and both truly ground, so that when the spindle is down 

 in its place, the conical part of the spindle fits and becomes air-tight, in the 

 manner of the common valve known by the name of the " spindle or conical 

 valve," and thus prevents the passage of air through or by this passage ; or, 

 instead of making the part conical, make a simple flat shoulder ground true 

 to the edges (horizontally) of the upper part of the passage. Another method 

 is a combination of these two, as shown by fig. 9, where, instead of the flat 

 shoulder, is a flat plate or disc, through which the spindle passes, having a 

 conical part ground to a corresponding surface in the plate, as at i. This 

 modification is for the purpose of preventing much friction, when the 

 passage is required to be large, in case of the pinions turning round when 

 pressure is upon them, thus permitting the smaller circumference of the two 

 (the conical) turning instead of the larger flat one at its outer edges, where 

 it will lie upon the "pinion box." That the pinions may be lifted up, 

 and therefore the valve part also from its seat, (as shown by the pinions 

 in fig. 9) the pivots are made long enough and the " chamber " in the tube 

 and " box" large enough to permit of it. When the pinions are lifted up, a 

 free passage is allowed for the ingress of air into the tube ; and to make this 

 passage under these circumstances as lar,L;e and free as possible, several side 

 Passages may be made also, as shown at 3, fig. 9. when the " piston rack" is 

 within the tube in its desired situation, and the cogs of the pinions in gear 

 with those of the rack, the lower surface or end of the pinion cogs 4, will 

 rest upon the plain piece (before explained) on the " piston rack," which 

 makes a kind of shelf or ledge for the cogs or teeth ; and thus, if this rack 

 be so arranged as to move in a line rather higher than the pinions are placed 

 when down, (as in fig. 2) it will cause them to be lifted up when it passes 

 them, so avoiding the friction of the air-tight shoulders, and permitting air 

 to enter into the tube during this action as may be essential to the efficacy of 

 the apparatus, as will be hereafter explained. 



The '• carriage rack" may be attached to the under part of any railway 

 carriage (the first carriage of a train) by any suitable means ; but the ni- 

 ventor prefers the following mode of doing it, which will be understood by 

 reference to figs. 6, 7, and 8, the two parts 5, 5, arc firmly fastened to 

 the under part of the carriage, or to a piece of timber supported by and suit- 

 ably attached to the axles of the carriage ■, in the under part of these sup- 

 ports is|formed a groove or slot, 6, 6, and upon the rack are fixed suitable pro- 

 jections, 7, 7, through which bolts, 8, 8, are passed, going also through the 

 slot in the support. These bolts, then, resting at the bottom of the .slots, 

 support the rack in the horizontal position shown, a little lateral play being 



