Cyclopedia of locomotive engineering, with examination questions and answers; a practical manual on the construction care and management of modern locomotives . against its seat,and inventors have racked their brains for many yearsn efforts to produce a valve that would work withoutfriction, and at the same time give a correct distribu-tion of the steam to and from the cylinders. The piston valve, while practically balanced, owing£o the pressure of the steam acting upon each end, is,pevertheless, not a perfectly balanced valve unless the 161 162 LOCOMOTIVE ENGINEERING valve rod extends through
Cyclopedia of locomotive engineering, with examination questions and answers; a practical manual on the construction care and management of modern locomotives . against its seat,and inventors have racked their brains for many yearsn efforts to produce a valve that would work withoutfriction, and at the same time give a correct distribu-tion of the steam to and from the cylinders. The piston valve, while practically balanced, owing£o the pressure of the steam acting upon each end, is,pevertheless, not a perfectly balanced valve unless the 161 162 LOCOMOTIVE ENGINEERING valve rod extends through both ends of the valvechamber, and this necessitates an extra gland and setof rod packing. In order to more clearly illustrate!this idea, reference is made to Figs. 69 and 70. shows a plain D slide valve, and it will be noticedthat the full pressure of steam in the valve chest actsupon the back of the valve. Of course there is a cer-tain amount of back pressue from the steam port andexhaust port that tends to overcome the direct pressure;,,still there is an enormous strain on the valve gear that-is required to move a valve under such Figure 70 Fig. 70 shows a solid piston valve with outside admis-[sion, being thus identical in action with the D valve rod is shown in either cut, but it willeasily be seen that with the valve rod attached^to but one end of the piston valve the area of thatend will be decreased just so much, and the valvewill be unbalanced by an amount equal to the sectionalarea of the valve rod, but this amount is so insignifi-cant that builders very seldom add the extended valverod, and so the piston valve may be considered asbalanced, the only friction being that due to the PISTON VALVES AND BALANCED VALVES 163 1 height of the valve and the friction of the packinglings when the valve is fitted with them. In some!/pes of piston valves the live steam is admitted,^side, between the heads, as shown in Fig. 71, andrie exhaust passes out
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectlocomot, bookyear1916
