. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . Effort 63 75% Cut-Off 211^ Pounds B. Starting Ports Min. Starting= =43,400 lbs. Effort 63 August, 1927 RAILWAY AND LOCOMOTIVE ENGINEERING 243 Assume now a similar locomotive having the same sizeof cylinders, but with the cut-off limited to 75 per cent ofthe stroke. With this reduction in cut-off it will be nec-essary to increase the boiler pressure to 2\\y2 pounds toobtain an equal nominal starting effort of 68,700 will further assume that the startin
. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . Effort 63 75% Cut-Off 211^ Pounds B. Starting Ports Min. Starting= =43,400 lbs. Effort 63 August, 1927 RAILWAY AND LOCOMOTIVE ENGINEERING 243 Assume now a similar locomotive having the same sizeof cylinders, but with the cut-off limited to 75 per cent ofthe stroke. With this reduction in cut-off it will be nec-essary to increase the boiler pressure to 2\\y2 pounds toobtain an equal nominal starting effort of 68,700 will further assume that the starting ports are omit-ted. The gray circles will then indicate the position ofthe cranks at the moment of cut-off of the main steamport. In this position the leading crank is only 30 the back dead center, giving a maximum startingeffort of 27,750 pounds, or only 64 per cent of that givenby the locomotive with full gear cut-off. By the addition of auxiliary starting ports, the virtualcut-off is lengthened to 88 per cent of the stroke. Theposition of the cranks will then be as shown by the black. Fig. 4—Effect of Starting Parts on the Minimum Starting Forceof a Limited Cut-Off Locomotive circles, and by this means the starting effort is increasedto 43,400 pounds, or equal to that of the full gear is obvious from this illustration that for any cut-offless than the maximum with which it is compared, aux-iliary starting ports must be provided to give equalstarting power. Thermal Efficiency The two outstanding reasons for the adoption of thelimited cut-off principle in locomotive construction are,increase in capacity and economy in fuel. Both of thesedesirable objects may be realized in the same design. While the major portion of the fuel economy is at-tributable to the reduction in cut-off a significant meas-ure of it is due to the improved valve conditions whichaccompany the limitation of the maximum cut-off. There is a decided tendency today toward longer valvetra
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectrailroa, bookyear1901
