. Supplement to Spons dictionary of engineering, civil, mechanical, military, and naval. lutions a minute, the friction required to transmit the same amount ofhorse-power is proportionately less, and accordingly falls below the limit at which the belt beginsto slip. This formula is represented as a curve in Fig. 1068by means of which the value of the ratio of W to P maybe readily found, for any values of the coefficient offriction and arc of contact. Thus if the coefficient offriction / be i or 033, and the arc of contact a be 2,that is twice the radius, then the product/ x a is 0*67;and findi
. Supplement to Spons dictionary of engineering, civil, mechanical, military, and naval. lutions a minute, the friction required to transmit the same amount ofhorse-power is proportionately less, and accordingly falls below the limit at which the belt beginsto slip. This formula is represented as a curve in Fig. 1068by means of which the value of the ratio of W to P maybe readily found, for any values of the coefficient offriction and arc of contact. Thus if the coefficient offriction / be i or 033, and the arc of contact a be 2,that is twice the radius, then the product/ x a is 0*67;and finding this point on the bfiseline, the correspondingheight is 1*95, which is therefore the value of the ratio of — . In order to check the formula, the drums were heldfast in their bearings as before, and an adjustable rollerwas introduced between the belt and the circumference of the drum, so as to vary the extent ofcircumference embraced by the belt. The number of degrees in the arc of contact was approximatelyestimated. The following values of the ratio of W to P were obtained ;—. Numberot Diameter of Arc of 1Weight Weight Value of Mean Valueof Ratio ^. TheoreticalValue of Error percent. Experi-ment. Drum. Contact. of P. ofW. Eatio^. Ratio - . inches degrees lb. lb. 29 14 25 1-786 30 15-8 120 42 84 2-000 1-902 1-938 1? 31 70 147 2-100 32 14 24 1-714 33 24-0 123 42 78 1-857 1-809 1-778 If 34 70 130 1-857 35 14 34 2-429 36 16 39 2-437 37 38-8 144 21 52 2-476 2-506 2-491 i 38 28 70 2-500 39 42 109 2-595 40 70 182 2-600 the These experiments fully confirm the results arrived at by theorv,friction to the arc of contact; and this relation mav b^ illns+mip , in reference to the relation ofand this relation may be illustrated by the fact that the frictionobtained by two turns of rope round a post, whatever be its diameter, is the square of that obtainedby a single turn, while three turns raise it to the cube, and so on. Thus a single turn of a hemprope round an oak post gives a val
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectenginee, bookyear1879
