. Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish . he frictionwhich results against the slides of this gate is 62 • 32 /. L E H,/ being the ratio of the friction to the pressure for the surfacesin contact, a ratio whose value should be taken from the firstTable, if we are to calculate the effort required to put the gatein motion. Example.—1Î L = 6-56 Fig. 3049, E = 1-148 ft., H =4-92 ft., the first Table gives for a wood gate of oak slidingwith crossed fibres upon oak wet with water / = 0*71 ; we liave
. Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish . he frictionwhich results against the slides of this gate is 62 • 32 /. L E H,/ being the ratio of the friction to the pressure for the surfacesin contact, a ratio whose value should be taken from the firstTable, if we are to calculate the effort required to put the gatein motion. Example.—1Î L = 6-56 Fig. 3049, E = 1-148 ft., H =4-92 ft., the first Table gives for a wood gate of oak slidingwith crossed fibres upon oak wet with water / = 0*71 ; we liavethen for the friction 62-32 x 0-71 X 6-56 X 1-148 X 4-92 1639-4 lbs. The effort should be transmitted in the direction of the racksfixed upon the gate ; and as it is considerable, it will be properto arrange a kind of screw-jack, suitably proportioned, for theestablishment of which we may take as the effort to be exertedby a man upon the winch, at any instant, from 55 to GQ lbs. at most, and during the motion from22 to 26-5 lbs. When the gate is in motion, the effort to be transmitted to the racks is much less, because 5 I. 1586 FEICTION. the ratio of the friction to the pressure diminishes, and is reduced for a gate with moistenedslides to 0 ■ 25, which gives for the friction during motion, 62-32 X 0-25LEH = 62-32 x 0-25 x 6-56 X 1-148 x 4-92 = 577-2 lbs., at the first instant, and a value decreasing with the raising of the gate, or as the head H upon itscentre is lessened. We hardly need to say that, in working the gate, we must calculate for the maximum eíFort. Application to Saw-frames.—If we have, for example, the frame of a saw for veneering, subjectedto a pressure of 110-274 lbs., and provided with iron strips sliding in brass grooves, greased withlard, we have, if the surfaces are well lubricated, for the friction, 0-07 X 110274 = 7-719 lbs., andif they are unctuous, 0-15 x 110-274 = 16-54 lbs. If the stroke of the frame is 3*936 ft., and the number of st
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Keywords: ., bookcentury1800, bookdecade1870, bookidsp, booksubjectengineering
