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Supplement to Spons dictionary of engineering, civil, mechanical, military, and naval (1879) (14784201702)

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Supplement to Spons dictionary of engineering, civil, mechanical, military, and naval (1879) (14784201702)

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Identifier: supplementtospon02spon (find matches)
Title: Supplement to Spons dictionary of engineering, civil, mechanical, military, and naval
Year: 1879 (1870s)
Authors: Spon, Edward Byrne, Oliver Spon, Ernest Spon, Francis N
Subjects: Engineering
Publisher: London, New York, E. & F.N. Spon
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Smithsonian Libraries



Text Appearing Before Image:
ork for upwards of eighteen months, in a seamvarying from 22 in. to 30 in. in thickness. The coal is hard and is worked on the long wall system,in a face of about 200 yds. in length. The average of one months work in this mine is 130 yds. a shiftof nine hours, inclusive of stoppages, or 14; yds, an hour ; the undercut is 3 in. high, 3 ft. into thecoal, and close to the floor of the seam. The maximum speed of undercutting is said to be 60 yds.an hour; but this can only apply to a seam in which the holing is very easy, Alexanders coal cutter is supported by wheels, and carries two cylinders with their pistons,valves, and usual details for obtaining motive power from the action of compressed air. Figs. 891and 892 are vei-tical sections at right angles to each other, showing the gearing for obtaining theprogressive movement of the machine along the coal face; Fig. 893 is an inverted plan showingthe mode of connecting the jib to the under side of the frame; and Figs. 894 and 895 are a plan
Text Appearing After Image:
and an edge view of one of the links of the endless chain of cutters. In this machine the jibD is mounted so that it can be swung round in either direction from its usual position, wldch is atrio-ht anodes to the coal face, into a position parallel to the face. This enables the machine to beused to cut its way into and out of the coal face without previous undercutting by hand. For thispurpose the inner end of the jib D is curved out of the plane of the endless chain, and formedwith a laro-e eye, to fit and turn on an annular flange, formed on the under side of the main plate.The jib D is held by an annular plate bolted beneath it to the flange after it is put in its place.The rim is formed with worm-wheel teeth, and the jib is turned as required by means of a wormscrew engaging with these teeth, the shaft of the worm being turned with a ratchet lever by hand,or by progressive gearing worked by the machine itself. The jib D is fixed in its right angle positionafter being entered into

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