Logging; the principles and general methods of operation in the United States . The gate is raised by the pressure of water from the upperpool, which is conveyed in a channel, controlled by a sluicegate, to a chamber (^), Fig. loi. constructed under the second channel, also provided vvdth a gate or stopcock, con- FLOATING AND R.\FT1NG 355 nects this chamber with the lower pool. When the connectionwith the upper pool is opened, while that wdth the lower poolis closed, water from the upper pool fills the chamber underthe gate. This causes the downstream leaf to rise, first by-flotation an
Logging; the principles and general methods of operation in the United States . The gate is raised by the pressure of water from the upperpool, which is conveyed in a channel, controlled by a sluicegate, to a chamber (^), Fig. loi. constructed under the second channel, also provided vvdth a gate or stopcock, con- FLOATING AND R.\FT1NG 355 nects this chamber with the lower pool. When the connectionwith the upper pool is opened, while that wdth the lower poolis closed, water from the upper pool fills the chamber underthe gate. This causes the downstream leaf to rise, first by-flotation and then by the impulse from the flow of the upper leaf is raised by the lower leaf which slides under it,the friction being reduced by rollers. The height to which thegate rises is limited either by stay chains, or by a wood cleatnailed on the under side of the upper leaf. In lowering the gatesthe operation is reversed, the connection with the upper poolbeing closed while that with the lower pool is opened. Thegate may be made to assume any intermediate position by. Fig ioi.—? The Bear-trap Sluice Gate. regulating the extent to which the two valves controlHng theinlet and outlet of the chamber under the gate are opened. The objections to this form of gate are: (i) the overlap of theupper leaf over the lower one necessitates lifting a considerableamount of water when the gate is raised; (2) the head of waterobtainable is only about one-third of the total width of theleaves; (3) the friction between the two leaves, even when re-duced by rollers makes it difficult to operate the gate smoothly;(4) the gate must be made in one section and if the gate is wideone side is apt to go up faster than the other, causing twistingstrains; (5) any driftwood or stones which may lodge betweenthe leaves make the lowering of the gate impossible until theobstruction is removed. Water can be let out of the reservoir very rapidly with a gateof this character, and the latter can be raised a
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisheretcet, bookyear1913
