MICROFICHE REFERENCE LIBFUUW - Cd3wd.com

43This device can be quite simple constructed, e.g., using a largecan, cut off diagonally on one end and attached with a wooden pole on theother. No cost estimates are available.This throwing method can be modified by another device to increaseperformance. The water balance shown in Figure 3.6 makes use of a scoopvertically attached to a balance beam which pivots about a centrallysupported axis. Ry alternately pulling on ropes at opposite ends of thebeam, one or more pairsof people can push water up the channel in whichthe scoop travels. The channel profile is circular within the arc ofscoop motion. To facilitate the scoop’s entry into the water, flap valvesare often used which open on the return stroke. Although the oscillationsper unit time will vary with size of balance and number of operators,Weisback and Herrmann (1897) report that about 4700 to 5500 cfh can beraised4 feet.3.2.2.3 GutterRather than pushing water through a channel, as with the balance,and encountering high leakage and friction losses, the gutter actuallylifts the entire channel. These gutters or troughs were originally hingedat one end to the upper elevation and the other end dipped into the waterand lifted, allowing the water to run out. However, the bending andlifting action is very tiring, so gutters’are often fitted with handles asin Figure 3.7a (also note flap valve). Where this device is used extensivelyin Portugal, it is called cegonho (translated as swipe, from Dias, 1953).Another modification is to use the picottah principle and have the operatorshift his weight back and forth on a “seesaw” gutter as seen in Figure 3.7b.Dias presents this design with the outboard flap valve to ease fillingand the inner fiap valve (probably) to prevent the return of any undrained