Environmental Engineering Reference
In-Depth Information
well-fitting box to reduce spillage and to increase the lift.
Wheel diameters ranged between 1 m and 3.6 m, and the
number of blades was from 8 to 24. With lifts of less than
50 cm, one man treading the wheel's perimeter could
deliver up to 12.5 m
3
/h. These devices were commonly
used in India, Korea, Vietnam, and Japan to irrigate small
paddies. In China the same function was done largely by
water ladders, commonly known as dragon backbone
machines (long gu che). Square-pallet wooden chain
pumps with a series of small boards passing over sprocket
wheels formed an endless chain drawing water through a
trough; the driving sprocket was inserted on a horizontal
pole trodden by two or more men who supported them-
selves by leaning on a pole (fig. 6.6). Alternatives were a
slower manual operation with cranks or animal traction
transferred by the means of cogged wheels. With a typi-
cal lift of 0.9 m, two men could raise about 8 m
3
/h, and
a recorded performance has four of them lifting 23 m
3
/h
to the same height.
All of the following devices were always energized by
animals or by running water (wind-powered machines
were much less common). The rope and bucket lift, es-
pecially common in India (monte or charsa), used one or
two pair of oxen walking down an incline while lifting a
leather bag fastened to a long rope; instead of manual
tipping a self-emptying bucket might be used. The ar-
rangement worked well for lifts up to 8-9 m, with two-
oxen drives and three workers delivering about 8 m
3
/h
or four oxen and three workers, 16-17 m
3
/h. An an-
cient device best known by its Arabic name of s¯q¯ya car-
ried an endless chain of clay pots on two loops of rope
upside down below a wooden drum to fill at the lower
end and discharge into a flume at the top. The practical
lift was limited by the power available, usually that of
a single blindfolded animal walking in a circular 7-m-
6.6 China's long gu che (dragon backbone machine) was
powered by people treading a spoked axle.
diameter path. Consequently a s
¯
q
¯
ya was rarely used to
lift water from wells deeper than 9 m and usually did
not have discharges over 8 m
3
/h. An improved Egyptian
version, zaw
¯
fa, delivered up to 12 m
3
/h from 6-m-
deep wells.
Finally, the Arabic noria (from the more proper
na¯ra) and the Chinese hung che (some with diameters
up to 15 m) had clay pots, bamboo tubes, or metal buck-
ets fastened to the rim of a single wheel and driven either
through right-angle gears by animals or, if equipped with
