| Wells construction: hand dug and hand drilled |
This chart is based on a similar chart found in Engineer Field Data (1969) FM5-34, Headquarters Department of the Army, 554 pp. The original chart was given in English units which have here been converted to metric units.
The safe loads listed are for new rope used under favorable conditions. These have been calculated by dividing the breaking strength of the rope by 4. As rope ages or deteriorates, progressively reduce safe loads to one-half of the values given.
Here is an example of how the chart can be used.
A 1 meter high lining ring 10 cm thick with a 1.2 m interior diameter contains 0.41 m³ of concrete. Since concrete normally weighs about 2300 kg. per m³ the lining ring weighs about 943 kg. or 0.943 tons. A new manila rope with a diameter of at least 2.54 cm and a circumference of 7.98 cm will be needed to safely handle the lining ring.