Description: The Pounder Rig has been derived from sludging, but has been designed to deal with the weathered overburden, also known as regolith, which lies on top of basement formation. These conditions are common in much of Africa.

The principle of drilling is the same as for sludging. It involves reciprocating a steel pipe (of 25 to 40mm diameter) vertically in a shallow pit, which is kept full of water. However, rather than a bamboo frame, a steel frame is used (Figure - above left). This ensures that the hole is drilled vertically and assists in separating the cuttings from the water and thus the recirculation of the drilling fluid. A see-saw mechanism is used to raise and lower the drilling pipe, and a steel and leather flap at the top of the pipe (inside an upturned bucket) acts as a valve. The drill pipe comprises carbon steel “wireline” drill pipe, which is considerably stronger than galvanised iron (GI) pipe and able to resist the stresses imposed by the impact on the very hard layers. Hardened steel drill bits are used to penetrate hard rock (Figure - above right).

Capability: The Pounder Rig can drill through clay, sand, silt, gravel, laterite and limited amounts of hard rock. The limitations are primarily due to the slow progress in hard formations.

Locations: Uganda.

Equipment Availability: One rig has been manufactured and is currently in Uganda.

Documentation:

BALL, P. & CARTER, R. C. (2000) Specification And Drawings For The Pounder Rig. a human-powered drill rig for constructing shallow small diameter wells for domestic and agricultural water supply , Silsoe College , Cranfield University , Bedfordshire, UK

CARTER, R. C. (2001) Private Sector Participation in Low Cost Water Well Drilling in Uganda. Knowledge and Research (KAR) Project R7126 FINAL REPORT , Silsoe College , Cranfield University , Bedfordshire, UK