Here a copy of the very old story about Demotech's design of the Rope Pump from www.demotech.org. This site became too big for detailed reporting with more than sixty other designs and all of the Wike-comments in its research part. Below you find the main document that describes our highly successful design for a water pump that has all the pre's: very low cost, very high efficiency, easy local repair and copyng by the user. 

Paddy pump version December 2009. The pump here is shown pumping with an 85cm lift. Achieved 2L/s without to much effort. The biggest problem was stability on this uneven clay bank. As you can see at the end of the video, the top pipe needs to be extended and cut at a bigger angle.

Rope pump dave102190 and Rope pump with Negros Oriental visitor:

Student from JRMSU driving a pump using only rope, old slipper, rubber, PVC pipe, and Iron bars. Hey what keeps it from slipping when wet? are there grooves on the wheels for the rubbers or some soft of thing like that? How do u make the pump? how does water travel upward? Materials are rubber, pipes, old slippers/ flip flops, Ropes, cements, and iron.

The successful prototype solar powered rope pump paid for by Solar Aid, IMechE and EWB and installed at Mzuzu University in the north of Malawi, October 2008.
 

Foundation Connect International is a Dutch NGO for development aid, working mainly in Africa. Connect International has developed an integral concept to facilitate the alleviation of poverty in developing countries, with a main focus on rural areas, on active beneficiary participation and on effective low cost solutions that are mostly produced locally.

Plastic washers are made with a small and cheap extruder. The raw material comes from old beer crates. The washers are used in the Life Rope Pump in Ghana. Thesamse washers give 15 % more yield and last longer than the traditional rubber washers.

The owner of a "paddy" version of the rope pump for a low lift situation irrigating a rice field from a channel. She has used in in the past, and her neighbours have borrowed the pump widely for use. The model is only a demonstration, and there are many small opportunities to improve efficiency.
 

Higly interesting is the comparation between rope pump and Treadle pump:

Small scale irrigation in Africa. Manufactured treadle pump vs farmer made rope and washer pump. Africa Windmill Project teaches village farmers how to build and use rope and washer pumps. The rope and washer pump enables farmers to irrigate their gardens year round for food sustainability.