Cambridge Zimbabwe Expedition Gonville and Caius College Cambridge CB2 1TA Telephone: (01223) 351101 Registered Charity Number: 311460

In January 1996, an intrepid team of keen Caian engineers formed a surprisingly successful alliance with an SPS student from Emmanuel in a move that was to change to face of rural Zimbabwe. Their mission was to construct and disseminate the rope and washer water lifting pump, and they chose to accept it.

The background to the expedition started in 1994 when Joanna Graham spent her gap year teaching at St Matthias School in Watsomba, and met Ian Thorpe, the Project Trust Representative for Zimbabwe, who stayed in contact. Ian heard of the pump which is based on a Chinese design several thousand years old, updated to use modern materials by Bobby Lambert, an engineer from Loughborough University, in 1986. Bobby lead a project to build the pumps and train local artisans in Murewa, Zimbabwe. Ian heard of these pumps and tried building some locally with some Project Trust volunteers, but without any technical input they were sometimes badly constructed and very inefficient. He appealed to Jo to rally some engineering friends to provide this badly needed technical aspect and muster some funds.

The first step was to research the design. We talked to many appropriate technology experts in the U.K. and found that many subsistence communities in Zimbabwe are dependant upon bucket and chain systems for water collection which are inefficient in terms of time and energy. Out of the many designs for pumps existing, the rope and washer pump seemed most suitable for the area. It could operate on up to a twenty metre head, could supply a high output, and could increase the hygenicy and safety of the water collection. The most important aspect, however, was that it used cheap and locally available materials and simple tools.

The second and most daunting part was raising funds. After appealing to hundreds of companies and charitable trusts we eventually reached our target and went on to get three thousand pounds more.

We flew out to Zimbabwe at the end on July. Our itinerary was to spend six weeks in Watsomba, and one in the Honde Valley. We were living in an isolated rural community where we had to quickly adapt to the absence of many things you take for granted in England - from running water, electricity and transport to pillows, appropriate cutlery and marmite. In the field we found that most homesteads had a Bush pump within a few kilometres, which gives clean hygienic drinking water from a deep, sealed borehole. They are expensive and factory made, with the result that if one goes wrong it can take weeks for a specialised maintenance engineer with the right parts to come and fix it. We realised that the priority in Zimbabwe had been to get drinking water to the people as soon as possible, but now that aim had been largely realised, many areas wanted to move on to being able irrigate their own crops more easily. This confirmed our design decision - the rope and washer pump is ideal for small-scale irrigation as it has a high output, and crucially it can be constructed, operated and maintained at a village level.

Work in the field

Our priority was to develop the design to make it as reliable as possible, whilst keeping it low technology. This lead to many difficult conflicts. We developed the design slowly, using "weakest link" analysis to modify the least reliable and efficient aspects of construction. Firstly, we toured all the existing pumps built by the Project Trust volunteers which gave us plenty of areas to improve upon as only three out of fourteen pumps were still working. Many problems were very small and easily remedied, but the families had not seen sufficient worth in the pump to invest time and money in its repair, or simply did not understand how it worked. This made us aware of many "social" issues which had to be addressed in order for this project to succeed. We developed a system of interviews which assessed the needs of different families, and this decided where we would build pumps in conjunction with which locations would get the most publicity. During construction, we ensured that one or more members of the family understood the principle of the pump and what they needed to do to keep it running, for example checking the rope and knots for fraying any applying grease to the bearings.

We worked closely with three local counterparts who were initially too in awe of our education and the engineering expertise they assumed we possessed to forward many of their ideas. However, we were initially at a bit of a loss without the electric tools, supascrews and 3" x 2" planks we used in Cambridge to build a trial pump up 18m of the South Wing stairwell in the Engineering Department. Our amusing ineptitude with hand tools and inability to get 6" nails into wood soon convinced them that they had a lot to offer, and we quickly got into a working relationship where we were all putting in suggestions to the problems identified. Their help was invaluable in organising and giving one-day workshops, of which we staged three during our time in Africa. These aimed to disseminate the idea of the pump, to explain how it works and to teach basic construction and maintenance techniques.

Our biggest design change was to replace the wooden axle and bearings with metal ones. We believed that this would be more durable and efficient, as the friction on the wooden axle pumps was prohibitive. This lead to the problem of how to attach the wheel and handle to the axle without using welding or electric drills. We used galvanised metal water pipes for the axle, which had a 25mm diameter and were stiff and strong. The bearings were made out of short lengths of a larger diameter pipe, held in place on the support posts with notched wooden brackets which were bolted on. Over the next two months we experimented with different methods.

Our first idea was to hacksaw two small triangular holes in each side of the axle pipe, which a masonry nail could be knocked through. The wheel, attached by metal bars to a squared-off wooden hub, could then be attached to this nail with U-nails. The main problem with this was that the masonry nail was brittle and showed an alarming inclination to simply snap or drop out, and the wood also seemed to be fairly unreliable on a long term basis due to its splitting and/or rotting skills.

We tried widening the holes to use 8mm metal rod in place of the masonry nail, which was made long enough to act as one of the spokes on the wheel. This seemed to be stronger and safer, but we were worried about making such large holes in the axle at the location of maximum bending moment in case of fatigue problems. These worries culminated in one axle actually snapping as the hacksawed holes in it had been made too large, and we brainstormed for a better solution.

The final, and we think best, solution for wheel attachment came in the last week when we realised that making any holes in the axle was a bad idea and tried using friction instead. We clamped two thick, rectangular sections of tyre tread onto the axle using two pieces of sheet metal and small bolts. This seemed to grip very well, left the axle unscathed and gave a rectangular cross-section to attach the wheel spokes to. Only time will tell if this idea is reliable long-term.

Another problem with the design is that it required a man to be lowered down the well to fix the up-pipe to the wall, or to get the pipe out again for maintenance. We were unhappy about this from a safety point of view, and developed stakes made out of metal bar wired onto the "U" bend at the bottom, that could be driven into the ground at the bottom of the well. The pipe would also be attached to the top of the well using masonry nails, and was stiff enough not to need additional attachment. This makes maintenance and construction potentially a lot safer, quicker and easier.

The expedition was successful. We built fourteen pumps during our stay and left enough money for another forty to be built over the next two years by our fully-trained local counterparts. We developed a follow-up structure involving regular pump visits and log books to record any problems with the pump and what affect it has upon the gardens and lives of the families involved. With the records from this two year pilot programme, we may be able to get an aid organisation to help long term with funding and training. We gained mainly valuable skills, ranging from practical ones such as use of hand tools and slaughtering chickens to better communications, team work and project organisation. Perhaps the most rewarding aspect was the response of the local people for who the pump had a very big impact. One family named their new-born son after us and another man said "You have been sent by God as this pump is surely a miracle". It is on behalf of people like this that we would like to thank everyone at Caius and the Engineering Department for their help and support.

Pippa Smith

Cambridge Zimbabwe Expedition

U.K. Team
Joanna Graham, Ian Thorpe, Pippa Smith, Peter Harris, Daniel Edwards, Julian Morgan

Zimbabwe Team
Tendai Mawunga, Amos Chitungo, Boneface Nyanza, Sam Jones