In rural areas of the developing world, quality of life can be significantly impaired by the lack of a reliable means of delivering fresh water from naturally occurring local sources to locations where it is urgently required – such as fields growing crops. But last summer, production started on a device that could alleviate this problem.
The device in question is a manually operated pump designed by David Hutton, a young British engineer, with low cost, robustness and ease of maintenance as prime objectives. The project to develop it was one in which modern CAD software and ‘additive’ rapid prototyping played a role, although one that was constrained by the need to keep within strict cost limits.
Hutton graduated from the University of Bath in 2011. Although only just past his mid-20s, he now operates his own company, Hutton Technologies, based in Norfolk. The device, the Flexipump, developed out of his final-year university project.
But Hutton says that the first version of the device was quite different from today’s product. It was powered by compressed air provided by a bicycle pump, and could not achieve the required drawing power.
So he worked up a new design that could meet the performance requirements – initially by old-fashioned paper-based drawing and manual physical prototyping. Essentially, he says, it is a fairly straightforward ‘piston pump’ whose core mechanics are similar to those of a bicycle pump. That fact is crucial, because in its intended areas of use local mechanics know how to repair such pumps.
To test the new design, Hutton went to Zambia for six months. He took with him enough standard plastic plumbing parts to fabricate pumps on-site from the back of his car, although he had to supplement them with other parts that he made from local materials. Perhaps the most important parts he took with him, he says, were standard 16.5mm plastic ball bearings, which open and close the device’s two one-way valves. The crucial point about them is their size, which means that if necessary a toy marble can be used as a substitute.
The venture cost £10,000, which Hutton managed to raise from charitable sources. When he returned, he had the essential features of his design worked out – a piston moving up and down in a cylinder fastened by a simple hinge to a foot stand. The design included minimal moving parts – just the piston and valves.
He then needed to refine and recreate the design in a digital CAD format, to provide the database from which the product could be made. But he could not afford a licence for a software program, he says.
Fortuitously, he became aware first of the offer of a 45-day free trial and then via reseller Prion Cutting Edge of the possibility of a monthly rental scheme for the very CAD program he had used at university – the Solid Edge 3D modelling system from Siemens PLM. That was also the system used by Ken Symonds, a freelance designer of plastic parts whom Hutton contracted to provide expertise as he sought to bring the design to the point where it could be manufactured – specifically, to enable the main elements to be made by injection moulding.
As Hutton used the same software system as his collaborator, all forms of data transfer between them were seamless. The pair were also communicating with their chosen mould toolmaker, based in Italy. That company, says Hutton, was not a Solid Edge user and it lacked English speakers. Neither Hutton nor Symonds can speak Italian, so communication involved a mix of ‘neutral format’ IGES files for CAD geometry and Google Translator for text. Hutton says the combination worked surprisingly well.
The choice of manufacturer was again primarily a matter of cost. Hutton says the company could fulfil requirements at “Chinese prices”, while being only two hours’ flying time away. By this time, the project was reliant on loans from family and friends. When asked how much money was involved, he says: “A lot.”
But, he adds, this situation also meant that he became reacquainted with just how much a powerful CAD system could accelerate and support the design process. In particular, he identifies the enhancement of the system since his experience of it as a student by the addition of what Siemens terms ‘synchronous design’ capability, which facilitates rapid design changes by obviating the need for intensive recomputing.
This capability meant the design could be modified for manufacturability without fundamental redesign of parts from scratch. Hutton says that two months of intensive work with Symonds was necessary to achieve this modification. Apart from the basic “nuts, bolts and washers”, every other piece of the pump is of original design, he says.
This was also the point where another modern product development technique – rapid prototyping through additive manufacturing – came into play. It was vital to be sure of factors such as satisfactory form and fit of parts before committing to manufacture, says Hutton, and rapid prototyping was the obvious way to achieve this.
Again, cost was a constraint. But an outlay of £700 bought him an Up Mini printer that could make parts in an ABS material that could be handled and used to prove out such factors as the movement of the pump’s valves inside their housing, although the fabrication of a working prototype was not possible. Compared with the cost of getting prototype parts made by a bureau, Hutton says the machine paid for itself many times over.
Despite the use of modern technologies to develop the pump, the basic principle is that the product should be capable of repair in the field by simple means. A study in 2001 found that more than one-third of pumps in the developing world were unusable at any one time because of a lack of spare parts, says Hutton.
Perhaps the most striking example of how the Flexipump tackles this issue – even more than the interchangeability of the ball bearings with marbles – is that the seals of the piston cups have been designed so that replacements can be made by craft workers from simple sheets of rubber or leather.
To this end, a further rubber washer has been added between the main seal and the wing nut used to tighten the seal against the piston. In turn, this enables manual adjustment of the wing nuts after repair, to achieve a more reliable and accurate degree of contact between the seal and the piston, ensuring the combination can withstand the pressures encountered during operation. The right tolerance lies within a range of three turns of the nuts rather than just a more demanding three-quarters of a
single turn.
The pump’s ease of repair is its defining feature, says Hutton. Rival products require industrially manufactured spare parts, which are unobtainable in much of southern Africa, he says.
The pump is now on sale, and several thousand were sold in the final quarter of 2014 in South Africa, Zimbabwe, Mozambique, Malawi and Uganda. A typical price is $70-80, which Hutton describes as affordable for the average small farmer. The potential market is huge – worldwide, he says, there are 500 million smallholder farmers supporting
two billion people.
The device weighs just 2.5kg, and can draw water from 6m below ground and raise it to a height of 10m above ground, although Hutton says that in trials it has drawn water from a depth of 9m. He is confident that the official above-ground capability could also be exceeded, although no testing has yet taken place. The claimed horizontal distance the pump can push water is 100m. The output pressure of the device is 2bar.
That capacity allows around a fivefold increase in the efficiency for watering a field, compared with the physical carrying of water from a nearby source. Two people using buckets would need five hours to irrigate a field 0.04ha in size if the water source were 20m away. Flexipump would reduce this time to just one hour. Five times less
work could mean five times more food production.
The pump offers another benefit. Rivers can be home to dangerous animals that may attack people who approach the water’s edge. A reliable pump can enable people to avoid such areas, thereby saving lives.
Lightening the load: Flexipump allows around a fivefold increase in the efficiency for watering a field