«THE MALAWI CART: An Affordable Bicycle-Wheel Wood-Frame Handcart for Agricultural, Rural and Urban Transport Applications in Africa Arnold P. ...»
The Chinese-style wheelbarrow, although with its single large-centrally-positioned wheel is far more efficient than the conventional type, is unknown in SSA, being relatively difficult to build, load and balance.
The same objections apply to the SFTV (Small Farm Transport Vehicle) developed by I.T. Transport Ltd.
and the Intermediate Technology Development Group (ITDG) (Hathway, 1985). Large-scale adoption of this latter design is further impeded by its reliance on welded steel construction.
The two-wheeled handcart is a great improvement over the wheelbarrow: it is more stable, since the weight of a properly loaded one is balanced over the axle (in the case of the Malawi Cart, the axis) connecting the two wheels; it requires neither lifting nor balancing by the operator; and its large-diameter wheels enable it to negotiate relatively uneven terrain. Because a handcart is simply pushed or pulled, when fitted with ball bearing hubs and pneumatic tyres considerable loads--200-250 kg--can be carried impressive distances in it--20-24 km in it (Dennis, 1993). (These figures from Dennis are for handcarts having two wheels on a common axle and generally heavier duty wheels and tyres.) A wide variety of handcarts are used in and around SSA marketplaces. These are generally of crude construction, employing salvaged components ranging from industrial castors to auto rear-axles. They are frequently so heavy, even without a load, that two men are required to propel them. They are, with few exceptions, unsuitable for agricultural transport around the smallholder farmstead. In West Africa there are numerous handcarts made from welded-steel and employing discarded moped or motorcycle wheels.
However as welded steel construction is generally too expensive for subsistence farmers to afford, as used moped or motorcycle wheels are rare, and as spare tyres and bearings for such wheels are expensive, the possibility of widespread adoption of this handcart design is unlikely. A comparison of the simple metalworking shops described in the development literature (Boyd, 1994; Dennis, 1995) with the reality on the ground in most of SSA, further underscores the need to rely on the skills and tools of carpenters for the manufacture of handcarts rather than on those of scarce steelworkers.
Attempts have been made before now to design both independent-wheel and wheel-axle handcarts for use in SSA. But these designs have generally used steel frames (Dennis & Smith, 1995; Maganya, 1997), a fact which makes their implementation highly problematic in terms of both handcart availability and cost. Equally problematic is the indigenous manufacture of wheels (Dennis, 1994; Maganya, 1997).
This is so because manufacture in welded steel poses a severe constraint on widespread handcart adoption:
only a small number of carts can be produced in this way: the distribution network is limited; the wheels, while rugged, with their solid rubber tyres and plain bearings are ergonomically inefficient; the cost of producing carts to this design is beyond the means of most smallholder farmers.
The Malawi Cart [NOTE: For additional details and photographs, see the Malawi Handcart Project web site at www.malawihandcartproject.org. The alternative URL is www.geocities.com/malawicart/.] The Malawi Cart derives from existing bicycle-wheel-handcart designs, most of which have until now been executed in steel, plywood, or some combination of the two. (Sullivan, 1983; Hathway, 1985;
Barwell et al. 1985; Dennis & Smith, 1995; Doran, 1996; Stiles & Stiles, 1998). All of these earlier designs have only limited potential for widespread adoption in SSA due to their use of these expensive, difficult-towork and/or hard-to-find building materials. The Malawi Cart was designed to require only common lumber and two ordinary bicycle wheels. Fasteners are common nails, along with a few wood screws and small bolts. Several large (8mm x 15mm) bolts were used in the prototype, but when such bolts were found to be unavailable in the nearest large town, widely available and cheaper bicycle rear axles were substituted for them in all later models.
The Malawi Cart rides on two 28-inch bicycle rear wheels (see photos on page 8 for details). Rear wheels were chosen over front wheels because of their greater strength. They have 40 spokes (as against a front wheels’ 36), their axles are longer and thicker and their ball bearings larger. In Malawi, the cost of a rear wheel differs from the cost of a front wheel merely by the price of the four extra spokes. The rims commonly available in Malawi are of the archaic and inherently weak Westwood pattern. Where available, the far stronger Westrick (or Endrick) pattern rims should be employed. Twenty-eight inch wheels were 4 chosen for the design because of their widespread availability and that of their spares, an availability that translates into the lowest possible initial and maintenance costs. For many, and especially for urban uses, 26-inch diameter and even smaller wheels are suitable and even desirable for handcart construction. The tyres should be of the widest and strongest (nylon ply) construction available.
Each wheel of the Malawi Cart is enclosed in a horizontal frame of two planks having holes in their middle for the wheel’s axle. The two hub axle nuts secure the wheel in place, and the ends of the frame are formed of wood spacer blocks bolted in place, using bicycle wheel rear axles as bolts. The use of bolts to secure the outboard side of each frame allows the wheel to be readily removed for maintenance and repair.
The two longitudinal wheel frames and their enclosed wheels are held together by two transverse sets of planks sandwiching the top and bottom ends of each frame. The two wider upper transverse planks form part of the floor of the handcart, while the two narrower bottom transverse planks, primarily subject to tension as they resist the splaying outward of the wheel-frames, can be made narrower, thinner and therefore lighter. Both upper and lower transverse members are screwed to the frame spacer blocks rather than into the frame longitudinals, so as not unnecessarily to weaken these relatively highly-stressed members. The prototype and early models of the Malawi Cart were fabricated from locally available hardwood planks, some 2 centimeters thick. They are probably thicker, and therefore heavier, than necessary. The body of the cart could be fashioned of thinner lighter wood, depending on the species of timber available.
The Malawi Cart was designed so that its body--four sidewalls and most of the floor--can be easily removed without tools (it is fastened in place by four wooden swivel catches) to facilitate the carriage of long poles and planks. The design also allows for alternative, purpose-built cart-bodies to be dropped in place on an existing cart chassis. For example, cart bodies for vendors selling cooked meats or baked goods, fruits and vegetables, grain, flour and dry goods, or for radio or watch repair can be built at modest cost and used for hawking goods and services at the market, and then, at home, they can be removed and replaced with the standard box body for use around the homestead. The front wall of the standard cart body, (assuming the cart is pushed and not pulled) is held between two sets of vertical battens so that it can be slid out to enable bulk loads--manure, bricks, sand--to be dumped, rather than having to be lifted out. This feature also facilitates the use of the cart as an ambulance if the patient can be carried in a sitting position.
In that case, the removable front serves as a backrest. In the event the patient must lie on his or her back, the cart body can be removed entirely and a bed (or a few planks) placed over the two upper transverse frame members. The Malawi Cart is also readily converted for use as bicycle cart.
Simplicity of construction was a major consideration in the design of the Malawi Cart. No sophisticated metalworking or joinery is called for. Simple wide (ca. 5cm) screwed finger jointing was used to better secure the rear wall of the body to the two sides. All other body joints are by nails to battens. The carpentry skills required are far less sophisticated than those needed to build a chair or table having mortised joints. To build this design, only basic hand tools are called for: wood saws (crosscut and rip), hacksaw, hammer, chisel, plane, brace and bits, screwdriver, spanner, and file. It is expected that, as a rule, wheels for the Malawi Cart will be purchased as separate components (hubs, spokes, rims, rim tape, tube and tyre), and a skilled wheel-builder--commonly found in towns near any bicycle retailer--hired to assemble them at a nominal cost. Fasteners (bolts, nuts, washers, screws and nails) are obtained at the nearest marketplace, lumber from local sawyers. Ideally, hardwood should be used for the cart’s longitudinal frames and upper transverse members; for the rest of the frame and body, lighter softwood should be adequate. Well-seasoned lumber is, for obvious reasons, desirable. But as the frames are screwed and bolted together, any shrinkage that may take place there can readily be taken up.
Although in 2000 the prototype Malawi Cart cost MK 2,400, material and labour costs are of course variable, as are the costs of imported components. It is difficult, therefore, to give a precise estimate of the future cost of a Malawi Cart. I believe, though, that it is reasonable to expect the selling price of a cart will be under or about half that of a bicycle—an excellent bargain when one considers that, for the small farmer, the cart’s utility is far greater than a bicycle’s.
As a test of the ability of village-level carpenters to build a Malawi Cart, a rural carpenter was invited to Livingstonia Technical College (LTC) to examine the prototype Malawi Cart and then build a copy at his home. He took measurements and notes, and was given a set of wheels and fasteners. Beginning with raw lumber, he then successfully built a cart entirely by hand in four days’ time. The World Bank 5 funded Malawi Rural Travel and Transport Programme (MRTTP) recently purchased sixteen Malawi Carts from LTC for evaluation, and it is planning to “train local artisans/suppliers on the manufacturing of common IMTs e.g. hand carts” (MRTTP, 2002).
The major problem encountered with the Malawi Cart is the tendency of its widely available but relatively weak Westwood pattern rims to buckle when overloaded and making a sharp turn. With their shallow cross-section, Westwood rims are far weaker than the channel cross-section Westrick or Endrick rims. Moreover, the cart’s bicycle wheels, with their relatively narrow hubs, are ill-suited to resist the axial forces generated when a handcart make a sharp turn, and unlike a bicycle, is unable to bank into it. The immediate solution is in better driver training--educating handcart operators to avoid making high-speed turns and overloading their handcarts.
Handcart Dissemination Strategies For getting the handcart into widespread use in SSA, two strategies need to be pursued, the first short term, the second long term. In the short term, because the materials and components needed to execute the Malawi Cart design are all readily available at this time, development efforts should concentrate on interesting as many people as possible in the cart and on turning those potential customers into owners. The longer-term strategy derives from the fact that the Malawi Cart, for all its clear advantages over alternative designs and over transport means currently in use, is still undesirably weak because it relies on ordinary bicycle wheels, and is excessively heavy due to its independent-wheel design. That design was chosen over the superior wheel-axle alternative because it was capable of widespread, affordable implementation in the African here and now. Looking to the future, efforts should be made to convince importers and distributors of bicycle components that there is a strong market in SSA for the kind of heavy-duty wheel-axle sets specifically designed for handcart applications that have long been in use in China, India, and elsewhere in Asia, and that they will profit from importing and distributing such sets.
After the prototype Malawi Cart was built at the Livingstonia Mission in July 2000, an order for ten carts placed with the production workshop of the Livingstonia Technical College (LTC) gave rise to the first attempt at mass production (Chirwa, 2000). The LTC’s next order, for eight carts, was from CARE Malawi, for a women’s road repair project. CARE’s assessment of the cart’s performance was that, despite some breakdowns due to twisted rims, “They have been of very great assistance as they provide cheap transport … [and that] overall they are handcarts with very broad applicability” (M. Lemekeza, technical coordinator, CARE Malawi, personal communication, October 4, 2001). The MRTTP placed an order for sixteen Malawi Carts with LTC in 2001, for field-testing at four different sites (MRTTP, 2002). This large order afforded carpentry students at LTC the opportunity to gain further expertise in handcart construction.
It would be valuable for other vocational training establishments to follow the lead of the LTC and introduce handcart construction to their carpentry students. I suggest that funding be made available to provide construction materials for such students so that each could build his or her own cart and take it home upon graduation. This will not only give them valuable experience in handcart construction, it will result in their neighbors coming to learn of the advantages of handcart ownership and so create a demand for carts that the graduates can satisfy by building and selling Malawi Carts locally.