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Three common types of primary collection vehicles are:
• the handcart which is pushed by the operator as he walks along.
- very limited capacity in terms of volume and capacity
- carries 0.25 to 1 cu.m. with a maximum range of 1 km
- very cheap
- operated by one person
• the pedal tricycle with a tray or box in front of or behind the operator.
- loads up to 1.5 cu.m.
- range greater because of higher speed when empty
- lifetime about 2 years
- no negative impact on environment
• animal-drawn cats, often pulled by donkeys.
- common around the world; until recently Cairo Municipality used donkey carts
- carry up to 1.5 cu.m. and range of up to 7 km.
- cost of feeding and caring for animals added factor
- negative impact on environment is excreta
Simple, motor powered vehicles should be considered where longer distances require larger payloads and higher speeds, or where slopes are based on small motorbikes.
A wide variety of trucks are used for collection. Factors to consider in selecting include:
• the weight of waste that the truck can actually carry
• cost of purchase and operation, including fuel and maintenance
• delays in obtaining spare parts
• suitability of the vehicle for the local roads considering width, congestion, and surface conditions
• ease of loading and unloading
Note: Use same make and models as in other sectors.
Criteria for design of handcarts
How much to carry?
If material is required to be moved over 500 meters, it will be preferable to minimize the unproductive travelling time and maximize load. A labourer can push 150 kg of waste in a well-designed and maintained cart.
If the cart is used for street sweepings, it is appropriate for the capacity to be less because:
- the waste takes more time to collect so it may not be possible to collect the full 150 kg during the day.
- there may be community storage containers at frequent intervals so that it is not necessary to carry the waste over a long distance.
How is the waste transferred:
Too often one sees labourers tipping the contents of their carts onto the ground and then scooping the waste up into another container for transfer. This practice is inefficient (wasting time), unhealthy (forcing the labourer to touch or have close contact with waste), polluting (often some of the waste is left on the ground or is scattered by the wind).
There are two simple ways of avoiding this problem:
- use a split-level site so that waste can be tipped directly from the cart into the bulk container.
- containerize the refuse in a number of bins that are small enough so that they can be lifted and tipped into the bulk container.
General design features:
- The size of the bins should be large enough that big items of waste cannot bridge across the rim and prevent the efficient utilization of the bin’s capacity.
- Bins that are rectangular may be difficult to pack if the dimensions of large items are larger than the smaller horizontal dimension of the bin.
- Square and rectangular bins may be easily deformed and develop dangerous jagged projections at the corners.
- Bins that are circular do not fit together well, considerable space is lost between bins.
- Wheels:
- Number: If the cart has only two wheels, the operator is always required to apply a lifting force, adding to fatigue and possible back injuries. At least three wheels are suggested. But carts with three wheels may roll by themselves if left on sloping ground. Four wheels make the cart more stable allowing easier crossing of a hole in the road.
- Size: Large wheels are better on rough surfaces, and, with poor bearings, cause less rolling resistance. However, larger wheels are heavier and more expensive, and may obstruct the removal of containers.
- Contact surface: A wide rim is necessary on soft ground. A contact surface - pneumatic tire or solid rubber tire - reduces the difficulty of pushing on stony or rough ground, but - Bearings: Simple journal bearings are rarely lubricated as they should be. Ball or roller bearings are more expensive and must be protected from dust.
- Durability: Bicycle wheels are generally not strong enough for this kind of duty. Motor cycle wheels have proved well suited, but they are likely to be more expensive.
Note: It is important to design and specify all items of equipment carefully - even simple equipment such as brooms, other tools, and carts. These items are used in large numbers and so the impact or a more efficient design or durable design can be very significant in economic terms.
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