MUNICIPAL SOLID WASTE TRICYCLE TRUCK WITH LIFT- TIPPING MECHANISM FOR IMPROVED SANITATION Fiagbe 1 Y.A.K., Mensah 2 M.Y., Sackey 1 M.N. and Andoh 1 P.Y. 1 Department of Mechanical Engineering, KNUST, Kumasi, Email: yakfiagbe@yahoo.com 2 Department of Chemical Engineering, KNUST, Kumasi ABSTRACT Sanitation is a hygienic means of promoting health by preventing human contact with waste. As such, safe removal and disposal of municipal solid waste within a community is critical in the environmental sanitation. A number of small waste collection trucks such as tricycles are in use in Ghana and other developing countries. This paper presents a design of lift-tipping mechanism for small solid waste collection trucks that enhances the safety of the waste collection component of the sanitation management. A five bar mechanism is developed with one degree of freedom. The prototype of the system built is such that for manual operation system, reverse paddling of the tricycle cycling paddle is employed in lifting and tipping. The test of the prototype result shows the torque requirement of the system ranges between 16.0 Nm and 25.0 Nm with a maximum load of 50.0 kg. A height of 1.15 m and tilt angle of 38 o were obtained. Key words: lift-tipping mechanism, tricycle truck, solid waste collection INTRODUCTION Sanitation of a country is of much concern to Government and much effort is put in to handle issues to acceptable level. Sanitation may be defined as the hygienic means of promoting health through prevention of human contact with the hazards of wastes. In developing countries, waste management has been a major challenge for most municipalities. According to Boadi and Kuitunen (2003) weak institutional capacity and lack of resources, both human and capital, contributed to a lot of difficulties in ensuring that all waste generated in the city of Accra, Ghana is collected for disposal. The system of pick-up waste collection method is used in some communities as well as drop-off system. The pick-up system is where a service provider moves from house to house in community to collect household waste. To facilitate and improve the waste collection within a community, some waste collection companies have introduced the use of small tricycle trucks. The use of tricycle trucks in solid waste collection is increasingly becoming popular and very instrumental in waste management in developing countries. However, the mode of operation of these small trucks is very much limited. The operation of the tricycle truck is such that the operator moves it round and collects the household waste together with waste from public places. It is then sent to a designated point where the contents are dump into a disposal container. The disposal containers are of the height of about one (1) metre from the ground. It is therefore not possible for the contents of the tricycle truck to be dumped directly into the disposable containers. The bed of the tricycle truck is 0.4 m from the ground. The contents are, therefore, dumped onto the ground and is later or immediately collected into the disposal container. Fig. 1 is an illustration of the current mode of operation of the waste collection truck. This situation usually created insanitary environment and also exposed the operators to unhealthy conditions. This mode of operation is also cumbersome and involves much labour. The picture of Fig. 2 and Fig. 3 show the practice of empting the tricycle beside the disposal 1
container to be later collected. This practice has serious health implication on the operators. Some of which is associated with organic dust from the municipal solid waste (MSW). According to Krajewski et al (2002) organic dust concentration in the raw MSW is 7.7 mg/m3. It will be very much appreciated if the tricycle contents are directly dumped into the disposal container thereby preventing the operator coming into direct contact with the waste and creating better sanitary condition. Tricycle with collection bin Waste Collection bin Disposal Container Fig. 1: Illustration of current solid waste truck operation Disposal Container Tricycle Bin Waste Fig. 2: A tricycle being emptied beside the disposal container Fig. 3: An operator collecting the waste into the disposal container 2
This paper presents a design of a system that is incorporated into tricycle trucks, to discharge its contents directly into the disposal container available at community dumping site. This will lead to better sanitary environment and reduction in the health risks that are associated with organic dust present in the municipal solid waste. The conceptual operation of the system is illustrated in Fig. 4. The mechanism would lift to a desired height and tilt through a desired angle more than the angle of repose of MSW. The height of the disposal containers provided by most waste collection companies ranges between 0.9 m and 1.0 m. Therefore, the system is expected to raise more than 1.0 m above the ground. Glancey and Hoffman (1996) gave the maximum friction coefficient of Municipal Solid waste (MSW) and poultry manure with wood surface as 0.75. This is equivalent to friction angle of 36.8 o which is the minimum tilt angle desire. As such, the system should tilt through angle more than 36.8 o. The limited angle through which to tilt is the friction angle of the municipal solid waste with respect to the surface. Waste Tricycle with collection bin 37 o Collection bin 1 m Disposal Container Fig. 4: Illustration of operational concept with lift-tipping mechanism SYSTEM DESIGN AND METHOD The lift-tipping mechanism developed by Fiagbe et al (2011), was considered and employed. The mechanism is made up of five bar mechanism. The system consists of component as illustrated in Fig. 5. The components are: 1 is the frame; 2 is the lifting bar; 3 is the lifting support bar; 4 is tipping arm and 5 is the bin. 6 is a slider. The lifting bar and lifting support bar are connected at the point C. The tipping arm is connected to the lifting support bar at point D. The tipping arm and the lifting bar are connected to the bin at point E and F respectively. The lifting support bar is also connected to the frame or ground at point B. The lifting bar is connected to the ground at point A and is allowed to move or slide horizontally. All joint are pin joints but joint A which is a sliding joint. 3
4 E 5 D C F A 6 2 3 B 1 Fig. 5: Schematic of kinematic linkage chain Based on the current operation of the manual tricycle, a design criteria set is to maintain manual operation status. As such the actuation of the mechanism was achieved by employing power screw with worm and wheel connection. The cycling paddle was used in operating the system in such a way that to lift-tip the system, reverse paddling is used whist forward paddling is used to lower the system as well as move the tricycle in the forward direction. The power transmission is by chain connection from the paddle through the worm to the power screw (Fig. 6 and 7). A clutch-coupling device is developed and used to enable isolation of the lift-tipping mechanism (Fig. 8) from riding of the tricycle. The clutchcoupling device helps to engage the lift-tipping system for actuation when needed so that the same paddle is used, in riding the tricycle. The system dimensions and parameters are chosen so as to minimise modification on the existing tricycle frame work. With respect to tricycle bin, the length of the lifting bar and lift support bar are 1.2 m each. The length of the tipping arm is 0.45 m. In the case of the motorised tricycle, the same engine is used to actuate the tip-lifting mechanism. As such a gear box is designed with three positions selection and two output shafts (Fig. 9). 4
Fig. 6: Tricycle drawing: 1. Tricycle frame; 2. Bin; 3. Wheel; 4. Lifting support bar; 5. Lifting bar; 6. Tipping bar; 7. Power nut; 8. Power screw; 9. Worm wheel; 10. Sprocket Worm and Wheel Power Screw Fig 7: System transmission Lift-Tipping Chain 5
Fig. 8: Coupling Clutch for manual tricycle 1. Clutch base; 2. Sprocket hub; 3. Coupling hub; 4. Butterfly Lock; 5. Sprocket; 6. Ring. Fig. 9: Gear box for Motorised tricycle; 1. Input shaft; 2. Riding output shaft; 3. Tipping output shaft; 4. Tipping output gear; 5. Riding output gear; 6. Input selector gear; 7. Idler gear SYSTEM PROTOTYPE Two prototypes were constructed, one for manual truck (Fig. 9 and 10) and one for motorised truck. The prototype of the lift-tipping tipping mechanism was built according to some design specification. The system is designed with the consideration of the already in-use tricycle trucks. As such the existing trucks can easily be converted with minimal work. Likewise the system can be built from scratch ch with already existing expertise in building of the tricycle 6
truck. Fig. 9 is the truck with the mechanism in rest position whist Fig. 10 shows the truck in lift-tipping position. Fig. 9: Tricycle with Lift-tipping mechanism at rest position Fig. 10: Tricycle with Lift-tipping mechanism at lift position RESULTS AND DISCUSSION The test of the prototype of the manually operated lift-tipping mechanism was conducted in the laboratory. The system was found to rise to the height of 1.2 m and tilt through to an angle of 38 o. For torque requirement, an empty system could be raised with torque of 16 Nm or an effort of 20 N. Loading with the weight of 50 kg, the torque of 24 Nm is required to lift and tilt the system. These test results shows that, the system could be useful for waste handling and will reduce operator contact with the MSW. The operation of the system is far better than it is with the existing tricycle. With the new technology single operator can conveniently work with it within shortest possible time. 7
CONCLUSION The tricycle truck with lift-tipping mechanism developed and prototype tested for MSW collection in communities will improve sanitation condition at community dumping site. It will enable direct dumping of the truck content into the disposal container at dumping site. The system operates by reverse paddling of the cycling paddle to lift and tip the bin. Also, forward paddling courses lowering of the bin and move the tricycle. The system could lift to the height of 1.15 m from the ground and tilt through an angle of 38 o. As such the equipment is able to meet the requirements of waste collection facilities in use. The technology can be used where the original tricycle technology is in use and could be extended to other places. The use of the technology will improve sanitary condition at the community dumping site and operator s exposure to organic dust from the solid waste will be minimised. With the implemented of the mechanism with the small solid waste collection trucks in use in Ghana, good sanitary environment would be created at the dumping site of these small trucks. Also, the use the tricycle truck with tipping mechanism will result in enhancing working conditions of the operators. Also, neatness of the damping site with disposal containers will improve. ACKNOWLEDGEMENT The authors will like to acknowledge the contribution of Benjamin Acquah, Mavis Larkwor Tetteh and Rashid Uthman Abubaka in the construction of the prototype as their Final Year Project in Department of Mechanical Engineering, KNUST. REFERENCES Adelstein, B.D., Ho, P. and Kazerooni, H. (1996), Kinematic Design of a three degree of freedom parallel hand controller mechanism, Proceedings of the ASME Dynamic Systems and Control Division, DSC. 58, pp. 539-546. Boadi, K.O. and Kuitunen, M. (2003), Municipal Waste Management in the Accra Metropolitan Area, Ghana, The Environmentalist, 23,211-218 Dixon, N. and Jones, D.R.V. (2005), Engineering Properties of Municipal solid waste, Geotextiles and Geomembranes 23, 206-233. Fiagbe, Y.A.K., Sackey, M.N., Mansah, M.Y. and Agbeko, E.E.K. (2011), Kinematic Design of Lift-Tipping Mechanism for Small Solid waste Collection Truck, JUST 31(2) Glancey, J.L and Hoffman, S.C., (1996), Physical Properties of Solid waste Materials, Applied Engineering in Agriculture by American Society of Agriculture Engineering. 12(4): 441-446. Jan A. Krajewski, Stanislaw Tarkowski, Marcin Cyprowski, Jadwig Szarapinska- Kwaszewska and Bozena Dudkiewicz, (2002), Occupational Exposure to Organic dust associated with Municipal waste collection and Management, IJOMEH, 15(3) 8