Being the  fourth instalment of an inaugural lecture delivered  by Lawson Olabosipo Adekoya, Professor of Mechanical Engineering,  at Oduduwa Hall, Obafemi Awolowo University, Ile Ife

OHWORORIOLE et al (1988) reported a simple manual rig that worked on the principle of peel/flesh separation through compression followed by peel removal with knives. The principle looked promising for further research. However, before the design could commence, experiments had to be carried out on the physical properties of the cassava tuber. This resulted in the characterisation of the cassava tuber (Adetan et al, 2003).

Prof. Lawson Olabosipo Adekoya

The data obtained was used in the development of a cassava tuber peeling machine (Adetan et al, 2005). The machine works on the principle of peel/flesh separation by compression and peel removal with knives. It comprised a horizontal belt conveyor unit and a spring-loaded knives unit. In operation, the belt conveyor transfers slices of cassava tubers which are peeled under an array of spring-loaded knives.

Tests were carried out on root slices of different sizes with the conveyor belt driven at a linear speed of 1.31 m/s. For root slices having mid-section diameters ranging from 45 mm to 55 mm, the peel removal efficiency ranged from 92% and 97.3%, while for root slices between 55 mm and 65 mm, the peel removal efficiency ranged from 95.3% and 100%. For the above tuber slice ranges, no breakage of roots was experienced during peeling. However for root slices with relatively larger diameters than those quoted above, the peel removal efficiency ranged from 15.2% to 82% and root breakage was observed to occur in some instances. In all cases, however, there were no losses of useful tuber flesh (Adetan et al, 2005).

Environmental  Management

Lawn maintenance has always been a challenge in green areas within human communities. The need to provide ecologically-friendly and effective lawn mowing solutions is crucial for the well-being of humans and the planet as a whole. The work done in this area involved the development of a human-powered lawn mower blade system designed to cut tall grasses on small lawns in residential areas.

The work entailed the design and fabrication of a reel-type mower blade system and a pedal-powered source of energy for the blade system. It also evaluated the performance of the fully-assembled unit. This was done with a view to providing an appropriate and affordable human-powered alternative for domestic lawn mowing involving tall grasses and weeds. A reel-type mower blade system capable of cutting tall grasses and weeds was designed and fabricated. The system was based on the shear cutting principle to enable low-speed human-powered operation.

A human-powered pedal-operated cycling mechanism incorporating a chain drive was used to power the machine as well as the cutting knives. Provisions were made for adjusting the height of the mower blade system (Plate 12). The mower blade system was tested on some overgrown grass plots within the University campus. Each test plot was measured to determine the total area within which cutting took place.

From the data obtained during the testing, the field efficiency and effective field capacity were determined. The blade system’s cutting effectiveness and the quality of cut achieved by the unit were also studied and documented. The information gathered during testing was used to compare the performance of the fabricated system with other human-powered lawn mowing techniques.

Calculations gave the theoretical field capacity of the mower as 0.098 ha/h while field test results showed that the fabricated cutting system produced an effective field capacity of 0.0614 ha/h.

Theoretical field capacity

These figures are clearly superior to the theoretical field capacity of 0.0247 ha/h obtained from the use of cutlasses for cutting. Results further showed that the unit performed in a manner comparable with the operation of standard reel mowers with similar effects in terms of quality of cut.

Moreover, the unit’s cutting system showed a substantial improvement over existing reel mower designs in its ability to cut on both the forward and reverse phases of its motion (Oladosu and Adekoya, 2014).

The study established that the designed blade system has the capacity to cut tall grasses and weeds. This device can therefore entirely eliminate the need for fuel-powered mowers on small residential lawns. The device can also be used for exercising the body during the mowing operation. Further work is presently being carried out on the machine to make it more functional.

Fatigue Behaviour of Locally-rolled Steels: Material selection is a very important aspect of machine design. This is because materials affect the service performance of machines. This is especially true in the selection of materials for the fabrication of rotating parts and structures that are prone to fatigue-induced failure.

In general, fatigue is the main cause of failure of machine components in mechanisms, structural functioning in aeronautics,      naval and automotive industry as well as in civil engineering structures such as bridges, buildings, etc.

Since fatigue failures occur suddenly without showing exterior plastic deformations, it follows that for many engineering applications, a comprehensive analysis of the elastoplastic deformation is necessary to ensure that accurate results are obtained from simulations in the process of designing or analyzing structures (As et al, 2008 and Heidari et al, 2009).

The Nigerian steel industry is dominated by private smelting and rolling mills from which mainly NST 37-2 steels (that represent about 75% of their volume) are produced. According to Balogun et al (2009), this particular grade of steel is produced from diverse raw materials that is mainly locally-sourced scraps. The indiscriminate use of the steel products, especially as machine elements without proper characterisation, is therefore a problem.

To alleviate the above problem, a joint research was undertaken by the Departments of Mechanical Engineering and Materials Science and Engineering. The work commenced with the characterization of NST 37-2 steel made at a local rolling mill from imported billets.

Tests were carried out on required specimens to establish the baseline material properties of the steel in annealed, as-rolled, normalized and hardened tempered conditions. Fatigue tests were then carried out at 60%Su, 70%Su and 80%Su of the test material and fractographic examinations were eventually carried out on the specimens. Based on preliminary results, the steel material is recommended for use in low-cycle, quasi-static fatigue operations (Malomo et al, 2010 and Malomo et al, 2011). Further work is being carried out on locally-rolled steels made from locally-produced billets that were manufactured from locally-sourced scraps.

Ergonomic Appraisal of Existing Machines: Ergonomics is the scientific discipline which is concerned with the understanding of the interactions among humans and other elements of a system. The objectives of ergonomics are those of achieving functional effectiveness of whatever physical equipment or facilities people use and of maintaining or enhancing human welfare or well-being (such as health, safety, and satisfaction) by appropriate design of equipment, facilities and environments (Adekoya, 1999). Ergonomic appraisals  are carried out on existing machines in order to discover their shortcomings with respect to functional effectiveness, so that improvements could be incorporated in them through re-design.

Agricultural Tractors: Agricultural tractors, as the workhorse of mechanised farming, were evaluated to determine their ergonomic suitability (Adekoya, 1993). Tractor brands used for the tests were Massey Ferguson (MF), David Brown (DB), Ford, Steyr, Fiat and John Deere (JD). Tractor models surveyed were MF 165 and 125; DB 990; Ford 5000 and 6610; Steyr 768, 8075, 8090, 8120 and 8130; Fiat 640 and 660; and JD 1120.  Comparison of the anthropometric data of 31 tractor operators (from 11 agricultural organisations that were fairly spread across the country) with the design data of the above tractors showed that even though 96.8% of the operators said that the heights and widths of the seats were satisfactory, 46.7 and 43.3% of them experienced backaches and leg pains respectively during the cropping season.

According to Purcell (1980), discomforts such as backaches could be caused by (i) wrong angles for various tilts of the seat (i.e. wide deviations from the 5-100 from the horizontal, proposed by Rebiffe, 1969); (ii) inadequate padding of the parts of the seat which come in contact with the ischial tuberosities (the two round knobs on the underside of the pelvis which bear most of the upper body weights while sitting); and

(iii) bucket-shaped seats which tend to rotate the femur bones upwards, causing abnormal stresses in the hip muscles. The leg pains and backaches are therefore strongly suspected to have been caused by unsuitable seat designs and/or adjustments.

None of the tractors surveyed had a roll-over protective structure (ROPS), cab, or sun roof. Although there were no reported cases of tractor overturns by the operators, a roll-over protective structure is definitely desirable. Data made available to the US Consumer Product Safety Commission show that overturn of machinery was the most common fatal accident, and that agricultural tractors were involved in 99% of all equipment overturns.

Three times as many persons died from farm tractor overturns as from any other fatal injury episodes  (McKnight and Hetzel, 1985). Consequently, a retro-fitting of the existing tractors with roll-over protective structures (ROPS) was recommended.

To this end, one of my postgraduate students is currently working on the design of ROPS for tractors being used in Nigeria.

Molue Buses: In public transportation, clearance at various levels is important for ingression and egression, for easy grasping and movement within the vehicle, and for adjusting the body properly for comfort (Woodson, 1972). Many passengers face some problems in getting on to the bus, going to the seat, in seat, going from the seat, and getting off the bus. Problems encountered by all bus passengers are worse for the elderly because of their reduced mobility (Gilmore, 1994).

Public transportation

Therefore in public transportation, the scope for the application of ergonomics expertise is enormous and the effects seen in terms of improved safety and users’ comfort, convenience and satisfaction are almost limitless (Brown, 1979).

Molue buses are the huge yellow locally-built commuter buses found mostly on Lagos roads (Plate 13). They ply some defined routes listed in Lagos State Government’s Designated Bus Routes (Agbomeji, 2000). They are of two major sizes and are built on Mercedes Benz 911 or Bedford chassis. The big molue buses are recommended for 47 to 52 sitting passengers, while the small ones are recommended for 29 to 32 sitting passengers.

However because of the acute shortage of commuter buses, the molue buses routinely carry more than the specified number of passengers with the extras standing crowded in the aisles and on the steps. This situation motivated the late Afrobeat maestro to release the popular song “44 sitting, 99 standing; suffering and smiling”. Standing in the aisles and on the steps of molue buses make entering and exiting the bus to  become more arduous.

Molue buses are built by roadside metal fabrication workshops, located mainly in Lagos and Ogun States, without reference to any formal design specifications. Because there are no specifications guiding the design and construction of these buses, their fabrications are based wholly on the whims and caprices of the technicians at the fabrication workshops. Consequently, no two molue buses are exactly the same even when built by the same workshop. This has resulted in a wide variety of molue buses on the roads, especially in Lagos. Additionally, anyone who has boarded molue buses before will attest to their tight internal spaces, difficulty in getting on and off, and a host of other problems.

In order to alleviate these problems, Ajayeoba and Adekoya (2009) initiated a research to carry out a comprehensive study of the problems of the design and construction of molue buses by the local metal fabricators. The ultimate goal of the research is to spearhead legislation on the standardization of the design and fabrication of molue buses. This is because currently, there are no generally-accepted design and fabrication standards for molue buses.

Fabrication standards

In this work, the anthropometric dimensions (stature, maximum body depth, maximum body breadth, buttock-knee length, buttock-popliteal length, popliteal height sitting, shoulder breadth, and shoulder height sitting) of some selected groups of male and female users of molue buses were measured. Design data (internal hand rail height, roof height, aisle length, aisle width, backrest-backrest frame height, backrest depth, backrest length, backrest width, seat length, seat width, backrest frame length, seat depth, seat frame-backrest height, seat height, seat depth, overall seat height, space between seat rows, and the relevant dimensions of the back seat) of both small and big molue buses were also measured (Ajayeoba and Adekoya, 2009; and Ajayeoba and Adekoya, 2012).

The data was analysed using percentiles (Hertzberg, 1972). Many shortcomings were discovered with respect to the design data resulting in discomfort for passengers. Based on the research result, the design data to accommodate the 95th percentile of the passengers were specified. There is a plan to collaborate with the Standards Organisation of Nigeria (SON) to standardise the design and fabrication of molue buses by local fabricators in Nigeria in order to make them more commuter-friendly.

Machine  Management

Agricultural Tractors: The workhorse of mechanised agriculture is the tractor, the evolution of which has accompanied changes in farm technology and sizes of farms. The tractor has progressed from its original primary use as a substitute for animal power to the present units designed for multiple uses. Tractors work for long periods without breakdowns if they are properly serviced.

By service (or preventive maintenance) is meant cleaning, oiling, greasing, adjusting and similar tasks carried out on the tractor to keep it in operative condition and help maintain its efficiency (American Society of Agricultural Engineers, 1982). If the preventive maintenance is not carried out regularly, breakdowns occur, necessitating repairs.

Repairs may also result from wear, accident, etc. Because agricultural operations have a time within which they have to be performed, breakdowns could prove to be economically disastrous to the farmer in mechanised agriculture.

The costs of owning and operating machinery in the business of farming are important to the farm owner or farm manager when making a decision on whether to buy or lease machinery or to hire work done by custom operators. One of the components in making this decision is the cost of maintenance.

Engineers, mechanization specialists and economists have published very little data properly to estimate farm machinery maintenance costs in developing countries. Apparently, when such estimates are needed, data are taken from US or European experiences (Beppler and Hummeida, 1985).

Adekoya and Otono (1990) carried out research on the maintenance of agricultural tractors in established maintenance workshops in Lagos and Ibadan. These workshops served the   then four contiguous States of Lagos, Ogun, Oyo (now Oyo and Osun) and Ondo (now Ondo and Ekiti).

The workshops operated at the depot level of maintenance. The research data were obtained from the job cards of each tractor and the tractors were then grouped on the basis of the model and the year of purchase.