**6. Modification and improvement of mobile maize shellers**

Modification of maize shellers can lead to improvement of the existing shellers for better performance. Most engineering designs are classified as systems created by human effort and did not exist before or improvements on the existing ones. These designs do not suddenly appear from nowhere. They result from merging technologies to meet or solve existing problems from time to time. Modification of maize shellers can be aimed at improving the performance of the existing shellers by adjusting mechanisms to certain working conditions [44]. Abagissa and Befikadu [45] noted that modification of maize shellers can result in causing no damage to maize kernels at all. Their study further revealed that the shelling efficiency was 99.67% at a moisture content of 14.7%. The evolution of motorized mobile maize shellers is a result of modification of the immobile motorized maize shellers to solve the power and transportation problems.

## **6.1 Case study 1: multi-purpose farm vehicle mobile maize sheller**

According to [1], a study was conducted to evaluate the performance and optimize the shelling operation of the multi-purpose farm vehicle shelling technology. The study was aimed at: (i) improving the available market maize sheller and evaluate its performance and (ii) optimizing the shelling operation of the multipurpose farm vehicle using the modified sheller. At present, transportation of maize shellers and engines (power source) from place to place is a big challenge in maize shelling. In Uganda, shellers and engines are transported on motorcycles, which not only require an extra cost, but also extra time and energy. In an effort to improve maize shelling in the country, a multi-purpose farm vehicle with a provision for hitching a maize shellers was developed to solve the power and transport problems faced by maize farmers. The three-wheeled vehicle can be used for water pumping, maize shelling, rural transport, and phone charging. This technology involves use of a multi-purpose farm vehicle power take off (PTO) power to run the maize shellers using a V-belt and a pulley. The multi-purpose farm vehicle was evaluated using a motorized market sheller and the mean broken percentage of the shelled maize was 8.43%, which was higher than the 2% recommended [20]. As a result, the holes of the concave were increased to 15 mm from 12 mm so that maize grains could easily fall through, a hollow shaft was used instead of the solid shaft for the main shelling shaft, the clearance between the concave and the spikes was modified from 22 to 25 mm which was just enough to allow the grain from being detached from the cob without damaging them and the number of the fun blades was increased from 4 to 8 [1]. The modified maize sheller was evaluated (**Figure 6**) to assess if the results were satisfactory. One way analysis of variance (ANOVA) was done using R-studio. The economic feasibility of the shelling technology was also conducted.

It was noted that the output capacity, cleaning efficiency, and grain damage percentage of the modified maize sheller was significantly different (*P* < 0.05) from the values obtained by the market maize sheller (**Table 1**). However, there was no significant difference between the shelling efficiency of the modified maize sheller and the market maize sheller. Hence in terms of shelling efficiency, both the market maize sheller and the modified maize sheller were good since their values were all above 97%.

The results of the benefit–cost analysis of the modified maize sheller powered by the multi-purpose farm vehicle are presented in **Tables 2** and **3**.

The benefit–cost-ratio and pay back period of the modified maize sheller were 1.07 and 1.37 years, respectively (**Table 3**). These results were in agreement with [42] who obtained a benefit–cost ratio of 2.34 for a maize sheller for which it

### **Figure 6.**

*Operational view of the modified multi-purpose vehicle maize sheller [1].*


### **Table 1.**

*Market maize sheller versus modified maize sheller [1].*


### **Table 2.**

*Various costs for the modified maize sheller [1].*


### **Table 3.**

*Payback period and benefit–cost ratio of modified maize sheller [1].*

required to be greater that one. In addition, the modified sheller investment would pay back the initial investment within 1.5 years or approximately three maize growing seasons. Hence the maize shelling operation of the modified maize sheller powered by the multi-purpose vehicle is a profitable venture for entrepreneurs.
