Design and Fabrication of Groundnut Shelling Machine

Research Paper (postgraduate), 2015

19 Pages

S.O. Ejiko (Author)




2.1 Materials
2.2 Description of the Groundnut Shelling Machine
2.3 Design Analysis and Calculation
2.3.1 Determination of Crushing Power to Break the Pod
2.3.2 Determination of the Pulley Diameters
2.3.3 Determination of the length of the belt
2.3.4 Determination of Tension in the Belt
2.3.5. Determination of the bending moments acting on the shaft
2.3.6 Determination of the shaft diameter for auger
2.3.7 Determination of the shaft material
2.3.8 Determination of the size of power to drive the fan
2.3.9 Determination of auger capacity
2.3.10 Determination of a size of the key
2.4 Fabrication Process
2.5 Operation of the shelling machine
2.6 Performance Evaluation





Groundnut product demand is on the increase and the application is largely dependent on the cleanness of the nuts. The separation process is usually an energy sapping task that requires a lot of time. In order to separate the nuts from its shell effectively a shelling machine was developed. The machine employs an auger screw as a means of breaking the groundnut pod. The machine basically comprises of shelling chamber, separating chamber and a motor (1HP). The arrangement of these parts is connected by a compound belt of type B standard V-belt of pitch length 1694mm. With the Von-mises equation, the material for the shelling shaft is taken to be mild steel. The materials used in the fabrication of the machine are sourced locally so as to ensure that it is cheap, affordable and easily maintained by the peasant farmers. The shelling efficiency and material damage are 84% and 14% respectively for groundnut seeds of 86.5% dry.

Keywords : Groundnut, pods, shelling machine, design methodology, efficiency, fabrication


Groundnut (Arachis Hypogea) originated from latin America (Brazil) and was introduced into West Africa by Portuguese traders in the 16th century. Its actual origin dates back to 350BC (Komolafe et al., 1985 and Hommons, 1994). It is botanically a member of the papilionaceae and is the largest and most important member of the leguminosae (Shankarappa, Robert and Virginia, 2003). This crop is considered to have great potential for both food and industrial purposes in the tropical regions of Africa (Milner, 1973). In some parts of Nigeria like Kano, Sokoto, Kaduna, Bauchi and Borno States, it is used as a source of revenue generation to support rural development (Maduako et al., 2006).

One of the important processes involved in the production of groundnut is shelling and separation. Shelling is the removal of the groundnut seed from its pod by impact action, compression and shearing or combination of two/more of these methods. The shelling operation is majorly divided into two, namely: traditional and mechanical methods. The traditional shelling could be by stick beating, animal trampling or pod pressing by hand. Pod pressing is mostly practiced in Nigeria and it has low efficiency, high energy requirement, time wastage, high labour and fatigue.

Several shelling machines based on different techniques have been developed over the years. Among these machines are hand-operated groundnut sheller, baby groundnut sheller, powered rubber groundnut sheller to mention but few (Rodriquez, 1985). Due to custom charges, these machines are very expensive and are not affordable by the small-scale producers and farmers.

Maduako and Hamman (2004) determined some physical properties of three groundnut varieties. The materials used were ICGV-SM-93523, RMP-9 and RMP-12. Some of the physical properties considered were weight, bulk density, moisture content etc. Anova was used for analysis at 0.5 probability level.

Okegbile et al., (2014) designed and fabricated groundnut shelling and separating machine. With 1hp motor, the machine has shelling capacity of 400kg/hour and shelling efficiency of 78% and material damage is 17.25%. The materials used were sought locally. The machine used spike to crush the pods.

This research aimed at using anger shaft in the crushing of the pod to replace the existing design. Also, to improve on the shelling capacity at low cost by using locally – available materials. Then, the machine is evaluated based on shelling efficiency and percentage material.


2.1 Materials

The materials used were locally obtained from a town called Ado-Ekiti which is the capital of Ekiti State in Nigeria. The selection of these materials was based on durability, cost and availability, strength and rigidity, weight and friction.

2.2 Description of the Groundnut Shelling Machine

Various components were put together in the fabrication of this machine. These parts are: the frame, hopper, seed discharge outlet, shelling chamber, fan and chaff outlet.


It holds the hopper, shelling, and separating unit as well as the prime mover (electric motor). Being the main support for the machine, it must be able to withstand stresses and loads and have good welding properties. Hence, mild steel in form of angle bar was used.


It contains the unshelled groundnut before and during the shelling operation. It must be able to withstand the vibration loads and stresses, have good strength and good corrosion resistance. Hence, the material is mild steel sheet of 2mm thickness.

Shelling Chamber

It houses the auger and the shelling drum. The shelling operation is done inside it. Therefore, it must be able to withstand load and stresses, good weld ability and corrosion resistance. The diameter of the shelling drum is 206mm and pitch of the anger screw is 100mm.The active length of the drum is 500mm. So, mild steel of 2mm thickness was selected.

Seed Discharge Outlet

The shelled groundnut seed is collected through this outlet. The seeds fall under gravity from the shelling chamber into its tray. It must have good strength and high resistance to impact loads. So, mild steel of 2mm thickness was used.

Chaff Outlet

The broken pod is separated from the groundnut by pressure provided from the fan. Mild steel of 2mm thickness is selected.


It is made from aluminum due to its light weight. It has diameter of 30mm with length and thickness of 300mm and 2mm respectively.

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Figure 1: The Schematic Diagram of the Assembled Machine and Exploded View

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Figure 2: The Assembled Machine and Part List


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Design and Fabrication of Groundnut Shelling Machine
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design, fabrication, groundnut, shelling, machine
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S.O. Ejiko (Author)J.T. Adu (Author)Osayomi Peters (Author), 2015, Design and Fabrication of Groundnut Shelling Machine, Munich, GRIN Verlag,


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