# Design and Construction of Rotary Potato Grader (Part I)

R. FARHADI^{1}, N. SAKENIAN^{2} and P. AZIZI^{1}

^{1} *Department Of Agricultural Machinery Engineering, Shahrekord University, Iran*

^{2} *Islamic Azad University, Engineering Dept, Shahrekord Branch, P. O. Box 166 Shahrekord, Iran*

### Abstract

FARHADI, R., N. SAKENIAN and P. AZIZI, 2012. Design and construction of rotary potato grader. (Part I). *Bulg. J. Agric. Sci., *18: 304-314

One of the main potato usages is seed consumptions. According to researches, seed potatoes should position on the 50-80 g Mass range. Two hundred potato samples were selected from the conventional varieties (Morfana and Agria) in Iran. Dimension and mass was measured and regression equations were calculated at Excel software. These equations solution at Matlab software eventuated numbers of 36.36 and 42.68 mm corresponding with 50-80 g for Morfana, also 31.66 and 29.55 mm for Agria. These numbers indicated the situation of separator plates on the system. A new mechanism was suggested for gradation included a helix with variable distance. Effective parameters on the gradation helix were identified and attempts were done for their suitable selection. Hence, computer model prepared from the system. Then, coefficient of friction between polyethylene pipe and potato was obtained respectively 0.5583 and 0.4531 for Morfana and Agria using inclined plane at ten repeats. Finally, effective parameters on the system were chosen according to software analyses, conditions and limitations. Some experiments were done after set construction for achieving maximum gradation precision with optimal place determination of separator plates. Experiments results were numbers of 35 and 45 mm for Morfana, 28 and 33 mm for Agria. Theoretical and actual product transfer volumes were acquired 4.36 and 3 tons/hour. System required torque and power were 75 N.m and 71 Watt.

*Key words: *gradation, potato, precision, rotary helix, mass range

*Abbreviations: *ω: Rotational speed, V : Linear speed, t: Time, T: Alternation time, x, y and z: Distance in three dimensions, θ, α: Angle, l: Pitch le ngth, L: Total length, r, R: Radius, A: Area, *y *: Centroid, a: Distance, s: Arc length, ν_{T,T}, : Transferred product volume at alternation time, *v*_{T,1} or ν_{T} : Transferred product volume at time unit (1s), *M*_{T}: Theoretical transferred mass at time unit (1s), *M*_{A}: Actual transferred mass at time unit (1s), K, c: Constant, *Q** I*= *M*: Input transferred mass at time unit (1s), P: Precision, g: Acceleration due to gravity, b: Total distance in helix, n: Number of pipe, d, D: Diameter, ρ: Density of material

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