# Design and Experimental Study of Potato-Soil Separation Device for Sticky Soils Condition
## 3 Key Component Parameter Design and Analysis  
### Parameters of Soil-Crushing Mechanism and Kinetic Analyses during Shearing Area  
According to Figure 3a, the soil-crushing mechanism consisted of an installing axis, a roller core, as well as a roller tooth. Its principal effects were the striking and shearing on potato-soil mixture. Moreover, the potato-soil mixture was transported, backward assistant. As indicated from existing studies, the broken soil effect and the degree of potato damage were impacted by parameters of the soil-crushing mechanism (e.g., the tooth number of roller and the spacing between teeth) [31; 32]. Accordingly, the soil-crushing mechanism with a roller core length of 630 mm (\(L_{1}\)), a roller core diameter of 80 mm (\(D\)) and six roller tooth lengths of 60 mm (\(L_{3}\)) were set. To ensure the homogeneity of force and crushing, three rows of roller teeth were aligned uniformly and circumferentially with an included angle of 120\({}^{\circ}\) between rows. Two adjacent rows were arranged in a misaligned axial direction, and the distance between adjacent teeth in the identical line was set to 115 mm (\(L_{2}\)). According to the field study, the potato tubers were planted at a depth of 150 mm, and the growth of the tubers range was nearly 100 mm [33]. Thus, the potato-soil mixture exhibiting a height of approximately 150-200 mm was transported to the potato-soil separation device after being dug by a digging shovel. For this reason, the distance adjustable between the roller tooth tip and the surface of the first-stage lifting chain was set to 80-150 mm. Figure 2: Schematic diagram of potato-soil separation device. 1—Soil-crushing mechanism; 2—first-stage lifting chain; 3—support wheel; 4—rubber roller; 5—smooth roller; 6—second-stage lifting chain. The potato-soil mixture was transported backwards on the first-stage lifting chain after being dug with a digging shovel. In Figure 3b, when the potato-soil mixture passed over the surface of the first-stage lifting chain beneath the soil-crushing mechanism, the potato-soil mixture would be broken and transported backward efficiently as impacted by the striking and shearing of rotarod roller tooth. The friction force (\(F_{f1}\)) and shear force (\(F\)) were applied to the potato-soil mixture since the roller tooth was partially cut into the soil when the roller tooth was in contact with the potato-soil mixture. The potato-soil mixture slides backward relative to the chain surface due to the driving force of roller teeth. Moreover, the potato-soil mixture was subjected to gravity (\(G_{1}\)), and friction force (\(F_{f2}\)) and supporting force (\(F_{N1}\)) of the chain surface. Shear force (\(F\)) was calculated by:  
\[F=\frac{M}{R}=\frac{\Delta vJ}{R^{2}} \tag{1}\]  
From Figure 3:  
\[\left\{ \begin{array}{l}\Delta v=v_{2}-v_{1}\cos\theta\\ v_{2}=\omega_{1}R\end{array} \right. \tag{2}\]  
Shear force (\(F\)) was calculated by Equations (1) and (2):  
\[F=\frac{(\omega_{1}R-v_{1}cos\theta)J}{R^{2}} \tag{3}\]  
where \(F\) denotes the shear force applied from the roller tooth, N; \(M\) represents the moment of momentum when the soil-crushing mechanism rotated, N\(\cdot\)m; \(R\) expresses the radius when the soil-crushing mechanism rotated, m; \(v_{1}\) denotes the linear speed of the first-stage lifting chain, m/s; \(\omega_{1}\) represents the angular velocity of the crushing roller, rad/s; \(v_{2}\) expresses the linear velocity at the tip of the soil-crushing roller tooth, m/s; \(J\) is the moment of inertia of the soil-crushing mechanism; \(\theta\) is the angle between the linear speed of the first-stage lifting chain and the shear force (\(F\)), \({}^{\circ}\). Besides the shearing, the potato-soil mixture was further impacted by thrust (\(\sum F_{x}\)) upward following the chain surface. The equation of resultant force by complying with the linear velocity direction of the first-stage lifting chain for the calculation is written as.