# Design and Experimental Study of Potato-Soil Separation Device for Sticky Soils Condition
## 3 Key Component Parameter Design and Analysis
### Parameters of First-Stage Lifting Chain and Kinetic Analyses during Bending Area  
As presented in Figure 4a, the first-stage lifting chain consisted of a support wheel, chain rod, chain and sprocket, and its principal effects consisted of vibration, bending, sieving, and delivery. In this study, the length of the first-stage lifting chain was 980 mm (\(L_{4}\)), and a support wheel of 100 mm diameter (\(D_{3}\)) was mounted under the first-stage lifting chain to form a bulge-shaped domain on the upper chain surface. The angle of a front bulge of 4.26\({}^{\circ}\) (\(\theta_{2}\)) and angle of behind bulge of 7.67\({}^{\circ}\) (\(\theta_{3}\))as indicated after the position of the support wheel was fixed. The chain rods of the lifting chain were arranged in equal spacing, and its principal effect was the sieving of small soil blocks during transportation. Accordingly, the separation efficacy was impacted by the gap between chain rods. As revealed from the field study, the diameter of winter potatoes during the harvest period in South China was generally more than 40 mm. For this reason, the diameter of the chain rod of 15 mm (\(D_{2}\)), the wheelbase of 50 mm (\(L_{5}\)), and the spacing of 35 mm (\(L_{6}\)) were set.  
The first half of the potato-soil mixture hung due to a chain bulge formed by the support wheel when the potato soil mixture passed via the support wheel, and the potato-soil mixture was snapped by gravity at the point O. The force situation of the first half of the potato-soil mixture was sketched in Figure 4b.  
\[M_{O}=G_{2}d=\frac{1}{2}mg[S\cos(\alpha+\theta_{2})-H\sin(\alpha+\theta_{2})] \tag{5}\]  
where \(M_{0}\) denotes the crushing moment, N\(\cdot\)m; \(G_{2}\) represents the gravity of the first half of potato-soil mixture, N; \(d\) expresses the distance between point O and gravity \(G_{2}\), m; \(m\) denotes the mass of the first half of potato-soil mixture, kg; \(H\) represents the thickness the potato-soil mixture, m; \(S\) expresses the length of the first half of potato-soil mixture, m; \(\alpha\) represents the inclination angle of lifting chain, \({}^{\circ}\); \(\theta_{2}\) is the angle of the front bulge, \({}^{\circ}\).  
If the potato-soil mixture was snapped, its crushing moment would be more significant than the adsorption moment of internal force. The equation is as follows:  
\[M_{O}\geq\frac{1}{2}F_{2}H+\frac{1}{2}F_{3}H \tag{6}\]  
where \(F_{2}\) denotes the force of the surrounding objects on the potato-soil mixture, N; \(F_{3}\) represents the soil cohesion force, N.  
Figure 4: (**a**) Structural parameters of the first-stage lifting chain; (**b**) the force analyses of potato-soil mixture during the bending area.  
The mass and length of the first half of the potato-soil mixture and crushing moment increased since the potato-soil mixture was delivered backward. The potato-soil mixture was designated as snapping when the crushing moment was more significant than the adsorption moment of internal force.  
Equation (6) shows that the magnitudes of the crushing moment were impacted by the inclination angle of the lifting chain (\(\alpha\)) and the angle of the front chain bulge (\(\theta_{2}\)), and the angle of the front chain bulge is tiny and negligible.