Optimization of rack tooth forms of monorail mountain orchard transporter

Abstract: Due to the rugged terrain, there are many difficulties in the transportation of fruits and materials in hilly lands in the south of China. In order to solve the problem, self-propelled monorail mountain orchard transporter and its corresponding rail were designed and manufactured. However, in reality, the accumulative pitch error of tooth is unavoidable due to uncertainties such as manufacturing and tolerances, assembly errors and wear. And the driving wheel is the main power-consumption component. In order to reduce energy consumption and cost of transport, and increase transport efficiency and the mechanical property of the transporter, it is of great significance to research the influence of the rack tooth forms on the mechanical property of self-propelled monorail mountain orchard transporter and attempt to find the optimal rack tooth form. The paper designed another 3 kinds of tooth forms, which were chain wheel tooth form, pin tooth form and cycloidal tooth form. The original tooth form is arc tooth form, which is very sensitive to center-distance error and pitch error. And the 2 errors have great impact on the mechanical property. Meanwhile, the dynamic models of the transmission system including the driving wheel and racks were established based on the dynamic theory. As the trend of the driving torque variation is the same with the resistance torque variation which is not convenient to be measured, the experiment was carried out with tooth forms, rail gradients and angular velocity as experiment factors and with the driving torque as assessment index. The experiment was conducted from July 10 to July 22, 2017 at the Machinery Electronic Engineering Training Center in Huazhong Agricultural University. A torque sensor and a data acquisition and analysis system were used to measure the driving torque. Four kinds of racks were manufactured and spot welded to the rails, and the relation between the tooth forms and the resistance torque of the driving wheel was investigated while engaged with the racks. Experimental results indicated that the tooth forms had great influence on the driving torque, as on the resistance torque. For the 4 racks, the driving torque and the amplitude of the driving torque were the least when the driving wheel was engaged with the rack of chain wheel tooth form, while the largest when the driving wheel was engaged with the rack of pin tooth form. Contribution to the average driving torque and the fluctuation range of the driving torque, from small to large order, was chain wheel tooth form, cycloidal tooth form, arc tooth form and pin tooth form in identical condition. Under the working condition that the (rear drive) transporter moves forward along the level track at +88.08 rad/s, the average driving torque was decreased by 20.80% when the driving wheel was engaged with the rack of cycloidal tooth form than the rack of arc tooth form, while increased by 158.73% when the driving wheel was engaged with the rack of pin tooth form than the rack of arc tooth form. Compared with the rack of arc tooth form, experimental results showed that the rack of chain wheel tooth form had a better comprehensive performance by decreasing the average driving torque by 33.82%, 33.45% and 21.59% respectively under the condition that the angular velocity of the drive wheel was +88.08 rad/s, and the rail gradients were +0°, +6°, +12°, respectively; while by 35.55%, 27.24% and 30.43% respectively under the condition that the angular velocity of the drive wheel was ?88.08 rad/s, and the track gradients were ?0°, ?6°, and ?12°, respectively. By the experimental results, the rack of chain wheel tooth form is more suitable for the rail transport. This research provides the important reference for the structural optimization design of the rail.