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There are two methods for the rollers of conveying equipment. One method is the electric drum, which integrates the motor and gear reduction equipment all within the drum. Although it has a compact structure and small size, it is not easy to install or disassemble, which hinders maintenance and repair; moreover, its manufacturing process is complex and heat dissipation is difficult. Another method is the gear drum, which incorporates gear reduction equipment within the drum, taking advantage of the compact structure and small size of electric drums. However, it suffers from the same poor heat dissipation conditions as electric drums, so it can only be used in low-power conveying equipment. In this article, we use a low-power drum with a power of only 15 kW as an example to illustrate the gear drums used in conveying equipment. The main advantages of gear transmission are: reliable operation and long service life. Its instantaneous gear ratio remains constant, ensuring smooth operation and high efficiency. There are many methods of gear transmission, such as spur gear transmission, bevel gear transmission, planetary gear transmission, and so on. Since the transmission ratio of the reducer planned for this application is only 12.828, and its operating conditions are favorable, a conventional gear drive is sufficient to meet the requirements. For economic reasons, we have decided to use a secondary cylindrical gear drive. 1. Planning of the gear drum transmission system (1) Original data: The service life of the drum is 10 years, with 300 working days per year; production takes place in one shift per day, for 7 hours per shift. Minor repairs every year, major repairs every three years. The operating environment temperature shall not exceed 400°C. Its process parameters are as follows: Drum diameter (mm): 500 ； Conveyor belt width (mm): 800 ； Drum width (mm): 950 ； Device scale (mm): 1,300 ； Conveyor belt operating speed (m/s): 210 ； Motor power (kW): 15 ； Motor speed (r/min): 980. (2) Gear drum drive design: This design employs a two-stage cylindrical gear transmission. The motor’s output power is transmitted to shaft I, which in turn drives the pinion 1 on that shaft. Pinion 1 meshes with gear 2, and at this point the power is transferred to shaft II. Shaft II then drives pinion 3 to mesh with internal gear 4, thereby transmitting motion to the drum to achieve deceleration. The entire gear transmission equipment is placed within a support frame, and a butterfly-shaped support rib is designed to connect the internal gear 4 to the drum. 2. To determine the transmission parameters of the gear drum system, it is first necessary to allocate the gear ratios between the two pairs of meshing gears. The following principles should be considered when assigning these gear ratios: ① The gear ratios for each stage of the gear drum transmission must remain within a reasonable range, not exceeding the allowable maximum values, in order to comply with the transmission requirements for each stage ； ②Attention should be paid to ensuring that the gear drums maintain harmonious transmission ratios at various levels, resulting in a balanced and rational structure ； ③Strive to keep the overall dimensions or weight of gear roller drive equipment compact ； ④Make sure the oil immersion depth of the large gears at each stage of the gear drum is reasonable ； ⑤It is necessary to ensure that there is no dry contact or collision between the transmission components of the gear drum. 3. Gear design: Both pinion 1 and pinion 3 are treated by quenching and tempering using 40Cr; their hardness ranges from HB241 to HB286, with HB260 being the average value ； Both the large gear 2 and the internal gear 4 are quenched and tempered from 45 steel, with a hardness of HB229–HB286; HB240 is taken as the average value. This plan adopts a standard helical gear drive without any modification. The design of gears is considered from two aspects: ① The gear drum is calculated based on the contact fatigue strength of the tooth surface ； ②The gear drum is checked based on the root bending fatigue strength. Since there is no severe overload in the transmission, a static strength check is not performed. The module and pitch circle diameter of the gear can be calculated, and the module is rounded to determine the exact diameter of the pitch circle. After completing these, a suitable and safe gear is obtained. Oil lubrication is selected for this plan. 4. Design of the gear drum shaft: The gear drum shaft is the primary component in this design, therefore it must be designed properly. In this plan, two axes were prioritized for planning, namely High-Speed Axis I and Central Axis II. After the preliminary planning of axis I, we found that this axis was not firmly fixed in the axial direction; therefore, a sleeve and two round nuts were used to secure it, ensuring axial stability. After the initial planning of the shaft’s structure, it is necessary to conduct a strength check on the shaft. First, verify the shaft diameter, and then check the shaft’s strength using the safety factor method. When checking the strength of the shaft, the appropriate calculation method is selected based on the detailed loading and stress conditions of the shaft, and its allowable stress is chosen accordingly. Based on the structural diagram of the shaft, a simplified calculation diagram of the shaft is prepared; from this diagram, bending moment diagrams, torque diagrams, and equivalent bending moment diagrams are created. The critical section is then identified as the center section of the pinion. The strength of the shaft is checked using the combined bending and torsional stresses, with attention being paid primarily to the sections that experience the maximum calculated bending moments. Finally, the fatigue strength of the shaft is evaluated. After the above planning and calculations, it is shown that the design of this shaft is safe and reliable, meeting the application requirements. 5. Selection of gear drum bearings: Since the loads acting on these bearings are radial and axial, tapered roller bearings are chosen. The bearing type we have chosen is 7308. The rated dynamic load of this bearing is 48,440 N, while the rated static load is 43,540 N. Its maximum operating speed is 5,600 rpm (with oil lubrication). The coefficient of dynamic axial load is 211, and the coefficient of static axial load is 112. After initially determining the bearing type, we conducted calculations and verifications from three aspects: ① Life expectancy calculation ； ②Calculation of static load ； ③Check of allowable speed. 6. Structural design of other components of the gear drum: In this design, a support frame and a butterfly-shaped support rib were also included to fix the gear assembly inside the drum. There are other components as well, including the planning for some standard and non-standard parts, which will not be discussed here in detail.