Analysis of the Mixer Truck Tank Structure and Introduction to Mixer Trucks

　　A concrete mixer truck is a specialized vehicle used to transport concrete for construction purposes. Due to its distinctive shape, it’s often referred to as a “snail truck” or an “olive truck.” These trucks are equipped with cylindrical mixing drums that hold the mixed concrete. During transportation, the mixing drum is kept rotating at all times to ensure that the concrete remains fluid and doesn’t start to set. After delivering the concrete, the interior of the mixing drum is typically rinsed with water to prevent any residual concrete from hardening and occupying space, which could gradually reduce the drum’s effective capacity.

　　Recently, many car enthusiasts have been asking questions about the components of concrete mixer truck tanks. While researching this topic, I discovered that there’s quite a bit to know about the structure and internal design of these tank bodies. Today, I’ll provide you with a detailed explanation of the structural features of concrete mixer truck tanks.

　　Introduction to Tank Structure

　　As shown in the figure, the mixing drum of a concrete mixer truck typically consists of three sections: a front cone, a middle cylinder, and a rear cone. Inside the drum, there are two helical blades—welded symmetrically to the drum wall at an angle of 180° apart. These two helical threads, together with the drum wall, form spiral channels through which concrete is fed, mixed, and discharged. Generally, the front and rear cones each feature logarithmic spiral blades with the same pitch angle, while the middle cylinder is usually cylindrical and equipped with cylindrical helical blades that have different pitch angles.

　　Mixing operating principle

　　The mixing drum of a concrete mixer truck relies on the rotating drum itself to drive two spiral blades, which in turn mix and discharge the concrete. During operation, the mixing drum rotates around its own axis, causing the concrete to move along the helical paths formed by the mixing blades. The spiral curves propel the concrete toward the opposite end and the top surface—this is the primary motion during concrete mixing. At the same time, due to the friction between the concrete and both the drum wall and the blades, as well as the inherent cohesive forces within the concrete, once the concrete reaches a certain height inside the drum, it will, under the influence of its own weight, overcome the aforementioned friction and cohesion forces and begin to tumble and slide downward. Furthermore, at the bottom of the blades, because the blade shape is curved, the concrete undergoes rotational agitation when subjected to external forces. Since the mixing drum rotates continuously, the concrete experiences a combined motion involving three distinct types of movement—a three-dimensional mixing action. As a result, the concrete is thoroughly mixed, ensuring its homogeneity.

　　Mixing Truck Tank Analysis

　　The figure below shows a sectional view of the mixer truck’s tank. As you can see, the interior of the tank is mainly composed of eight major components: the sealing pipe, blades, mixing vanes, end cap plate, mixing drum shell, mixing drum raceway, connecting flange, and inspection port.

　　Sealed tube A is funnel-shaped with a large opening, ensuring smooth material feeding and preventing concrete from overflowing.

　　The blade B has a curved surface, which helps improve the discharge performance of low-slump concrete.

　　Mixing blade C has excellent mixing performance, which helps maintain the quality of pre-mixed concrete.

　　The head plate D is integrally roll-formed from high-strength steel plate and, after being welded to the head reinforcement plate, exhibits reliable rigidity.

　　The mixing drum shell E and various types of blades are all made from high-strength, wear-resistant steel plates specifically designed for concrete mixers, offering exceptionally high wear resistance.

　　The mixing drum’s raceway is integrally rolled, offering excellent wear resistance. The raceway is used to support the mixing drum on the supporting rollers.

　　Connect flange G to the gearbox and support the mixing drum on the frame.

　　The inspection hatch H is for emergency maintenance.

　　Principles of Tank Structure Design

　　The mixing drum’s structure should be simple, compact, and lightweight, in order to minimize the vehicle’s curb weight as much as possible. This helps increase the effective loading capacity of the mixer truck and relatively reduce the power consumption of the vehicle. At the same time, the structural layout must accommodate the chassis’ narrow and elongated shape as well as height restrictions. The overall height and center of gravity of both the mixing drum and the mixer truck should be minimized as much as possible to ensure driving stability and off-road capability. Additionally, the vehicle should have sufficient effective loading volume to meet the specified requirements for mixing, loading, and unloading operations, and its structure must be tailored to the characteristics of the carrier chassis and the mixing process itself. The mixing drum’s external shape is relatively complex, with a varying cross-sectional diameter along its axial direction. The middle section has a larger diameter, gradually narrowing toward both ends. For large-capacity mixing drums, a cylindrical section is added between two frustums of cones to expand the loading volume while avoiding an excessively large diameter in the middle section of the drum.