A brief analysis of the structural characteristics of motorcycle frames and their maintenance

As a part of the motorcycle assembly, the motorcycle frame bears a variety of complex loads. The strength, stiffness and inherent characteristics of its structure are important design indicators of the frame. Most motorcycle frames adopt complex tube and plate welding structures, which are the supporting framework of the motorcycle. In the whole vehicle, it must not only meet the requirements of many body parts installation, but also ensure the smooth running of the vehicle, therefore, the structural size and shape accuracy of the frame are required to be high. Motorcycle frame is often deformed after welding, which not only directly affects the assembly and performance of the whole vehicle, but also may reduce the carrying capacity of the frame structure and cause accidents. Therefore, it is very important to limit and eliminate welding deformation in manufacturing. It is of great practical value to carry out the optimization design of motorcycle frame structure and improve its performance.

1 The function, composition and common form of motorcycle frame
The motorcycle frame is not only to connect the engine, suspension device, walking device and other parts, but also to provide installation positions for the wheels. More importantly, it can give full play to the respective functions of each part. When driving on complex roads, it can effectively Resist bumps and impacts from the road. Therefore, the frame is a very important member, and in particular, it is required to have sufficient strength and rigidity.

Compared with other vehicles, motorcycles have their own particularity due to their differences in the connection and composition of the main components. For example, a two-wheeled motorcycle runs through the front and rear wheels. When the vehicle is at a standstill, it cannot maintain balance without the help of the support beam. The steering handle must be used to maintain the balance of the vehicle during driving. The strength and rigidity of the frame cannot be obtained with huge structural steel. Special pipes or plates with light weight and good rigidity should be used to form the frame. In addition, the composition of the parts of the vehicle is mostly assembled in a certain space range of the vehicle beam in the form of exposure, and the appearance is also very elegant. Therefore, the motorcycle frame is a demanding component.

Motorcycles are used in a wide range and variety. In order to meet the requirements of various vehicles, frames with different characteristics must be designed. Generally speaking, the form of motorcycle frames varies with the size of the engine, specifically It is determined by the form of vehicle performance processing and the different use conditions. From the perspective of large combined structure, it is divided into two categories: 1) Multiple simple parts pass through certain processes, combined into a space frame structure, that is, space structure type frame; 2) with a main beam as the main frame, plus some auxiliary installation parts composed of the main beam structure frame.
2 the use of motorcycle frame characteristics and requirements
The motorcycle frame looks like a few rods welded together, which is relatively simple. In fact, its design involves many considerations. The frame, like the human skeleton, must have sufficient strength and rigidity, and there are corresponding requirements in terms of quality and shape.
a) The frame shall have sufficient strength to bear the mass of the engine, other parts and the rider, restrict the movement of the assembly parts and affect its movement performance. The strength of the motorcycle frame of different objects is different, for example, the strength of the street car is lower than that of the off-road vehicle.
B) The frame shall have sufficient rigidity. The so-called rigidity refers to the ability to resist deformation. Compared with cars, two-wheeled motorcycles have a greater range of freedom of movement, such as sharp turns and uneven mountain roads. The rigidity of the frame is low, and the frame is easy to deform when the vehicle is impacted, but the rigidity of the frame is too large to affect the elasticity of the system within a certain range, thereby affecting the rider's riding feeling.
c) The structural dimensions of the frame shall meet the requirements. Some parts of the frame are very critical, which will affect the smoothness of the motorcycle.
d) When designing the frame, the designer should consider the agility of the vehicle but not too flexible, and the stability but not too heavy. For example, the steering shaft head involves size issues such as front fork inclination, wheel drag distance, offset distance, and two wheel torque. The larger the inclination angle of the front fork, the smaller the angle of the direction handle movement when turning; the larger the drag distance, the greater the torque in the front wheel and the more stable the vehicle. Therefore, although the American motorcycle model is larger, it is very stable due to the large angle of the front fork. However, the greater the towing distance, the heavier the steering hand, so the towing distance of the general light motorcycle is between 85 and 120mm. The steering force, centrifugal force and vehicle bumps generated by the motorcycle during driving will cause the steering shaft to twist sideways. In order to resist this lateral torsion, the frame often uses thick tube beams and reinforcing rods from both sides of the engine Welding extends to the steering shaft head.
e) The frame should be light in weight, and high-strength steel is mostly used in materials. This steel contains trace elements such as Chin, ingot, and vanadium. At present, some vehicles use aluminum alloy frames or Chin alloy frames. Reduce the mass of the motorcycle itself, and so dry increases the power of the engine.