The connection between the wheels and the carriages on the train is usually achieved through a device called an "axle box". The following is the general connection method:

Train Wheelset and Axlebox:

The wheels are usually connected to the axle by a wheelset (a unit of two wheels). There are two wheels on each axle, and each wheel pair is usually mounted in an assembly called an axle box.

Design of the train axle box:

The axle box is a closed structure that accommodates the wheel set and has the function of fixing and connecting the wheel set. Axle boxes are usually made of strong metal to withstand the loads and vibrations of the vehicle during operation.

Connecting the train axle box and carriage:

The axle box is combined with the carriage through various mechanical connections. This may involve support structures on the axle boxes, which are connected to the bed of the car or chassis by means of springs, bolts or other connections.

Suspension System:

The axle box also usually includes a suspension system, which helps reduce vibrations and shocks when the vehicle is driving. This suspension system can include springs, shock absorbers, etc. to help provide a smoother ride.

Breaking Discs and Braking Systems:

Wheel connections on freight trains may also include breaker discs and braking systems. These components are located on the axle boxes and are used to control the speed and braking of the train.

Generally speaking, the wheel set is connected to the vehicle through the axle box, and the axle box is tightly integrated with the bottom of the carriage or chassis through a series of mechanical connections. This connection method ensures that the vehicle remains stable while driving and can effectively transmit traction and braking forces.