The traction machine because the traction force is the weight of the car and the counterweight together through the traction rope on the traction sheave groove generated, the weight is the traction rope and traction rope groove friction necessary conditions. With it, the hoisting machine tends to balance the weight of the car with the weight of the payload, which in turn reduces the power consumption of the transmission when the elevator is running. Therefore, the weight is also called balance weight, relative to the car hanging at the other end of the traction sheave, play a role in balancing the weight of the car.

       T1 = T2 when the weight of the car is equal to the weight of the counterweight, and the traction machine can easily run only by overcoming various frictional resistances without considering the change of the weight of the rope. In practice, however, the weight of the car varies with the load of the goods (passengers), so that it is impossible for the fixed counterweight to completely balance the weight of the car under various loads. Therefore, the heavy weight match will directly affect the traction and drive power.

       In order to make the elevator fully loaded and no-load conditions, the absolute value of the load torque is basically equal, the national standard of traction machine balance coefficient K = 0.4 ~ 0.5, that is, the balance of 40% ~ 50% of the rated load. Therefore, the total weight of the heavy side should be equal to the weight of the car plus 0.4 ~ 0.5 times the rated load. This 0.4 ~ 0.5 is the balance coefficient.

       When K = 0.5, the elevator at half load, the load torque is zero. Car and counterweight are completely balanced, the elevator is in the best working condition. When the elevator load varies from no-load (no-load) to rated load (full load), the change of torque reflected on the traction sheave is only 50% of the earth, reducing the energy consumption and reducing the burden of the traction machine.

       Equivalent friction coefficient f and rope groove shape
       When the drag rope and the traction sheave come into contact with different shapes of rope grooves, the friction force generated by the traction machine is different, and the larger the friction force is, the larger the traction force is. From the current use to see there are several: semi-circular groove, V-groove, semi-circular groove with slots. Semi-circular groove f smallest, for the winding traction sheave. V-type wheel f maximum, and with the opening angle decreases, but also increased wear and tear, while the rope wear and rope rope. As the wear will tend to semi-circular groove. Semi-circular incision groove f between the two, and its basic does not change with the wear and tear, the current wider application. Rope lubrication in the rope groove also has a direct impact on the friction coefficient, only the slight lubrication of the oil core rope can not be coated with lubricating oil in the rope, so as not to reduce the friction coefficient, resulting in slippage and reduce traction.

       Traction rope in the traction sheave corner
       The wrapping angle refers to the arc that the hoisting rope touches through the rope groove and is used. The larger the wrapping angle is, the larger the friction force is, and the traction force of the hoisting machine also increases, which improves the safety of the elevator. At present, there are mainly two ways to increase the angle of the wrapper. One is to use a 2: 1 drag ratio to increase the wrap angle to 180 °. The other is a wraparound (for α1 + α2).

        Rope traction rope rope winding method depends on the traction conditions, rated load and rated speed and other factors. It has many kinds. The winding method can also be seen as a different transmission mode, different winding method has a different transmission speed ratio, also known as traction ratio, which is driven by the lift elevator run-round pitch line speed and car speed ratio . The number of windings on the traction sheave can be divided into single winding and rewinding. When the single winding is around, the rope is wound only once on the traction sheave with the wrap angle less than or equal to 180 °. When the winding machine is rewound, Round about the second wheel, the package angle greater than 180 °.