The quality of friction material will directly affect the braking safety of brake mechanism. The characteristics of friction material include friction coefficient, friction loss, hardness, impact strength, water absorption and oil absorption. For the manual hoist, the friction coefficient and hardness are mainly considered in the design. Friction coefficient is an important property of friction material, which directly affects the braking performance of brake mechanism. The friction coefficient is not fixed, it is related to the working temperature of the brake mechanism, the linear velocity of friction and the specific pressure of the brake surface. The friction coefficient generally decreases with the increase of specific pressure, and decreases with the increase of temperature and friction linear velocity.
For the manual chain block, because the work is intermittent and the speed of lifting and lowering weights is not large, there is almost no effect of temperature and friction linear velocity. But because the brake surface design of the brake has a certain slope, the specific pressure of the friction pad is larger, so the influence of specific pressure should be considered when selecting the friction coefficient. The friction coefficient of the friction disc of manual hoist is usually μ=O.38~O.44c.
The hardness of the friction disc has a certain effect on the braking performance. Soft friction disc and brake parts have good duality coincidence, sensitive friction reaction, but poor strength, easy to break; hard friction disc and brake parts have poor coincidence, small contact surface, but good strength, not easy to wear. Friction materials with hardness of HB25~HB30 can be selected for manual hoist.