圈上泽支大峰 Self-Locking Solving for f gives f>I cos a /πdm orf>tanλcosa If a square thread is used,this reduces to f tan >Notice that this is for static-loading situations >The presence of any vibration from dynamic loading or other sources can cause the screw to back down. 圈上泽夫道大学 Effect of Collar A thrust or collar bearing is normally used between rotating and stationary members when transmitting power to a load by lifting or lowering it >To carry the axial component Assuming load is concentrated at mean collar diameter,d and collar has a friction of f,then extra torque is >T。=Ffd。I2 screw >which must be added to the torque 2626  Solving for f gives f > l cos  /  dm or f > tan cos   If a square thread is used, this reduces to f > tan  Notice that this is for static - loading situations  The presence of any vibration from dynamic loading or other sources can cause the screw to back down. Self-Locking Effect of Collar  A thrust or collar bearing is normally used between rotating and stationary members when transmitting power to a load by lifting or lowering it To carry the axial component  Assuming load is concentrated at mean collar diameter, dc and collar has a friction of f c, then extra torque is Tc = F fcdc / 2 which must be added to the torque