Gearhead efficiency at blocked state

Topic:

What's the efficiency of a gearhead in case of blocking?

Solution:

Actually, the term efficiency should not be applied in the case of a gearhead in blocked shaft state. Efficiency gives the ratio of two powers. At standstill (speed = 0) the power is zero at the input as well as at the output.

What we talk about here is the ratio of torques:

In principle, in the event of blocking, there is a static power transmission via levers present. If it might then be wrongly assumed that there is no friction present in such a case, an efficiency of apparently 100% might be used to calculate output shaft torque. However, this is an oversimplified theory that the full motor torque M_mot multiplied with the gearhead reduction i will be available at the gearhead output (torque M_L):

M_L = M_mot * i * η = M_mot * i * 1

Unfortunately, assuming 100% efficiency (as in above formula) at standstill in blocked state does not consider internal static friction, which is difficult to quantify.

Rule of thumb:

Based on measurements, it can be stated as a rule of thumb from practice that the specified maximum gear efficiency should also be used to calculate the gear's output shaft torque at blocked state.