Abstract
From an aerodynamical point of view I have shown that the lift of a hemispherical cup of radius a in a steady air flow of velosity V considered as an ideal fluid is (ρ, the air density) for the angle of attack α. The Robinson factor is obtained from the balance of the aerodynamical moment due to 4 cups and the frictional moment due to the bearing in the form where γ is the length of arm and κ the coefficient of friction.
