This paper aims to detail Frisch’s choice of setting the accelerator principle at the core of his impulse-propagation model (1933a), referred to as the “rocking horse model.” The innovative aspects of this model rest not only on the rise of macrodynamics regarding the equilibrium concept but also on the reformulation of business cycles in terms of production of capital goods. This is a deliberate choice, which relies on his work on business cycles started in 1927, and can be obviously traced back to his debate with John Maurice Clark and the American Institutionalists, but relies more deeply on a specific appropriation of Norwegian approach to this principle.