  Recent experiments demonstrate that molecular motors from the Myosin II
family serve as cross-links inducing active tension in the cytoskeletal
network. Here we revise the Brownian ratchet model, previously studied in the
context of active transport along polymer tracks, in setups resembling a motor
in a polymer network, also taking into account the effect of electrostatic
changes in the motor heads. We explore important mechanical quantities and show
that such a model is also capable of mechanosensing. Finally, we introduce a
novel efficiency based on excess heat production by the chemical cycle which is
directly related to the active tension the motor exerts. The chemical
efficiencies differ considerably for motors with a different number of heads,
while their mechanical properties remain qualitatively similar. For motors with
a small number of heads, the chemical efficiency is maximal when they are
frustrated, a trait that is not found in larger motors.
