This example shows a block and tackle system that is represented by the Belt Pulley and Rope blocks from the Simscape™ Driveline™ library. This compound pulley is rigged as a threefold purchase with two triple blocks. The system has a mechanical advantage of 6.
A payload of 10 metric tons subject to gravity is raised by an Ideal Velocity Source pulling on the rope end. The system starts at rest with the Velocity Source providiing a force that is in equilibrium with the load. As the velocity source accelerates and decelerates, the rope tension increases and decreases, respectively.
These plots shows the pulley rotational velocities and rope segment tensions. Successive pulleys along the driveline rotate at slower velocities. Each rope segment supports a tension load that is one-sixth of the payload force. The rope tension increases as the paylod accelerates and decreases as the payload decelerates.