Winch Crab – Double Purchase is a heavy-duty mechanics laboratory apparatus used to demonstrate the working of a double-purchase lifting machine. It is designed for studying how a double gearing arrangement increases mechanical advantage and reduces the effort required to lift a load.

The apparatus is provided with a 25 cm diameter grooved wheel and precision machine-cut gears for smooth and efficient motion transmission. Its double purchase gear system allows students to compare load, effort, velocity ratio, mechanical advantage, and efficiency in a practical way.

 Mounted on a sturdy cast iron wall bracket, the apparatus offers excellent stability during experiments. It is suitable for schools, colleges, universities, and engineering physics laboratories. Supplied without weights.

Experimental Objectives

To demonstrate the working principle of a double-purchase winch crab.
To determine the mechanical advantage of the apparatus.
To determine the velocity ratio of a double-purchase winch crab.
To calculate the efficiency of the lifting machine.
To study the relationship between load, effort, mechanical advantage, velocity ratio, and efficiency.