Which one of the following couplings is not a flexible coupling? 

Explanation:

Couplings are devices used to connect two shafts together and are divided into two categories: Rigid and Flexible. Both are used for the purpose of transmitting power, rigid couplings being more limited in applications as compared to flexible couplings. Rigid couplings are used where shafts are already positioned in precise lateral and angular alignment. Their design does not allow for any misalignment between shafts, but are generally able to transmit more power than flexible couplings. Flexible couplings are designed to accommodate misalignment between shafts and various types of load conditions.

Types of Rigid Couplings

• Sleeve or muff coupling
• Clamp coupling, compression coupling or split muff coupling
• Flange coupling
• Marine coupling

Types of Flexible Couplings

• Universal Joints
• Oldham Couplings
• Flexible Shaft Couplings
• Bushed pin flexible coupling