A motor coupler is used to connect two shafts so that they will rotate synchronously. A motor coupler is used in applications where rotary motions need to be transmitted to another device. A motor coupler should be carefully selected according to your application because there are many factors that can damage your system if not selected properly. Things to consider; weight, length, bore diameter, overall diameter, torque rating, speed rating, stiffness, and backlash. The dimensions of the coupling are important if your application has size limitations. Torque rating is very important because if you apply more torque than the max torque rating the motor coupler can easily fall apart and possibly ruin your system. Speed rating must be verified between the motor and the motor coupler because if ignored the coupling can fail. Stiffness is important in both flexible motor couplers and Rigid motor couplers. For flexible couplings stiffness will determine how flexible this coupling really is and there a fine line between to flexible and not flexible enough. For the Rigid motor couplers flexibility is important in terms of the spider. The spider comes in various stiffness's, the more stiff the spider the more vibrations and shocks the shafts will feel, the more flexible the elastomer spider less vibration and shocks will be transferred from shaft to shaft. Ideally you would want your coupling to have zero backlash so that you have zero lost motion in your system.
Motor couplers are typically placed into two different categories; Flexible motor coupler and Rigid motor coupler. Flexible motor couplers are couplers that allow for shaft misalignment because of the flexibility of the coupling. These flexible motor couplers are flexible due to the slits along the center of the motor coupler allowing for room to bend. The material of the coupling is also a factor that allows the coupling to be flexible but there is a fine line between to flexible and not flexible enough. Flexible motor couplings are primarily manufactured out of Aluminum and can range from 3° to 5° of angular misalignment. The Flexible Motor Coupler can generally only be used with low torque applications. It is susceptible to more wear than a rigid motor Coupler. There are many different types of Flexible Motor Coupler products. These include: Flanged Pin Bush Motor Coupler, Bibbly Motor Coupler, Gear Tooth Motor Coupler, Tyre Motor Coupler, Elastomeric Motor Coupler, Oldham Motor Coupler, Thompson Motor Coupler, Resilient Motor Coupler, Disc Motor Coupler, Diaphragm Motor Coupler, Universal Motor Coupler, Hooke's Motor Coupler, Bellows Motor Coupler, and Spider or Jaw Motor Coupler. A Rigid Motor Coupler is used when the two shafts are required to be precisely aligned; shaft misalignment will affect the performance and the life of the Coupler. The Rigid Motor Coupler is made of a metal or plastic material that is inflexible. Rigid jaw couplings are made up of three parts; two hubs and a spider. The two hubs are connected by the spider and act as interlocking teeth. The spider of the motor coupler comes in various stiffness', this is determined by the torque, speed and temperature specifications. The spider allows for torsional-flexibility and has shock absorbing and misalignment capabilities. The fact that the jaw motor coupler comes in three pieces is very important because this allows for different bore sizes at each end of the motor coupler.
Before the Motor Coupling was developed, belt and transmission drives were used to transfer torque. These drives took up a lot of space, were hard to install, had low flexibility at different speeds, had high danger of accidents, and had high needs of energy. The Motor Coupling was made to solve all of these problems. The first Motor Coupling needed only to connect the input to the output shaft. This resulted in the making of Rigid Motor Coupling products like clamp couplings, flange couplings, bolt couplings and jaw-type couplings. They were inflexible and made large amounts of peripheral noise. The first systems of the Motor Coupling resulted in coupling unbalance because the casting process had a high tolerance. These couplings only partly solved the problem and were only suitable for low speeds. The un-machined jaw-type Motor Coupling was then developed. This Motor Coupling had the first generation of elastomer spiders which dampened the shock loads.