Low speed heavy load should avoid using only suitable for small and medium power coupling. For example: elastic sleeve column pin coupling, core type elastic coupling, polygonal coupling rubber, tire coupling; overload protection shaft control is needed, appropriate chooses the safety coupling; load changes larger and shock and vibration of shafting, appropriate choice with elastic element and the buffering and damping effect better elastic coupling. The bearing capacity of the metal flexible coupling is higher than that of the non metallic elastic coupling. The elastic element is affected by the elastic coupling of the elastic coupling.