The durability of a universal joint is largely determined by the transmitted torque, angle of operation, and the rotational speed (rpm) of the propeller shaft. Any combination of high torque, angle, and rpm values will effectively increase stress on the joint.
As the angle of operation increases, the U-joint pins oscillate in the bores in a greater magnitude — resulting in increased movement and wear between the bearing components.
Excessive torque can cause the joint to break … and an excessive speed and angle at an acceptable torque may cause lubrication failure. That in turn leads to increased friction, heat generation, and wear. It is therefore crucial to identify typed of universal joint to avoid failures during operation.
Technical data and calculations for specific torque and speed can also aid in the size and type selection of the universal joint. Information pertaining to the acceptable amount of torque and torsional backlash (also called play) for a given application should inform the design and manufacture of the universal joint employed on that axis.
Universal joiont materials and coatings Special applications often require carefully selected materials to deliver high strength, improved corrosion and wear-resistance or other desirable qualities. Alloy steel is typically the strongest and most widely used family of metals for universal joints.
Alloy steel universal joints are capable of handling high-torque applications and can be further strengthened by hardening. 300-series stainless steel is commonly used in sterile, sanitary and corrosive environments.
Specialty stainless steel may be necessary for extreme corrosion or temperature resistance. Titanium, bronze, brass alloys, and nitrogen-strengthened materials can deliver additional improvements with regards to strength-to-weight ratio, wear, or corrosion resistance.
Product qualities can be further enhanced by applying special coatings, such as nickel, zinc, cadmium, MoS2, PTFE, black oxide and finishing methods such as anodizing, polishing and surface passivation.
Mechanical quality, testing, and certifications for U-joints Many customers’ quality requirements call for the highest standards in manufacturing — most commonly ISO9001 or AS9100 certifications.
It is vital that the quality system is integrated into all aspects of the manufacturer’s operations, with materials and hardware sourced from suppliers complying with the same standards. For new product development, the design concept can be further validated using backlash testing as well as dynamic and static life tests.