U Joint

There are many varieties of U-Joints, a few of which are very complex. The easiest category called Cardan U-Joints, will be either block-and-pin or bearing-and-cross types.

U-joints are available with two hub styles solid and bored. Solid hubs don’t have a machined hole. Bored hubs have got a hole and are called for the hole shape; round, hex, or square style. Two bored types that deviate from these common shapes are splined, which have longitudinal grooves inside the bore; and keyed, which have keyways to prevent rotation of the U-joint on the matching shaft.

Using the wrong lube can cause burned trunnions.
Unless in any other case recommended, use a superior quality E.P. (excessive pressure) U Joint grease to support most vehicular, commercial and auxiliary travel shaft applications.
Mechanically flexible U-Joints accommodate end movement by simply by using a telescoping shaft (square shafting or splines). U-Joints function by a sliding motion between two flanges that happen to be fork-designed (a yoke) and having a hole (attention) radially through the attention that is linked by a cross. They allow larger angles than adaptable couplings and are being used in applications where great misalignment has to be accommodated (1 to 30 degrees).

Always make sure new, fresh grease is evident at all four U-joint seals.

Can be due to operating angles which are too big.
Can be the effect of a bent or sprung yoke.
Overloading a travel shaft could cause yoke ears to bend. Bearings won’t roll in the bearing cap if the yoke ears aren’t aligned. If the bearings stop rolling, they stay stationary and will “beat themselves” into the surface area of the cross.
A “frozen” slip assembly will not allow the drive shaft to lengthen or shorten. Every time the travel shaft tries to shorten, the load will be transmitted into the bearings and they will tag the cross trunnion. Unlike brinnell marks caused by torque, brinnell marks that happen to be caused by a frozen slide are often evident on the front and back surfaces of the cross trunnion.
Improper torque about U-bolt nuts can cause brinelling.
Most producers publish the recommended torque for a U-bolt nut.
Improper lube procedures, where recommended purging isn’t accomplished, can cause a number of bearings to be starved for grease.

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