Wouldnt it be wonderful to live in an ideal world where mechanical components never failed? A bad u joint can cause all sorts of problems for you application.
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Top 6 Signs of a Bad U Joint
For those of us who live in the manufacturing real world, we all know that components do break, especially when selected or applied incorrectly. Our goal in this article is to help you understand the main failure modes of universal joints, and how to correct for them. Lets dive into the most common signs of a bad u joint.
1. Too Much Torque
If your system is applying too much load to a universal joint, it is likely to fail. A complete failure will most likely appear as a shearing of the ears of the yoke or a pin failure. On a joint made from unhardened stainless steel, a deformation failure from high torque is likely, which will be noticeable as poor articulation or binding of components that limits future operation. Even if the loads are not enough to break or deform the joint, excessive loads lead to increased wear. Increased wear can increase play and backlash and will remove material, which will lead to weakened components.
Solution: if you are confident that the rest of your system is designed correctly, it is possible that you need a larger universal joint size or a different style u-joint such as our High Strength or Leveler Strength designs to handle the elevated loads.
2. Too High of an Angle
Each universal joint design has a maximum operating angle. That maximum angle decreases as loads and speeds on the u joint increase. An excessive angle failure will appear as notchiness, or a lack of smooth operation, in the u joint.
Solution: If reducing the operating angle is not an option, it may be worth considering a double u-joint to decrease the operating angle of the coupling per joint. In some cases, it is the combination of angle, speed and torque that overloads the joint. A reduction in torque or RPM leads to a higher allowance for the operational angle.
3. Too High of Speed
It is possible for a universal joint to fail if the RPM applied to the coupling is too elevated. The recommended max operating speed of a u-joint depends on several factors:
the bearing configuration (needle bearing designs can generally handle higher speeds than friction bearings at significant angles)
the torque that is being applied (higher torque requires lower speeds, all else equal)
the operating angle (higher angles require lower speeds)
the length of a Double or Telescoping U-Joint assembly
the type of lubricant used
Friction-bearing joints at elevated speeds and angles will wear out much faster than properly sized needle-bearing joints.
High torques in connection with high RPM and especially at continuous operation will create a lot of friction heat that will lead to lubrication failure, excessive wear, and joint damage.
High angles increase the movement on the bearing surfaces (at 00 angle the is actually no movement in the bearings of the joint), so angle is a major contributor to bearing speed even more than the actual RPM.
The length of a double joint or telescoping drive shaft limits the maximum speed due to the natural frequency of the assembly.
At very high speeds, a friction bearing joint with an oil filled boot will provide better lubrication and thus better lifetime than a grease filled boot and will be significantly better than a joint running dry.
Solution: if your u-joint is struggling with an excessive RPM failure, work with your universal joint application engineer to determine whether the design of the joint is correct for the application. If you are using a pin & block joint, perhaps a needle bearing or composite bearing design would be more suitable for high speed, continuous operation. If the angle is too great to accommodate the speeds required, a double universal joint may be the best solution to accommodate high RPM at a high angle.
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4. Not Enough Lubrication
Any bearing surface must be properly lubricated to operate effectively and efficiently. If your u-joint is binding or you notice unusually high wear in operation, a lubrication failure might be occurring.
Solution: there are several ways to add lubrication to a universal joint. Regular relubrication is one option most easily done when the joint is equipped with lubrication fittings. If a u-joint features a protective boot, this boot cannot only keep dirt and debris away and protect the u-joint components, it can also be filled with lubricant that forms a grease reservoir close to the bearing surfaces and ensures constant relubrication. If a protective boot is not feasible with your design, there are several dry film coatings and platings that can provide long-term lubrication to bearing surfaces. An external oil drip or oil spray system can also be used on larger friction bearing u-joints. If your application allows you to consider a needle bearing design, the enclosed bearings are pre-lubricated to allow for long term operation without the need to add or replace grease over the lifetime of the u joint.
5. Poorly Installed Universal Joint
Any universal joint must be installed properly to work as intended within your machine. A poorly connected driving or driven shaft, a missing support bearing, or an incorrect mating shaft dimension may result in signs of play or sloppiness and can make the joint fail in a number of ways due to the improper application of stress.
Solution: Belden Universal offers many standard and custom machined hub configurations to make installation simple and straightforward for operators and maintenance technicians. Our design engineers can come up with a solution to perfectly mate with the input and driven shafts within your system. If you can engage Belden early in the design process, we would be happy to walk you through which bore configurations are standard and most economical for your needs.
6. Imprecise Machining
Remember, not all universal joints are created equal! Inexpensive, offshore u-joints are often produced on antiquated, imprecise equipment. This will predictably produce sub-standard, wide tolerance bearing surfaces and mating features. If you have a demanding application that requires tight tolerances to be held, an offshore product will not be right for you.
Solution: Belden Universals products are precision machined on modern CNC equipment to ensure precise bearing surfaces and mating features. Our in-house design and engineering team can bring to life the universal joint that your specific application needs, all in a cost-efficient manner.
At the end of the day, if youre having trouble with the universal joint or drive shaft in your highly demanding application, dont hesitate to give Belden Universal a call at 708-578- or Contact Us. Our highly skilled application engineers are standing by to help you get exactly the right u joint or drive shaft at a competitive price.
1. What is a universal joint cross bearing?
A universal joint cross bearing is a key component of a universal joint (U-joint), responsible for allowing the joint to transmit rotary motion between misaligned shafts.
2. Where are universal joint cross bearings commonly used?
Universal joint cross bearings are used in various applications, including automotive drivetrains, industrial machinery, agricultural equipment, marine applications, and aerospace.
3. What materials are universal joint cross bearings made of?
Common materials include steel, alloy steel, aluminum, and stainless steel, chosen based on factors such as load capacity and environmental conditions.
4. How are universal joint cross bearings manufactured?
They are typically forged, heat-treated, machined, drilled, ground, and assembled, with quality control and testing at each stage.
5. What are the advantages of using universal joint cross bearings?
They accommodate misalignment, transmit motion efficiently, and are durable and versatile.
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6. What types of lubrication are used in universal joint cross bearings?
Commonly, grease is used to lubricate the needle bearings within the cross.
7. How do you maintain universal joint cross bearings?
Regular lubrication and periodic inspection for signs of wear and damage are essential for maintenance.
8. What factors affect the service life of universal joint cross bearings?
Service life is influenced by factors such as load, operating speed, maintenance, and environmental conditions.
9. Can universal joint cross bearings be replaced individually or must the whole U-joint be replaced?
In most cases, individual universal joint cross bearings can be replaced without replacing the entire U-joint.
10. What are the symptoms of a failing universal joint cross bearing?
Symptoms include vibration, noise, and a feeling of looseness in the drivetrain.
11. How do you diagnose a universal joint cross bearing problem?
By inspecting for visual wear, performing a driveline angle check, and listening for unusual sounds during operation.
12. What are the steps to replace a universal joint cross bearing?
Steps typically involve removing the driveshaft, disassembling the U-joint, pressing out the old cross bearing, and installing a new one.
13. Can universal joint cross bearings be greased, and how often should they be lubricated?
Yes, they should be regularly greased according to the manufacturers recommendations, often during routine maintenance.
14. Are there different types of universal joint cross bearings, and how do you choose the right one for your application?
Yes, there are different types, including plain, needle-bearing, and sealed. Selection depends on factors like load capacity and maintenance requirements.
15. What is the typical lifespan of a universal joint cross bearing?
Lifespan varies depending on factors like load, maintenance, and environmental conditions but can range from tens of thousands to hundreds of thousands of miles or hours.
16. Can universal joint cross bearings be repaired, or do they need to be replaced when damaged?
Typically, they need to be replaced when damaged or worn beyond acceptable tolerances.
17. What is the function of needle bearings within the universal joint cross bearing?
Needle bearings reduce friction and allow for smooth and efficient rotation of the bearing journals within the cross.
18. Can universal joint cross bearings be customized for specific applications?
Yes, manufacturers can provide custom solutions based on specific application requirements.
19. What are some common failure modes for universal joint cross bearings?
Common failure modes include wear, brinelling (indentations on the bearing surface), and loss of lubrication.
20. Are there maintenance tips for extending the life of universal joint cross bearings?
Regular lubrication, alignment checks, and early detection of issues can help extend the life of universal joint cross bearings, as can following the manufacturers maintenance guidelines.
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