Tech Talk Blog

Moly filled cast nylon bearings have been used very successfully for many years. The known drawbacks of nylon has always been it’s inherent tendancy to absorb moisture over time and thus causing swelling of the material. More than that, the constant absorption and drying cycle leads to fatigue failure over time. The CJ bearing has zero absorption in moisture, is stronger in terms of compressive strength and resistance to deformation, has a thermal expansion rate the same as steel and has a very low friction. Since the CJ requires no lubrication, it is as close to maintenance free as you can get. In independant testing it was shown that wear life of the CJ is significantly better as well. In rotary wear tests we found that the Nylon/MOS2 had a weight loss of over 180mg after 50 hours. The CJ had 100.5 mg of loss in the same test. Load for the test was 2000 psi at 25 sfpm and temperatures and humidity were controlled in the lab at 78F and 50% humidity. For more information on the CJ Bearing products visit www.tstar.com and check out the Video Library and our on line catalog.

The life expectancy of filament wound composites like TriStar’s CJ product can be improved by understanding some of the typical failures. One consideration is the shaft material. In some applications where the motion is oscillating and at variable frequencies, the bearing can experience rapid wear. This is caused by small angle oscillation or small amplitude vibration and the resultant fretting corrosion. The wear debris that occurs can quickly become an abrasive that dramatically shortens life.

There are a couple of possible fixes for this problem. First, consider going to a 400 Series stainless pin. Testing by an independent company showed a 26 times improvement in wear life by making this simple change. The improvement was directly related to the elimination of the fretting corrosion that occurred on the 1215 carbon steel pin used before.

A second fix is improving the shaft finish and hardness. Another test showed that by going to a 50-55 Rc hardness on the shaft and improving the surface finish to 4-6 rms extended the wear life of an application from 500,000 cycles of life to over 1 million cycles.

One thing to look for if you are experiencing rapid wear of composite filament wound bearings is the debris. If the debris is a fine brown powder than the wear is normal. If the debris looks more like shavings or accumulates in large clumps on the shaft, then you may have a shaft material, surface finish or pin hardness issue that needs addressing.

That being said – CJ bearings are crucial for transportation and other roles. Find out more in our Shooting Star Archives!

TriStar’s CJ bearings are filament wound composite bearings with various liner materials for specific applications. CJ bearings are able to operate from cryogenic to +350 temperatures with NO LUBRICATION. CJ bearings are primarily for high load, medium speed linear or oscillating applications such as lift and tilt points on equipment. The FCJ and Super CJ are designed for high loads and high speeds with 400 sfpm attainable without lube. CJ bearings are truly maintenance free bearings and cost effective even when compared with bronze bushings. For more information on CJ bearings visit www.tstar.com. And don’t forget to contact TriStar to learn how CJ bearings can help with your product performance.