Log onto
www.rentech.org.Forums and under heading for 996 Series (Carrera, Carrera 4, Carrera 4S, Targa
see Casper Labs Ceramic IMS Bearing.
The whole gambit is interesting but especially post #39, on page 2 from Casper Labs head honcho regarding steel vs plastic cages and ceramics in general. Casper are Aero engineers have been trialling an alternative IMS bearing application.
Bill Ryan is far more experienced than I am in detailing the respective materials....
Our production bearings will be shipped with steel ball cages. We have tested two types of steel designs, nylon, and an exotic made of a low density phenolic. The phenolic one is put in a bell jar immersed in Mobil 1. You pull a vacuum on it, and the oil gets sucked into the phenolic. It will wick enough oil for years of dead storage to start-up lube a ceramic hybrid...... even if the sump oil level is below the bearing. These have to be custom CNC machined, and double the bearing cost. If you really want the phenolic cages, we can special order them (2 week delivery).
Why did we pick steel as the baseline? Many reasons, 1) steel cages are fitted more loosely to the balls due to the limitations of forming sheet metal. This gives the consumer the perception of a lack of quality in a precision device. They move around a bit relative to the ball. Does not hurt the bearing, but perception can be a difficult thing to get around. 2) Nylon nests the balls precisely and has slightly better capillary attraction for the oil film between the ball and cage (providing more oil "storage"). 3) If either of these cage materials gets some level of damage, the nylon will not damage the OD race when the hard ball rolls over a piece of it. 4) From a temperature standpoint, steel cages have the highest rating. The phenolic is second highest (about 350F), and nylon the lowest. The highest temperature rated nylons are just too close to this boxer engine's red line coolant temp (remember this engine uses a coolant/oil heat exchanger). We never encountered this problem, but it is too significant to consider production worthy. If this really catches on, we may consider investing in the tooling to mold out of a higher temp plastic, none are available now in this size.
We ship the bearing with a very, very light lube that really lets you feel the rolling action. If anything gets in the bearing during assembly, you will feel it. Once we are certain it is clean, we take a veterinary's large animal syringe (.040" needle) and inject some engine oil supplement to both rows of balls before slipping the support in place. This is where the looser fitting steel cage comes in handy, you can get the needle past the first row of balls.
Billl Ryan
Casper Labs, Inc.
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