Ball/roller temperature
Ball/roller temperature
(OP)
I have read properly older threads concerning bearing temperature and changes in clearance, fits, preload, etc. It seems to me that one thing was not mentioned yet and this is the rolling element (RE) temperature.
Tmoose in thread821-120829 mentions typical ring temps during steady state conditions. Then, I suppose, could be stated such a typical temperature of RE for specified type of lubrication (which probably determines the heat losses on RE). I understand, that it is just the result of heat transfer in the bearing.
In some article I've read an assumption, that at each contact (RE/IR or RE/OR) half of the heat enters the ring and half enters the RE. When heat losses from lubrication are small and thermal resistances of RE contacts are large, the RE temp could be high enough to affect internal clearance together with IR and OR temperatures.
Does any of you have any experience, theory, opinion on the "typical" RE temp assuming known temps of rings and type of lubrication? I saw some pictures from WZL Aachen, where guys were using some kind of "IR endoscope" to examine spindles.
Thanks, H-up
Tmoose in thread821-120829 mentions typical ring temps during steady state conditions. Then, I suppose, could be stated such a typical temperature of RE for specified type of lubrication (which probably determines the heat losses on RE). I understand, that it is just the result of heat transfer in the bearing.
In some article I've read an assumption, that at each contact (RE/IR or RE/OR) half of the heat enters the ring and half enters the RE. When heat losses from lubrication are small and thermal resistances of RE contacts are large, the RE temp could be high enough to affect internal clearance together with IR and OR temperatures.
Does any of you have any experience, theory, opinion on the "typical" RE temp assuming known temps of rings and type of lubrication? I saw some pictures from WZL Aachen, where guys were using some kind of "IR endoscope" to examine spindles.
Thanks, H-up





RE: Ball/roller temperature
RE: Ball/roller temperature
Although the ball diameter is much smaller than the ring radius, its contribution to thermal problems could be also signaficant due to higher temperature. This way I explain to myself the superiority of oil-air lube in high-speed applications.
RE: Ball/roller temperature
Assuming other factors to be equal and there is no thermal transfer, it is conceivable the ball temperature will increase more than the rings. However, in a >normal< system this does not exist because there is efficient thermal transfer between the metal parts. As to oil -V- grease, Oil-mist provides an auto-replacing super clean lubricative surface film, reduces overall drag and overall assists with cooling. Grease provides only a lubricative film.
RE: Ball/roller temperature
Concerning heat flow generation, I performed several "coast tests" on my test spindle with spring-preloaded ACBBs. Observing spindle's deceleration in time I figure out frictional moments and heat flow produced by bearings.
In Harris and also in many catalogues, formulas for the speed-dependent part of total heat (mostly viscous and some spin) contains speed with 2/3 exponent. Nevertheless from my measurements it looks like the exponent must be greater than 1 in any case (making function H=f(n) convex instead of concave). A also saw some papers from other people having similar results.
RE: Ball/roller temperature
In modern times air-oil and oil mist are 2 distinctly different lubrication methods. Even some semi-modern literature fails to differentiate between them, but the spindle innards and the lubrication equipment are not the same, or interchangeable. Any body who has worked around machines with each system can see (and breathe) the difference.
RE: Ball/roller temperature
Anyway the spindle I mentioned is grease-lubricated and well run-in. So I would expect the well-reputed semi-modern literature to work.
RE: Ball/roller temperature
Nevertheless the issue remains.
RE: Ball/roller temperature
Bonerigo