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Bearing material? 3
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patprimmer
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Zorg
The idea behind using a soft material like white metal is that the replaceable bearing will suffer damage and wear before the more expensive crank shaft. Also by having one soft metal. contamination can embed in that metal instead of scoring the crank
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pat pprimmer@acay.com.au
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The idea behind using a soft material like white metal is that the replaceable bearing will suffer damage and wear before the more expensive crank shaft. Also by having one soft metal. contamination can embed in that metal instead of scoring the crank
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
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One of the 3 or 4 solid advantages of "ceramic" ball and roller bearings is their remarkable resistance to surface damage under marginal lubrication, compared to steel-on-steel in a regular bearing.
But, Rolling element bearings must rely on "elastohydrodynamic" lubrication (squishing/stepping up onto an oil film, like tires hydroplaning) instead of the sliding motion that produces "hydrodynamic" lubrication at the hard working locations in an engine.
I believe there are almost no "steel-on-steel" bearings in an engine, and the hydrodynamic lubrication is pretty successfully established where its needed in modern engines, so improved surface behavior would have very few places to help.
The other advantages of hardness, low thermal expansion, lightness and stiffness don't sound too useful in an engine to me either.
But, Rolling element bearings must rely on "elastohydrodynamic" lubrication (squishing/stepping up onto an oil film, like tires hydroplaning) instead of the sliding motion that produces "hydrodynamic" lubrication at the hard working locations in an engine.
I believe there are almost no "steel-on-steel" bearings in an engine, and the hydrodynamic lubrication is pretty successfully established where its needed in modern engines, so improved surface behavior would have very few places to help.
The other advantages of hardness, low thermal expansion, lightness and stiffness don't sound too useful in an engine to me either.
"Ceramic material is brittle"
Hi Azmio! see if you have a company near you that rebuilds machine tool spindles. Ask them if you can have a ceramic ball out of a used HC bearing. You might mention you need to test it for brittleness by wailing on it with a steel hammer to settle a bet. I suspect you will get a ball, and be advised to bet on the side of NO damage to the bearing.
Hi Azmio! see if you have a company near you that rebuilds machine tool spindles. Ask them if you can have a ceramic ball out of a used HC bearing. You might mention you need to test it for brittleness by wailing on it with a steel hammer to settle a bet. I suspect you will get a ball, and be advised to bet on the side of NO damage to the bearing.
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Tmoose,
I have no doubt about the capability of ceramic ball, it has been well known throughout the world. However, I didnt write about ceramic ball. I made my comment on the crankshaft bearing shell. Please refer to Zorg's original question.
I appreciate that you mentioned about how hard the ceramic ball is. Why not you come up with your points on why you think it is a good idea to make the crankshaft bearing shell from ceramic.
One reason I join this forum is to learn and for experts out there to correct me for any gap that I have in my knowledge and experience. So i guess this is a good chance for me learn about the practical application of ceramic bearing shell.
I have no doubt about the capability of ceramic ball, it has been well known throughout the world. However, I didnt write about ceramic ball. I made my comment on the crankshaft bearing shell. Please refer to Zorg's original question.
I appreciate that you mentioned about how hard the ceramic ball is. Why not you come up with your points on why you think it is a good idea to make the crankshaft bearing shell from ceramic.
One reason I join this forum is to learn and for experts out there to correct me for any gap that I have in my knowledge and experience. So i guess this is a good chance for me learn about the practical application of ceramic bearing shell.
I'm sorry I was not clearer.
My reply was intended to encourage getting some first hand practical experience RE: the "brittleness" concern.
I think it is probably NOT a good idea to make the crankshaft bearing shell from ceramic for the IMPORTANT reasons of "embeddability" and "conformability" as mentioned by others.
Here are some specs comparing bearing steel and the (silicon nitride?) ceramic material used in ball bearings. Note it is about half as dense, 50% stiffer, much harder, and only expands about 25% as much when warm.
For what its worth, other specs suggest the thermal conductivity is beween 0% and 50% less than steel.
The specs do not indicate how just-plain-RUGGED the material is when used in ball (and recently roller) bearings.
It is not uncommon to take apart a high speed HC spindle bearing that has failed CATastrophically (siezed, 15,000 rpm to zero in about 2 seconds, plenty of stinky grease and phenolic retainer smoke) to find the steel rings smeared, discolored, and cooked, and the ceramic balls looking perfect and feeling smooth.
I am not aware of specs that describe the ductility, although I kind of recall that installing a (rare) ceramic ball bearing inner ring with inerference fit (commonly required) can be a problem, and might be PART of the explanation of limited use of full ceramic bearings.
Especially because the many performance increases just using cermaic balls.
My reply was intended to encourage getting some first hand practical experience RE: the "brittleness" concern.
I think it is probably NOT a good idea to make the crankshaft bearing shell from ceramic for the IMPORTANT reasons of "embeddability" and "conformability" as mentioned by others.
Here are some specs comparing bearing steel and the (silicon nitride?) ceramic material used in ball bearings. Note it is about half as dense, 50% stiffer, much harder, and only expands about 25% as much when warm.
For what its worth, other specs suggest the thermal conductivity is beween 0% and 50% less than steel.
The specs do not indicate how just-plain-RUGGED the material is when used in ball (and recently roller) bearings.
It is not uncommon to take apart a high speed HC spindle bearing that has failed CATastrophically (siezed, 15,000 rpm to zero in about 2 seconds, plenty of stinky grease and phenolic retainer smoke) to find the steel rings smeared, discolored, and cooked, and the ceramic balls looking perfect and feeling smooth.
I am not aware of specs that describe the ductility, although I kind of recall that installing a (rare) ceramic ball bearing inner ring with inerference fit (commonly required) can be a problem, and might be PART of the explanation of limited use of full ceramic bearings.
Especially because the many performance increases just using cermaic balls.
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