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Did you at least share your knowledge at this point, or did you just walk around chuckling all day?
Get a hat.
Temperature and Bearing Wear Relations
- Thread starter AEHaas
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Patman
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Or just drive around with the roof completely out!quote:
Originally posted by XS650:
Not for the summer here.quote:
Originally posted by Patman:
That's another reason why you should just put on the transparent roof!
It still seems that the primary impact of temperature will be on viscosity and hence film thickness, and will affect bearing wear more than the impact of temperature on bearing material composition. See below for an article on familiar but somewhat unrelated subject, but an article that has a nice graphic of bearing wear vs oil film thickness in figure 3. It's an 'industrial' bearing application.
http://www.practicingoilanalysis.co...eid=126&relatedbookgroup=ContaminationControl
Cleanliness Requirements for Journal Bearing Lubrication
Wear rate measurements which compare journal bearing wear of two different materials (Babbitt and Copper-Lead) was obtained by Ronen, et al. as shown in Figure 3. These tests were conducted over a 20-hour period with interruptions for wear measurements, at five hour intervals. It can be seen that more than a ten-fold increase in bearing wear results from contaminated oil.
http://www.practicingoilanalysis.co...eid=126&relatedbookgroup=ContaminationControl
Cleanliness Requirements for Journal Bearing Lubrication
Wear rate measurements which compare journal bearing wear of two different materials (Babbitt and Copper-Lead) was obtained by Ronen, et al. as shown in Figure 3. These tests were conducted over a 20-hour period with interruptions for wear measurements, at five hour intervals. It can be seen that more than a ten-fold increase in bearing wear results from contaminated oil.
The Corvette bearings have a coating on them - I believe it's a type of teflon.
I don't think an oil would ever get hot enough to melt any bearing - it would be from metal to metal contact.
I don't think an oil would ever get hot enough to melt any bearing - it would be from metal to metal contact.
I also don't think the oil would get hot enough to melt the bearing, but I think the concern is the babbit layer of the main bearings, which is often extremely thin (i.e. 0.0005").
The motorcycle crankshaft main bearings I've worked with typically consist of 3 layers; steel, copper & the babbit layer. The babbit layer is the softest of all the layers and is usually a dull gray color when the bearings are 100% new. The reason the babbit layer is soft is to allow tiny particulate (i.e. metal fragments) to embed into it rather than scoring / damaging the crank. The copper layer is the 2nd hardest layer and is there to support the softer babbit layer, but yet its soft enough to give a little bit should a larger piece of metal embed into the babbit layer. The steel layer gives the bearing its strength and spring to allow it to be installed with an interference fit. It can be normal to see the babbit layer polished to a brighter sheen of gray / silver after use and that’s usually not a problem, but if you see copper, then you're definitely in trouble. There are times when the oil temperature in our race bikes have exceeded 300F and even though these engines are flogged quite hard for long periods of time, the main bearings always look just fine as long as the engine doesn’t ingest too much particulate and is properly maintained, properly warmed up, etc. I’m just not worried about the babbit layer melting / wearing even at normally high oil temperatures.
The motorcycle crankshaft main bearings I've worked with typically consist of 3 layers; steel, copper & the babbit layer. The babbit layer is the softest of all the layers and is usually a dull gray color when the bearings are 100% new. The reason the babbit layer is soft is to allow tiny particulate (i.e. metal fragments) to embed into it rather than scoring / damaging the crank. The copper layer is the 2nd hardest layer and is there to support the softer babbit layer, but yet its soft enough to give a little bit should a larger piece of metal embed into the babbit layer. The steel layer gives the bearing its strength and spring to allow it to be installed with an interference fit. It can be normal to see the babbit layer polished to a brighter sheen of gray / silver after use and that’s usually not a problem, but if you see copper, then you're definitely in trouble. There are times when the oil temperature in our race bikes have exceeded 300F and even though these engines are flogged quite hard for long periods of time, the main bearings always look just fine as long as the engine doesn’t ingest too much particulate and is properly maintained, properly warmed up, etc. I’m just not worried about the babbit layer melting / wearing even at normally high oil temperatures.
Lead is greatly reduced in modern bearing materials. Lead is still one of the material alloyed into the mix but not in as great of amounts as in the past. Babit bearings are really rare today. In a lot of cases modern import designs are relying on aluminum and cadium more and more as the main materials makeing up the alloy. Vechiles that still use a lot of lead in the bearing material are also useing drasticly different matrix then in years past.
Sorry if my post is even worse then normal. I am operateing on 3 hours sleep. I did not get to bed until 1AM and was awake by 4 AM. I was cramming for a State Exam and was nervious. I passed but am now a walking zombie!!!
If you google "main bearing" "engine bearings" etc...... You will come across a paper written by Federal Mogul(sp) for the SAE on what materials are now being used and why. I read this paper about 4 years ago so it might be a bit dated now as well. It was a good read though.
To properly determine oil flow to various parts of an engine and correlate that to heat and wear of various part Toyota came up with a simple idea. They used a hot wire in the various parts of the oil galley and right before the bearings to determine oil volume and flow to each componet. It works ont he same idea as a mass air flow sensor with hot wire. From what I read in their paper it is rather hard to accurately predict dynamic oil flow to each part of the engine. This sytem gave them the raw data they needed to come up with new formula's for predicting dynamic oil flow. This allowed them to reduce oil flow and volume to places that did not need the volume and down size their oil pump's accordingly to reduce oil pump drag. Wish I had the SAE paper number but it was a while ago when I was working for General Motors that I read it.
The trick to combine the above with radio-isotobe(sp) wear studie's and analytical tear down. For those that do not already know in analytical tear down all the parts of the engine are weighted bofore the engine is built and then after testing on an analytical scale. This gives you the true amount of wear. If you took AP Chemistry or AP Anotomy and Physiology in H.S. you will already know what an analytical scale is.
[ May 31, 2006, 08:15 PM: Message edited by: JohnBrowning ]
Sorry if my post is even worse then normal. I am operateing on 3 hours sleep. I did not get to bed until 1AM and was awake by 4 AM. I was cramming for a State Exam and was nervious. I passed but am now a walking zombie!!!
If you google "main bearing" "engine bearings" etc...... You will come across a paper written by Federal Mogul(sp) for the SAE on what materials are now being used and why. I read this paper about 4 years ago so it might be a bit dated now as well. It was a good read though.
To properly determine oil flow to various parts of an engine and correlate that to heat and wear of various part Toyota came up with a simple idea. They used a hot wire in the various parts of the oil galley and right before the bearings to determine oil volume and flow to each componet. It works ont he same idea as a mass air flow sensor with hot wire. From what I read in their paper it is rather hard to accurately predict dynamic oil flow to each part of the engine. This sytem gave them the raw data they needed to come up with new formula's for predicting dynamic oil flow. This allowed them to reduce oil flow and volume to places that did not need the volume and down size their oil pump's accordingly to reduce oil pump drag. Wish I had the SAE paper number but it was a while ago when I was working for General Motors that I read it.
The trick to combine the above with radio-isotobe(sp) wear studie's and analytical tear down. For those that do not already know in analytical tear down all the parts of the engine are weighted bofore the engine is built and then after testing on an analytical scale. This gives you the true amount of wear. If you took AP Chemistry or AP Anotomy and Physiology in H.S. you will already know what an analytical scale is.
[ May 31, 2006, 08:15 PM: Message edited by: JohnBrowning ]
Things have been changing fast in the industry the last few years with regards to lead. Dana has a 100% lead free bearing that is being used in the industry.
From Dana
"As more and more OE manufacturers shift to aluminum bearings in OE engines, Clevite 77® has introduced a new line of engine bearings designed to be the highest quality replacement bearings in the industry. Clevite 77 BiMetal™ engine bearings carry on the tradition and reputation that Clevite 77 has built throughout the course of time.
Clevite 77 BiMetal engine bearings feature a 100% lead free aluminum silicon bi-metal material; this includes 60% more silicon than leading competitor's bi-metal material for better conditioning of journal surfaces. These BiMetal bearings also offer greater wear resistance than leading competitor's bi-metal material, as well as greater seizure resistance than the leading competitor. Clevite 77 BiMetal bearings feature 100% bored ID's for precision and surface characteristics and where appropriate - straight shell main bearings utilizing an "umbrella" groove that allows for superior oil control and improved pressure."
I higher output engines, whether they're sporty air cooled models like a Porsche, or turbo diesels in heavy duty trucks, one tends to see larger sumps and maybe oil coolers being used. Oil will tend to start breaking down, oil film thickness will become too thin if the temps are too high for the viscosity, and bearing wear will increase.
I have a hard time believing this. I've seen my share of Hondas later than this spew lead in UOAs when things weren't right. Very rare for a Ford modular, where we know for sure it has aluminum alloy bearings, to have double digit lead in UOAs.
I believe that some aluminum bearings have a very thin layer (well under 0.001") of babbit type material on them. That would 'splain lead in a UOA of acar with aluminum bearings.
It seems to me that a 1983 Camry engine I rebuilt eons ago has aluminum bearing, but memory can remember what you want to remember instead of what actually was.
In my finite mind...I see oil as the cooler. If you push oil past the bearing in a higher volume...the oil takes more heat with it.
It would be very interesting to see an actual temp of the oil as it passes through the bearing area.
Second, if the shear strength of the oil is superior (synthetic vs. dino) it protects the bearing and crankshaft etc better.
So with a high volume oil pump pushing thinner synthetic oil past all the bearings...you should have the best of both worlds.
It would be very interesting to see an actual temp of the oil as it passes through the bearing area.
Second, if the shear strength of the oil is superior (synthetic vs. dino) it protects the bearing and crankshaft etc better.
So with a high volume oil pump pushing thinner synthetic oil past all the bearings...you should have the best of both worlds.
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Sure, LCM, no doubt about it. The thing is, in any truly hot condition, volume isn't a function of viscosity for all but the fringe few.
Does bearing life shorten measurably if it's kept at 275F vs 230F? ..or is just the life of the oil shortened. Is there a progressive fatigue factor on bearings below a certain temp assuming no metal to metal contact occurs
Oh...I believe we mentioned it at least a dozen times in the UOA section. I also posted a slideshow on engine bearings from one of the major manufacturers.quote:
Originally posted by moribundman:
Did you at least share your knowledge at this point, or did you just walk around chuckling all day?
Most of those values are off by a factor of 2-4 for modern engines in vehicles.
Kinda' depends on when you reach the oil pump bypass relief pressure doesn't it? E.g., if you reach the bypass pressure at 3,000 RPMs when the oil is very hot, and are racing where the RPMs are above this most of the time, you've limited flow to the bearings. Let's say you lower viscosity so that it now takes 5,000 RPMs to reach the oil pump bypass relief pressure, but you still maintain a minimum of 10psi/1,000RPM and/or other engine oil pressure specifications. You then effectively increased the flow to the bearings. No? In my best French accent.
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