F1 engines use shell bearings for mains and rods like most engines, although they are trying to do away with that by using direct deposition of babbit/bearing material on the block and rods. It's mainly to increase heat transfer.

Roller bearings have lower friction up until about 7K RPM, above that standard oil wedge shell bearings are superior.

F1 oils don't really have a tough life. Oil is preheated before the engine is started, the hottest it gets is during pitstops, and only has to last a few hundred miles. Road oils have to deal with 160+F extremes and last 6-10K miles

punisher - 15 November 2009 08:55 PM

F1 engines use shell bearings for mains and rods like most engines, although they are trying to do away with that by using direct deposition of babbit/bearing material on the block and rods. It's mainly to increase heat transfer.

Roller bearings have lower friction up until about 7K RPM, above that standard oil wedge shell bearings are superior.

F1 oils don't really have a tough life. Oil is preheated before the engine is started, the hottest it gets is during pitstops, and only has to last a few hundred miles. Road oils have to deal with 160+F extremes and last 6-10K miles

Add 'hot-soaking' and coking to the list of things road car engine oils must deal with; they indeed have a much tougher life.

wilmywood8455 - 15 November 2009 09:05 PM

punisher - 15 November 2009 08:55 PM

F1 engines use shell bearings for mains and rods like most engines, although they are trying to do away with that by using direct deposition of babbit/bearing material on the block and rods. It's mainly to increase heat transfer.

Roller bearings have lower friction up until about 7K RPM, above that standard oil wedge shell bearings are superior.

F1 oils don't really have a tough life. Oil is preheated before the engine is started, the hottest it gets is during pitstops, and only has to last a few hundred miles. Road oils have to deal with 160+F extremes and last 6-10K miles

Add 'hot-soaking' and coking to the list of things road car engine oils must deal with; they indeed have a much tougher life.

Well Wilmy, I did a little research over the weekend and rechecked my oil analysis sheets this morning when I got to work and I have some bad news for you. You'll probably want to dispute it, but the fact is, in regards to how the viscosity in multi-grade oil works, you were right! So there! That will teach you to mess with us old timers and our long held beliefs!
Actually, in reviewing the oil samples I never paid much attention to the viscosity other then to note that it was usually right around 40 at 100 C. Turns out that the number was given in centistokes and that 40 just happens to be the correct number for that oil at that temperature. Plus, when multi-grades were introduced over 40 years ago there was a lot of resistence at first to using them. I think it was intentional that the oil companies let people believe that the viscosity actually improved as the heat rose. I cannot remember any oil supplier ever claiming otherwise.

An added note: the 40 I referred to was not the centistokes for the oil. It was another reference in the same column on the report. Since it was never red-flagged I never paid it any attention till now.

CHEMENG - 14 November 2009 02:33 PM

I am fascinated by your statement about gears and other parts moving into each other as they heat up. I would think that should depend on the construction of the case or block. If a transmission has an aluminum case, then assuming reasonable heat distribution, the shaft centers should move away from each other faster than the gears would grow into each other when heated, and the clearance should increase. Maybe that is a good reason not to drive through deep water and cool off the case too fast.

The gears I was referring were timing gears which will definitely grow into each other. In comparison to the gears, the block on which the gears mount is relatively stable because of the coolant.
You keep mentioning expansion of bores, but you forget that the metal expands in all directions, not just outwards. Bores can and do get smaller as temperature rises. Not always, but in certain circumstances. Many manual transmissions with aluminum cases require the use of a light oil such as ATF instead of the older 80W-90 because until they reach operating temp the ball or roller bearings that the shafts ride on are not secure in their bores and the extra drag of a heavier oil can spin the entire bearing, damaging the case. In contrast, to insert the wrist pins into the pistons of a 14L Cummins I have to put the pins in the freezer overnight and then heat the pistons before assembly to open the bores slightly.
Ball and roller bearings on a crankshaft have a limitation in comparison to conventional bearing inserts. Lack of loadbearing surface. Think of the contact patch of a tire compared to a snowmobile track and you will get the picture. I will absolutely guarantee you that you can flatspot a roller or split the outer case of a ball bearing if the load gets too high. I've done it. In regards to the question of oil versus grease, the answer is both, actually. The preferred lube for heavy duty wheel bearings in trucks is a synthetic semi-fluid grease. Trailer hubs using that lube come fully sealed (instead of with a pop-out fill plug) and normally require no maintenance for 1/2 million miles.
BTW, aluminum does not always expand at a different rate then steel. Air cooled piston engines commonly use a steel sleeve inside a finned aluminum barrel. To do that successfully they use an aluminum alloy developed in the 30's specifically for that purpose in aircraft engines. It has the same expansion rate as steel.

Cat-Man-Do - 16 November 2009 08:19 AM

CHEMENG - 14 November 2009 02:33 PM

I am fascinated by your statement about gears and other parts moving into each other as they heat up. I would think that should depend on the construction of the case or block. If a transmission has an aluminum case, then assuming reasonable heat distribution, the shaft centers should move away from each other faster than the gears would grow into each other when heated, and the clearance should increase. Maybe that is a good reason not to drive through deep water and cool off the case too fast.

. . . You keep mentioning expansion of bores, but you forget that the metal expands in all directions, not just outwards. Bores can and do get smaller as temperature rises. Not always, but in certain circumstances. . . .

I keep mentioning it because it is a hard myth to break. Let me help you. Do a thought experiment. Draw a large circle. Now draw a series of smaller circles all the same size with their centers on the circumference of the large circle. The circumference of the large circle is the sum of the diameters of the smaller circles. Now expand the small circles and observe that the circumference of the large circle must grow. Rationalize that there is no difference if the big circle is on the inside or outside and you will understand why holes grow when heated. The atoms in a metal are held in place. They can not swell into the hole. The hole must grow.

CHEMENG - 16 November 2009 10:20 AM

I keep mentioning it because it is a hard myth to break. Let me help you. Do a thought experiment. Draw a large circle. Now draw a series of smaller circles all the same size with their centers on the circumference of the large circle. The circumference of the large circle is the sum of the diameters of the smaller circles. Now expand the small circles and observe that the circumference of the large circle must grow. Rationalize that there is no difference if the big circle is on the inside or outside and you will understand why holes grow when heated. The atoms in a metal are held in place. They can not swell into the hole. The hole must grow.

All those circles made me dizzy, so I went out into the shop and did a little test. I have some 1" steel plate with some finely machined holes in it. 3.739" diameter. After applying heat to the plate I re-checked the diameter. 3.740". So, I can't argue your point, despite what I've seen or heard to the contrary. Your original contention that clearances in an engine don't tighten as an engine heats up is still inaccurate. Many clearances do tighten up. Pistons definitely do. A fact that was a problem for early engine builders before cam grinding of the pistons was discovered 80 or 90 years ago. Valve trains tighten up. Gears tighten up. Crank bearings do in part because the journals generally run hotter, and thus expand more then the rods or main bearing supports. More then once I've had an engine bearing seize to the point where the starter would not turn over the hot engine, but the next day that cold engine would fire right up. As a teenager some friends and I decided to destroy a flathead Ford by running it with the oil drain plug out and the radiator hoses cut. After about a half hour that thing, squealing like a pig, seized tight. Nothing could make it turn over. The next morning we went out and fired it back up without a problem. Idiot kids! Just shows what you can do when you have more time and car parts on your hands then brain cells!

Cat-Man-Do - 16 November 2009 03:55 PM

CHEMENG - 16 November 2009 10:20 AM

I keep mentioning it because it is a hard myth to break. Let me help you. Do a thought experiment. Draw a large circle. Now draw a series of smaller circles all the same size with their centers on the circumference of the large circle. The circumference of the large circle is the sum of the diameters of the smaller circles. Now expand the small circles and observe that the circumference of the large circle must grow. Rationalize that there is no difference if the big circle is on the inside or outside and you will understand why holes grow when heated. The atoms in a metal are held in place. They can not swell into the hole. The hole must grow.

All those circles made me dizzy, so I went out into the shop and did a little test. I have some 1" steel plate with some finely machined holes in it. 3.739" diameter. After applying heat to the plate I re-checked the diameter. 3.740". So, I can't argue your point, despite what I've seen or heard to the contrary. Your original contention that clearances in an engine don't tighten as an engine heats up is still inaccurate. Many clearances do tighten up. Pistons definitely do. A fact that was a problem for early engine builders before cam grinding of the pistons was discovered 80 or 90 years ago. Valve trains tighten up. Gears tighten up. Crank bearings do in part because the journals generally run hotter, and thus expand more then the rods or main bearing supports. More then once I've had an engine bearing seize to the point where the starter would not turn over the hot engine, but the next day that cold engine would fire right up. As a teenager some friends and I decided to destroy a flathead Ford by running it with the oil drain plug out and the radiator hoses cut. After about a half hour that thing, squealing like a pig, seized tight. Nothing could make it turn over. The next morning we went out and fired it back up without a problem. Idiot kids! Just shows what you can do when you have more time and car parts on your hands then brain cells!

I calculate that it took a 41 deg. F temperature rise to expand your steel plate by 0.001 inch across a 3.739 inch hole. Correct?

^Could be. I just circled the hole with a torch a few times to raise the temperature of the metal. Any temperature rise should have produced a change, and it obviously did.

I think that the areas where clearances tighten are where two materials with different coefficients of thermal expansion are involved or where parts warm up at different rates. So, do F1 engines use ceramic bearings? i know a lot of hi performance engines do but i almost remember hearing that they were banned in F1. I would imagine that there is a big difference in the thermal coefficients between ceramics and metals like steel and aluminum.

Audiophile426 - 24 November 2009 08:40 PM

I think that the areas where clearances tighten are where two materials with different coefficients of thermal expansion are involved or where parts warm up at different rates. So, do F1 engines use ceramic bearings? i know a lot of hi performance engines do but i almost remember hearing that they were banned in F1. I would imagine that there is a big difference in the thermal coefficients between ceramics and metals like steel and aluminum.

ALL clearances tighten with heat, some more than others. Materials expand in all directions. Th single clearance that tightens the most, I think, is piston to wall, assuming aluminum alloy pistons and some sort of ferrous cylinder wall (or sleeve). The piston crown, combustion chamber, upper end of the cylinder and the exhaust valve and port see more heat than any other areas.