Mercedes Power Unit Hardware & Software

[gruntguru]

Overall low oil pressure is unlikely because all the other bearings would turn to sloppy pulp too.

A brief drop in oil pressure is all it takes and a rod bearing is usually the first to go. The process is:
- temporary breakdown of oil film
- temporary metal-metal contact removes some material from the surface of the bearing shell
- Increased clearance means rod can "hammer" up and down on the crank
- hammering increases clearance
- bearing shell begins to spin in the rod (probably)
- repeat last 4 steps until rod breaks (bearing cap parts company with rod) and escapes crankcase area

The other bearings in the engine will exhibit damage ranging from "nothing at all" to severe.

Don't forget the possibility of a bearing rotating in it's bore and starving that journal of oil.

Good point - forgot to mention that possibility (probability in fact)

[Brian Coat]

I think there are many potential root causes and there is not much point trying to list them.

I want to come back to the block/crankcase construction of this unit.

Credible witnesses call it a crankcase (not a block) and say it is fully machined.

I conclude it could feature a combined cylinder head and bore (cast) with separate machined crankcase.

We know for sure that BMW did this. See attached picture of P85 V10.



Make sense?

[sosic2121]

I think there are many potential root causes and there is not much point trying to list them.

I want to come back to the block/crankcase construction of this unit.

Credible witnesses call it a crankcase (not a block) and say it is fully machined.

I conclude it could feature a combined cylinder head and bore (cast) with separate machined crankcase.

We know for sure that BMW did this. See attached picture of P85 V10.

http://i.imgur.com/9jfs7PB.jpg

Make sense?

IMO it makes very much sense. This way they can eliminate head bolts and gasket which could be a weak point in these engines. Engine can be made lighter this way.

[Tommy Cookers]

..... Engine can be made lighter this way.

unlikely, though of course the journalists and publicists would make that claim, that's their job
(and weight saving is anyway undermined by the conservative minimum weight limits for the PU and its constituent parts ?)

the engine structure must have great beam strength and beam and lateral etc stiffness
because of the high dynamic loads from the basic explosion/piston/crankshaft action and loads from doing the chassis-structural job
structural depth and width are priceless here (as the lightest way to the strength and stiffness)
otoh and speaking loosely stiffness will increase with the cube of the depth or width dimension (and strength with the square ?)

the benefits of 'modern' engine casting form (one-piece from below the crankshaft centreline to the head faces) certainly included weight saving

ok the seperate crankcase route might allow some use of a somewhat superior material

now, away to dust off my late model '3 piece' RR Merlin .......

[Brian Coat]

TC: To clarify - Are you saying the concept does not make sense to you because of the compromise to engine structural stiffness?

[basti313]

A brief drop in oil pressure is all it takes and a rod bearing is usually the first to go. The process is:
- temporary breakdown of oil film
- temporary metal-metal contact removes some material from the surface of the bearing shell
- Increased clearance means rod can "hammer" up and down on the crank
- hammering increases clearance
- bearing shell begins to spin in the rod (probably)
- repeat last 4 steps until rod breaks (bearing cap parts company with rod) and escapes crankcase area

The other bearings in the engine will exhibit damage ranging from "nothing at all" to severe.

Don't forget the possibility of a bearing rotating in it's bore and starving that journal of oil.

Good point - forgot to mention that possibility (probability in fact)

The point I do not like about the list is, that is covers more a classic sinter 2-layer bearing (for example 0.5mm AlSn15Cu on Al, or the lead containing equivalent).
F1, or modern motorsports in general uses bearings with a 10 micron sputter layer of for example AlSn20Cu (or again with lead, as it must not comply with European law). As soon as material is removed, the bearing is gone. The next thing is, that it jams. Rotating is just a result of jamming, can happen must not happen.

On these bearing there is also nothing like no damage visible on the other bearings, if there was a temporary breakdown of the oil supply. They do not have a wearing layer, so as soon as they touch metal you will see marks, that should not be there at all.

A local breakdown of oil supply without finding the part that causes it after the failure, is hard to imagine for me. A piece big enough to block the oil supply should not be behind the oil filter and if it is, the engine will be gone after one lap. The same accounts for a particle, which might have gone into the bearing.
Both theories also do not fit the change of oil.

To me it looks 100% like a cooling issue. Ham was going flat to get past Button and the oil temp went too high due to bad cooling behind another car.

[Tommy Cookers]

TC: To clarify - Are you saying the concept does not make sense to you because of the compromise to engine structural stiffness?

imo structural stiffness and strength requirements (likely to be related) will give as heavy an outcome as would a conventional type

though iirc Cosworth said stiffness/strength/depth requirements were not trivial in the head/camshaft region (with their conventional designs eg CA)

[ringo]

What is going to preven this failure from repeating itself in the other engines hamilton has?
Malaysia was a very hot race, and this may have contributed to the engine failure in some way. I'm not sure if the temporary fix is bigger oil coolers for better temperature management.

[rscsr]

What is going to preven this failure from repeating itself in the other engines hamilton has?
Malaysia was a very hot race, and this may have contributed to the engine failure in some way. I'm not sure if the temporary fix is bigger oil coolers for better temperature management.

afaik they said, that they switched to an older, more viscous oil specification.

[PlatinumZealot]

They said he was not pushing so that rules that out.

They have still yet to find the cause of failure. This means they haven't found anything in the oil-system. If there was a blockage or damaged filter they would have found it already.

Whatever it is, we know by now it is not a physical item that can be found in the parts or running of the engine.

To the engine Guru's here... if the cause of the failure was excessive force from the piston what would fail first the wrist pin's bearing surface, or the big- end bearing? Which one is actually stronger? And why is there not a fancy bearing on the wrist pin? come to think of it, i never questioned why the wrist pin itself is good enough a bearing...

[basti313]

They said he was not pushing so that rules that out.

He was not putting a 20sec gap on the Bulls and he was not trying to get past Button for two laps. Surely he was not pushing.

To the engine Guru's here... if the cause of the failure was excessive force from the piston what would fail first the wrist pin's bearing surface, or the big- end bearing? Which one is actually stronger? And why is there not a fancy bearing on the wrist pin? come to think of it, i never questioned why the wrist pin itself is good enough a bearing...

Since DLS coating on the wrist pin was introduced 10 years ago, I do not remember a single failure.

[Vortex Motio]

Paddy Lowe Friday evening on the BBC 5Live podcast said,

... the other bearings on the same crank were absolutely perfect so there is something there still to understand."

[Edis]

Overall low oil pressure is unlikely because all the other bearings would turn to sloppy pulp too.

A brief drop in oil pressure is all it takes and a rod bearing is usually the first to go. The process is:
- temporary breakdown of oil film
- temporary metal-metal contact removes some material from the surface of the bearing shell
- Increased clearance means rod can "hammer" up and down on the crank
- hammering increases clearance
- repeat last 4 steps until rod breaks (bearing cap parts company with rod) and escapes crankcase area

The other bearings in the engine will exhibit damage ranging from "nothing at all" to severe.

Don't forget the possibility of a bearing rotating in it's bore and starving that journal of oil.

I would expect that the Mercedes crankshaft is nose fed with oil, as that have been the prefered design in F1 for a number or years. That means the big end bearings are supplied with oil directly from the crankshaft, using an oil gallery that runs the length of the crankshaft instead of the more conventional solution that supplies oil from the mains using drilled holes in the crankshaft between the mains and the big end bearings. A nose fed crankshaft should not be starved of oil at the big end bearings due to a spun bearing. A spun big end bearing could however starve the small end bearings of oil, since there is probably a small drilling through the con rod used to supply the small end with oil from the big end.

It's pressure fed like every other engine. I can't think of many engines less than 100 years old that rely on dipping the crank in the oil sump

Some lawnmowers

These engines use roller bearings. With hydrodynamic bearings you need to supply the oil to the bearing somehow.

[gruntguru]

Re - lawnmowers. It is generally 2 stroke small engines that use roller big-end bearings. It is difficult/impossible to lubricate a journal bearing with fuel-oil mix. There are many examples of 4 stroke small engines using a "dipper" to lubricate a journal type (hydrodynamic) big-end bearing - Briggs and Stratton being one of the most common. These engines will often use rolling element bearings for crankshaft support so no oil pump is required.

[wuzak]

Ted and Ant showed the "big end" on the TV for Sky F1.

They showed and talked about a needle roller bearing. Really? I'm not buying it.