Mercedes Power Unit Hardware & Software

[hardingfv32]

Why the requirement for large clearances? Smaller clearances can carry more load. Modern race engines use almost 'zero' clearance on the journal bearing when cold. Must be preheated before starting.

I am not sure how the cooling requirement of the journal bearings is satisfied in these modern race engines… higher temp bearing material etc. ?

I do not see how the pressure from the oil system (50-100 psi) is adding much to the 1-2000 psi required at the bearing interface.

Brian

[MrPotatoHead]

Why the requirement for large clearances? Smaller clearances can carry more load. Modern race engines use almost 'zero' clearance on the journal bearing when cold. Must be preheated before starting.

I am not sure how the cooling requirement of the journal bearings is satisfied in these modern race engines… higher temp bearing material etc. ?

I do not see how the pressure from the oil system (50-100 psi) is adding much to the 1-2000 psi required at the bearing interface.

Brian

Up to a certain point a larger clearance provides an increase in the minimum oil thickness and thus a greater load that the oil wedge can support.
A common practice in modified production engines is increasing this clearance for longer life and in some cases being able to survive the loads in question. It's the only way to get the main bearing caps or the engine block itself to survive in many cases. A 2JZ is a classic example of this.

Another factor that comes into play here is that the tighter the clearance the more heat that is generated. So in some ways too tight can mean more flow is needed to aid in cooling.

The wedge zone gets complicated. The Hydrodynamic effect that supports the load is of course created by the rotation of the shaft and the loads on it. But it relies on the oil being there in the first place. No oil, no wedge of course. So the flow of oil has to counter the leakage and the force of the journal trying to compress it. The oil pressure is needed to get the flow required.
It's a fun balancing act of cooling vs clearance vs loads vs flow vs pressure.

I may not have done a good job of explaining my point of view yesterday.

There are some nice charts showing the minimum thickness at different clearances at the following location:

http://www.substech.com/dokuwiki/doku.p ... e_bearings

[PlatinumZealot]

The journal bearings actually do not need much flow or pressure to maintain clearance. Flow is mainly for cooling. The journal inside the bearing does not stay center. On the side where the clearances are reduced the oil is pinched down creating a wedge (pressure) of oil that prevents contact between the two surfaces. This system/design creates its own oil pressure. Note: as long as there is movement/rotation a clearance is maintained… hydrodynamic regime.

The loading on one of the main bearings in these engines is between 2000 and 5000 psi. That's some serious load.
That load is supported by the oil pressure in the oil wedge between the bearing and the crank journal.
If you had no pressure the oil thickness would quickly be zero.

The rod bearing journals have a load of about double the main bearings. Once again the pressure in the oil wedge is what stops contact.

I am no tribologist. But you are thinking like an accountant here. Only looking at the numbers at face valve.

Rmember the the bearing is rotating circle. The oil spins around it by friction and moves down to the contact point.. Think of two circles.. One inside the other and touching at a tangent (to exaggerate). There is a wedge formed at this poiny.. A geometrically infitinite wegde wheenever the circles are not concentric. The oil gets forced into the wedge by the rotating action. So it has the mechancial advantage and lifts up the inner bearing floating it. This happens all around anywhere the inner circle tries to touch the outer one a wedge starts to form and the process repeats.

The mechanucal advantage is so high that 2000 psi is easy for the oil to lift up.

[MrPotatoHead]

The journal bearings actually do not need much flow or pressure to maintain clearance. Flow is mainly for cooling. The journal inside the bearing does not stay center. On the side where the clearances are reduced the oil is pinched down creating a wedge (pressure) of oil that prevents contact between the two surfaces. This system/design creates its own oil pressure. Note: as long as there is movement/rotation a clearance is maintained… hydrodynamic regime.

The loading on one of the main bearings in these engines is between 2000 and 5000 psi. That's some serious load.
That load is supported by the oil pressure in the oil wedge between the bearing and the crank journal.
If you had no pressure the oil thickness would quickly be zero.

The rod bearing journals have a load of about double the main bearings. Once again the pressure in the oil wedge is what stops contact.

I am no tribologist. But you are thinking like an accountant here. Only looking at the numbers at face valve.

Rmember the the bearing is rotating circle. The oil spins around it by friction and moves down to the contact point.. Think of two circles.. One inside the other and touching at a tangent (to exaggerate). There is a wedge formed at this poiny.. A geometrically infitinite wegde wheenever the circles are not concentric. The oil gets forced into the wedge by the rotating action. So it has the mechancial advantage and lifts up the inner bearing floating it. This happens all around anywhere the inner circle tries to touch the outer one a wedge starts to form and the process repeats.

The mechanucal advantage is so high that 2000 psi is easy for the oil to lift up.

I'm an Engineer actually not an accountant. But that did make me laugh.

And any way you spin it a gallon of oil every 2 seconds is a crap load of flow.

[PlatinumZealot]

Yes. You are both correct but the high pressure numbers can be convince the untrained redears that a lot of oil pressure is needed. I, with my rusty memory was almost swayed.

[MrPotatoHead]

Yes. You are both correct but the high pressure numbers can be convince the untrained redears that a lot of oil pressure is needed. I, with my rusty memory was almost swayed.

I didn't do a very good job of explaining my point
The pressure is needed to get the volume required. And the volume is high.

Anyway - no Mercedes on the front row for this race... that hasn't happened in a while!
While a shame for Lewis I'm happy to see a front row lockout with parts I had a hand in

[lawnmower]

Mercedes brings engine upgrade at silverstone

[Jordan44]

Mercedes brings engine upgrade at silverstone

Any info on what exactly it is?

[63l8qrrfy6]

Mercedes brings engine upgrade at silverstone

Any info on what exactly it is?

A turbo v6

[Craigy]

Mercedes brings engine upgrade at silverstone

Any info on what exactly it is?

It'd be hilarious if it was a second oil tank...

[63l8qrrfy6]

Mercedes brings engine upgrade at silverstone

Any info on what exactly it is?

It'd be hilarious if it was a second oil tank...

Won t be as they are not running a new spec engine at silverstone.

New spec is rumored to be introduced at Spa.

[F1NAC]

So mercedes is planning to introduce 4th ICE, turbo and mguH according to Tobi gruener.

Do you guys think that Mercedes is trying to avoid that rule that is on after monza (regarding oil stuff that all new introduced PU's from monza onwards must follow?)

Because they had new ICE only 2 races ago?


Or classic new PU's for most demanding tracks (high throttle %)

[Just_a_fan]

Thought the general consensus was that Ferrari were the most likely being hit by the oil burns issue.

Spa is one circuit that needs a strong engine so this is why they want a new IC here.

[godlameroso]

So the new engine will handle the next 5 rounds and they will cycle the older power units at the remaining 4 races?

[63l8qrrfy6]

It would make sense to only use the final spec PU for the power circuits. Unless it blows up.