Driver-adjusted differential locking

[Tommy Cookers]

My question is why they have two sets of clutches, is it achieving something like brake steer?
928S

Something like..

'brake steer' is surely a myth
(mostly it would be counter-productive, having to brake (harder) the inner (lighter loaded) wheels to steer in the right direction)
(it could be useful at the apex, this is what was tried, before the ban ?)

LSDs in part impede corner entry,(adjustably) resisting the wheels rotation at different speeds in curves they add understeer
(this effect persists on the exit of a curve, but is trivial compared to the LSD benefits to exit traction)
hence the need to adjust the LSD 'stiffness' in the corner (twice between one straight and the next ?)

'brake steer' effect (synthetic) could be done easily and better with a more capable diff type (Torsen etc) under intelligent control
(higher torque would be useable on the outer wheels, this 'steers' with the direction)
this is banned surely ?
is even the basic Torsen etc type diff now outside the F1 rules ? (despite 'road relevance')

[Jersey Tom]

LSDs in part impede corner entry

"Impede" sounds like it has negative connotation. I would make the argument that on many platforms, adding some entry understeer / stability is a good thing... as being overly unstable or free while entering a corner while braking is what will impede a good lap time.

[Dragonfly]

'brake steer' is surely a myth

Wasn't the '98 McLaren third brake pedal aimed just at that?

[FoxHound]

@Dragonfly

Yes, you are correct.

I got this from wiki:

During the season, F1 Racing photographer Darren Heath noticed that the rear brakes of the McLarens were glowing red in an acceleration zone of the track. The magazine discovered through photos of the inside of the cockpit, that McLaren had installed a second brake pedal, selectable by the driver to act on one of the rear wheels. This allowed the driver to eliminate understeer and reduce wheelspin when exiting slow corners, dubbed "brake steer"

[Tim.Wright]

'brake steer' is surely a myth

Wasn't the '98 McLaren third brake pedal aimed just at that?

Yes but this was biasing the torque in the opposite direction to the diff. A normal LSD cannot do this.

Tim

[Dragonfly]

'brake steer' is surely a myth

Wasn't the '98 McLaren third brake pedal aimed just at that?

Yes but this was biasing the torque in the opposite direction to the diff. A normal LSD cannot do this.

Tim

Normal, yes. But what about dual clutch electronically controlled? And I think as long as this is torque distribution summing up to the amount of input torque, it is not regarded as traction control.

[Jersey Tom]

Normal, yes. But what about dual clutch electronically controlled? And I think as long as this is torque distribution summing up to the amount of input torque, it is not regarded as traction control.

I suppose you could apply different clutch plate pressure left versus right. Not intuitively obvious to me how it would work out leaving one half of the diff open and one with heavy clutch engagement. Gut feeling is that I'm convinced it would gain you much or anything and just add complexity.

[Dragonfly]

It was just an idea of mine without having any insight on F1 diff design and operation. But we know that teams are looking to exploit every possibility and complexity is not a deterring force for them.

[Jersey Tom]

It was just an idea of mine without having any insight on F1 diff design and operation. But we know that teams are looking to exploit every possibility and complexity is not a deterring force for them.

Sure. I suppose my point is more that just because it's different doesn't necessarily mean it's better nor that there is inherently more to exploit just by adding that additional complexity or adjustment. Could end up that equal clutch engagement is still the best or fastest setup.

[Tim.Wright]

Normal, yes. But what about dual clutch electronically controlled? And I think as long as this is torque distribution summing up to the amount of input torque, it is not regarded as traction control.

No I don't think so. A diff using clutch plates can ONLY direct torque from the faster spinning wheel to the slower spinning one. The hydraulic actuation can only change the magnitude of the locking torque not the direction.

So normally on corner exit, the inside wheel is spinning slower and has more driving torque. If I remember correctly, the McLaren system was braking the inside wheel on corner exit to reduce this torque on the inner wheel and allowing the driver to add more throttle. This effectively biases more torque to the outside wheel which has more vertical load.

Tim

[928S]

Brake steer is no myth and I was sort of on the right path, in fact the diff is torque vectoring as seen here in this Audi demonstration. This is the reason the diff helps turn in and general corning stability.

http://www.youtube.com/watch?v=viWJUaak ... ata_player


http://www.youtube.com/watch?v=zHoVVFZf ... ata_player

My question is why they have two sets of clutches, is it achieving something like brake steer?
928S

Something like..

'brake steer' is surely a myth
(mostly it would be counter-productive, having to brake (harder) the inner (lighter loaded) wheels to steer in the right direction)
(it could be useful at the apex, this is what was tried, before the ban ?)

LSDs in part impede corner entry,(adjustably) resisting the wheels rotation at different speeds in curves they add understeer
(this effect persists on the exit of a curve, but is trivial compared to the LSD benefits to exit traction)
hence the need to adjust the LSD 'stiffness' in the corner (twice between one straight and the next ?)

'brake steer' effect (synthetic) could be done easily and better with a more capable diff type (Torsen etc) under intelligent control
(higher torque would be useable on the outer wheels, this 'steers' with the direction)
this is banned surely ?
is even the basic Torsen etc type diff now outside the F1 rules ? (despite 'road relevance')

[strad]

sometimes you want understeer....trust me.

[928S]

sometimes you want understeer....trust me.

Fair enough Strad but that is why the F1 systems are adjustable.

[langwadt]

Normal, yes. But what about dual clutch electronically controlled? And I think as long as this is torque distribution summing up to the amount of input torque, it is not regarded as traction control.

No I don't think so. A diff using clutch plates can ONLY direct torque from the faster spinning wheel to the slower spinning one. The hydraulic actuation can only change the magnitude of the locking torque not the direction.

So normally on corner exit, the inside wheel is spinning slower and has more driving torque. If I remember correctly, the McLaren system was braking the inside wheel on corner exit to reduce this torque on the inner wheel and allowing the driver to add more throttle. This effectively biases more torque to the outside wheel which has more vertical load.

Tim

I think that is basically variation of what some call " brake-force traction control system " on road cars

[Tim.Wright]

Brake steer is no myth and I was sort of on the right path, in fact the diff is torque vectoring as seen here in this Audi demonstration. This is the reason the diff helps turn in and general corning stability.

A torque vectoring diff is something different to a normal LSD. This is what we would like to know, if this is allowed in an F1 differential, but I have the impresison that its not.

To get torque steer from one of these, there is a gear stage which steps the rotational speed of the clutch so its faster than the carrier speed. Then you can send torque to the left or right by operating one of two independant clutch packs.

Yes there are advantages but also massively increased complexity. Diffs could be a bottomless pit for development money if its allowed, and thats the main reason why they are restricted now.

Id be surprised if such a torque vectoring diff is allowed in F1.

Tim