Modern Formula 1 Differentials?

[sdimm]

Hi,

I´ve been thinking some about how the differentials have changed in F1 during the years.
Going back like 30 years or so I´ve heard that they used differentials that would either be fully locked like a gokart or completely open depending on things like speed of the car or was it maybe the speed-difference between the inside and outside tyres.

Later on like in the early 2000s when they had TC and anti lock on the rear tyres into corners they used some type of hydralic diff which then could program however they wanted. They could look at Yaw rate to determine how the car was balanced, individual wheel speeds so they wouldn´t spinn the inside tyres too much on exit as well as many other factors as I understand it.
I guess Ferraris E-diff that they put in their roadcars is the closest to this.

However I wonder if anyone can either correct me on these facts or maybe even knows even more on how this years differentials work and what they actually set on them, preload, drive %, coast % or is it all just done by a computer profile?

// Mattias

[Jersey Tom]

Some old F1 cars used cam-and-pawl diffs, which are open until a certain amount of torque is applied, at which point they lock like a spool.

I don't know the exact specifics of the current diff internals, but they aren't a pure plate-and-ramp where you just adjust preload, plates, and coast/drive angles. The behavior may be pretty similar.

On F1 steering wheels there's typically a knob for "In/Entry", "Mid/Preload", and "Exit". There's obviously some amount of electronic and/or hydraulic control in how the differential behaves at different parts of the corner or under positive, negative, or neutral applied torque.

[xpensive]

I wonder what happened to the Torsen diff, which was so popular in the eighies, overtaken by hydraulics perhaps?

[Downforce]

Here is the best picture that I could find. Season 2000.



Planetary gearset of this type:

I guess that the number of teeth is set up in a way that you get 50/50 torque and speed ratio. I did not go deep in this calculation...for now. Something that looks like mitsubishi 3000GT center differential, just more tightly packed.


Source: http://www.stealth316.com/2-awd3.htm#cdvcu

They could use viscous coupling to change the amount of locking between the left/right wheel, or they could use hidraulic piston that pushes friction plates, like in the first picture. The hidraulic pressure (or amount of oil in the viscous coupling)would depend from the difference in left/right wheel speeds. If the speed difference is high, apply greater pressure to slow down the wheel that is slipping. That would be the basics. The way that the computer read this speed difference and apply pressure would depend from the phase of the corner in which the car is (braking, turning in, mid corner, exit).

I guess that the pressure could depend even from the steering angle, brake pedal position etc. if you want to max complicate it.

[Jersey Tom]

I wonder what happened to the Torsen diff, which was so popular in the eighies, overtaken by hydraulics perhaps?

It's popular, just not in F1.. nor some other racing series. Doesn't allow you to independently tune car balance through different parts of the corner.

[sdimm]

Ok, so it´s quite possible that the current 09 F1 cars are using something very similar to ferraris e-diff

I took this screenshot from one of the promo videos for the new Ferrari 458 italia.



It clearly shows how they set the car up to have oversteer which makes it feel light and all that good stuff and then use the diff to control the yaw rate which I assume will make the car feel very stable. At least in a way that the driver doesn´t have to make alot of small corrections to keep the balance right unless of course the tyres are running out of grip.

[sdimm]

I wonder what happened to the Torsen diff, which was so popular in the eighies, overtaken by hydraulics perhaps?

It's popular, just not in F1.. nor some other racing series. Doesn't allow you to independently tune car balance through different parts of the corner.

With Torsen you just set a momentum which to lock the diff with right?

[mep]

Nice post downforce =D>
I just read that Ferrari used such a diff 2002.

I wonder whether it is possible to make such a diff with just 3 gears as planets insted of 6.
It is interesting to see that the sun gear and the planet gears have a much smaler modulus.

[Downforce]

Thanks mep. Where did you read about Ferrari 2002 diff?

I wonder whether it is possible to make such a diff with just 3 gears as planets insted of 6.

No, it wouldn't be possible. The function of additional 3 planet gears is that planet carrier and sun gear rotate in the same direction.

[mep]

Thanks mep. Where did you read about Ferrari 2002 diff?

I wonder whether it is possible to make such a diff with just 3 gears as planets insted of 6.

No, it wouldn't be possible. The function of additional 3 planet gears is that planet carrier and sun gear rotate in the same direction.

That would be the case with 3 planet gears.
Hm, when you hold the ring gear and turn for example the sun gear then the carrier has to turn in the opposit direction and you get this with 6 planet gears.
So yes for cornering you need 6 planet gears.

[autogyro]

Thanks mep. Where did you read about Ferrari 2002 diff?

I wonder whether it is possible to make such a diff with just 3 gears as planets insted of 6.

No, it wouldn't be possible. The function of additional 3 planet gears is that planet carrier and sun gear rotate in the same direction.

That would be the case with 3 planet gears.
Hm, when you hold the ring gear and turn for example the sun gear then the carrier has to turn in the opposit direction and you get this with 6 planet gears.
So yes for cornering you need 6 planet gears.

You do need six planets minimum in a diff with helical gears but three is plenty for a bevel gear diff, where the planets bevels are set at 90 degrees to the axle line.
I presume Ferrari use helicals to achieve less torque loss when unlocked but IMO this would only occur when the vehicle was running in a strait line where no diff action is necessary so no real gain.
Both types can be progressively locked with either. lockers. plates (dry or wet) or hydraulics. Hydraulic diffs lend themselves better for electronic control of course.

[Brian.G]

Regards,

Brian,

[autogyro]

Nice compact design Brian.
Can you show us the assembly that connect to it giving the locking action?

[bigpat]

Downforce is right on the money. Simply use a hydraulic pump, and Moog servo valves to control diff lock up.

Patrick Head quoted it best: "We are restricted to emulating the characteristics of passive differentials, but that doesn't mean that we can't emulate different types of diffs in different parts of the same corner!"

[timbo]

I wonder what happened to the Torsen diff, which was so popular in the eighies, overtaken by hydraulics perhaps?

I read that it was used in 1997 on Ferrari F310.