Shock Load?

The short answer to that concern is that the F1 system DOES ensure that the gear train is aligned properly when the exchange is made. That's one of the things that makes the system so sophisticated

As to exactly how any (many other makes' systems out there nowadays besides Ferrari) automotive gearbox accomplishes that is a question for the Engineers who designed them. Or, someone (with the appropriate background of understanding) who has dissected and studied one of those boxes --- I have not had the opportunity (yet ) to "play" with one myself.

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But, for what it's worth and for your curiosity........From my own design involvement with similar systems --- we have used automatic clutches and automatic gear selection systems for several spacecraft instrument mechanism applications such as gimbals with drive transmissions requiring multiple gear ratios ---- I can offer the following approach as an example.

In simplistic terms, we use toothed clutches with "special" tooth profiles (sorry, the details of such designs are still proprietary) that make the statistical probability of misengagement (misalignment) extremely low just by virtue of their geometry. Also, immediately (very few milliseconds) prior to engagement, the carriers of the interfacing teeth are subjected to a brief magnetic field which orients and holds them into the correct positional alignment while engaging.

The gear mating scenario is similar in that more "special" teeth are used on the gears. But, extremely accurate position encoders, which are intimately tied (via electronics and software algorithms) to solenoid-like (in actuality, they are ultra-high speed voice coil devices) actuators (which move and engage the gears), are used to accurately predict (after relative momentum is measured, and the appropriate calculations are made by the software) when the gears are to be in alignment before the gear change is allowed to be initiated. This is a lead-type movement ----- think of it as tossing a baseball to intercept and hit another baseball that's already been thrown and is still moving

An automotive gearbox does not require this degree of precision and design targets of essentially "zero" noise ---- "noise" meaning mechanical vibration and shock. So, I am quite certain that none of them are (or will ever be) using any of these techniques or equipment.

Not to mention, the cost of such a system would add about another $750K to the price tag of any car sporting it !

But, there is more than one way to skin a cat (especially if you don't have to remove every last scrap of skin )......not that I have anything against cats

 

In theory, couldn't matching revs allow an upshift without the clutch simply as fast as one could mechanically make the shift? Works for truckers.

 

B.S. --- University of Iowa
Ph.D --- RPI (Rensselaer Polytechnic Institute)

.....I am actually recently retired (2006), by the way.....But, yes, I very much enjoyed my work. I was privileged to have worked with some amazing people on some amazing things

 

Your profile says that you are a "student" ---- assuming that does not simply mean "a student of life" (as we all are ), do you have any inclinations towards a technical occupation in your future ?

 

Yes....as can matching "momentum" for a downshift

That is precisely the fundamental concept that all the automotive automatic (F1) gearboxes use ---- which is why there are speed sensors on the engine output (flywheel) and the transmission input/output shaft(s)......and an ECU functionality to measure relative rotational speeds before a shift gets actuated.

It's also why MOST of them are limited to (up and down) sequential gear changing only ---- easier to go from 2nd to 3rd, as opposed to, 2nd to 5th.....with more safety margin on the engine if a shift is "missed", and more safety margin on the gearbox components if gears get balked / clashed.

In fact, the only real purpose an engageable / disengageable clutch serves (other than a quick and easy way to get into "neutral" when stopping / idling) on a modern, properly designed F1 drivetrain is to prevent inadvertent "re-bound" loads from being transferred to the crankshaft (and against engine component momentum) during aggressive up/down shifting. A clutch is not actually needed to make the gear changes themselves ---- you can demonstrate this for yourself with a manual transmission car by "matching revs" and shifting gears WITHOUT depressing the clutch pedal (i.e., not disengaging the clutch) ------ with some practice, you can often find the "sweet spot" where the shift is as smooth as if you had used the clutch. Race car drivers used to do this all the time when their clutches failed during a race

I used to have an old Triumph TR6 that had one of the lousiest-designed hydraulic clutch linkages I've ever seen ---- damn thing was always failing in one way or another. If I hadn't become adept at "clutch-less" shifting with that car, I wouldn't have made it back home on many occasions

 

I suspected something along those lines !

Yes, UT has a good reputation. Stick with it ---- the first 2 years are the toughest Get through those, and it's smoother sailing. Best of luck to you with your goal.

When you get to Ferrari, let us know ---- some of us would love a guided tour

 

Just curious if anyone posted have actually changed the transmission fluid on a F1 transmission car? And what have you noticed?

 

Do a search ----- several threads from some folks who have

 

I know nothing about F1 transmissions but you asked about superfast transmissions generally. My wifes VW has an automatically shifted manual. It is two transmissions in one. While accelerating in 1st gear the 2nd transmission selects second gear so when the vehicle selects the next gear it does it with clutches without any gear change, while accelerating in 2nd the 1st transmission can select 3rd gear from 1st and when time the clutches do the work again. I think I was quoted .08 seconds for a gear change. It's an 09 VW Eos, but numerous models have the same transmission. I believe this is how the Veyron operates as well.

 

Bryan- If you use the fastest mode in F1 Superfast transmissions all the time and shift at high rpm, you will put wear on the drivetrain (CV joints, etc) slightly more quickly than using a lower speed mode. The main reason the F1 can shift so quickly is 800-900 lbs of hydraulic fluid making the shifts and the reason it does less damage and does not shock components more is that the Motronic ECU cuts the digital throttle on upshifts to match revs. There is no difference between an F1 and three pedal transmission (since someone asked, Bryan knows this) or clutch. Only the throwout bearing and a clutch position sensor and rear angular speed sensor are different. On downshifts in the highest speed modes (RACE or CST off, Sport on some), the F1 system actually double clutches according to the tech literature, so all the components (clutch, flywheel, gearshafts etc) have identical rotation speeds. In slower modes it just matches revs on downshifts and uses the synchros to match gear speeds.

Ferrari's transmissions have been beefed up for F1 and manual shifter operation with triple cone synchronizers in 1st and 2nd and that benefits both F1 and three pedal shifting, although it does tend to make the manual shifters a bit more notchy getting past all those synchro rings.

So to answer your question on how it does better than you, it can match revs better on quick upshifts because it uses the digital throttle way faster than you can think about lifting your foot to synchronize revs, and it can also get back on the throttle way quicker because it is digital. When everything lines up, it has 800-900 psi of hydraulic pressure to ram the shifter forks home way faster than you can move the shift lever. All of this rev matching also reduces the loads on CV and other joints, which last longer if the load is kept on them rather than loading and unloading. During those really quick shifts, the joints essentially stay loaded the entire time. On your manual shifts, the times are slow enough that there is some unloading and reloading of all the joints and gears between you and the wheels.

If you read Phil Hill's, or other racers, accounts of shifting dog clutch transmissions with no synchronizers, they effectively did what the F1 transmission does with their feet. On upshifts, just the slightest hesitation with a light flywheel engine matches revs, on downshifts double-clutching faster than you can imagine to match revs on flywheel, gearshaft and clutch made for extremely clean shifts. All that has just been mechanized in F1 systems and theoretically you could have put F1 on a dog clutch transmission and had it work pretty well. It would not have worked for the three pedal types, though, without a whole lot of training and practice. Since Ferrari uses the same transmission for both shift mechanisms, they had to be synchro gearboxes.

Taz
Terry Phillips

 

With all do respect to Terry , if he will be gracious enough to allow me the indelicacy of adding one small detail to his excellent overview of the F1 system’s operation…..

Anytime there is a friction-type clutch in the system, some amount of slippage will occur during engagement and disengagement. While the F1 system greatly minimizes clutch slip, it does not eliminate it completely.

This is a good thing because slipping of the clutch is a very practical way to dampen undesirable momentum imbalances between the driveline and the engine. And, the excess energy absorbed in the process is effectively dumped out of the system through conversion to frictional heat.

As efficient as the F1 gear changes are, they are not perfect. So, the friction clutch is still a key system element to help smooth out the imperfections.

 

David- Affirmative. In fact using the fastest F1 modes will accelerate wear on the clutch and throw-out bearing (and CV joints, etc) because of the extra clutch cycles during the double-clutch actuations. On the Superfast F1, the slower mode (usually SPORT), will cause a little more wear on the synchronizers than RACE or CST OFF, but not enough to be a cause for concern.

A trade-off. I usually run my older F1 system in NORMAL unless in a hurry, the equivalent of SPORT in Supersport F1 systems.

Taz
Terry Phillips

 

Bryan- if you want to see how effective the digital throttle can be, take an F1 car and run it just beyond redline in second gear and watch what happens when you hit the fuel cut-off or soft rev limiter. The revs stop rising and fall almost immediately. Will not damage the engine, by the way. On my 575M, for example, the cut-off is 7600 rpm and the redline is 7500. The Motronic ECU has similar authority on throttle control and there is virtually no rev rise once it cuts the throttle, especially considering the relatively light flywheels with which Ferraris are fitted.

All the drivtrain components help absorb the shock including the clutch, transaxle shafts, rear end, CV joints, etc. All except the clutch have clearances and lubricants that help aborb the shock. The clutch sacrifices a bit of its friction material on every shift, also helping absorb the shock, just like your brake pads sacrifice some friction material as brake dust on every stop. The softest component in the drive-train is the clutch friction plate, and it does a large percentage of the shock absorption, like David said.

Taz
Terry Phillips