9 replies to this topic

[Vitek]

I have only recently become a keen F1 enthusiast (since last season) and am fascinated by the level of technology employed by the teams. I'm a mechanical engineering student, hence the technical aspects of the sport are beginning to appeal to me as much as the actual racing. Having no racing or mechanical background, however, I sometimes find it difficult to understand what the commentators are on about. Which brings me to my question. We regularly hear of drivers stalling their cars while in the pits or post-incident. How can this be? Don't all of the cars use semi-automatic transmission?
I have read a little about the different types of automatic transmissions currently being used by commercial manufacturers (Autozine Technical School online). A little knowledge can be dangerous, hence, I would appreciate it if someone could please explain the basics behind this type of transmission.

[Ross Stonefeld]

The actual workings I dont know, but the mechanism goes like this. The driver approachs the shift point, he pulls the upshift paddle on the steering wheel. It sends a signal to the Electronics in the engine which momentarily cuts out the engine (I think?) and shifts the gears. On downshifts they pull the downshift paddle, it sends another signal to the Engine, changes down a gear and modulates the engine to keep the revs in the right range (to prevent rear wheel lock up)

The system is automatic but the activation is "manual" ie pulling the paddle system.

I've heard in CART that while you have "shift without lift" which means the F1 system where you keep your foot flat on the floor while upshifting, you do have to manually -blip- the throttle on downshifts to release the gear dogs (?) and allow teh gear to change down. Clutch is only needed from a standing start and to go from neutral into first.

Ross Stonefeld
Aztec Group Motorsport

[PDA]

Vitek - althjough they are called aemi automatic gearboxes, they are mechanically the same as a manual gearbox. There is no torque converter such as one has on road cars. When the car is stationary, they clutch must be disconnected, either by a foot lever, or a hand lever (more usual). As Ross states, when the driver flicks the shift button, and elecric signal is sent to a hydraulic system which pushes the gearchange mechanism to the next gear. Teh clutch is not disengaged for either up or down shifts.
I read recently that all F1 cars are fitted with an anti-stall feature, in which the clutch is disengaged if the revs drop be;low a pre-defined limit, and the engine revs set to a "fast idle" this only lasts for a few seconds, then the driver must take over the clutch and throttle control or the throttles will shut down.

[Robban]

The possibillity of stalling is when the driver missjudges the clutch. The cltches are very sensitive, i think they are six diskers, and if you releases the clutch t fast with to little rev the engine stalls.

The stiff clutch is needed as it is used automatically through downshifts. You have to syncronize whellspeed with transmissionspedd during downshift, it cannot be done by modulating the engine rev because it would appear unnatural to the driver if the engine was reving independently of his handling with the throttle.

[tak]

To understand an F1 automatic gearbox, it will help to understand how a standard race transmission works. Check the hewland site below, and download the on line manual for the LD 200 gearbox. This is the light duty tranny used on all new formula fords and sports racers.

http://www.hewland-e.../svga/index.htm

Note that the gear "sets" are always engaged. Shifting is done by engaging a "dog ring" into the side of the gear set you want to engage.

An F1 semi-automatic is fundamentally similar--it has more gear ratios (7 I think). Actuation is still by shift forks on shift rails, but in the F1 box each shift rail is attached to a small hydraulic ram and a servo valve. Each time the driver presses a shift paddle to shift, the computer moves the throttles enough to release tension on the gearbox and disengages the gear. While the box is between gears, the computer adjusts the engine speed so that the next gear and dog to be engaged are roughly the same speed. Then the computer then engages the next gear and returns throttle control to the driver. (Note that there must be some speed difference between gears so that the dogs will actually engage. Other wise it's like getting first gear on a BMW Boxer!)
The clutch is not involved either in upshifts or downshifts.

Clear as mud right?

[Robban]

The clutch must be used through downshifts.

[tak]

The clutch is only necessary for starting and stopping. On the F1 cars the computer synchronizes the engine speed to wheel speed while the tranny is between gears.

With manual race boxes it's done with a gentle blip of the throttle. I've done it in a Swift DB2 with a Hewland MK9 tranny. It just takes rythm and consistincy with shift points.

Recall that race transmissions are close ratio boxes, and the RPM difference between gears is rarely more than 1500 rpm--even with a 4 speed.

[desmo]

To clarify on F1 ratios:

Crankshaft speed drops around 1200/1300rpm on average per upshift. Top gear would be less- around 1000, and second/third would be more, perhaps 1800/1900rpm.

[Robban]

All what I have read until now says that the clutch is activated trough downshifts. I don't know why, but that is what they says. Maybe it is better to the reliabiullity of the engine, and therefore only used in F1...

[PDA]

The clutch is NOT activated on downshifts. It is not needed, so isn;t done. The clutch is only activated for standing starts.

http://www.autoracing1.com

See article on shift without lift (which also discusses downshifts)