Seldom have engineers privy to the workings of this new generation of gearboxes been forthcoming, furtively evading questions on the matter. For that reason, ascertaining information is exceedingly difficult as it pertains to how shifts can be made with minimal loss of drive, while at the same time smoothing torque spikes across the drivetrain. However, details have slowly emerged pointing to the use of two systems in F1: The Weismann Quickshift, first tested by Williams on the FW15, and it's successor, the Zeroshift transmission.

* Some photos and graphs of gearboxes can be found at http://www.f1network.net/main/s491/st128890.htm

First, we'll touch on some basics regarding the implications of the gearbox case. An F1 gearbox is a fully stressed member of the chassis. It is the point through which the rear wishbones and dampers are attached to the car. The rear crash structure is also mounted on the gearbox. Because the gearbox is situated relatively high in the chassis, ballast is affixed to the under-side of the box to improve the overall centre of gravity. As one would imagine the gearbox casing is incredibly robust, with teams opting from a range materials, such as carbon fibre, titanium, aluminum and magnesium. As a seamless shift gearbox carries an additional weight penalty of 1 to 2 kg in comparison to conventional box, this makes carbon fibre (the lightest of the options avaiable) an attractive option in order to offset the weight penalty. A combination of these materials is the solution employed by several teams. According to Autosport's 2007 technical review, Honda and McLaren were the only teams to use fully carbon fibre casings.

For teams who opt for a hybrid of materials, they must consider the rear suspension geometry and it's attachment points to the casing. In some cars, the gearbox panels are the stress bearing structure, where in others, it is the frame. For example, if the panels are the stress bearing structure, then it would be best to choose a carbon fibre pane(light, but rigid in the face of torsional stress) and a titanium frame (also light, but much higher durability than carbon).

The current regulations state that gearboxes must last 4 races, and must consist of between 4 and 7 forward gears and a reverse gear. Teams can still replace the clutch, gear ratios, dog rings, oil filters and hydraulics. This is significant, owing to the fact that most of the gearboxes failures in 2007, particularly with BMW's F1.07, were caused by hydraulic sealings. This may be why the new "4 race" rule has had little effect on reliability in the 2008 season.

Until 2005, all teams used a gearbox that resembled conventional sequential gearboxes that are commonplace in racing series worldwide. Like their manual H pattern counterparts (sometimes referred to as "dog boxes" or "crash boxes") these sequential gearboxes lacked synchros. In most production based cars, a synchromesh is a type of cone clutch, usually machined from brass, that sits between the dog collars of the gearbox's output shaft and the dog teeth of the gears. As a gear is requested, and the selector fork moves the collar to the desired gear, the cone on the side of the gear meets a chamber inside the synchro. The friction between these two components would slowly bring the dog teeth on the side of the gear and the teeth on the side of the collar to the same rotational speed, allowing the next gear to be enganged smoothly to the drive-shaft through the collar.

Because this system relies on friction to get the dogs and gears spinning at the same speed, it is quite slow and not suitable for racing applications. In many racing series, drivers have to double clutch in order to bring the engine RPM to a level where the next gear is being driven at the same speed as the the output shaft. This means pausing during upshifts after the second "clutch-in," and heel & toe-ing during downshifts in order to increase the speed of lower ratios to match the speed of the driveshaft. In F1, this responsibility falls on the ECU. Instead of relying on the friction of the synchros, or the driver to manage the engine speed, the ECU (by either manipulating spark, or fuel) ensures that the gear in the process of being selected is being rotated at road speed.

Another feature that F1 gearboxes (inluding the new SSG designs) share with conventional racing boxes, is the method for moving the selector forks along the output shaft. It is of course these selector forks which move the collars that engage the next gear. When the driver uses a paddle on the steering to effect a gear change, this actuates a hydraulic piston through an electronic linkage, which then activates a "cam and pawl" mechanism. The cam and pawl is responsible for rotating the selector drum. The drum is axial to the output shaft, sitting directly below it. The rings connecting the selector forks rest in grooved pathways around the circumference of the selector drum. The pathways have "curves" or "notches." When the drum rotates such that the ring of a selector fork reaches one of these notches, the selector fork moves a collar along the output shaft, engaging the next gear.

            

Autosport's 2007 technical review also alludes to the fact that all SSG designs continue to have two-shafts(one input and one output) and a single clutch. This is crucial because FIA dogma dictates that a dual clutch system would represent a CVT transmission, and therefore banned. This means that the SSG bears no resemblance to a DSG. A DSG would also have larger packaging implications which make it unsuitable for an F1 chassis. The DSG uses two countershafts, one for each clutch. The second countershaft is rotating inside the hollow centre of the first, and extends the full length of the gearbox. In many dual-clutch gearbox configurations, the following two measures are taken to reduce the length of the gearbox, which are both important space saving features in power trains with a transaxle configuration:

a) There are 2 different output shafts, which each connect to the driveshaft via 2 seperate helical gears. The 2 output shafts have gears 1 through 6 divided between them.
b) The 4th and 6th ratios both use the same gear on the first countershaft as part of their gear pairing.

While these measures are convenient for a transaxle configuration, they drastically increase the width and height of the gearbox, and is therefore counter-productive within the framework of an F1 chassis, because the gearbox must be built as narrowly as possible to maximize space for the diffuser.

In part 2 of this feature we will investigate how the principle behind the SSG allows it to almost instantenously select the next gear, and is effectively in 2 gears at once...

*The 2nd part of the article, which will be coming soon.

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