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Xtrac tests new gearbox components on a test rig to confirm their performance after simulating them with modeling software.

Xtrac reveals 2014 Formula One gearbox technology

Formula One rules for the 2014 season have changed in many areas, most notably the use of smaller-displacement turbocharged engines and a stronger hybrid-electric drive motor.

Accompanying these changes are new gearbox specifications for 2014. The new rules call for eight forward speeds rather than the seven gears used in 2013. But while there are more gears in the box, there are fewer in the garage, because teams are required to nominate the eight ratios they plan to use for the entire season, and use only those, despite the huge disparities between slow tracks like Monoco and fast ones like Spa-Francorchamps and Monza.

For this season only, if teams miss the target in their first try, they are permitted to change their nominated ratios once during the season. Or, more likely, they will live with lower-than-ideal ratios until Monaco and then switch to a set of higher gears (numerically lower) afterward in anticipation of the faster tracks later in the season.

Gearboxes must now run for six complete race weekends before replacement, which along with the ban on changing ratios, means they will go unopened for months. This imposes a significant durability requirement on the new transmissions, as teams will only be able to use three gearboxes over the course of the 18-race season. This is a duty-cycle equivalent to 3300 km (2050 mi) at qualifying and race speed, which compares to the 4750 km (2950 mi) of a Le Mans race winner.

Additionally, the new turbocharged engines produce significantly more torque than the previous normally aspirated powerplants, and the new hybrid-electric motor introduces still more power than was added by the previous kinetic energy recovery system (KERS).

In response to these new demands, Xtrac revealed its 2014 Formula One gearbox technology at the Autosport show in Birmingham. Its cluster and bevel gears are more robust to handle the added strain. New FIA specifications require gear sets measure at least 12 mm (0.47 in) in width and have a spacing of at least 85 mm (3.35 in) between their centers. Further, they must be made of steel and weigh at least 600 g (21 oz) each, according to the FIA 2014 Technical Regulations.

Xtrac generally provides teams with its gearbox internals, for installation into their own proprietary cases designed to specifically fit their cars, explained Technical Director Adrian Moore. An exception is the Marussia team, for which Xtrac supplies a generic gearbox complete in a case, he added.

To address the new rules, the new transmission features gear ratios that are both wider and larger in diameter than those in the 2013 transmission. The goal was to balance the need for strength with the desire to minimize friction. 

“There are counterarguments,” for different solutions, Moore acknowledged. “We believe we’ve taken the route that gives a good vehicle package,” he said.

“We use a gear rating method that rates the strength and pitting resistance of a gear,” he said. Small changes in gear topography that are modeled using finite element analysis tools can maximize the strength of the teeth while minimizing power loss. “That allows us to have a very reliable, efficient gear tooth.”

The gears are made of XM031 steel from Tata Steel (formerly Corus Engineering Steels) co-developed with Xtrac. It is a nickel-chromium-molybdenum alloy optimized for temperatures of more than 350°C (662°F) for use in gear ratios, dog rings, crown wheels, and pinion, according to the company.

Xtrac applies a low-friction coating to reduce losses in the transmission. A challenge has been that the application process for such coatings has required temperatures so high that they can temper the steel they are being applied to, Moore said.

The company has identified a low-friction coating that can be applied at a tolerable 300°C (572°F). However, Moore said he is unable to identify either the material or its supplier for competitive reasons.

“It is based on commercially available coatings with some subtle changes,” he said.

The need to extract maximum strength from minimal mass with minimal loss will only grow, both in road and race cars, said Moore.

“The downsizing and lightweighting trend is highly relevant to the packaging of an internal-combustion engine and electric motor into a hybrid road car, where you have two sources of power to squeeze into the space available for the powertrain, reflecting the benefit of the new regulations and the relevance F1 technology will bring to road cars,” he said.

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