F1 2014 tech: Gearboxes under pressure

In part three of his series on Formula 1's 2014 technical rules revolution, Craig Scarborough looks at the implications of the changes for F1 gearbox design.

With gearbox layouts static for a couple of decades since the introduction of seamless shift technology, Formula 1 gearbox design has been evolutionary for many years.

Even the rise of engine power and RPM has failed to inject major new demands into transmission design.

But for 2014 the humble gearbox is subject to some harsh new conditions and regulations, forcing every team into a new design for the new season.

With far greater torque from the new power units, more gears and limits on life and ratio changes, there's a surprising amount to cope with.

F1 GEARBOXES - THE BASICS

Mounted to the back of the engine, the gearbox is part of the new unified powertrain regulations. It comprises the gear case, clutch and the gear cluster itself.

Power passes from the engine's crankshaft into the carbon fibre clutch, then into the input shaft and via seven gear ratios out to the differential.

Rules limit the minimum width and weight of the gears, as well as how far apart their centres are spaced.

Gear selection is controlled by the electro hydraulic system and shifts are now regarded as seamless, in that there is no break in power to the driven wheels.

This is done by an extraordinarily fast gearshift, which engages the next gear with one selection mechanism, while the other selection mechanism is in the current gear.

This brief moment of two gears being engaged occurs in between engine firings and the phasing of the gears and the dog rings. The current gear becomes unloaded as the next gear starts to speed the gearbox up, then the current gear is disengaged before the gearbox self-destructs.

Any error or delay in this process will wreck the gearbox, so the team can phase the gearshift timing from mild to aggressive, by sequencing the two selection mechanisms, to reduce this risk during the race.

Seamless shift technology spread through F1 in 2005 © LAT

Surrounding the gear cluster is the gear case. This has to handle the stresses of the gear cluster, as well as forming the chassis structure behind the engine by mounting the rear suspension.

Cases can be made in either moulded carbon fibre with titanium reinforcement plates, or cast in titanium or aluminium.

Carbon fibre is expensive and labour-intensive, but is more durable and lighter. Each team will have their own ideas on what works best for them and their resources.

GEARBOXES IN THE 2014 REGULATIONS

Starting with the gear case, the size and shape will need to change to accommodate both the revised layout of the car and the mandatory engine mounting points.

As the new V6 engine and 100kg fuel tank will be shorter, it's likely teams will keep the same wheelbase, for aero reasons, then extend the gearbox.

Already gear cases are far longer than the gear cluster inside demands. The space afforded by this allows teams to mount the inboard rear suspension inside the casing. With even more space inside in 2014, it's unlikely any team will revert to a push rod rear suspension.

This new longer case needs to mate to the rear of the engine, which will have a new crankshaft position and new mounting points.

The engine's crankshaft is some 3.2cm higher than the 5.8cm previous position. This means the clutch must be larger in diameter, which will be useful for handling the engine's increased torque - especially at the start of the race.

The Lotus crew work on a gearbox in Malaysia last year © XPB

This change will also raise the gear cluster inside the case, which will be a handicap in terms of the centre of gravity. But there may be a small aerodynamic advantage as the bottom of the gear case can be slimmed or raised to clear its obstruction of the diffuser sat behind it.

To mate with the back of the engine, the gear case has to use the mandated engine mounting points and clear the turbo which will be mounted behind the engine and above the gearbox. To house the turbo it's likely the exhausts will need to pass through openings in the sides of the gear case to reach the turbine.

With the case's basic dimensions specified, the cluster within is now also subject to stringent regulations.

Firstly the gear ratios are fixed for the season, which means that the usual initial car set-up task of circuit-specific gear ratios will be a thing of the past. The cars will race from Monaco to Monza with the same gear ratios. After the selection of 30 ratios that the teams had in 2013, they will have just eight fixed ratios this year.

At first this seems an impossible task, but the gearboxes are now allowed eight forward gears and the way the new power unit produces its torque means the issue will be eased compared to the old V8s.

An eighth gear will give the team a wider spread of ratios to use at different tracks. It's worth noting that the gearbox must have eight gears - the weight advantage from continuing to run just seven gears is not an option.

As the current gearboxes have an odd number of ratios, the additional eighth gear will not add undue complexity to the cluster, the selection mechanism that operates the seventh gear will simply be modified to operate both seventh and eighth. However, the extra gear pair will add a minimum of 0.6kg and some 12mm in length to the cluster.

As the power unit has such a wide spread of torque, the driver can probably run with as few as six of the eight ratios for a particular circuit, i.e. for Monaco first to sixth will be used, and for Monza second to eighth.

Esteban Gutierrez's Hungarian GP retirement was the last DNF put down to a failure of the last generation of F1 gearboxes © XPB

Maximum theoretical top speed will be fixed for the year too, as the final drive is included in the fixed ratios, but the engines will not efficiently rev to the maximum allowable 15,000rpm due to the fuel flow restrictions so the effective top speed will be a variable below the maximum speed.

There will be no doubt that the driver will encounter turns or situations where the car isn't geared to the optimum, but the teams will have simulated every track and different conditions to predict the ideal eight ratios.

A dispensation for 2014 only is that the team may nominate a new set of ratios during the season, these replacing the initially nominated ratios. From 2015 the gearing will be completely fixed for the whole season.

Although a benefit in gear ratio selection, the increased torque from the power unit will give the gear cluster a far harder time than the peaky V8 engines. Punishment meted out from the ERS and turbo engine will demand a stronger gearbox.

With this in mind the additional demand that gearboxes last two more races than the four of the previous rules means that the 2014 gear clusters will need a rugged design.

Lasting six races should be possible as gearbox reliability under the four-race regulations has been excellent, and the rules do allow some parts to be replaced for identical-spec items if they become damaged.

Even the gears and dog rings themselves can be swapped, as well as the clutch, seals, filters and electronics. The penalty for gearbox swaps remains a five-place grid position drop.

Coming up this weekend, the final part of the Formula 1 2014 tech series looks at how the new rules will affect aerodynamics