Features - Technical
NOVEMBER 24, 1999
Formula1 Steering Wheels
BY PETER WRIGHT
At the same time, the cockpits of Formula1 cars have become so small and crowded, and the driver so reclined, that the steering wheel has obscured any possibility of having a useful display on the dash panel behind it. The solution to telling the driver what he needs to know, is an array of LCD displays and lights added to the steering wheel, already crowded with switch buttons and knobs and the gear-change and clutch levers. The end result is a steering wheel that is mechanically and electronically extremely complex, can reputedly costs in excess of $250,000, and which has prompted a NASCAR veteran to remark, "A Formula1 steering wheel has more technology in it, than in the whole of a Winston Cup car." No wonder team managers wince when they watch one of their drivers spin to a halt, take off the wheel and throw it out of the cockpit.
Ever since a photograph was taken of the inside of the McLaren cockpit at the end of 1997, revealing the existence of an extra brake pedal and that led to the banning of their "fiddle-brake" system, security surrounding cockpits and all they contain has tightened noticeably. As a result, it is not possible to accurately determine exactly what function each button and knob performs, but it is possible to review each of the tasks to which they might be allocated. Any speculation as to what a particular control may do is further complicated by the fact that the switches send a signal to the central computer, and the resulting action is determined by the software settings. A given switch may do one thing one day, and another the next. Technical Regulation changes at the end of 1998 limited further the variability of certain control systems and in particular, banned the driver from making changes to most systems while the car is moving. The effect of these changes has been to simplify steering wheels, as some of the switches have been deleted.
Gear-change switches. All steering wheels are fitted with a sprung-to-centre, double-acting rocker switch to command gear changes. The system is mounted behind the rim of the wheel and is operated by the driver's fingertips, pulling on paddles shaped to the driver's individual requirement. A single pull on the right hand paddle commands a single up shift, and a single pull on the left hand one commands a single down shift. The gearbox computer (or the software section controlling the gearbox, in the car's central computer) will check that a down change will not over-rev the engine, and it will then operate throttles, clutch and the gearbox selector mechanism to give the driver the gear he has asked for. If the over-rev. protection software predicts an over-rev., it must, according to the regulations, only prevent engagement - not delay it - and the driver must re-select the gear.
Clutch lever. Most cars now have hand operated clutches. One or two paddles mounted behind the wheel rim, are operated with the fingertips in a similar manner to the gear-change paddles. However, while the gear-change paddles operate switches, the clutch paddles operate a position sensor against spring pressure. The position of the paddle determines the position of the clutch slave cylinder, via the computer and hydraulic system. The driver will only operate the clutch during starts, pit stops and if he spins - gear change operation is automatic - and he must learn to control the clutch take-up precisely, even though he is denied the force feedback he would be used to with a foot-operated clutch. Wear of the clutch, which affects the take-up point during engagement, is compensated for automatically.
Neutral button. In sequential change gearboxes, whether operated by a lever or steering wheel paddles, it is notoriously difficult to select neutral. The position of the selection mechanism does not indicate the gear selected, as an H-pattern shift does. Motorbikes, which also have sequential gearboxes, have this problem. In order to try and avoid stalling while groping for neutral after a spin or during a pit stop, a button is mounted on the steering wheel which, when pressed, automatically sequences the gearbox into neutral.
Skip-shift. The regulations permit multiple gear-changes as a result of a single command by the driver. These will always be downshifts (the equivalent of skip-shifting a manual gearbox), and must only be commanded under conditions that would engage the lower gear without over-revving the engine. Commanding it too early must result in either the box being left in the original gear or neutral - very unsettling for the driver. Some drivers however, like to have a button on the wheel to skip-shift down several gears e.g. 7th to 2nd for a slow corner at somewhere like Monaco, where gear changing can get very busy.
Radio. The Press to Transmit (PTT) button for the car-to-pits radio is usually fitted to the steering wheel. The driver must operate this switch in order to be able to talk to the team, while in the car.
Pit Lane Speed Limiter. Exceeding the Pit Lane Speed Limit (80kph in practice and qualifying, 120kph during the race) results in a hefty fine during practice and qualifying ($250 per kph above the limit; more for a second offence), and a Stop-Go penalty during the race. It did not take long for the drivers to demand a technical solution to speeding in the Pit Lane. All cars are fitted with a button on the wheel that imposes a speed limit to the car. It can only operate in 1st, 2nd and 3rd gears, must be selected and de-selected by the driver, and only used in the Pit Lane - these regulations are to ensure that it is not used on the track as a crude traction control system.
Pressing the button changes the engine rev-limit, according to the gear selected and the limit in force at the time. Drivers must remember to press it before crossing the pit entry line, as it does not instantly slow the car to the correct speed, as some drivers once thought!
In the race, this button may also operate the latch on the refuelling flap. When it is pressed, the flap pops open ready for refuelling, and it closes again when the speed limiter is de-selected by the driver as the car rejoins the circuit. Some cars have a separate button for the flap.
Brakes. One of the most important adjustments that a driver has to make to a car while running, is brake balance. Following the banning of the McLaren "fiddle brake" system, the regulations were tightened right up, faced with the prospect of all sorts of brake distribution systems. Brake balance, front to rear, is critical to the stability of a racing car during the braking and turn-in phase; too much rear brakes will tend to cause the car to spin; too much front and it will not turn in. Settings will change as the fuel load lightens, the track grip changes, and particularly if it rains. So critical is it that it is not feasible for the race engineer to determine the correct setting; the driver must set it up by feel.
Brake balance is adjusted by altering the leverage ratio between the pedal and each master cylinder. For years the driver has been able to adjust the balance by rotating a knob in the cockpit, driving a flexible cable that moves the pedal pivot to a new position on the balance bar. Such a system requires the driver to reach down into the cockpit, usually with his left hand, and turn the knob. Turning the knob the wrong way because the sign was invisible down in the cockpit, has caused more than one accident. To adjust brake balance from the steering wheel requires an electronically signalled servo-system. Not all teams have gone down this route, but some have. One regulation that must be adhered to is that it must not be possible to make adjustments while the brakes are applied - that would be a sort of active brake balance. It is virtually physically impossible for the driver to adjust the balance, with a mechanical system, while the brake pedal is loaded, but with a servo system it would undoubtedly be possible.
A knob, with several numbered switch positions, would be used for brake balance adjustment.
Engine air-fuel ratio (Mixture). It is permissible to adjust the air-fuel ratio of the engine, with a maximum of three settings. Steering wheels are fitted with a three-position knob for this purpose. The mid-position is likely to be the best compromise between power and economy, with a richer setting for maximum power for overtaking and a leaner setting for stretching out the fuel load if necessary.
RPM limit. It is permissible to change the rev-limiter setting, provided all the settings are above the RPM for peak power. It is unlikely that many drivers would be provided with a knob for this purpose, but a button to occassionally raise the rev-limit for overtaking might be an option.
Electronically controlled systems. All Formula1 cars are fitted with electronically controlled engine fuelling and ignition, differential, clutch, drive-by-wire throttles, and power steering. In 1998, the Ferrari steering wheel was a mass of multi-position knobs for adjusting settings, maps and even algorithms for these systems. From 1999, the regulations ban the driver from making adjustments to any of these systems while the car is in motion (in the case of the clutch, while the engine is running). As the engineers can change the settings once the car is stationary in the pits, most of the knobs disappeared. However, when it rains, the ideal settings for the differential and engine response (engine fuel and ignition map and throttle progression) are very different from those best suited to dry conditions. Rain is usually accompanied by a pit stop for wet tyres and so while the car is stationary in the Pits, the driver may legally change settings, changing them back when he next stops for dry tyres.
Under wet conditions, the last thing a driver wants is a sudden increase in torque just as he is feeding in the throttle coming out of a corner. In the dry the same is true, but the throttle openings and speeds (and therefore probably engine RPM) are both greater. Drive-by-wire characteristics and the engine map can both be tuned to make the driving task easier in slippery conditions. The schedule of differential locking under the three critical phases - braking, turn-in and power-out of the corner - is set up in software. Wet conditions will probably need greater lock-up under braking to give stability, and under power-out to avoid the inside wheel spinning, while less lock-up during the turn-in phase, to minimise understeer, may be desirable. If the driver can swap between settings, depending on whether dry or wet tyres are fitted, he will have an advantage. Not all teams offer this facility to their drivers, only those that have the resources to develop alternative settings and intelligent drivers. It is noticeable that Ferrari spend a considerable time testing in the wet at Fiorano, where they have the facility to spray water on the circuit, and that Schumacher has more knobs on his steering wheel than drivers in other teams, and that he is very quick in the wet.
Displays. Gone are the days when drivers were presented with a rev-counter and a variety or other gauges telling him oil and water temperatures and maybe pressures. The RPM of today's 18,000rpm engines changes too fast to be of any use to the driver as an aid to changing gear. Instead, a series of LED's flash on in sequence to tell him when to change up a gear, automatically adjusting to different rev-limits. Intelligent software monitors all the significant parameters of the engine, gearbox and hydraulic systems, and any deviation from normality is warned to the driver by a message on an LCD display or by illuminating a light (the engineers in the pit garage receive all the data by telemetry, and will be aware of the situation simultaneously). The driver can then select, via yet another button, a display that gives him more information about the problem, and he will be able to monitor the important parameters, relevant to the ailing system. The driver will be alerted to a potentially catastrophic situation, with a more urgent display (red, flashing light or flashing LCD) e.g. the engine being about to blow-up, and no doubt an urgent message from the pits will be received over his radio.
The LCD displays can also be configured in a wide variety of ways, according to the requirements of the driver, and indexed through the modes by pressing the display-mode button. This operates in much the same way as mobile phones can be indexed through displays of information about callers, messages, phone book etc. The driver normally has it set up to display the lap time for the last lap, triggered automatically by his trackside beacon.
All these switches, buttons, knobs, lights and displays, packed into a hollow, CFRP steering wheel, results in dense wiring inside the wheel. It would be virtually impossible for all these wires to connect individually to the computer(s), via a wiring loom inside the steering column and a multi-way disconnect plug to allow the wheel to be removed. Formula1 cars use networked electrical systems, with each module - engine, gearbox, differential, power-steering, hydraulics, steering wheel, on-board computers, race engineer's notebook computer etc - being a node on the CAN network. Thus the steering wheel only needs electrical power and the CAN data bus to connect it to the car. Inside the steering wheel is a microprocessor, which communicates with the network and controls all the switches, lights and displays on the wheel.
The software inside the steering wheel, and the software in the car and engine computer(s) that it communicates with, are among that which is most closely scrutinised by the FIA's software "police". Given its potential to change the largely banned settings of the car and engine, the steering wheel has become an extension of the drivers hands. What he can do with it is watched very carefully.