Tyre Testing Sensors – What was seen in Abu Dhabi

The recent Young Driver and Tyre test in Abu Dhabi was a rare chance to see F1 cars in pure testing mode. Although team’s programmes varied, many teams used the test to gather ‘before and after’ data to see the effect of the change to Pirelli tyres. A change in supplier will have an impact not only on tyre usage, but also subtle change in tyre shape which will also affect aerodynamics. Hence we saw teams with a wide range of tyre temperature monitoring and air flow mapping sensors.
Since the introduction of the SECU teams have had to keep their telemetry system separate to the chassis engine management functions. For simplicity the race weekends tend to gather telemetry from the SECU and its homologated sensors. In testing the car is rigged up with dedicated data acquisition hardware and sensors. Some of these are complimentary to the normal range of sensors and are hardly seen, while some systems are fitted only for specific runs aimed at gathering a specific type of data from the car.

Tyre Temperature
Often run on race weekends, normally only for Friday practice, tyre temperature can be measured in several ways. Either by simple infrared sensors looking at specific band of the tyre, cameras monitoring the entire tread width and even wheel mounted sensors measuring the carcass temperature inside the tyre.

Simple Infra Red (IR) Sensors

Force India used simple IR sensors to measure a band of tyre temperature

The simplest sensors are IR sensors, they only look at one band around the tyre and hence they tend to look at the inside tread, due to the suspension camber loading this section of tyre most heavily. These sensors need to be in relatively close proximity to the tyre, and hence packaging can be an issue. They will map a single temperature over time.

On race weekends these can be seen on the floor in front of the rear tyre, a specially design niche in the floor allows a smooth cover to be fitted over the sensor and provide a route for cabling to enter the cars wiring loom around the gearbox engine interface. They are more difficult to package at the front, before the 2009 wide front wing rule the front wing endplate provided a useful location to mount a sensor, albeit one that only measured when the wheel was in the straight ahead position.

Before 2009 the endplate provide a home for a single 2D sensor

FIF1 used the usual floor mounted sensor, plus this endplate mounted one

In testing teams prefer to fit booms to the upright to have a single or array of sensors to steer with the wheel, thus getting data from around the whole lap rather than the few moments when the cars is in a straight line. Both Williams and Force India exploited these booms in the recent test. While red bull had a cable hanging from beneath the front wing, suggesting they had fitted an IR sensor there.

Without the wheel fitted you can see the array of three sensors

Williams used these booms in Abu Dhabi

IR Cameras

Force India also use IR cameras to measure the entire width of tyre temperature

A more recent development has been the adoption of IR cameras to monitor the entire width of the tread through out the lap. Pioneered by McLaren in 2003, using Thermoteknix hardware, the set up has since been adopted by most teams and teams outside of F1. The tiny camera is easy to package and have been used in heavy industry, they are rugged enough for F1 too. As the camera can be focused to look at the entire face of the tyre and from a distance, their positioning much easier. They no longer need to be mounted to the upright to steer with the wheel, as the camera will automatically pick up the edge of the tyre and read the temperature across the full profile. Although the camera sees the entire face of the tyre, it narrows down the data collected to just a strip across the tyre. The resulting data plotted as a graph of time versus position over time.

This provides freedom to mount the camera in one of many locations; they are often inside the mirror casing or in the sidepod fronts for the front tyre camera, while the rear tyres are easiest monitored form a pod mounted on the floor ahead of the rear tyre. Force India fitted their rear tyre camera on the roll hoop fitted inside a dummy FOM camera pod.

Virgin used tyre cameras mounted inside holes in the sidepod

Sauber used a grey 'camouflaged' IR Camera inside the pod wing

Tyre Carcass temperature sensor

Beru have this wheel mounted IR sensor system to measure temperature inside the tyre

Measuring the temperature of the surface of the tyre is one factor; the temperature of the core of the tyre is harder to measure. Simply measuring the temperature of the gas inflating the tyre is not accurate enough. Beru have developed a wheel mounted IR sensor for measuring the inside surface of the tyre.

Tyre shape
A tyres shape is not a simple cylinder, the tyre in fact has a complex shape, as the tyre deforms in both side and front elevation as it contacts the track. This shape changes with steering and speed/downforce. Mapping this complex dynamic shape is important as it will feed back to correlate to the shape seen on the rubber wind tunnels tyres provided by Pirelli and also modeled in CFD. The shape changes are subtle, but equally very different to the Bridgestone and the flow off the front wing and around the rear end will be heavily influenced.

Ferrari fitted a pod inside the diffuser view the tyre

Ferrari modeled the side profile of the tyre in detail using special pods, there were two pods fitted to the left hand of the car, one at the front and another at the rear. The front tyre pod fitted to the upright to turn with the wheel, while the rear pod was placed inside a cutaway section of the diffuser, the exhaust resited to blow away from the sensors. This would have impacted aero but the test results would still be representative enough for the team.

Williams used this 'Rake' an array of pressure taps to map the flow off the wheel

Williams and latterly McLaren also mapped the flow off the front tyre, to do this an array of pressure taps were fitted to a boom that could rise and lower to get a wider map of the flow. These would see how the tyre affected the flow off the front wing; tests were repeated with both tyres using a baseline set up on the car, so as not to confuse the results.

Tyre temperature article http://www.thermoteknix.com/content/english/misc/publications/press/documents/RACETECH.pdf

McLaren Electronic Systems (MES) – Sensors

As well as providing the SECU and other homologated electronics on the cars, MES also produce this range of Tyre temp sensors