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Professional Motorsport Data Analysis: Brake Temperature

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Brake Temperature

07.42

00:00 - Being able to monitor brake temperature is very helpful when trying to understand both the performance and the reliability of our braking system.
00:08 Traditionally, one way to understand the braking temperature range is to apply temperature sensitive paint to the discs.
00:15 This paint generally comes in a set with different paint colours for each temperature range and when this paint is heated to a pre defined temperature, that area will change colour.
00:26 Now while this is helpful to understand the maximum temperature our discs are reaching, it gives us very little detail about what's happening on track, only a single maximum.
00:34 The paint also needs to be continually reapplied over time as it reacts to the temperature.
00:41 Each disc and pad combination has a temperature window within which it's both safe and can operate at peak performance and we can use the surface temperature of the brake disc to understand where we are in the range at all points on track.
00:54 This is not only useful when reviewing the log data after a run but can be made use of live, both in the car by the driver and in the pits by the engineers if live telemetry is available.
01:06 The most common sensing method is to point an infrared sensor at the surface of each brake disc which gives us a real time surface temperature measurement.
01:15 The infrared sensors used for disc temperatures are designed specifically for this purpose and have a sufficient temperature range as well as the ability to survive within close proximity to the brakes.
01:26 Different disc materials such as ferrous vs carbon discs for example, also have a different surface emissivity which requires matching the sensor and sensor calibration to the application.
01:37 So what factors do we need to consider when looking at our brake temperature data? Starting with safety and reliability, there's a maximum temperature each disc is safe to be run at.
01:48 The brake disc is an extremely highly stressed component, not only being subject to enormous mechanical stress from the braking forces, but also from thermal stress.
01:57 The material used in the brakes will determine the safe temperature range which is information we can easily get from our brake supplier.
02:04 This can vary quite a lot over different tyres of ferrous discs as well as carbon.
02:09 In many cases, the minimum temperatures the brakes are running at when they're applied can be just as critical as the maximum.
02:16 This means that the brakes must be gradually warmed to avoid excessive thermal shock and stress.
02:22 Another safety consideration for minimum temperature is the coefficient of friction.
02:27 If the brakes haven't been gradually brought up to temperature, the coefficient of friction between the disc and the pad, may be a lot lower than normal which will translate to the car not being able to slow down as quickly.
02:39 These sorts of characteristics tend to get more extreme as the components we use diverge further away from OEM type discs and pads.
02:48 OEM components intentionally tend to provide a relatively consistent performance even from cold at the expense of peak performance at high temperatures.
02:57 From a performance perspective, we care about the temperature range because it affects the coefficient of friction between the pad and the disc.
03:04 It is not simply the peak coefficient of friction we're interested in getting, as we not only want good braking effectiveness but also consistency so the driver can have repeatable performance throughout the lap, stint and race.
03:18 In the situation where the coefficient of friction is varying significantly throughout a lap, this can often cause brake bias issues even if the brake pressure bias ratio between the front and the rear is constant.
03:31 The torque ratio from varying friction levels can be changing drastically.
03:36 Most often, this results in unpredictable wheel locking and instability issues.
03:41 In this case, it may be preferable to aim for a temperature range that gives a consistent friction coefficient rather than the peak.
03:49 It's crucial that we consult with our braking supplier here as they can give us the appropriate temperature ranges for each end of the car for both safety and consistent performance.
03:59 Using the brake temperature data we can use the peaks and troughs for each end of the car to tune the system to get the temperature ranges we want.
04:08 Clearly, the physical components such as the discs and the pads, will have a large impact on the temperature ranges and the rate of change of temperature.
04:16 Assuming these are appropriate for our application, then we can focus on the tool we use the tune the temperatures of the brakes which is the cooling.
04:24 In a motorsport context, this is done through directly air through ducts and varying the flow through these ducts with different amounts of blanking.
04:32 The amount of blanking we run will be affected by many things, our ideal temperature range, temperature of the day, session type, circuit type, street circuits tend to give us less cooling compared to an open circuit for example, as well as the proximity we are running to other cars.
04:50 For example, in the case of qualifying where we know we need to extract the maximum performance over a single lap, it's typical to add blanking to reduce airflow over the front brakes.
05:01 One of the reasons for doing this is that running more blanking typically also results in more downforce at the front of the car.
05:08 During qualifying, the brakes also have less time to reach peak temperature, compared to running consistently lap after lap in a race.
05:15 Running more blanking, helps to get the brakes to the correct temperature range more quickly.
05:21 Throughout a race weekend, we use the brake temperature data from previous sessions to predict how much blanking we'll either need or can get away with, depending on what we're trying to do.
05:32 However, during a race, where the brakes are having to sustain many laps consecutively, we would often be running less blanking to maintain the target temperature range, as well as having some safety margin.
05:44 In the case of running behind the safety car during a race, the brake temperature will drop a long way and by measuring the brake temperature, the drive can get useful feedback to know if they're keeping the brakes adequately prepared for the restart.
05:57 If the brakes aren't kept in a suitable temperature range, it'll hurt the braking performance on the restart.
06:02 Another thing brake temperature data, particularly when it's available in real time is useful for, is bedding of the discs and pads.
06:09 When either the pad, disc or both are new, they need to be bedded together.
06:14 While some of this is about physically matching the face of both components to each other, it's more about the initial chemical reaction and the transfer of friction material that takes place with the interaction of dissimilar materials.
06:26 The bedding process is critical, both for longevity and performance of the brakes.
06:31 WIth temperature being such an important part of any chemical reaction, being able to monitor the temperature during the bedding process can be very helpful.
06:40 Again, the brake supplier will be able to recommend the correct bedding procedure and temperature targets.
06:47 It's also worth considering, particularly when you're out testing, doing many short back to back runs, warming up and down of your brakes gradually.
06:54 A lot of damage tends to happen to brakes when the car is stopped in the pits with brakes that haven't been adequately cooled.
07:02 When this happens, you end up with uneven temperature distribution and potentially harmful disc to pad chemical interactions.
07:09 When possible, give yourself a gentle cool down lap where you only use the brakes gently.
07:15 Like many of these modules, brake temperature is a big subject.
07:18 And there's a 1000 different rabbit holes we could fall down.