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Dying Man Condition: How Strong Do Brake Components Need to Be?
How strong do brake components need to be?
They need to withstand many load conditions with a lot of variation in temperature, environment, fatigue, etc.
For this post, I’m only focusing on one specific area: minimum burst pressure.
This is not something that is directly related to a level of deceleration. It would be easy to carry out system calculations and say that the minimum burst pressure should be that seen for a specific level of deceleration, plus a factor of safety. But the driver should be capable of pushing much harder on the pedal than this.
Therefore, the minimum burst pressure of brake components must be related to pedal effort.
This is where the “dying man condition” comes in.
Let’s imagine that a tall, heavily built person is driving a car that is speeding toward a brick wall. He’s pushing as hard as he can on the brake pedal, clutching onto the steering wheel, while almost in a standing position to use all his weight and the mechanical advantage of pushing against the back of his seat. Also, as they are in fear of crashing and dying, adrenaline is pumping, giving them extra strength. The fact that ABS will have already kicked in (or the wheels have locked) makes no difference; they're still pushing harder.
Now, let’s imagine that they've now crashed. As a brake engineer, I don’t want this to have been because of brake failure. This means that I need the brake components to withstand a higher pressure than the tall, heavily built person can apply at the pedal.
Using this, along with the pedal box and actuation specification (pedal and boost ratios, etc.), you can work out the minimum burst pressure that the component will need to withstand and add whatever factor of safety is appropriate.
Technical article provided by Alcon Components Ltd. Published by AlconKits with permission.