New cars on the market now have energy cycles that get the heat energy from your wheels and transform it to electrical energy that goes to the battery. That got me thinking on how much energy is there in the wheels (or actually the brakes of the wheels).
Think about yourself on a bicycle going at a slow and easy speed and then using only your hand around a pole or a tree in order to stop. No brakes, just you. That is a lot of energy, maybe even to much and you will fall over or won’t stop.
That was stooping about 100 kg (220 Lb) going at about 20 km/h (14 Mile/h). without going into math and physics we all can appreciate that stooping a small car (1000 kg – 2200 Lb) going at normal to slow speed (90 km/h – 55 Mile/h) will absorb a lot of energy and generate a lot of heat. doing this over and over again during a routine drive will undoubtedly make the situation even more extreme.
With all the talk about tires (that do transfer energy during acceleration and absorb some during skidding) we should remember that the majority of the braking energy is taken up by a few metal pieces that are your brakes. When they are not of good quality or are too abused they just won’t take the heat and melt away – as shown in this pic and clip.
Maybe we should describe how the brakes brake.. well, in this pic you see the brake disc, it is rotating along with the wheel on the same axle when we operate the brake the disc pads (that are stationary and don’t rotate) come closer to the disc and when they touch the speed (kinetic) energy of the disc changes to heat energy in the pads and disc (by friction) and so the wheels spin slower and the car slows. so you see it’s all a matter of friction, heat and how much of it the brakes (pads normally) can take.
Some example of just how much energy is in such a stopping action is given in the next clip. The power of friction is used in the industry to fuse metals together in a very powerful way – you really don’t want that to happen to your brakes… Friction welding