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stainless steel coffee mug
copper bottom cooking pot
So why haven't the big names in aircraft brakes, such as Cleveland Wheel and Brake, or Rapco, made a stainless steel brake disc?

Even their brake pads come with a warning not to use them with a stainless steel disc. Why? The short answer is that the brake pads may overheat and fail when used on stainless steel because stainless steel is a relative poor heat conductor

Different metals and metal alloys conduct heat at different rates. Stainless steel heats up about 1/3 as fast as steel and 1/25th as fast as copper. This is one reason coffee thermos's are made from stainless steel and not copper; your coffee would cool 25 times faster with copper.

Take a cooking pot for example; A copper bottom pot is 25 times better than stainless at conducting the heat from the burner into the food. From an energy efficiency standpoint, one would rather have a copper bottom cooking pot than a stainless steel bottom cooking pot.

The cook doesn't want hot spots that might burn the food. Copper diffuses the heat faster across the bottom resulting in a more even cooking temperature.

The cook also wants the heat to stay in the pot and cook the food and not leak out the sides or lid. Stainless is 25 times better than copper at preventing the heat from conducting out the sides or lid of the pot. An added benefit is that the handle stays cooler to the touch.

Stainless steel also has the advantage that it doesn't dissolve into the food as does aluminum or copper, so lets put a thin layer of stainless steel on the inside bottom of the pot.

Our energy efficient cooking pot has copper on the outside bottom with thin stainless steel on the inside bottom. Sides and lid are thicker stainless. But since stainless steel is cheaper, good copper bottomed cooking pots are hard to find and expensive.

Like a copper bottom pot, our brake disc needs to be a good heat conductor to take the heat away from the brake pad. The more heat stays at the pad, the hotter the brake pad gets. Everything works fine until you need to do a high performance stop and the hot pad starts to fade and off the end of the runway you go. Stainless steel conducts heat at 1/3 the rate as ordinary steel, so the maximum braking performance is less.


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