Rotor Convection Coefficient

[NoodelT65]

Hello my name is Theo and I'm the brake lead for San Diego State University's car. I have done some calculations to predict the temperature of the rotors during endurance. I'm using the equations that predict convection coefficient and repeated braking temperature; found in Rudolf Limpert's book "Brake Design & Safety" 2nd edition. I have it setup for 70 braking applications from 45 to 0 mph at 1.6g with a convection coefficient of 40 W/m^2K. The rotors are reasonably sized ( cast iron, 653 grams) however the temperature after repeated braking is around 2200 K.

Is 40 a reasonable average value for convection at 45 mph ?

What values have others calculated or measured?

[Hector]

I've seen h values ranging from 20-100 W/(m^2*K) depending on vehicle speed, so your value seems in the ballpark. It may be silly to ask, but are you accounting for all 4 rotors? I have made this mistake more than once!

[MCoach]

That coefficient may be in the ballpark...but I wouldn't believe that temperature value for a second.

I would believe a 1/4 of that value for a single rotor though.

[Z]

I have done some calculations to predict the temperature of the rotors during endurance.
...
What values have others calculated or measured?

Noodel,

Try this "Brakes Revise" thread (http://www.fsae.com/forums/showthread.php?9170-brakes-revise&p=42945&viewfull=1#post42945). Ten pages there covering a lot of what an FSAE brake guy might need to know (the more detailed brake temp calcs are towards the end).

Z