[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

*To*: quattro@coimbra.ans.net, STEADIRIC@aol.com*Subject*: Re: A6 styling re A4/A8*From*: rsco@lubrizol.com (Robert S. Cohen)*Date*: Mon, 12 Feb 1996 14:42:40 -0500*Sender*: quattro-owner@coimbra.ans.net

STEADIRIC wrote- >>Sure, less is better, but c'mon man! >>You tryin' to tell me that the relative rotational mass of the prowler >>brakes Vs that of the viper brakes accounts for the better braking *more* >>than does the relative mass of the vehicle and relative amounts of swept >>area? > >Yes I am, do the math....... Don't know the math, LEARN IT if your going >to pontificate. I know it....... Graydon knows it........ Scott knows >it......... FALLACIOUS ARGUMENT ALERT. I'm gonna pontificate. Where's my mitre? AHEM, Eric, the rest of us don't _ know_ it! It is not manifestly obvious to me how this can be the case. Perhaps you could share the math with the rest of us....? Before you accuse me of being lazy, I've briefly discussed the problem with a physicist here. the upshot of our admittedly naive investigation was that aluminum rotors would probably make for somewhat diminished stopping due to the specific heat of the (light) aluminum rotor vs the (heavy) iron rotor. Decelerating at the same rate, the aluminum rotor will get 40% hotter. Al Fe Density g/cm^3 2.7 7.86 Sp. Heat J/(g*degK) .9 .44 with these numbers, I calculate that for equal volumes (we simply swap aluminum for iron) the iron rotor will be 2.9 times more massive. for equal masses, the iron rotor will heat 1 degK for each .48 degK the aluminum rotor heats. 2.9*.48= 1.392. So, a rotor of Al equal in volume to the original Fe rotor will be increase in temperature 40% more than the iron rotor for a given deceleration (energy input). There. I did the math. regarding the kinetic energy of the rotors themselves, which I think is the factor Eric is alluding to, it is (m w^2 r^2) I think, where m is the mass of the ring, w is the angular velocity, and r is the radius of the idealized ring. Frankly, I (waving my hands) think this will pale in comparison the energy of a 3000 lb car travelling at 100 kmph or so. End of Audience. Get out of my basilica..... ;-) > >Later! > > >Eric Fletcher >'87 5KCSTQIA2RSR2B > >STEADIRIC@aol.com _____________________________________________________________________________ Robert S. Cohen NewMedia Inc., 503 E 200th Street, Cleveland OH 44119-1545 voice 216.481.7900 fax 216.481.1570 The Lubrizol Corp., 29400 Lakeland Blvd MS 228, Wickliffe OH 44092 voice 216.943.1200 x 2012 fax 216.943.7215 Email: rsco@lubrizol.com rsc2@po.cwru.edu cohen@nmedia.com ____________________________________________________________________________

**Follow-Ups**:**Al rotors***From:*"Graydon D. Stuckey" <graydon@apollo.gmi.edu>

- Prev by Author:
**What's the Holdup? was: oil info** - Next by Author:
**Re: Scrick cams/ A4-tested** - Prev by thread:
**Re: A6 styling re A4/A8** - Next by thread:
**Al rotors** - Index(es):