Re: Al Rotors

[Noel Jason Bolduc <astros@WPI.EDU>]

> > >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). 
> 
> What does the temperature profile look like, though?  This doesn't
> take into account the far-superior thermal conductivity of Al, which
> will also dictate how efficiently the venting will work.
> 
> Besides, I would guess that this is dwarfed by the savings in 
> angular momentum due to reduced mass.
> 
 
Being a Chemical Engineering student i follow all the conversation about 
the physical properties of Al and Fe (iron).  What comes to my mind, 
though, is that Al is relatively speaking a very soft metal.  Unless an 
alloy were formed to greatly increase its durability, an Al rotor 
wouldn't last you very long at all, due to wear.  Aside from that though, 
i would agree with the second guy here.  Al would dissipate the heat 
much, much faster than Fe due to its thermal conductivity.  It's the same 
with an aluminum block engine, it gives off heat faster and is easier to 
cool. 
						-Noel