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Discussion Starter #1
Here's a thread from an Audi site on Titanium Brakes:

http://forums.rs246.com/forums/showflat.ph...33990#Post35022

I made comparisons to some other metals down near the bottom. Also I should have posted there that at least 80% of friction generated with brakes is Adherant friction. Because the rotors they are discussing are etched to increase friciton I would imagine they're primarily abrasive. Abrasive compound pads and rotors typically don't last as long, and are extremely temperature limited. Very bad idea for long lasting rotors. Though I think they might stop you REAL quick once or twice, and they are lightweight so your handling would increase quite a bit ... just a matter of long term reliability, and the fact that Titanium isn't nearly as good a conductor as Iron. Oh well ... interesting idea, perhaps it works better than the data would imply?

All thoughts welcome.

Cheers,
Dubbya
 

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Link isn't getting the thread for me. Anyways, I have never ehar of using titanium for brakes before. I do know that some aircraft have beryllium (probably not spelled correctly) and newer aircraft use carbon for brakes.

Of course, for aircraft, you need quite awesome stopping power. A C-5 Galaxy has 24 brakes. Each has, if I remember correctly, 6 rotors, 7 stators and 8 pistons. You need quite a bit of stopping power for a plane, with cargo and normal landing fuel, that weighs a mere 500,000 lbs or so.
 

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Discussion Starter #3
Their site appears to be down for a bit. I'll post some comparisons I posted there between Iron and various other metals in relation to hardness thermal capacity, thermal conductivity etc ...

Coefficient of Linear Thermal Expansion
Fe: 1.176E-05cm/cm/°C (0°C)
Al: 2.39E-07cm/cm/°C (0°C)
Be: 0.0000116cm/cm/°C (0°C)
W: 0.0000046cm/cm/°C (0°C)
Si: 0.0000042cm/cm/°C (0°C)
C: 0.0000021cm/cm/°C (0°C)
Ti: 8.41E-06cm/cm/°C (0°C)
Cu: 0.0000166cm/cm/°C (0°C)

Thermal Conductivity
Fe: 0.802 W/cmK
Al: 2.37 W/cmK
Be: 2.01 W/cmK
W: 1.74 W/cmK
Si: 1.48 W/cmK
C: 1.29 W/cmK
Ti: 0.219 W/cmK
Cu: 4.01 W/cmK

Density
Fe: 7.874g/cc @ 300K
Al: 2.702g/cc @ 300K
Be: 1.848g/cc @ 300K
W: 19.35g/cc @ 300K
Si: 2.33g/cc @ 300K
C: 2.26g/cc @ 300K
Ti: 4.54g/cc @ 300K
Cu: 8.96g/cc @ 300K

Elastic Moduli

Fe:
Bulk: 170/GPa
Rigidity: 82/GPa
Youngs: 211/GPa

Al:
Bulk: 76/GPa
Rigidity: 26/GPa
Youngs: 70/GPa

Be:
Bulk: 130/GPa
Rigidity: 132/GPa
Youngs: 287/GPa

W:
Bulk: 310/GPa
Rigidity: 161/GPa
Youngs: 411/GPa

Si:
Bulk: 100/GPa
Youngs: 47/GPa

C:
Bulk: 33/GPa

Ti:
Bulk: 110/GPa
Rigidity: 44/GPa
Youngs: 116/GPa

Cu:
Bulk: 140/GPa
Rigidity: 48/GPa
Youngs: 130/GPa


Hardness

Fe:
Brinell: 490 MN m-2
Mohs: 4
Vickers: 608 MN m-2

Al:
Brinell: 245 MN m-2
Mohs: 2.75
Vickers: 167 MN m-2

Be:
Brinell: 600 MN m-2
Mohs: 5.5
Vickers: 1670 MN m-2

W:
Brinell: 2570 MN m-2
Mohs: 7.5
Vickers: 3430 MN m-2

Si:
Mohs: 6.5

C:
Mohs: 0.5

Ti:
Brinell: 716 MN m-2
Mohs: 6
Vickers: 970 MN m-2

Cu:
Brinell: 874 MN m-2
Mohs: 3
Vickers: 369 MN m-2


Melting point
Fe: 1535°C 2795°F
Al: 660.25°C 1220.45°F
Be: 1278°C 2332°F
W: 3407°C 6165°F
Si: 1410°C 2570°F
C: 3500°C 6332°F
Ti: 1660°C 3020°F
Cu: 1084.6°C 1984.3°F


Specific Heat
Fe: 0.44J/gK
Al: 0.9J/gK
Be: 1.82J/gK
W: 0.13J/gK
Si: 0.71J/gK
C: 0.71J/gK
Ti: 0.52J/gK
Cu: 0.38J/gK

I don't want to get into too much detail about analyzing all that. But Beryllium appears to be the best overal brake material as it's lightweight, strong, good thermal conductor, and has a high melting point. Carbon is a reasonably good thermal conductor, very light, reasonably strong, but is quite soft and wears easily. Making it good for racecar brakes and not much else. Silicon is better than iron but worse than Beryllium, and Tungsten, while VERY heavy (heavier than gold) is very hard, has a very high melting point, and conducts quite well. Might be good for truck brakes or something similar where wear is very important. Titanium appears to be a very poor brake material.

Anyway ... hope this is usefull.

Cheers,
Dubbya

Edit: I added copper at the last second. It appears to be reasonably good. It conducts almost twice that of Beryllium.
 
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