BrakeDiscInertia=

lordpantsington

// inertia per meter of thickness
Click to expand...
Sure the comment says something, but what exactly? IDK.

Roughly, I've seen values around this used 0.700.
The Panoz has values from ~2 to ~6.

So off to the solid modeling program I go.

I get
Ixx and Iyy as .078 kg m^2
and Izz as .149 kg m^2

Disc is 350mm in dia. and 33mm thick.
Inner radius is 0.109m

Rear is 330mm/ 28mm
Inner radius is 0.1035 m

Ixx=Iyy=0.070 kg m^2
Izz=0.133 kg m^2

Z is the rotational axis.

Numbers aren't close, but my thickness is also not a meter.
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If I were to default to basic shapes, I would use a tube:
Iz=0.5*mass*((RadiusInner^2)+(RadiusOuter^2))

or with density:

Iz=0.5*pi*Thickness*Density*((RadiusOuter^4)-(RadiusInner^4))

Density of cast steel=7850 kg/m^3

Solving for Iz using 1 meter of thickness gives 9.824... kg m^2

___________________________________________________
If "Solid Izz"/"Target Izz"=.033/1,
.033* TIzz= SIzz
SIzz/.033=TIzz=4.515 kg m^2 (a very Panoz like number).

Your thoughts are welcome on the subject.
 
Don't forget to also calculate inertia of a disc bell (not only for a disc itself) ;-)

I use 12.0 for 380mm and 9.0 for 350mm iron cast discs. For carbon - half of that. Those are rougly calculated values so you can use them.


BrakeDiscInertia is for inertia for 1m of thickness. When calculate it, keep in mind about cooling vanes - so you can't do it for a solid piece of material.

rF takes value from BrakeDiscInertia and multiply it by disc thickness defined in BrakeDiscRange
 
I see I've put this in the wrong section:eek:

12.0/9.0 kg
or 12.0/9.0 kgm^2
?
 
Inertia is an object's resistance to change it's state of motion (when you want to move it, when stationary or speed up or slow down when already moving) and is related to object's mass and how it is "layed down" within it, so shape - yes, but also how that shape is "filled" with object's mass.


If what you said would be true, then a paper box shaped as a car would have the same inertia as real car, made of steel... which is not true of course :)
 
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