- #1
feak1
- 4
- 1
Hi everyone !
i want to find the equivalent mass of a car rotating parts and i came across this site which provides some cars formula : http://www.thecartech.com/subjects/auto_eng/car_performance_formulas.htm
So far i understand almost everything until i get to the part where inertia resistance is calculated as an equivalent mass of rotating parts. Here is the quote :
meq = equivalent mass of rotating parts [kg]
= [ Iw (1/rw)2 + Ip hf (if /rw)2 + Ie ht (if ig / rw)2]
where:
Iw = polar moment of inertia of wheels and axles ≈ 2.7 [kg m2]
Ip = polar moment of inertia of propeller shaft ≈ 0.05 [kg m2]
Ie = polar moment of inertia of engine ≈ 0.2 [kg/m2] + polar moment of inertia of flywheel and clutch ≈ 0.5 [kg m2]
hf = mechanical efficiency of final drive
ht = mechanical efficiency of transmission system (hg x hf)
ig = gearbox reduction ratio [ig1 or ig2 or ………….]
if = final drive reduction ratio
rw = tire radius [m]
Now what i don't understand is the first part : Iw (1/rw)2 ?
Why do we divide 1 by the wheel radius?? is this a mistyping mistake??
Can someone explain this to me please?
Thanks !
i want to find the equivalent mass of a car rotating parts and i came across this site which provides some cars formula : http://www.thecartech.com/subjects/auto_eng/car_performance_formulas.htm
So far i understand almost everything until i get to the part where inertia resistance is calculated as an equivalent mass of rotating parts. Here is the quote :
meq = equivalent mass of rotating parts [kg]
= [ Iw (1/rw)2 + Ip hf (if /rw)2 + Ie ht (if ig / rw)2]
where:
Iw = polar moment of inertia of wheels and axles ≈ 2.7 [kg m2]
Ip = polar moment of inertia of propeller shaft ≈ 0.05 [kg m2]
Ie = polar moment of inertia of engine ≈ 0.2 [kg/m2] + polar moment of inertia of flywheel and clutch ≈ 0.5 [kg m2]
hf = mechanical efficiency of final drive
ht = mechanical efficiency of transmission system (hg x hf)
ig = gearbox reduction ratio [ig1 or ig2 or ………….]
if = final drive reduction ratio
rw = tire radius [m]
Now what i don't understand is the first part : Iw (1/rw)2 ?
Why do we divide 1 by the wheel radius?? is this a mistyping mistake??
Can someone explain this to me please?
Thanks !