Setting
up Compax3
C3I20T11 / C3I32T11
280
192-120103 N13 C3I20T11 / C3I32T11 December 2010
Rotary two mass system
M
M
1
1
M
M
2
2
J
J
1
1
J
J
2
2
D
D
The shown system corresponds for instance to a motor with a flywheel coupled via
a shaft. Hereby J1 corresponds to the motor moment of inertia and J2 to the
moment of inertia of the flywheel.
Calculation of the resonance frequencies in the rotary system with a hollow
shaft as elastic coupling element
+
⋅
⋅
⋅
=
2
1
Re
1
1
2
1
J
J
D
f
s
π
2
Re
2
1
J
D
f
s
A
⋅
⋅
=
π
(
)
l
r
r
G
dr
r
l
G
D
I
A
r
r
A
I
⋅
−
⋅
⋅
=
⋅
⋅
⋅
⋅
=
∫
2
2
4
4
3
π
π
G
Shear modulus of the material used [N/m²]
(e.g. approx. 80750N/mm² for steel)
D
Torsional rigidity in [m/rad]
rA
Outer radius of the hollow shaft
rI
Inner radius of the hollow shaft
l
Length of the hollow shaft
Linear two mass system
Resonance frequencies in the linear system
+
⋅
⋅
⋅
=
2
1
Re
1
1
2
1
m
m
D
f
s
π
2
Re
2
1
m
D
f
s
A
⋅
⋅
=
π
D
Rigidity in [N/m]
m1
e.g. motor mass
m2
e.g. load mass
