11.2 Reference Information for Servomotor Capacity Selection
11.2.3 Conversions between Engineering Units and SI Units
11-6
11.2.3
Conversions between Engineering Units and SI Units
The following table provides the conversion rates between engineering units and SI units for
typical physical quantities required for capacity selection.
General Formula When
Rotary Shaft Is outside
Rotating Body
GD
2
= Weight
×
(Diameter of rotation)
2
Continued from previous page.
d
Center of gravity
Rotary shaft
: Diameter of rotation when shaft that is parallel to rotary shaft and
runs through center of gravity virtually operates as a rotary shaft
General formula for diameter of rotation when rotary shaft Is
outside rotating body
=
+ 4
D
2
2
D
1
2
2
d
D
1
Information
Quantity
Engineering Unit
SI Unit
Conversion Factor
Force or load
kgf
N
1 kgf = 9.80665 N
Weight
kgf
–
The numerical values are the same for mass in
the traditional unit and the SI unit.
(The mass SI unit Wkg is used for objects in
the
W
kgf traditional unit.)
Mass
kgf
s
2
/m
kg
Torque
kgf
m
N
m
1 kgf
m = 9.80665 N
m
Inertia (moment of
inertia)
gf
cm
s
2
kg
m
2
1 gf
cm
s
2
= 0.980665
×
10
-4
kg
m
2
GD
2
kgf
m
2
kg
m
2
Relationship between GD
2
(kgf·m
2
) and
moment of inertia (kg·m
2
)
=
J
GD
4
J
2
J
