Harmonic Drive FHA-Cmini Series, Manual

Page: 41 / 68

2-3 Verifying and examining load weights
Selection guidelines
2-4
1
2
3
4
5
6
7
8
9
10
11
Apx
Se
lec
tion gui
de
lin
es
Calculating average loads (average radial and axial loads, average output
rotational speed)
When the radial and/or axial loads vary during motion, calculate and verify the life of the cross roller
bearing converting the loads to their average values.
Radial load coefficient and axial load coefficient
Table 2: Radial load coefficient (X), axial load coefficient (Y)

Formula (5) X Y
.5
1 ≤
La)/dp · Fa R) (Lr 2(Fr Fr
Fa
av av av
av
+ + +
1 0.45
1.5
La)/dp · Fa R) (Lr 2(Fr Fr
Fa
>
+ + +
av av av
av
0.67 0.67

Formula (2): Average radial load (Frav)
n n
10/3
n n n
10/3 10/3
10/3
t n ··· t n t n
Fr t n ··· Fr t n Fr t n
Fr
2 2 1 1
2 2 2 1 1 1
+ + +
+
=
av
The maximum radial load in section t
1
is given by Fr
1
,
while the maximum radial load in section t
3
is given by
Fr
3
.

Formula (3): Average axial load (Faav)
n n
10/3
n n n
10/3 10/3
10/3
t n ··· t n t n
Fa t n ··· Fa t n Fa t n
Fa
2 2 1 1
2 2 2 1 1 1
+ + +
+
=
av
The maximum axial load in section t
1
is given by Fa
1
,
while the maximum axial load in section t
3
is given by
Fa
3
.

Formula (4): Average output rotational speed
(Nav)
n
n n
t ··· t t
t n ··· t n t n
N
2 1
2 2 1 1
+ + +
+ + +
=
av
Symbols used in the formulas
Fr av
Average radial load N(kgf)
Refer to the
average load.
Fa av Average axial load N(kgf)
Refer to the
average load.
Lr ,La ———— m See Fig.1.
R Offset amount mm
See Fig.1 and
Table 1.
dp
Pitch circle diameter
of a roller
mm
See Fig.1 and
Table 1.
Time
+
Fr
1
Fr
2
Fr
3
R
adi
al
load
–
Time
O
ut
pu
t r
ot
at
io
nal
spe
ed
n
1
n
2
n
3
t
1
t
2
t
3
Fig. 2: Illustration of load
i i
+
–
Time
A
xia
l lo
ad
Fa
1
Fa
2
Fa
3
+
–