27
Formulae
Calculation example
Pitch length and drive centres with allowances
Nominal centres a
nom
a
nom
= K + K
2
–
K= – (d
wg
+ d
wk
)
a
nom
=
206.251 + 206.251
2
– = 408.71 mm
K = – (190.98 + 79.58) = 206.251 mm
(d
wg
– d
wk
)
2
8
(190.98 – 79.58)
2
8
Centre distance allowances for installation and
tensioning a
nom
see Table 5.1, page 43;
installation: allowance y
tensioning: allowance x
y= y
1,2,3
depending on which pulleys are flanged
x
a
min
≤ a
nom
– y a
nom
+ x ≤ a
max
With fixed centres, a tension idler is necessary,
see page 45
Flanges on small pulley y
2k
= 10 mm
x ≥ 0,32 + 0.002 · 408.71 1.14 mm x ≥ 1.2 mm
a
min
≥ 398.7 409.9 mm ≤ a
max
L
wSt
4
1250
4
3.4 ZRM/ZRP drive design
Drive calculation for
optibelt
ZRM/ZRP timing belts, z
emax
= 12
* Please send for our special brochure: Centre distance values for Optibelt timing belts.
Order example
Timing belt and pulley designation
Quantity, type, width, section, pitch length
(special constructions or features if required)
1 Optibelt ZRM timing belt 50 T10/1250
1 Optibelt ZRS pulley 66 T10/25-2 Type 6F
1 Optibelt ZRS pulley 66 T10/60-0 Type 6
π
8
π
8
Values for F
v
, e
v
and S
a
see page 28For calculation and setting of tension,
see page 28
→
Power P
spec
per tooth in mesh, 10 mm belt width
and one tooth of small pulley from Table 3.5, see
page 29
P
spez
(Profil, n
k
)P
spez
(T 10, 1450 min
-1
) = 6.850 W/cm
z
k
6
( )
d
wg
– d
wk
a
nom
25
6
Calculation for belt width b
th
, b
st
b
th
=c
3
from Table 2.3, page 13
Standard belt width b
St
page 16 to 19, b
St
≥ b
th
Drive width within specification?
Actual drive service factor c
2vorh
c
2vorh
= c
2
b
th
= = 47.8 mm c
3
= 1.0
b
St
= 50 mm for section T10 see page 17
Total pulley width B = 66 mm, face width b
1
= 56 mm
c
2vorh
= 1.8 = 1.88
Calculation of
z
enom
, z
e
in mesh with small pulley,
z
emax
= 12, to be taken into account
z
enom
≥ z
emax
z
e
= z
emax
z
enom
< z
emax
z
e
= z
enom
z
enom
=3 –
11 < z
emax
z
e
= 11 z
enom
round off
z
enom
= 3 – = 11.4
Timing belt and pulley width
b
St
b
th
50
47.8
190.98 – 79.58
408.71
()
P
B
· 10000
P
spez
· c
3
· z
k
· z
e
9.0 · 10000
6.850 · 1.0 · 25 · 11
→
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