13
Correction factors c
6
and c
8
Like the basic service factor c
0
, the factors to be added for pulleys
and idlers c
6
and for start/stop frequency under load c
8
are to be
taken as approximations only. These factors are allowances to
be made for unusual operating conditions and are added where
applicable to the basic service factor c
0
.
Table 2.2: Correction factors c
6
and c
8
for special operating
conditions
Type of operating Designation and Remarks
conditions value of
correction factor
Use of c
6
= 0.2 0.2 per idler
tensioning and to a maximum of
guide idlers 1.0
Start/stop c
8
= 0.1 ... 0.3 depending upon
and/or frequency, up to
reversing approx. 1.5 times
under load nominal torque
with low start-up
torque (e.g. star/
delta connection)
c
8
= 0.3 ... 0.5 depending upon
frequency, above
approx. 1.5 times
nominal torque
with high start-up
torque
The correction factor c
6
applies when more than two pulleys are
used. Such use of additional pulleys must be separately checked at
the design stage.
Large drive torque of inertia should be classified as external loads.
2 Basics of Drive Design
2.1 Service factors, additional factors and formulae
Length factor c
3
for ZRM/ZRP belts
The approximate values for the length factor c
3
are given in
Table 2.3 and apply only to rotating highly loaded drives fitted
with ZRM/ZRP timing belts.
The length factor c
3
takes into account the increase or decrease of
belt flexing when using a short or long belt.
Note the units used for the individual parts of the formulae. The formulae for the driven torque and driven power also apply for the driver
side using the formula symbols M
An
, P
An
, d
w1
and n
1
in place of M
Ab
, P
Ab
, d
w2
and n
2eff
.
General
For i = 1 or z = z
1
= z
2
Formulae for explanation of symbols see page 14
v
eff
==
i
eff
=== i =
d
w1
=d
w2
= (mm)
M
Ab
= (Nm) P
Ab
= (kW)
M
Ab
= (Nm) P
Ab
= (kW)
M
Ab
= (Nm) P
Ab
= (kW)
M
Ab
· n
2eff
9550
S
n3
· d
w2
· n
2eff
19100 · 1000
S
n3
· v
eff
1000
Generaldriven torque and driven power
d
w2
· S
n3
2000
9550 · P
Ab
n
2eff
d
w2
· P
Ab
2 · v
eff
d
w1
· n
1
19100
z
1
· t
π
d
w2
· n
2eff
19100
z
2
· t
π
Drive calculation ZRM/ZRP see page 26
Drive calculation ZRL-M see page 34
Drive calculation ZRL-V see page 37
m
s
( )
L
w
= 2 · a
nom
+ z · t (mm) a
nom
= t (mm) z
R
=
z
R
– z
2
L
w
t
z
2
z
1
d
w2
d
w1
n
1
n
2eff
n
1
n
2
Table 2.3: Length factor c
3
for ZRM/ZRP belts
Section Pitch length L
w
Length factor
(mm) c
3
MXL; T2.5 ≤ 190 0.8
> 190 ≤ 260 0.9
> 260 ≤ 400 1.0
> 400 1.1
XL; T5 (D); AT5 ≤ 440 0.8
> 440 ≤ 555 0.9
> 555 ≤ 800 1.0
> 800 1.1
L; T10 (D); AT10 ≤ 600 0.8
> 600 ≤ 920 0.9
> 920 ≤ 1500 1.0
> 1500 1.1
T20 (D); AT20 ≤ 1260 0.8
> 1260 ≤ 1880 0.9
> 1880 ≤ 3000 1.0
> 3000 1.1
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