b) Use high performance belts – for example XPB instead of
SPB – as a lower quantity of belts for the same transmitted
power may be necessary and a consequent shorter
resulting distance compared to the shaft shoulder (P.T.O)
"a" of Fig. 10.
c) Pull the belts according to manufacturer instructions.
Excessive pulling can cause reduced bearing life and wear
out the pulley prematurely. Pulling depends on different
variables as indicated in par. 9.12.
d) Belt length has a natural tolerance ≥ ± 0.75%. For this
reason, the 2 belts must be purchased as a pair.
e) Follow the direction of the belt pull as shown in Fig. 9 for
other needs, contact our Technical or Customer Service
Departments.
f ) Take care of the alignment of the driving pulley and driven
pulley grooves.
9.12
Definition of static pull to apply on belts
Static pull depends on:
a) The wheelbase between the two pulleys (belt length).
b) The load due to static pull of the belt.
c) The number of belts.
d) The winding angle of the smallest pulley.
e) Average speed.
f ) Etc.
Values of the static pull to be applied can be obtained from
the diagram in Fig. 11 for belts with a XPB profile in relation to
the wheelbase.
Lf= Wheelbase mm
Conclusion: with a wheelbase of 600 mm and with a
dynamometer, loading the belt branch with 75 N as indicated
in Fig. 12, a "te" bend of approximately 10.8 mm is obtained.
Lf = Wheelbase
te = Belt bend
Fig. 11
Fe = 75 N Dynamometer load
Note
. Unless otherwise stated by the supplier of the belts,
1
control of proper pull and its relative re-tensioning should be
performed after no less than 30 minutes of motion necessary
for the normal adjustment of the belts. Best performance and
durability will be achieved with proper tensioning.
Note
. In case of necessity or for routine maintenance, never
2
replace a single belt but the complete set.
30
Shaft shoulder
(P.T.O.)
Fig. 10
Fig. 12