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30<br />
Calculation<br />
optibelt OMEGA HL/HP and optibelt OMEGA<br />
Belt tension<br />
Belt tension for Optibelt OMEGA HP/Optibelt<br />
OMEGA HL and Optibelt OMEGA timing belts<br />
For faultless power transmission and for the achievement of<br />
acceptable belt service life, the correct belt tension is of the utmost<br />
importance. Too low or too high a belt tension will lead to the<br />
premature failure of the timing belts. Over tensioning often leads<br />
to bearing failure on the prime mover or the driven machine.<br />
Experience showed that unscientific belt tensioning methods, such<br />
as the “thumb pressure method”, are not suitable for applying the<br />
optimum tension to the drive for maximum efficiency and drive/<br />
bearing life. It is therefore recommended that the correct static belt<br />
tension should be calculated for each drive.<br />
By virtue of their extremely low stretch characteristics Optibelt<br />
timing belts do not require any further tensioning after correct<br />
installation if properly used.<br />
Symbol<br />
F = test force [N]<br />
Sa = static shaft loading [N]<br />
Sn3 = circumferential force to be effectively transmitted [N]<br />
Ea = belt deflection for given span length [mm]<br />
L = span length [mm]<br />
1. Calculation of the test force F<br />
F =<br />
S n3<br />
20<br />
P · 1000<br />
Sn3 = v =<br />
v<br />
2. Calculation of the belt deflection E a for the existing<br />
span length L<br />
L<br />
Ea =<br />
50<br />
L = a nom 2 –<br />
3. Calculation of the minimum static shaft loading<br />
S a = S n3 · 1.1<br />
dwg – dwk ( )<br />
2<br />
4. Calculation of the frequency for measuring the belt tension<br />
using the Optibelt frequency tension tester<br />
T<br />
f =<br />
4 · k · L<br />
T = 0.5 · Sa k belt weight in kg/m from Table 8, page 43<br />
L span length in mm<br />
2<br />
2<br />
d wk · n k<br />
19100<br />
Apply test force F in the centre of the span perpendicular to the belt<br />
top surface as shown in the illustration below; measure the<br />
deflection E a, correct the tension if necessary and re-check.<br />
1352<br />
F = = 67.60 N<br />
20<br />
18.5 · 1000<br />
Sn3 =<br />
13.68<br />
91.67 · 2850<br />
v =<br />
19100<br />
Sn3 = 1352 N v = 13.68 m/s<br />
Ea = = 8.3 mm<br />
L =<br />
142.60 – 91.67<br />
415.22 ( ) 2<br />
2 414.44<br />
50<br />
2<br />
–<br />
= 414.44 mm<br />
S a = 1352 N · 1.1 = 1487.2 N<br />
743.6<br />
f = = 78.9 Hz<br />
4 · 0.174 · 0.414<br />
T = 0.5 · 1487.2 N = 743.6 N<br />
k = 0.174 kg/m<br />
L = 0.414 m<br />
2
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