Optibelt ZRL, Technical Manual

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50
5 Design Hints, Dimensions and Tolerances
5.5 Length measurement, width tolerances
Table 5.12: Test forces for determining belt length, for standards see Table 5.6, page 48
Standard
belt width
b
St
(mm)
3.2 13 — — — — — — — — —
4.0 — — — 6 — — — — — —
4.8 20 — — — — — — — — —
6.0 — — — 10 20 — — 25 — —
6.4 27 36 — — — — — — — —
7.9 — 44 — — — — — — — —
9.5 — 53 — — — — — — — —
10.0 — — — 20 40 — — 50 110 —
12.7 — — 105 — — — — — — —
16.0 — — — — 60 90 — 80 170 250
19.1 — — 180 — — — — — — —
25.0 — — — — 90 140 — 125 270 400
25.4 — — 245 — — — — — — —
32.0 — — — — — 170 340 160 340 500
50.0 — — — — — 270 540 250 540 800
75.0 — — — — — — 800 — 800 1200
100.0 — — — — — — 1100 — 1100 1600
The following length measurement method refers to Optibelt ZRM/
ZRP timing belts.
The timing belt should be fitted on two test pulleys of equal size of
suitable section which should be free to rotate. One pulley is
mounted on a fixed centre shaft, whilst the other is mounted on a
parallel shaft that is able to move to vary the centre distance.
The movable test pulley should be loaded with the test force Q as
shown in Figure 5.6. Test pulley dimensional tolerances and the
values of force Q are shown in Tables 5.11 and 5.12.
Before measurement of the centre distance a, the loaded belt
should be rotated at least twice around the test pulleys. The belt is
Table 5.11: Test pulleys for determining belt length, for standards see Table 5.6, page 48
MXL 20 40.64 12.428
±
0.013 0.013 0.025
XL 10 50.80 15.662
±
0.013 0.013 0.025
L 16 152.40 47.748
±
0.013 0.013 0.025
T2.5 20 50.00 15.400 0.013 0.025
T5; AT5 20 100.00 31.000 0.013 0.025
T10; AT10 20 200.00 61.800 0.013 0.025
T20; AT20 20 400.00 124.500 0.013 0.050
then correctly located on the pulleys and both spans will be
uniformly loaded.
The permissible length tolerance a
LTol
in Table 5.2, page 43, refers
to the centre distance and is therefore half as large as the tolerance
on the pitch length. The pitch length is obtained from the following
equation:
L
w
= 2 · a + U
w
U
w
from Table 5.11
Section Number Effective diameter Outside diameter Eccentricity Axial runout
of teeth tolerance of tolerance
z U
w
d
a
outside diameter
(mm) (mm) (mm) (mm)
Test forces Q (N)
MXL XL L T2.5 T5 T10 T20 AT5 AT10 AT20