T–69
SECTION 18 DOUBLE-SIDED BELT TOLERANCES
This type of belt was introduced briefly in Section 5.1, page T-10. As previously described,
this type of belt has teeth on both sides to provide synchronization from both driving surfaces. This
special feature makes possible unique drive designs, such as multipoint drives, rotation reversal
with one belt, serpentine drives, etc. It may also provide solutions to other difficult design problems.
Double-Sided Belts are similar in construction to regular synchronous belts, including nylon-
faced teeth on both sides. This construction uses essentially the same design parameters as
standard synchronous belts. Their torque ratings are the same as conventional PowerGrip Belts of
identical pitch and width.
Double-Sided Belts are available in MXL, XL, L, 3 and 5 mm HTD and T5 and T10 pitches
from stock. See "Timing Belts and Pulleys Locator Charts" in the product section.
Double-Sided Construction
Tensile members of the PowerGrip Double-
Sided Belt are helically-wound fiberglass cords
providing the same load-carrying capacity as single
sided PowerGrip belts. The body is Neoprene
rubber providing oil and weather resistance and
protection for the fiberglass cords. Both sides of
the belt have a specially treated nylon tooth facing
that provides a tough wear-resistant surface with
minimal friction.
Double-Sided Tolerances
Since Double-Sided Belts are manufactured
and cut to the required width by the same method
as standard PowerGrip belts, the same
manufacturing tolerances apply, except for the
thickness and center distance tolerances listed in
Tables 38 and 39.
Overall thickness, opposing teeth symmetry
and pitch line symmetry are closely controlled
during Double-Sided Belt manufacture.
Specifying Double-Sided Belts
The available Double-Sided Belts and other
double-sided belts from stock can be found from
the Timing Belt Locator Chart, on page 1-2 of the
product section.
Double-Sided Drive Selection
Double-Sided Belts can transmit 100% of their
maximum rated load from either side of the belt or in
combination where the sum of the loads exerted on
both sides does not exceed the maximum rating of
the belt. For example, a Double-Sided Belt rated at
6 lb×in could be used with 50% of the maximum
rated on one side, and 50% on the other; or 90% on
one side, and 10% on the other.
Fig. 37 Double-Sided Belt Tolerances
15 to 20
20.01 to 30
30.01 to 40
40.01 to 50
50.01 to 60
60.01 to 70
over 70
± .020
± .024
± .026
± .030
± .032
± .034
To be specified
Table 39 Center Distance Tolerances
Fig. 38 Double-Sided Belt Application
Belt Length
(in)
Center Distance
Tolerances (in)
Belt
XL (.200")
3 mm HTD
5 mm HTD
MXL
L
T5
T10
Table 38 Belt Thickness Tolerances
T (in)
.120 ± .007
.126 ± .006
.209 ± .007
.060 ± .004
.180 ± .012
.130 ± .010
.268 ± .014
W (in) Ref.
.020
.030
.045
.020
.030
.035
.071
