PowerGrip® GT® Belt Drives

Polyflex ® JB ® Belt Drives
For information on additional Polyflex JB cross
sections, see the Polyflex JB Drive Design Manual
18595
Developed and produced by Gates, Polyflex JB Belts
provide more load-carrying capacity at higher
speeds on precision applications. “High power
density” puts more power in small spaces. Polyflex
JB Belts Features and Benefits:
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High modulus polyurethane compound resists
fatigue, wear, ozone and most environmental
conditions; and provides a high coefficient of
friction
Superior adhesion of tensile cords and specially
compounded polyurethane for high fatigue
resistance and long belt life
Precision cast for dimensional accuracy and
smooth operation
60° angle to provide greater undercord support to
the tensile cord and distribute the load more
evenly
Individual belts are joined for greater stability
Ribbed construction to relieve bending stress on
small sheaves and provide lateral rigidity
Polyflex JB Belts
Figure 12
b b
S g
Standard Table Belt 25 Nomenclature — 5M Polyflex JB
Reference Dimensions
h b
Nominal Nominal Belt Nominal
Strand Width Thickness
Cross Spacing (S g) (b b) (h g)
Section (mm) (in) (mm) (in) (mm) (in)
2 Belt
Strands 5.3 0.21 9.9 0.39 3.30 .13
3 Belt
Strands 5.3 0.21 15.2 0.60 3.30 .13
The Polyflex JB Belt is designated by a four-part
symbol consisting of: (1) the number of belt
strands; (2) the cross section; (3) the effective belt
length, and (4) the JB or joined band belt
construction.
For example, the belt designation “3/5M1000JB”
represents:
1. A belt consisting of 3 individual belt strands
joined together
2. A 5mm top width for each belt strand
3. An effective length of 1000 mm
4. A Joined Band (JB) belt construction
Polyurethane
Construction
Gates Polyflex JB V-belts are manufactured using
specially formulated polyurethane compounds
which have a higher coefficient of friction than
rubber compounds. Because of the higher
coefficient of friction, less wedging action between
the belt and the sheave is required. This increased
tractive action permits the sheave angle to be
increased. The benefits of this feature are discussed
in the 60° Angle section on the next page.
Polyurethane has excellent abrasion resistance. As
the sheave and belt wear, the belt seats deeper into
the sheave groove, contributing to tension decay.
This high abrasion resistance feature can mean less
frequent belt retensioning. Additional information on
abrasion resistance and drives operating in hostile
surroundings is provided in the 60° Angle section
below and the section E. Operating Environments on
Page 77.
Polyflex JB belts provide excellent resistance to
many chemicals, including some acids and
petroleum distillates. However, any chemical or
liquid can reduce the coefficient of friction, resulting
in excessive belt slipping. Liquids act as lubricants
that “grease” the belt, reducing the friction needed
for power transmission. Do not use Polyflex JB
belts in an environment where the belt is submerged
or where liquid in any form can get into the drive.
Drives should be completely enclosed or shielded to
prevent slipping problems.
Polyurethane also has a much higher compression
modulus (i.e., ability to withstand high compressive
forces), which permits it to effectively support the
tensile cord even when the amount of material is
reduced. This allows use of the 60° angle which has
30% less material in the bottom (or compression)
part of the belt, compared to a conventional 36°
angle belt of the same top width. See Fig. 13.
60°
Angle Polyflex JB Belt
36°
Angle V-Belt
Reduction in material in 60°
belt (shaded area “A”)
Figure 13
66 The World’s Most Trusted Name in Belts, Hose & Hydraulics.