Machinery's Handbook, 31st Edition
Double V-Belts
2589
where T r = allowable tight side tension for a double-V belt drive, lbf (not corrected for tension ratio or length-flex correction factor) d = pitch diameter of small sheave, inch S = belt speed, fpm/1000 Table 21. Tension Ratio/Arc of Contact Factors
Design R R 1 −
Design R R 1 −
Arc of Contact, θ (deg.)
Arc of Contact, θ (deg.)
300 290 280 270 260 250 240 230 220 210 200 190
1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.15 1.16 1.18 1.20 1.22 1.25
170 160 150 140 130 120 110 100
1.28 1.31 1.35 1.40 1.46 1.52 1.60 1.69 1.81 1.96 2.15 2.41
90 80 70 60 50
180 2.77 Minimum Sheave Size: The recommended minimum sheave size depends on the rpm of the faster shaft. Minimum groove diameters for each belt cross section are listed in Table 14. Light Duty V-Belts ANSI/RMA IP-23.— Light duty V-belts are typically used with fractional horsepower motors or small engines, and are designed primarily for fractional horsepower service. These belts are intended and specifically designed for use with small diameter sheaves and drives of loads and service requirements that are within the capacity of a single belt.
21/32 ”
1/2 ”
3/8 ”
1/4 ”
3/8 ”
5/16 ”
7/32
”
5/32 ”
No. 0 Section (2L)
No. 1 Section (3L)
No. 2 Section (4L)
No. 3 Section (5L)
Fig. 8. Light Duty V-Belt Cross Sections The four belt cross sections and sheave groove sizes are 2L, 3L, 4L, and 5L. The 2L is generally used only by OEMs and is not covered in the RMA standards. Belt Cross Sections.— Nominal dimensions of the four cross sections are given in Fig. 8. Belt Size Designation.— V-belt sizes are identified by a standard belt number, consisting of a letter-numeral combination. The first number and letter identify the cross section; the remaining numbers identify length as shown in Table 22. For example, a 3L520 belt has a 3L cross section and a length of 52.0 in.
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