Machinery's Handbook, 31st Edition
2614
Synchronous Belts
50,000 40,000 30,000 20,000 10,000
5,000 3,450 2,500 1,160 870 1,500 1,750
MXL
XL
L
H
100 400 300 200 500 690 515
XH
0.01
0.03 0.05 0.1 0.2 0.3 0.5 1 2 3 5 10 20 30 50 100 200 300 500
Design Horsepower (Horsepower × Service Factor)
Fig. 14. Selection of Synchronous Belt Cross Section Table 46. Teeth in Mesh Factor
Teeth in Mesh
Factor K z
Teeth in Mesh
Factor K z
6 or more
1.00 0.80
3 2
0.40 0.20
5 4
0.60 Horsepower Rating Formulas: The horsepower rating formulas for synchronous belts, other than the MLX section, are determined from the following formulas, where the num ber in parentheses is the belt width in inches. XL 0.38 ( ) HP dr 0.0916 7.07 –5 × 10 dr ( ) 2 – [ ] = L 1.00 ( ) HP dr 0.436 3.01 –4 × 10 dr ( ) 2 – [ ] = H 3.00 ( ) HP dr 3.73 1.41 –3 × 10 dr ( ) 2 – [ ] = XH 4.00 ( ) HP dr 7.21 4.68 –3 × 10 dr ( ) 2 – [ ] = XXH 5.00 ( ) HP dr 11.4 7.81 –3 × 10 dr ( ) 2 – [ ] = where HP = the maximum horsepower rating recommended for the specified standard belt width having six or more teeth in mesh and a pulley surface speed of 6500 fpm or less. Horsepower ratings for drives with less than six teeth in mesh must be corrected as shown in Table 46. d = pitch diameter of smaller pulley, inch; r = rpm of faster shaft divided by 1000. Total horsepower ratings are the same for double-sided as for single-sided belts. Contact manufacturers for percentage of horsepower available for each side of the belt. Finding the Required Belt Width: The belt width should not exceed the small pulley di- ameter or excessive side thrust will result. Torque Rating Method (MXL Section): Divide the design torque by the teeth in mesh factor to obtain the corrected design torque. Compare the corrected design torque with the torque rating given in Table 47 for the pulley diameter being considered. Select the narrowest belt width that has a torque rating equal to or greater than the corrected design torque.
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