PowerGrip® GT® Belt Drives
PowerGrip® GT® Belt Drives
PowerGrip® GT® Belt Drives
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Polyflex ® JB ® and Micro-V ® <strong>Belt</strong> Drive Selection Procedures<br />
How to Design Polyflex JB and Micro-V <strong>Belt</strong> <strong>Drives</strong>–continued<br />
Step 4 Determine the <strong>Belt</strong> Length<br />
Designation and Actual Center<br />
Distance<br />
A. For a two-sheave drive, calculate the belt<br />
effective length from Formula 10. If your drive<br />
requires an idler, determine the belt effective<br />
length from Engineering Section VII. Design of<br />
<strong>Drives</strong> With Idlers on Page 82.<br />
Formula 10<br />
<strong>Belt</strong> Effective Length (in) = 2CD + 1.57(D + d) +<br />
(D – d)2<br />
4CD<br />
Where: d = Small sheave outside diameter, inches<br />
D = Large sheave outside diameter, inches<br />
CD = Desired center distance, inches.<br />
Compare the calculated belt effective length from<br />
Formula 10 to the standard belt effective lengths<br />
given in Table 26 or Table 30 on Pages 68 or 70.<br />
Find the closest standard belt effective length in<br />
Table 26 or Table 30 and calculate the actual center<br />
distance using Formula 11 below.<br />
B. The approximate nominal center distance for the<br />
drive can be calculated using the following<br />
formula:<br />
Formula 11<br />
Center Distance = K + K2 – 32 (D – d) 2<br />
16<br />
K = 4EL – 6.28 (D + d)<br />
Where: d = Small sheave outside diameter, inches<br />
D = Large sheave outside diameter, inches<br />
EL = <strong>Belt</strong> effective length, inches<br />
Step 5 Calculate the Number of<br />
Strands/Ribs Required<br />
A. From the table on Page 74 or 75, find the basic<br />
horsepower rating based on the small sheave<br />
diameter and rpm of the faster shaft. Add the<br />
‘additional horsepower per strand or rib for<br />
speed ratio’ from the right of the table to find the<br />
rated horsepower per strand or rib. Interpolate if<br />
necessary.<br />
B. From Table 33, find the Arc of Contact<br />
Correction Factor (G) based on the quantity<br />
(D - d)/C. (D and d are large and small sheave<br />
outside diameters and C is the actual center<br />
distance. All values are in inches.)<br />
C. Based on the belt length and cross section that<br />
you selected, determine the <strong>Belt</strong> Length<br />
Correction Factor from Table 34 or Table 35 on<br />
this page.<br />
D. From Steps B and C, multiply the Arc of Contact<br />
Correction Factor (G) and the <strong>Belt</strong> Length<br />
Correction Factor (KL) to get the Horsepower<br />
Correction Factor.<br />
E. Multiply the rated horsepower per strand or rib<br />
by the Horsepower Correction Factor to obtain<br />
the Horsepower Per Strand or Rib.<br />
F. Divide the design horsepower from Step 1 by<br />
the horsepower per strand or rib to find the<br />
number of strands or ribs required. The answer<br />
may be a fraction, so always round to the next<br />
larger whole number.<br />
Table 33 – Arc of Contact Correction<br />
0.00 180 1.00 1.00<br />
0.10 174 0.99 0.98<br />
0.20 169 0.97 0.97<br />
0.30 163 0.96 0.95<br />
0.40 157 0.94 0.94<br />
0.50 151 0.93 0.92<br />
0.60 145 0.91 0.90<br />
0.70 139 0.89 0.88<br />
0.80 133 0.87 0.85<br />
0.90 127 0.85 0.83<br />
1.00 120 0.82 0.80<br />
1.10 113 0.79 0.77<br />
1.20 106 0.77 0.74<br />
1.30 99 0.73 0.71<br />
1.40 91 0.70 0.67<br />
1.50 83 0.65 0.63<br />
Table 34 – Polyflex JB Length Correction Factors (K L )<br />
<strong>Belt</strong> Length<br />
<strong>Belt</strong> Length<br />
<strong>Belt</strong><br />
Length Correction Length Correction Length<br />
Designation Factor Designation Factor Designation<br />
280 0.83<br />
500 1.00<br />
290 0.84<br />
515 1.01<br />
300 0.85<br />
530 1.02<br />
307 0.86<br />
545 1.03<br />
315 0.87<br />
560 1.04<br />
325 0.88<br />
580 1.05<br />
335 0.89<br />
600 1.06<br />
345 0.89<br />
615 1.06<br />
355 0.90<br />
630 1.07<br />
365 0.91<br />
650 1.08<br />
375 0.92<br />
670 1.09<br />
387 0.93<br />
690 1.10<br />
400 0.94<br />
710 1.10<br />
412 0.95<br />
730 1.11<br />
425 0.96<br />
750 1.12<br />
437 0.96<br />
775 1.13<br />
450 0.97<br />
800 1.14<br />
462 0.98<br />
825 1.15<br />
475 0.99<br />
850 1.16<br />
487 1.00<br />
875 1.17<br />
D-d<br />
c<br />
Factor<br />
Arc of<br />
Contact<br />
On Small<br />
Sheave<br />
(degrees)<br />
Table 35 – Micro-V Length Correction Factors (K L )<br />
<strong>Belt</strong> Length<br />
<strong>Belt</strong> Length<br />
<strong>Belt</strong><br />
Length Correction Length Correction Length<br />
Designation Factor Designation Factor Designation<br />
180 0.76<br />
360 0.97<br />
190 0.78<br />
380 0.98<br />
200 0.79<br />
400 1.00<br />
220 0.82<br />
420 1.01<br />
240 0.85<br />
430 1.02<br />
260 0.87<br />
440 1.03<br />
280 0.89<br />
460 1.04<br />
300 0.91<br />
490 1.06<br />
320 0.93<br />
520 1.08<br />
340 0.95<br />
550 1.10<br />
Polyflex JB<br />
Arc<br />
Correction<br />
Factor (G)<br />
Length<br />
Correction<br />
Factor<br />
900 1.17<br />
925 1.18<br />
950 1.19<br />
975 1.20<br />
1000 1.20<br />
1030 1.21<br />
1060 1.22<br />
1090 1.23<br />
1120 1.24<br />
1150 1.25<br />
1180 1.25<br />
1220 1.26<br />
1250 1.27<br />
1280 1.28<br />
1320 1.29<br />
1360 1.29<br />
1400 1.30<br />
1450 1.31<br />
1500 1.32<br />
Micro-V<br />
Length<br />
Correction<br />
Factor<br />
580 1.11<br />
610 1.13<br />
650 1.15<br />
730 1.18<br />
870 1.23<br />
920 1.25<br />
980 1.27<br />
72 The World’s Most Trusted Name in <strong>Belt</strong>s, Hose & Hydraulics.
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