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### V-Belt Classical Speed to Horsepower Formulas and Calculator for Cross Sections

**Belt Drive Design and Engineering
Mechanical Gear Design and Engineering**

V-Belt Classical Speed to Horsepower Ratings Formulas and Calculator for Cross Sections

Cross Section Design Selection: Use the chart given below to determine if the V-belt cross section for any combination of design horsepower and speed of the faster shaft. When the intersection of the design horsepower and speed of the faster shaft falls near a line between two areas on the chart, the possibilities in both areas should be investigated. Special circumstances (such as space limitations) may lead to a choice of belt cross section different from that indicated in the chart.

Design HP = Basic Horsepower Rating x Service Factor

Basic Horsepower Rating Formulas

V-Belt Cross Section "A"

HP = d_{p} r_{k} [ 1.004 - 1.652 / d_{p} - 1.5747 x 10^{-4} ( d_{p} r )^{2} - 0.2126 log( d_{p} r ) ] + 1.652 r ( 1 - 1 / K_{SR} )

V-Belt Cross Section "AX"

HP = d_{p} r_{k} [ 1.462 - 2.239 / d_{p} - 2.198 x 10^{-4} ( d_{p} r )^{2} - 0.4238 log( d_{p} r ) ] + 2.239 r ( 1 - 1 / K_{SR} )

V-Belt Cross Section "B"

HP = d_{p} r_{k} [ 1.769 - 4.372 / d_{p} - 3.081 x 10^{-4} ( d_{p} r )^{2} - 0.3658 log( d_{p} r ) ] + 4.372 r ( 1 - 1 / K_{SR} )

V-Belt Cross Section "BX"

HP = d_{p} r_{k} [ 2.051 - 3.532 / d_{p} - 3.097 x 10^{-4} ( d_{p} r )^{2} - 0.5735 log( d_{p} r ) ] + 3.532 r ( 1 - 1 / K_{SR} )

V-Belt Cross Section "C"

HP = d_{p} r_{k} [ 3.325 - 12.07 / d_{p} - 5.828 x 10^{-4} ( d_{p} r )^{2} - 0.6886 log( d_{p} r ) ] + 12.07 r ( 1 - 1 / K_{SR} )

V-Belt Cross Section "CX"

HP = d_{p} r_{k} [ 3.272 - 6.655 / d_{p} - 5.298 x 10^{-4} ( d_{p} r )^{2} - 0.8637 log( d_{p} r ) ] + 6.655 r ( 1 - 1 / K_{SR} )

V-Belt Cross Section "D"

HP = d_{p} r_{k} [ 7.160 - 43.21 / d_{p} - 1.384 x 10^{-4} ( d_{p} r )^{2} - 1.454 log( d_{p} r ) ] + 43.21 r ( 1 - 1 / K_{SR} )

Where:

dp = pitch diameter of small sheave, in.

r = rpm of the faster shaft.

r_{k} =
r / 1000

K_{SR} = speed ratio factor given in the accompanying Table below.

Speed Ratio Range = D_{p} / d_{p}

Where:

D_{p} = Pitch of Large Sheave

d_{p} = Pitch of Small Sheave

Speed Ratio Range |
K_{SR} |

1.00 - 1.01 |
1.0000 |

1.02 - 1.04 |
1.0112 |

1.05 - 1.07 |
1.0226 |

1.08 - 1.10 |
1.0344 |

1.11 - 1.14 |
1.0463 |

1.15 - 1.20 |
1.0586 |

1.21 - 1.27 |
1.0711 |

1.28 - 1.39 |
1.0840 |

1.40 - 1.64 |
1.0972 |

> 1.64 |
1.1106 |

FPM to RPM Equation:

r = s / ( π d )

RPM to FPM Equation:

s = r π d

Where:

r = rpm

s = ft / min

d = diameter of pulley in ft

Related:

- Synchronous Timing Belt Tooth Section Dimensions Table per ANSI / RMA IP-24
- Synchronous Timing Belt Pulley Dimensions Table per ANSI / RMA IP-24
- Synchronous Timing Belt Lengths and Tolerances per. ANSI RMA IP-24 Table
- Service Factors Synchronous Timing Belts
- Synchronous Timing Belt Standard Widths and Tolerances Table
- Synchronous Belt Standard Pulley Diameters
*ANSI/RMA IP-24*Table - Timing Belt Pulley Mechanical Tolerances per. ANSI RMA IP-24

References:

ANSI / RMA IP-24

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