Industrial Power Transmission Products - Bando USA

Useful Useful Formulas for for V-Belt Drives
Torque to horsepower
conversion
Load requirements for a drive may be given in terms of
torque (turning effort) rather than horsepower. For drive
design purposes, use the formulas below to convert
torque (expressed as pound-inches or pound-feet) to
horsepower. Be sure to use the rpm of the shaft for which
the torque is known, and do not mix the torque of one
shaft with the rpm of another shaft.
136
Horsepower =
(Torque, pound-inches) (rpm)
63,025
Horsepower =
(Torque, pound-feet) (rpm)
5,252
Power to or from machinery
Without accurate horsepower requirement data for a
drive, the formulas below may be used. Efficiency must
be known or estimated to use these formulas, and is
shown as a decimal (i.e. if a pump is 75% efficient, use
.75 in the formula). When a drive is providing power to a
pump or generator, estimate a low efficiency for the
driveN machine. For power input to a drive from a motor
or turbine, estimate a high efficiency for the driveR
machine.
A.C. Machinery
Kilowatts =
(volts) (amps) (pf)
Y
Where: pf = power factor
Single phase: Y = 1000
Three phase: Y = 577
Power required for generator/
alternator
Horsepower =
(volts) (amps) (pf)
(Z) (eff)
Where: eff = overall mechanical and electrical efficiency
pf = power factor
Single phase: Z = 746
Three phase: Z = 431
Power from motor
Horsepower =
(volts) (amps) (pf) (eff)
Z
Where: eff = overall mechanical and electrical efficiency
pf = power factor
Single phase: Z = 746
Three phase: Z = 431
D.C. Machinery
Kilowatts =
(volts) (amps)
1000
Power required for generator
Horsepower = (volts) (amps)
(746) (eff)
Where: eff = overall mechanical and electrical efficiency
Power from motor
Horsepower = (volts) (amps)
(746)
Where: eff = overall mechanical and electrical efficiency
Hydraulic Machinery
Power required by pumps
Horsepower = (Q) (P)
1714 (eff)
Where: Q = flow rate, gal./min.
P = discharge pressure for pumps, inlet pressure for
turbines, lb./sq. in.
eff. = overall mechanical and hydraulic efficiency
Power from turbine
Horsepower = (Q) (P) (eff)
1714
Where: Q = flow rate, gal./min.
P = discharge pressure for pumps, inlet pressure for
turbines, lb./sq. in.
eff. = overall mechanical and hydraulic efficiency
V-Belt Tension Formulas
Effective Pull
T 1 -T 2 = 33,000 ( HP )
V
Where: T 1 = tight side tension, pounds
T 2 = slack side tension, pounds
HP = design horsepower
V = belt speed, feet per minute
T 1 +T 2 = 33,000 (2.5-G) ( HP )
GV
Where: T 1 = tight side tension, pounds
T 2 = slack side tension, pounds
HP = design horsepower
V = belt speed, feet per minute
G = arc of contact correction factor
Tension Ratio
T 1 /T 2 =
1
1-0.8G
(Also, T 1 /T 2 = eK)
Where: T 1 = tight side tension, pounds
T 2 = slack side tension, pounds
G = arc of contact correction factor
e = base of natural logarithms
K = .51230, a constant for V-belt drive design
q = arc of contact in radians
Tight Side Tension
T 1 = 41,250 ( HP )
GV
Where: T 1 = tight side tension, pounds
HP = design horsepower
V = belt speed, feet per minute
G = arc of contact correction factor
Slack Side Tension
T 2 = 33,000 (1.25-G)( HP )
GV
Where: T 2 = slack side tension, pounds
HP = design horsepower
V = belt speed, feet per minute
G = arc of contact correction factor
Belt Speed
V = PD (rpm) = (PD) (rpm) (.262)
3.82
Where: V = belt speed, feet per minute
PD = pitch diameter of sheave or pulley
rpm = revolutions/minute of the same sheave or pulley
To find an authorized BANDO distributor, go to www.bandousa.com or call 1-800-829-6612