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.Dd $Mdocdate: March 31 2009 $
.Dt DESIGNTORQUE 7
.Os
.Sh NAME
.Nm designtorque
.Nd guidelines for computing design torque
.Sh DESCRIPTION
Follow these guidelines to compute the maximum design torque (in in-lbs),
from a given horsepower and RPM.
The design torque is used to select torque-limiting shaft couplings, or
servo/stepper motors in motion control applications.
The design torque
.Va Tmax
is computed as:
.Bd -literal -offset left
	Tmax = Tnom * (K1*K2*K3)
.Ed
.Pp
The nominal torque
.Va Tnom
is computed as:
.Bd -literal -offset left
	Tnom = (HP * 63025) / RPM
	Tnom = (kW * 9550) / RPM
.Ed
.Pp
.Em K1
is the application service factor:
.Bl -tag -width "K1 = 1.0 - 1.4 "
.It K1 = 1.0-1.4
Small masses to accelerate, uniform operation.
Pumps for non viscous fluids, light-duty generators, blowers, fans, conveyors.
.It K1 = 1.4-1.8
Medium masses to accelerate, uniform operation.
Wood / sheet metal working tools, textile machines, mixers.
.It K1 = 1.7-2.0
Medium masses to accelerate, nonuniform operation.
Pumps for viscous fluids, printing presses, generators, shredders, winding
machines.
.It K1 = 2.0-2.2
Medium masses to accelerate, nonuniform operation and shocks.
Compression pumps, propeller pumps, centrifuges, paper mills, cable cars,
concrete mixers.
.It K1 = 2.2-2.4
Large masses to accelerate, nonuniform operation and shocks.
Piston pumps, stamping and forging pressesshears, excavators, hammer mills.
.It K1 = 2.3-2.8
Very large masses to accelerate, irregular operation and shocks.
Piston compressors and pumps, welding machines, brick presses, stone crushers.
.El
.Pp
.Em K2
specifies the service factor for duty cycle:
.Pp
.Bl -tag -compact -width "K2 = 1.15 "
.It K2 = 1.0
Under 8 hours/day.
.It K2 = 1.1
Between 8 and 16 hours/day.
.It K2 = 1.15
Between 16 hours/day and continuous.
.El
.Pp
.Em K3
specifies the service factor for start/stop cycles per hour:
.Pp
.Bl -tag -compact -width "K3 = 1.0 "
.It K3 = 1.0
Up to 10 cycles
.It K3 = 1.5
Between 10 and 40 cycles
.It K3 = 2.0
Between 40 and 125 cycles
.It K3 = 2.5
Between 125 and 250 per hour
.El
.\".Sh SEE ALSO
.\".Xr drills 7
.Sh HISTORY
The
.Nm
manual page first appeared in FabBSD 1.0.