hydraulik - Jahns-Regulatoren

1.9 Torque
Tiso = limit torque
Transmittable torque of the gearbox, with continuous operation, calculated in accordance to ISO DP6336 for
gears and safety factor of 1. This torque corresponds to a life duration equal to 50.106 cycles of the most stressed
element (theoretically considered unlimited by the ISO DP6336; horizontal curve in the Wöhler fatigue diagram).
This torque does not represent a duration, but it is useful for a quick selection of the maximum size of the
gearbox.
Tcont = continuous torque
Transmittable torque of the gearbox, with continuous operation, that guarantees a duration of ‘h’ hours, with a
gearbox output rotation velocity of ‘n2’ RPM. Tcont is expressed as a function of the product n2 h.
Teq = equivalent torque
Teq represents the value of a constant torque which determines the same duration in hours of the torque
induced by the work cycle. Known as T21 … T2n the torque transmitted by the gearbox at the output velocity n2i
for a time duration in hours of hi, the equivalent torque is:
where
Timp = impulsive torque
value of the static torque or an istantaneous peak load that the gearbox can withstand.
1.10 Effi ciency
ηm = mechanical effi ciency:
ratio between the output power and input power; normally it is considered to be equal to 0,97 – 0,98 per
reduction stage that makes up the gearbox; it depends upon various factors, of which velocity, torque, ratio,
working position and lubrication.
2. Gearbox selection method
2.1 Selection
Once established the selection criteria, which can be defi ned using an ISO or AGMA safety factor, based upon the
class according to the F.E.M. standard or by expressing a minimum life duration, the equivalent output torque Teq is
determined as well as the required duration and the reduction ratio. Using these criteria the gearbox is selected.
- safety factor ISO/AGMA:
the gearbox must garantee the requested theoretical lifetime;
- F.E.M. class:
the gearbox must garanteee that the requested theoretical lifetime correspond to that indicated by the F.E.M.
class as a function of the max and Teq;
- life duration:
the gearbox must have a life duration greater than that required as a function of Teq.
For example, table... on page F.2 / F.9 shows the continuous torques as a function of gearbox size and the reduction
ratio. Please note that when an electric motor is used, the start up torque can be 2.5 times greater than its nominal
value.
H Y D R A U L I K
Page B. 8
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