The torque
requirements of a gear box are normally drilled down from the application,
where the gearbox is coupled. For example, in ready
made concrete mixer machine, the main torque requirement and speed
of the output shaft of the gear box comes from the rotating drum. And depending
upon the gear reduction ratio the torque requirement is transferred to the
input shaft of the gear box. So, from the above discussion it should be clear
that the torque requirement of the gearbox input shaft will be different. And
you can find out the torque requirement by two ways: Strain gauge
method and Calculation method.
If you apply torque to a shaft then the fibers of the shaft will be under torsional stress. Or, in other words, the fibers will be subjected to the tension in one direction and will be subjected to compression to another direction. The fact is true for the gearbox input and output shaft as well.
The strain
gauge transducer can sense the tension and compression of the gear
box shaft under torsion and can measure the torque in it.
The strain gauge
transducer has two parts: the strain gauge and the transducer display and
processing unit. The strain gauge senses the torque and sends the signal to the
transducer signal processing unit, which in turns connected to the digital
display unit. The display unit displays the torque value.
So, for finding out
the torque requirement of the gear box input and output shaft, you have to
place the strain gauge transducer to the shafts.
You can use the
standard equations available for calculating the torque requirement of
the gear box shaft. The basic equations used here are:
P (KW) =
(2/60000)*Π*N (Rpm) *T (N.m)……………..Eqn.1
N1/N2 = M2 /
M1………………..Eqn.2
Where,
P – Power in KW
N – Speed in Rpm
T – Torque in N.m
M- Number of teeth
of the respective gear.
First thing you have
to know is the Power requirement of the application. Take
the concrete mixer example again, after you know the power
requirement of the rotating drum, you can apply the Eqn.1 and
find out the torque requirement (T) of the gear box output shaft.
Next, use the Eqn.2 to
find out the speed (N) of the input shaft of the gear box and again use
the Eqn.1 and find out the torque requirement of the input
shaft of the gear box.
We have two methods
for how to measure torque requirement of gear box: either by using the strain
gauge transducer or by the calculation method using the known mechanical
design equations. Fitting the strain gauge is a skillful job
and requires different installation procedure prescribed by the respective
strain gauge manufacturer.