Please select a
product by using the
drop-down menu below.
What
is a Torque Multiplier?
A torque multiplier is a device that increases the
torque that can be applied by an operator. Because the power
output can not exceed the power input, the number of output
revolutions will be lower than the number of input revolutions
(Torque x rpm = Power).
How
Handtorque Torque Multipliers Work
Handtorque multipliers incorporate an 'epicyclic'
or 'planetary' gear train having one or more stages. Each stage of
gearing increases the torque applied by a factor of 5, allowing
Norbar to offer multipliers in ratios of 5:1, 25:1 and 125:1.
In the planetary gear system, torque is applied to
the input gear or 'sun' gear. Three or four planet gears whose
teeth are engaged with the sun gear therefore rotate. The outside
casing of the multiplier, or 'annulus' is also engaged with the
planet gear teeth, and would normally rotate in the opposite
direction to the sun gear. A reaction arm prevents the annulus
from rotating, and this causes the planet gears to orbit around
the sun. The planet gears are held in a 'planetary' carrier which
also holds the output square drive. Therefore as the planet gears
orbit around the sun. the carrier and so the square drive turns.
Without the reaction arm to keep the annulus
stationary, the output square will not apply torque.
Why
use a Handtorque Torque Multiplier?
Safety - use of long levers can be
dangerous. Torque multipliers mean a reduction in the lever
length or operator effort by a factor of 5, 25 or 125.
Space limitation - the use of a long
lever may be impossible due to the available space.
Accuracy - torque will be applied most
accurately when it is applied smoothly and slowly. Torque
multipliers enable this by removing much of the physical
effort from the tightening task.
Advantages
of the Norbar Handtorque System
Norbar
gearboxes are built to an extremely high standard of precision All
gears rotate on needle roller bearings about hardened and ground
journal pins. As a result, Norbar Handtorques can be relied upon
to have a torque multiplication accuracy of +4%, throughout the
operating range, taking the uncertainty out of high torque
tightening.
No
gearbox is 100% efficient and so the velocity ratio (the number of
turns that the input has to make to achieve one revolution of the
output) is not the same as the torque multiplication ratio. Norbar
multipliers are engineered such that each gear stage has a
velocity ratio of typically 5 45:1 which results in a true torque
multiplication factor of 5:1.
Torque output
calculations are therefore a matter of simple arithmetic with
little risk of incorrect bolt loading due to conversion errors.
Other manufacturer's multipliers often require graphs or formulae
to calculate the input torque to achieve a particular output.
The
Norbar Handtorque is the most comprehensive multiplier range
available. Standard products are available up to 47,500 N.m
(35,000 Ibf.ft) and 'specials' to 100,000 N.m (73,000 Ibf.ft). A
range of 'nose extensions' for reaching difficult to access bolts
and a full range of torque transducers for highly accurate torque
monitoring are available.
Norbar
Anti Wind Up Ratchet
With any high ratio gearbox (25:1 or more) a certain amount
of wind up (spring) has to be taken up before any useful
tightening work is applied to the nut.
Each time the input device is released, the
wind up will rotate it back against the direction of operation
The Anti Wind Up Ratchet retains all of the wind up forces as
they are created with the following benefits:
The torque input device can not fly backwards
against the direction of operation if it is suddenly released.
Without an Anti Wind Up Ratchet, it will often
be necessary to continue to make 360° sweeps with the torque
input device otherwise the multiplier will 'unwind'. However,
obstructions will often make this impossible.
With an Anti Wind Up Ratchet fitted, the
multiplier becomes locked onto the nut because the reaction
plate is held hard against the reaction point. This means that
even used upside down, the multiplier will support it's own
weight.
Safety Note: Additional support is
recommended as failure in the bolt, socket or multiplier will
release the wind up forces and cause the multiplier to drop.
No
gearbox is 100% efficient and so the velocity ratio (the number of
turns that the input has to make to achieve one revolution of the
output) is not the same as the torque multiplication ratio. Norbar
multipliers are engineered such that each gear stage has a
velocity ratio of typically 5 45:1 which results in a true torque
multiplication factor of 5:1.
