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Introduction to Torque Multipliers


Handtorque™ Multipliers

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 typically 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 gear, 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 or 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.

Norbar Anti Wind-Up Ratchet

With any high ratio gearbox (25:1 or more) a certain amount of wind-up (backlash) 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:

1.The torque input device can not fly backwards against the direction of operation if it is suddenly released.

2. Without an Anti Wind-Up Ratchet, it will often be necessary to continue to make 360º sweeps with the torque input device otherwise the multiplier will ‘unwind’. However, obstructions will often make this impossible.

3. 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.


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