HANDTORQUE MULTIPLIERS
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 lbf.ft) and ‘specials’ to 100,000 N.m (73,000 lbf.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.
Summary of Norbar torque multiplier advantages:
• The ratio stated is the true torque multiplication factor.
• No correction charts are needed to determine torque output.
• Strong, safe Anti Wind-Up Ratchet available on most models for safe and comfortable operation.
• A wide range of alternative reaction styles are available making the Handtorque adaptable to many applications.
• Electronic torque transducers are available on most models for precise torque control.
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.