Norbar Case Study

Caterpillar 797 Wheel Nut Breakout

A lighter and more reliable solution on a powered multiplier

Cat® 797 Rear Dump Truck

Cat is the world’s leading manufacturer of construction and mining equipment, engineered to withstand mining conditions.

The Cat 797 Rear Dump Truck is a tough, rugged frame that delivers on performance. The Cat 797 has earned itself the reputation of being one of the most productive 363-tonne (400-ton) trucks on the market.

Image: Cat 797 Dump Truck

The Problem – A Common Frustration

While the Cat 797 is a robust and obvious choice for the mining industry, finding a reliable option for the breakout of their wheel nuts has been a common frustration for those who maintain them.

According to manufacturer’s specifications, wheel nuts on the Cat 797 require a final torque value of 2280 ft/lbs. Safe work instructions on the rotation of rims and tires states tire fitters must operate torque tooling from beyond the edge of the rim. This directive makes the use of a nose extension critical in breakout and re-torque of wheel nuts. The combination of a powered multiplier and nose extension, exposes the tooling and operator to a long list of concerns around safety and reliability.

Image: Cat 797 Wheel Nut Breakout

Engineering an Outcome for Safety & Reliability

Norbar Australia has addressed the common safety and reliability concerns in the breakout of wheel nuts on Cat 797s with the following:

Norbar PTS-119-7000 Pneumatic Torque Multiplier
NES-119-800 Nose Extension
Custom built soft start control unit
PTT-007 Tool Trolley

Image: Norbar’s Solution

Feature	Benefit to User
No.5 Spline Drive	Reduces outside diameter so nose extension dose not foul on rims gutter. This also completely mitigates breakage of male square drives.
Nylon Bush Reaction Retainer	Eliminates the requirement for reaction retaining clip.
Splined Reaction Fixture	Allows for the use of double-sided reaction arms to aid in reduction of parasitic forces, and enables quick effortless change of reaction in case of damage or application specific requirements.
Integrated Roller Bearings	Drastically reduces torque losses down the length of the shaft, resulting in more accurate torque figures (when used clockwise).
Nose Extension Shaft	Nose extension shaft is fitted directly to annulus of tool, thus removing yield point that is the square drive. This ultimately gives the tool direct engagement. Furthermore, this engineered Nose Extension is over 8kg lighter than previous extensions used in this application.
4 Stage Gearbox	Norbar’s tried and tested 4 stage planetary gear box gives operators the confidence they need.
PTS Air Motor	Lightweight, durable and cost effective.
Custom Built Lubro Control Unit	Designed to reduce the torsional twist down the length of the nose extension. The custom-built soft start Lubro Control Unit allows the tool to slowly ramp up to pressure in aid of reducing shock load due break out.