Hydraulic drive system has grunt to pull a jumbo

Edited by the Engineeringtalk editorial team Oct 14, 2003

Brevini has supplied a complete hydraulic drive and clamping system for a new airport tow truck designed to tow commercial aircraft up to a Boeing 747 without the traditional drawbar linkage.

Brevini has supplied a complete hydraulic drive and clamping system for a new airport tow truck designed to tow commercial aircraft up to the size of a Boeing 747 without the traditional drawbar linkage.

The new arrangement provides faster taxiing at up to 30km/h, a tighter turning circle and better manoeuvrability.

Brevini's package includes planetary geared pump drives, wheel drives and piston motors designed to provide a high power, compact solution that is hard wearing and has low maintenance requirements.

The company's ability to supply a complete engineered solution set it apart from other suppliers and contributed to winning the business.

The initial aim of the project was to produce a stronger truck design capable of towing the new generation of airliners as well as older, larger planes such as the 747.

When a plane has landed, the truck taxis the aircraft to gangways or hangars by ramping its leading wheel into to the rear bay of the vehicle.

In order for the front wheel of the airplane to load easily, Brevini CWD hydraulic wheel drives are used to drive the rear wheels, removing the need for a single rear axle assembly.

The CWD units feature Brevini's compact planetary gearing that distribute the driving force throughout the gearbox, creating a lightweight but powerful and compact drive solution that acts as the wheel's hub.

By incorporating a manually operated disconnect device, the CWD units allow the vehicle to be towed easily in case of an emergency.

An integral multi-disc negative parking brake also adds vital protection by preventing the vehicle from moving in case of hydraulic failure.

This design solution enabled the truck to exceed the designer's expectations in terms of reliability and performance as the vehicle proved itself able to operate at speeds in excess of 30km/h and ascend inclines of up to 4%.

Although these figures may not at first seem impressive, it must be remembered that the vehicle is designed to tow new Airbus and Boeing planes that can weigh in excess of 350t.

Once the aircraft wheel is in place, it is secured via guides controlled by two hydraulic cylinders.

Both these positioning cylinders and the wheel drives are powered independently using four pumps connected to a Brevini BZ series pump drive.

The BZ series unit is driven directly by the main diesel power plant and again uses planetary gears to split the driving force four ways allowing all four pumps to be powered by a single drive shaft.

Due its use of planetary gear stages the drive is very efficient at 98% per stage, it is also highly compact allowing maximum space for the loading bay area and optimising the manoeuvrability of the tractor design.

The tractor manufacturer gained numerous benefits from sourcing the hydraulic system from one supplier, including shorter lead times, guaranteed compatibility and expert support, culminating in reduced development time and end unit costs.

This is especially true when using Brevini to supply complete drive and hydraulic systems as the group involves a partnership encompasses over 10 component companies manufacturing products such as hydraulic axial piston motors, control valves, power packs, winch drives as well as multistage planetary, parallel shaft and bevel helical gearboxes.