Design Challenge - March 2016


Adding a third axle to just about any vehicle improves its ‘cool’ factor, but the addition can have a dramatic impact on the performance and applications for light trucks in particular. Technically, a third axle will have an impact on three aspects of the vehicle in varying proportions:

  • Payload mass
  • Mobility
  • Payload length

The rated load for a light truck will double, and sometimes triple, as the result of the third axle, so it can carry substantially more, just like this crane carrier example. This vehicle is not one that would normally be considered as a crane carrier, but with a third axle it has the payload mass capability to carry a substantial crane, and even have a good pick and carry rating.

Combined with the knuckleboom crane, the small profile means it can operate in confined areas, making it useful for industrial equipment installations, for example. The use of a conventional on-highway chassis also means it can self-deploy at highway speeds, which is very useful in taxi crane applications. The same approach can be used for any high-load, low-profile applications.

Fire trucks are another example – for applications such as bushfire fighting, and fighting fires in parking lots, which need high water volumes, but low profiles. Even smaller vehicles can benefit from a third axle, particularly if they are not intended to carry heavy loads. Our ambulance concept is a good example of where tray length is important, but the vehicle still requires good mobility.

Depending on the application, 6x2, 6x4 and 6x6 configurations are possible. When a bogie drive is used at the rear, suspension and torque distribution issues need to be addressed, but solutions to these issues are now readily available.

The conversion of lighter vehicles into threeaxle units often means that light, indigenous vehicles can be used for bigger jobs, and that the smaller profile permits access on narrow roads and thoroughfares. There’s no doubt that adding a third axle to a light truck confirms that good things can come in small packages.

More images from Lance Procter

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Lance Procter

As a director of Motive Power in Sydney, Australia, Lance Procter specializes in designing complex vehicles. Many have related to mining equipment, and he’s designed towing tractors for heavy aircraft up to A380 size






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