Forestry in South Africa
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August : Technical developments for carrying timber that can improve efficiency and reduce road damage

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19 August, 2014

Technical developments for carrying timber that can improve efficiency and reduce road damage

Globally there have been a number of technical developments in recent years on vehicles for carrying timber that can improve efficiency, security, compliance and most importantly reduce potential road damage. South Africa poses a unique challenge due to the infrastructural backlog the government needs to deal with to improve and maintain the South African road transport system.However, this challenge to the government has led the transport industry to come up with technological advancements to ensure that timber transport vehicles minimises the damage they cause to the roads, as a global issue of concern. 

According to the author of, Managing Timber Transport - Good Practice Guide, Dr Ger Devlin, a Bio-systems Engineer based in Ireland, "The transport of timber poses a unique challenge. This arises because most of the forests are located at the end of the road network. It is estimated that over 80% of the private estate is accessed by local roads only."

Many of these roads are structurally weak. Timber is a low value product at the forest gate which requires timber to be transported at maximum efficiency which means that vehicles are operating at maximum payload.

On-board weighing - this can be achieved via the loading crane or by air pressure transducers on the vehicle via the middle axle of the tri-axle trailer and the back axle of the tractor unit. 

"It provides an accurate indication to the driver in the forest of the vehicle gross or load weight and is very important in delivering compliance with vehicle weights," says Devlin. 

Vehicle tracking - while this is not unique to timber transport it provides useful information on speed, location, fuel usage and engine management.

"In future this may be extended to record weights and tyre pressures and can be used to demonstrate compliance. This has also significant benefits in relation to timber security," he says. 

Currently there is some work being done to interact the GPS data with the on-board weight data.

Central Tyre Inflation (CTI) - this enables the drivers to select from a suite of tyre pressures the most suitable option for the operation such as operating empty or laden on primary roads and more particularly on forest or local public roads.

"The system will reduce the tyre pressures for operating on forest and local roads, thereby increasing the contact area and reducing the potential for road damage," says Devlin.

A CTI is a system to provide control over the air pressure in each tire of a vehicle as a way to improve performance on different surfaces. For example, lowering the air pressure in a tyre creates a larger area of contact between the tyre and the ground and makes driving on softer ground much easier. It also does less damage to the surface. 

This is important on work sites and in agricultural fields. By giving the driver direct control over the air pressure in each tire, manoeuverability is greatly improved.
Another function of the CTI is to maintain pressure in the tyres if there is a slow leak or puncture. In this case, the system controls inflation automatically based on the selected pressure the driver has set.

CTI is extensively used in many off-road transport operations. In many countries, especially Australia, New Zealand and South Africa, CTI is used in logging, in mining, and in power line maintenance. CTI significantly reduces environmental impact when transporting logs, or travelling on gravel or dirt roads. 

"Benefits include ironing out ruts and previous road damage, like washboards or corrugations. Reducing the tire pressure also reduces the grinding action on the gravel, significantly reducing dust and silt," says Devlin.

CTI also extends truck, tire, and drive train life, by significantly reducing vibration and shock loading. Feedback from Australian logging contractors show a doubling of transmission and differential life.

Maxi wide tyres - These are an extra wide tyre compared to the standard super single which will increase the contact area and reduce the potential for road damage. 

"There are other bespoke solutions involving multiple wheels on an axle which can be employed for particularly difficult situations. These vehicles will, however, require special permits to operate on public roads," he concludes. 

Source : Wood Southern Africa & Timber Times