Tow tractors can take the load – safely

Richard McKay* argues that tow tractors can improve safety without relying on training.

VER recent years and particularly the past two years, many articles have appeared in trade magazines regarding the safety issues associated with forklifts, in most cases to do with mixing them with pedestrians.

The simple answer is to separate forklifts and people, but often this is not possible or it is only possible in part. Workplace safety has been improved by recent innovations such as seatbelt interlocks, immobilisers that activate when the operator leaves the driver’s seat, stability control, and speed limiting technology that activates when tines are raised. These admirable design improvements still rely on the operator who must be trained and licensed.

But there is a better solution!

Use a tow tractor and several trailers in conjunction with forklifts. Most applications use three trailers in a train but much longer (up to 10 or more) trailers can effectively be coupled together. Battery electric tow tractors are available with tow capacities from 1t up to 30t.

The tractor operator drives from the front of the train giving an unimpeded forward and sideways view. This often is not the case with a forklift.

Towing three trailers, for example, six pallets can be delivered in each journey. Using a forklift only one pallet can be delivered in each journey.

Assuming the travel speed is the same for forklift or tractor, a large saving in time can be achieved as well as providing a safer environment for pedestrians due to less frequent movements. One argument put forward against the use of trailers is that wider aisles are needed to accommodate the train of trailers but this can be overcome simply and economically by using the correct configuration trailers.

Types of trailers

There are three basic types of trailers and choosing the correct configuration for a given site is an important choice.

A caster steer system involves two swivel casters at the drawbar end and two fixed wheels at the rear. This configuration provides good tracking in a train and is easy to manoeuvre by hand when disconnected.

This setup is often fitted with a push bar for manual handling and can be constructed in a square pattern. It offers the best stability as the deck can be lower to the ground and wheels can be placed at extreme corners of the chassis.

Unfortunately when on uneven concrete or bitumen surfaces, caster wheels can “shimmy”, causing premature wear and creating noise.

A two-wheel steer system involves a front axle on a turntable, with the rear wheels fixed. This offers better tracking in a train than the caster steer system and can be reversed if only a single trailer is attached. It needs to be a rectangular shape, containing two pallets or more, to allow steer axle clearance. The fixed rear axle also provides good stability.

Finally the four-wheel steer configuration involves front and rear axles on turntables and connected with a cross bar which steers the rear axle in the opposite direction to front axle. This system offers the best tracking in a train and very little corner cutting even with multiple trailers in a train.

However it does not offer stability as good as other configurations, particularly if loads are offset to one side. It is also very difficult to reverse, even if only a single trailer is attached, and it is difficult to manoeuvre by hand.

In all configurations, trailers can be built to suit individual crates and pallets, and goods can be loaded directly onto the trailer without needing a pallet or skid.

Wheels and tyres can be selected to suit particular application. For two and four-wheel steer, the most popular equipment is pneumatic tyres, with optional foam filling for puncture proofing and solid cushion tyres as another choice.

For particularly heavy loads such as plasterboard packs of say 6t, urethane on cast iron wheels are used.

For caster steer, there is a very wide range of wheels from pneumatic tyres to solid rubber tyres to urethane on cast iron to plain cast iron or nylon. In all cases non-marking tyres are available.

Less forklifts for car industry

Lean manufacturing, combined with the desire to minimise forklifts use in areas where people are, has driven logistics designers to rethink the whole scene.

This trend has largely been driven by automotive manufacturers and their suppliers. Component parts from off-site suppliers are now loaded into specific modules on wheels which are road trucked to the assembly site, lifted off by forklifts in a pedestrian-free zone, then towed in a train to the production line, where people are working.

Empty modules are returned to lift on/lift off area, sometimes in knock down configuration for return to the supplier.

Considering the investment that the motor manufacturers have in existing crates and stillages, and the traditional materials handling methods used to bring them to the production line via forklift, an improved safety regime needed to be found without breaking the bank. Enter the roll on/roll off trailer towed in a train.

Component parts packed into traditional stillages are unloaded from the supplier’s transport and placed on a roller storage conveyor in a pedestrian free zone by forklift. A tow tractor with a train of trailers fitted with rollers comes alongside the storage conveyor and stillages are pushed by hand or gravity onto the trailers. The stillages are offloaded at a marshalling point or offloaded directly at the production line where there is a static roller conveyor.

Over recent years there has been a consistent trend by manufacturers and warehouses to minimise the use of forklifts to improve safety. Forklifts will continue to be a key element in the movement of goods but a tractor and train of trailers can minimise the number of trips and therefore exposure to pedestrians and can produce more economical outcomes as well.

* Richard McKay is MD of Warehousing Equipment, 03 9314 2611.