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Materials Handling

How to choose a stacker

By Mark Nicholson

March 2021

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Within any warehouse equipment manufacturer’s stacker range you will find a potentially bewildering variety of model types. With help from Andreas Schock, Warehouse Product Manager at Cat® Lift Trucks, Mark Nicholson sets out the key issues to consider when choosing between them.

Stackers are compact, economical and versatile trucks designed for stacking, retrieval and horizontal transport of pallet loads in warehouses and racking systems. They may even be used for occasional order picking. Importantly, they can do these things in narrower aisles and smaller spaces than a counterbalance forklift or a reach truck.

When it comes to replacing a stacker, you might simply go for the same type as you had before – but perhaps with a newer model. However, it pays to be open-minded and consider whether a different solution might improve your operation.

“A good salesperson will ask you many questions, to understand your situation fully before recommending a product,” says Andreas. “This conversation will cover both your current needs and the effects of future trends on your business. You need to be sure that the stacker you choose will still be the best solution in five to eight years.”

The main stacker categories are pedestrian, platform, stand-on and sit-on, as illustrated by the images shown here. Within those groups, there are versions with or without initial lift and straddle legs. You will also have a choice of capacities.

Size

One of the most fundamental questions is aisle width. Andreas notes: “Unless the stacker’s dimensions are small enough to operate in the space available, its other qualities are irrelevant. Pedestrian stackers are the most compact of all, but it’s worth noting that a stand-on stacker needs less aisle width than a platform stacker with its platform deployed. Sit-on stackers need wider aisles than the others.”

Walk, ride or sit

To determine whether walking, riding or sitting will be most effective, Andreas looks at the typical distance travelled per transport movement and the frequency of such movements. “If the distance is less than, say, 25 or 30 metres, and the turnover of pallet loads is low, a pedestrian model will be fine. For occasional longer travel, some pedestrian stackers have a fold-down riding platform.

“A platform stacker is designed for longer and more frequent shuttle runs. It usually has a higher travel speed and is equipped with foldable side bars for added safety. When moving over shorter distances, or manoeuvring in narrow spaces, the operator can opt to fold up the platform and use pedestrian mode.

“If movements are regularly up to 80 metres, or maybe a little more, stand-on stackers make good sense. For the greatest distances, longest shifts and most intensive materials handling, a sit-on stacker can minimise fatigue.”

Capacity and performance

While some applications require limitations on drive and lift speeds, to avoid damaging vulnerable goods and facilities, others welcome faster performance. Stand-on and sit-on stackers are generally the fastest and most powerful, but you should check and compare the maximum speed figures for all types.

The weight and size of your loads, and the heights to which they must be lifted, need to be considered together when deciding on capacity. Andreas reminds buyers that the rated capacity which appears in a truck’s name or description reduces with increasing height. “You need to check that its residual capacity at the height of your top racking beam is sufficient for the loads you will place at that level. Real-life maximum capacity is also reduced by longer loads. For the highest residual capacities and lift heights you will usually need a stand-on or sit-on stacker.”

Initial lift and straddle

Another factor affecting stacker choice is the nature of your floor. If it is rough or uneven, or if it includes ramps, you need an initial lift model. This gives greater ground clearance by raising its load legs. Some of these trucks can be used to carry two pallets simultaneously, with one on the load legs and one of the forks.

If your business uses bottom-boarded pallets, you will need a stacker with straddle legs. These widely separated load legs go around the sides of the pallet, instead of under it, leaving the forks free to lift from ground level. They are also useful for extra-wide loads.

Fine details

In addition to the essential measurements on which the above decisions are based, you should tell the salesperson more. Andreas’ questions include: “What are the particular obstacles and challenges you face in your daily business? What do you and your drivers have to do, day after day, when working with the stacker? What aspects of your workflow involving the stacker would you like to improve? And is there anything about your current truck that you don’t like, or you think could be improved?”

All of the details collected will be pieced together, like a mosaic, to give a complete picture of your needs. The salesperson will then match this with the ideal stacker, adding specific optional features where necessary to achieve the perfect fit.

Click here to see the current Cat® stacker range.

Capacity ratings

The rated capacity of a lift truck tells you the maximum weight it can safely lift and transport under specified conditions. If your truck has a rating of 2 tonnes, for example, it will happily lift that weight to a height of, say, 2 metres. However, it may not be possible or safe to lift it several metres higher than that. The reduced maximum capacity available at a specific lift height is known as the residual capacity.

Specification of rated capacity depends on load centre distance. This is the horizontal distance between the load’s centre of gravity and the vertical face of the forks. If it is longer than specified in the rating, stability is affected and capacity is reduced. Rating is also reduced if the mast is tilted. For lift trucks with mast attachments, further adjustments in rating are needed.

The lift truck salesperson should ensure that the chosen truck’s rated and residual capacities are suitable for your operation.

The four main stacker categories

Pedestrian stacker

Operator walks – guiding the truck with a tiller arm. Some models have a fold-down platform for occasional riding, but there are no side bars.

Platform stacker

Operator rides on a fold-down platform – and can deploy foldable side bars for extra protection – but also has the choice of pedestrian operation. Note: EU regulations demand that side bars must be folded in when lifting above 1.8 metres.