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A crucial factor when buying a stacker truck is the mast. A stacker mast is the device that allows a stacker truck to lift and move heavy loads easily. This not only determines the maximum lifting height, but also influences the load capacity and the range of applications of the truck.
With different lifting heights, telescopic variants, and additional functions available, there is plenty of choice when it comes to selecting the right mast. You can match the equipment precisely to your warehouse and operating needs. In this guide, you will discover which stacker masts are available, how they differ from each other, what advantages they each offer and when it’s worth choosing a mast with a large free lift.
Hydraulic masts for stacker trucks
A stacker truck mast is operated either exclusively by hand hydraulics or with the support of an electric motor. You can read more about hydraulics in our guide. We have summarised the differences between manual hydraulic and electro-hydraulic lift masts below:
1. Manual hydraulic lift masts
On manually operated stacker trucks, the hydraulic pump is activated by hand. The load is lifted either by pumping the tiller, repeatedly pressing a foot pedal, or turning a hand crank.
2. Electro-hydraulic lift masts
In contrast, electric stacker trucks are fitted with an electro-hydraulic lift mast. The mast, also known as the stacker mast, moves the load carrier and the load vertically. The dimensions of the stacker truck’s masts are key when comparingdifferent machines. The following terms are of particular importance:
| Term/Parameter | Meaning |
|---|---|
| Stacker mast, overall height | The overall height is the greatest height of an industrial truck measured from the ground. For trucks with a lifting mechanism, this can vary depending on the mast, according to whether it’s retracted or extended. |
| Lift | The term refers to the vertical distance the load carrier travels from the lowered position to its highest point when raised, measured at the top edge of the load carrier (e.g. the fork or platform). |
| Maximum lifting height | The term refers to the greatest possible distance from the ground to the highest position reached by the load carrier (top edge of the fork or platform) when fully raised. |
The requirements that the truck must meet depend on the types of aisles in your warehouse – wide aisles (WA), narrow aisles (NA), and very narrow aisles (VNA). The mast that best suits your stacker truck depends largely on the following:
- How is your intralogistics organised?
- How are your warehousing processes organised?
- At what heights do goods need to be stored?
- What ceiling heights does the space have?
- Are there any low doorways or gateways to consider?
Simplex Mast
The simplex mast – also known as a single stage vertical lift mast – consists of a fork carriage that runs centrally within the mast. The fork carriage is raised either directly by a centrally positioned lift cylinder or by means of a chain deflection. The overall height of the simplex mast stays the same even when the forks are raised to the maximum lift height.
| Advantages | Disadvantages |
|---|---|
| • More stable mast profile than a single-column mono mast • Does not change overall height even when the forks are fully raised | • Reaches comparatively low lifting heights (lower than the overall height) |
Mono Mast
A mono mast is a narrow single column stand mast fitted centrally on the truck. The lifting mechanism, to which the load forks are attached, travels up along it. The overall height remains unchanged throughout the lifting process, as the lift carriage moves directly up the stand mast. Only when the maximum lifting height is reached does the overall height increaseslightly due to the fork carriage structure.
| Advantages | Disadvantages |
|---|---|
| • Comparatively low dead weight, meaning it can also be used on mezzanine floors • Safe to operate with a clear view of the goods and surrounding warehouse area at all times • Can double as a mobile worktable • Overall height does not change, so it is also suited to rooms with comparatively low ceiling heights | • Not as stable as duplex or triplex masts • Only achieves a low lifting height (lower than the overall height) |
Duplex Mast
The frame construction of the duplex mast is identical to the simplex mast. However, in addition to the outer stand mast, the duplex mast has an inner driving mast. The fork carriage runs within this inner lift frame and is moved together with the driving mast via a lift cylinder by means of a simple chain deflection. The duplex mast is a dual lift mast that telescopes.
What does telescoping mean? Telescoping lets you adjust the lift height of the stacker mast so that pallets or other loads can be lifted to different heights.
Duplex masts come in two versions:
- Duplex mast with dual telescopic mast (ZT mast): Most electric stacker trucks with ZT masts have a small free lift of 100 mm, depending on the vehicle model. The lift carriage first moves up to 100 mm without changing the overall height of the mast. Once this free lift has been exhausted, the lift ratio becomes 2:1, which means that raising the forks by 200 mm extends the mast by 100 mm.
- Duplex mast with additional lift (ZZ mast): A ZZ mast is designed like a dual telescopic mast (ZT mast) but has an additional lifting cylinder that delivers a particularly large free lift (additional lift). This free lift is also achieved by means of a chain deflection. Once the large free lift has been exhausted, the fork carriage and the driving mast extend in a ratio of 1:1.
| Advantages | Disadvantages |
|---|---|
| • Stable mast construction offers higher lifting heights than mono and simplex masts • Small free lift allows loads to be lifted and moved close to the ground without changing the overall height • Large free lift is ideal for stacking and unstacking goods in rooms with low ceilings, in wagons or shipping containers | • Cannot reach the same storage heights as vehicles with triplex mast • Some applications may still require a higher free lift |
Triplex Mast
Stacker trucks with a triplex mast (also known as a triple telescopic mast with additional lift or DZ mast) are particularly versatile. This is due to the telescopic mast, which can reach three times the height of the outer mast. The three-stage mast consists of a fixed outer stand mast attached to the vehicle, with two movable driving masts. The lift carriage and fork carriage move upward on the innermost mast. This design allows the mast to telescope a total of three times, achieving lifting heights of up to around 6 metres.
Industrial trucks with a triplex mast come with an additional lift cylinder as standard, giving them a particularly large free lift. The central cylinder extends the fork carriage at a 2:1 ratio with a chain deflection. Then the middle and inner lift frames extend at the same ratio. The fork carriage always sits at the highest point of the inner lift frame.
| Advantages | Disadvantages |
|---|---|
| • Best ratio of overall height to lift height: very high lift heights can be achieved from a low overall height • Equipped as standard with a particularly large free lift • Suitable for environments with low ceiling heights, doorways and passageways, as well as for loading and unloading tall storage racks | • More expensive, owing to the technically sophisticated mast |
The advantages of masts with free lift
In warehouse environments with low doorways and passageways, an industrial truck with free lift can be a worthwhile investment.
Free lift is the height to which the lift carriage of a stacker truck with a duplex or triplex mast can be raised without the inner driving mast extending. For a stacker truck with approximately 45 cm of free lift, you can raise the load to that height without changing the overall height of the truck.
There are two types of free lift function:
- Small free lift: This raises the fork carriage by up to 100 mm without changing the overall height of the mast. This allows pallets to be lifted and moved close to the ground, with no change to the truck’s overall height.
- Large free lift (full free lift): A large free lift is achieved by a second lift cylinder. The inner driving mast only extends once the free lift is exhausted. Stacker masts with full free lift are suitable for loading and unloading containers and trucks, even in rooms with low ceilings. They’re also ideal for stacking and retrieving goods in tall storage racks, such as high-bay warehouses.
On a stacker truck without free lift, the telescopic mast extends as soon as you raise the load. Due to the resulting change in the height of the mast, this has a big impact on where the truck can be used indoors. In warehouses or retail spaces with low ceilings or doorways, stacker trucks without free lift can only be used to a very limited extent or not at all.
FAQ for stacker masts
A mono mast is a single column lift mast positioned centrally on the truck. A simplex mast, on the other hand, is a two-column mast that can handle heavier loads due to its more robust design. Neither type of mast can be telescoped, so their overall height stays the same.
A free lift is the height to which the lift carriage of a stacker truck with a duplex or triplex mast can be raised without the inner driving mast extending. Within this range, the overall height of the truck does not change. There is a small free lift (approx. 100 mm) and a large free lift (also known as full free lift).
Only very few electric stacker trucks retain their full rated capacity at the maximum lift height, so always check the residual load capacity shown in the load capacity chart.
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