When choosing an electric stacker, buyers often focus on rated capacity, such as 1,000 kg, 1,500 kg, or 2,000 kg. However, rated capacity cannot be considered separately from the load center.
A stacker rated at 1,500 kg does not necessarily mean it can safely lift every 1,500 kg load. The rated capacity applies to a specific load center and other conditions specified by the manufacturer. If the load's center of gravity moves farther away from the fork face, the load creates a larger overturning moment and the allowable capacity may decrease.
For warehouse equipment buyers, understanding load center is therefore important when selecting the right electric pallet stacker.
What Is Load Center on an Electric Stacker?
The load center is the horizontal distance from the vertical face of the forks to the center of gravity of the load.
For a uniformly distributed rectangular load, the load center is approximately half of the load depth in the fork direction.
For example:
Load depth = 1,000 mm
Load center = 1,000 ÷ 2 = 500 mm
This is why 500 mm load center is a common reference point for many warehouse lifting machines. A 1,000 mm-deep load with evenly distributed weight has an approximate 500 mm center of gravity from the fork face.
Simple Load Center Examples
| Load Depth in Fork Direction | Approx. Load Center* |
|---|---|
| 800 mm | 400 mm |
| 1,000 mm | 500 mm |
| 1,200 mm | 600 mm |
| 1,400 mm | 700 mm |
| 1,600 mm | 800 mm |
*Assumes the load is evenly distributed and positioned against the fork face.
For irregular or unevenly distributed loads, simply dividing the load depth by two may not give the actual center of gravity.
Why Does Load Center Affect Electric Stacker Capacity?
The reason is basic leverage.
When a load is positioned farther forward, its weight creates a larger load moment. A simplified calculation is:
Load Moment = Load Weight × Load Center
For example, consider a 1,500 kg load.
At a 500 mm load center:
1,500 × 500 = 750,000 kg·mm
If the same 1,500 kg load has a 600 mm load center:
1,500 × 600 = 900,000 kg·mm
The load weight has not changed, but the load moment has increased by 20%.
| Load Weight | Load Center | Load Moment |
|---|---|---|
| 1,500 kg | 500 mm | 750,000 kg·mm |
| 1,500 kg | 600 mm | 900,000 kg·mm |
| 1,500 kg | 700 mm | 1,050,000 kg·mm |
| 1,500 kg | 800 mm | 1,200,000 kg·mm |
This illustrates why a longer or deeper load can reduce the usable capacity of a stacker even when its total weight remains unchanged.
Example: A 1.5 Ton Electric Stacker
Suppose an electric stacker is rated:
Rated capacity: 1,500 kg
Rated load center: 500 mm
Application: Warehouse pallet stacking
A simplified load-center calculation can be used to understand the relationship:
Estimated capacity = Rated capacity × Rated load center ÷ Actual load center
Using this simplified model:
| Actual Load Center | Simplified Estimated Capacity |
|---|---|
| 500 mm | 1,500 kg |
| 600 mm | 1,250 kg |
| 700 mm | 1,071 kg |
| 800 mm | 938 kg |
| 1,000 mm | 750 kg |
For example, at a 600 mm load center:
1,500 × 500 ÷ 600 = 1,250 kg
So, under this simplified load-moment model, a 1,500 kg-rated machine would correspond to approximately 1,250 kg at a 600 mm load center.
However, this is not a substitute for the manufacturer's actual capacity rating. Real equipment capacity is also affected by mast configuration, lift height, forks, attachments, chassis stability, hydraulics and other engineering factors. The manufacturer's capacity plate or load chart is the controlling reference.
Load Center vs. Fork Length
Load center and fork length are related, but they are not the same thing.
For example, an electric stacker may have 1,070 mm forks, but that does not automatically mean the load center is 535 mm.
The load center depends on where the center of gravity of the actual load is located.
Consider a 1,000 mm-deep pallet with evenly distributed goods:
1,000 ÷ 2 = 500 mm load center
If the pallet is not fully positioned against the fork face, or the load is heavier toward the front, the actual load center can be greater than 500 mm.
Therefore, buyers should evaluate:
Fork length
Load depth
Load distribution
Load positioning
Actual center of gravity
rather than using fork length alone to determine load center.
How Load Center Changes with Different Pallet Sizes
Consider three pallets with evenly distributed loads:
| Pallet Depth | Load Center | Example Weight |
|---|---|---|
| 800 mm | 400 mm | 800 kg |
| 1,000 mm | 500 mm | 1,200 kg |
| 1,200 mm | 600 mm | 1,500 kg |
| 1,400 mm | 700 mm | 1,500 kg |
The last two loads have the same 1,500 kg weight, but their load centers are different.
The 1,400 mm-deep load places its center of gravity farther from the fork face, producing a greater load moment.
This is particularly important for buyers handling long pallets, machinery, paper products, steel products, containers, or irregular loads.
Load Center Is Not the Only Factor Affecting Capacity
Although load center is important, it is not the only specification that determines actual lifting capacity.
1. Lift Height
Capacity can vary with lifting height and mast configuration. A machine that is rated for a certain load at a lower height may have a different allowable capacity at maximum lift height.
Therefore, when purchasing an electric stacker, buyers should provide both:
Required load weight + required lifting height
rather than only asking for a "1.5 ton stacker."
2. Mast Type
Duplex and triplex masts can have different capacity characteristics depending on the machine design.
For example:
| Specification | Example |
|---|---|
| Capacity | 1,500 kg |
| Load Center | 500 mm |
| Mast | Duplex / Triplex |
| Lift Height | 3,000–5,000 mm |
| Application | Warehouse stacking |
The exact capacity must be confirmed for the selected mast and lift height.
3. Attachments
Attachments can change the effective load center and overall capacity.
Examples include:
Side shifter
Fork positioner
Clamps
Special forks
Fork extensions
An attachment may add weight and move the load farther forward. Therefore, buyers should ask suppliers for the rated capacity of the complete configuration, not simply the base machine.
4. Load Distribution
Two pallets can have exactly the same weight but different centers of gravity.
For example:
Pallet A: 1,200 kg evenly distributed
Pallet B: 1,200 kg with most of the weight concentrated toward the fork tips
The second load may create a greater load moment.
This is why load weight alone is not sufficient when selecting an electric stacker.
What Should Buyers Ask an Electric Stacker Supplier?
When requesting a quotation, it is useful to provide the supplier with the following information:
| Parameter | Example |
|---|---|
| Maximum Load | 1,500 kg |
| Typical Load | 1,200 kg |
| Load Center | 500 mm |
| Maximum Lift Height | 4,500 mm |
| Pallet Size | 1,200 × 1,000 mm |
| Mast Type | Duplex |
| Working Environment | Indoor warehouse |
| Aisle Width | 2,800 mm |
| Daily Working Time | 6–8 hours |
With this information, the supplier can recommend a configuration based on the actual warehouse application instead of simply matching the buyer with a machine based on tonnage.
A Common Mistake: Choosing Only by Rated Capacity
One of the most common mistakes is asking:
"I need a 1.5 ton electric stacker. What is your price?"
This provides only one piece of the information required for proper selection.
A better inquiry would be:
"We need to handle 1,500 kg pallets at a 500 mm load center and lift them to 4,500 mm. Please recommend a suitable stand-on electric stacker."
This gives the supplier much more useful information for selecting the correct machine.
FAQ
Is 500 mm a standard load center for an electric stacker?
500 mm is a common reference load center in metric specifications, but the actual rated load center depends on the specific model and manufacturer. Always check the technical specification or capacity plate.
Does a longer fork automatically reduce capacity?
Not necessarily. Fork length itself is not the load center. However, if a longer fork or a different load arrangement causes the load's center of gravity to move farther forward, the effective load center increases and the allowable capacity may decrease.
Can a 1,500 kg electric stacker always lift 1,500 kg?
No. The 1,500 kg rating applies only under the specified conditions, including load center, lift height, mast and other configuration parameters.
How should I select an electric stacker for a long load?
Provide the supplier with the load weight, load dimensions, actual center of gravity, required lift height and operating conditions. For unusual loads, obtain the manufacturer's specific capacity confirmation rather than relying on a simple calculation.
Conclusion
Load center is an important part of electric stacker capacity. The farther the load's center of gravity is from the fork face, the greater the load moment and the more the available capacity can be affected.
For warehouse buyers, don't select an electric stacker based on "1 ton," "1.5 ton," or "2 ton" capacity alone. Check the load center, lifting height, mast configuration, pallet dimensions, load distribution and attachments together.
For preliminary planning, the load-moment calculation helps explain why capacity changes. For actual operation and purchasing, however, the manufacturer's rated capacity, data plate and load chart for the exact machine configuration should always take priority.