Click on the descriptions below to read about the functionalty factors of Equipment

General Description
  • The Outriggers and the body of the truck balances the weight of the load
  • The Load rests on the outrigger and during operation the outriggers move inside the shelf for stacking / unstacking purpose
  • Rated capacity is the maximum load that the truck can lift at the specific load center
  • Load center is the distance from the front face of the fork to the center of gravity of the load
  • Rated capacity reduces for load center larger than 500mm
  • Rated capacity reduces for lift height higher than 3900mm
  • Suitable for aisles with 2100mm to 2400mm width for straddle stackers and 2700mm to 3300mm width for counterbalance stacker
  • The Stacker trucks have a freedom of movement in five directions, namely
    1. Horizontal movement (driving wheel)
    2. Vertical movement of mast
    3. Forward and/ or backward tilting of mast
    4. Horizontal rotation (turning of wheel)
    5. Horizontal fork movement for handling multiple sizes of load (only available with fully electric stackers)
Types of Stackers

Stackers can be categorized on the basis of power supply. There are namely three types of stacker available in the market based on the power source namely,1) hydraulic pallet truck, 2) Scissor pallet truck, and 3) Battery operated pallet truck

Manual Stacker (Pallet + Walking + stacking + Manual): Manual Lifting and/ or traveling

Semi - Electric Stacker (Pallet + Walking + Stacking + Electric Power): Manual traveling and battery powered lifting & lowering mechanism

Fully Electric Stacker (Pallet + Walking + Stacking + Electric Power): Battery powered traveling and lifting & lowering mechanism

Based on the straddle design, fully electric stacker has three variations namely, 1) Wide Straddle type stacker, 2) Fork Over type straddle and 3) counterbalance stacker

While Wide straddle and counterbalance stacker can pick or drop load on the floor surface, Fork - Over straddle can only pick or drop loads placed on shelves.

Load Center

Load center is the distance between face of fork and center of gravity of load. Load center changes with change in the dimension of the load.

For Oversized load whose center of gravity is at a distance greater than the manufacturer's rated load center, the rated capacity should be equal to the weight of load at that particular load center for safe operation.

Load Capacity

Load capacity is the weight - distance relation between the load to be lifted and the rear counterbalance weight of the truck on the opposite sides of the fulcrum.

Deration(Reduction) occurs in rated load capacity due to height is caused due to the increase in distance between center of gravity of truck and the load to be lifted. The extended height affects the lifting moment and stability of truck.

Deration(Reduction) occurs in rated load capacity due to increase in load center/ attachment being used instead of forks due to addition of an extra weight of attachment to the load and increase in distance between the center of gravity of truck and the new center of gravity of Load + Attachment.

Heights to be measured during selection of Mast
  • Mast closed height: The distance from the floor to the top of the mast when the forks are in their lowest position is the mast closed height.

    For safe traveling of the truck, the mast closed height should be less then the roof/ door sizes of the working space (Fig. 1)

  • Mast overall raised height: The distance from the floor to the top of the load backrest extension when the mast is fully raised is the mast overall extended height.

    For safe working of truck, the roof height should be more than the maximum height of mast where stacking is done (Fig. 2)

  • Maximum fork height: The distance between the top of the fork and the ground when the mast is fully raised is the maximum fork height.

    The maximum height of stacking should always be less than or equal to the maximum fork height for safe operation (Fig. 3)

  • Free Lift: Free lift is the distance the forks may be raised from the floor before the mast begins to extend from its closed height/ collapsed height (Fig. 4).

    Free lift depends on the type of mast. Low free lift is applied to free lift of approx. 600mm or less. Full free free lift is available to slightly less than height of lowered mast at approx. 1520 mm.

    Full free lift allows stacking in low headroom conditions

Turning Radius
The turning space taken by truck to rotate by 90 degree without the load.
Aisle Width
Minimum Aisle width: The width of the road/ space between two adjacent shelves is called the aisle width (For safety reasons, the aisle width should be at least 150mm more on each side than the width of load or the truck, whichever is wider).
Minimum Aisle width = Clearance from wall (1) + Width of Truck/ load (2) + Clearance from wall (1)
90 degree stacking aisle width
The amount of space needed for a ninety degree turn of the truck for the purpose of stacking the load is the 90 degree Stacking Aisle Width 90 degree Stacking Aisle Width = Clearance from Wall/ shelf (1) + Turning Radius (2) + Truck length inclusive the back of fork (3) + Length of load/ fork (4) - Truck Length (5)

It is the ability of the truck to travel on slopes/ uphill roads/ inclined surface without a considerable loss of forward speed or drain on the source of the energy. The angle of incline is stated as percentage and is obtained by dividing the increase in height of slope per meter of slope/ road length

Electric motor: 10% (General)

Gradability = Height of slope/ Unit length of slope X 100%

Electric truck Battery selection

The battery selection is dependent upon voltage and Ampere - hour rating. The voltage is related to the speed of the truck. The ampere - hour is related to the number of continuous working hours of the truck i.e. higher the ampere - hour of battery, longer will be the running time. Batteries can be used until 80 percent discharged.

One Ampere - hour is equal to flow of one ampere current for one hour. Thus, a 750 Ahr (ampere - hour) will get discharged at 750 amperes in one hour or 375 amperes in two hours and so forth.

For a standard industrial battery, the running time can be calculated as,

(Ampere - hour rating) X Factor = Running Time
Average motor current

For an 8 - hour industrial battery, the factor is 0.95 & for a 6 - hour Industrial battery, the factor is 0.98

*Note: The equation is an approximation for calculative purpose only. The actual running time will depend on many other factors like size of the motor, terrain, driving condition and other specific truck application

Battery charger selection

Manufacturers offer two types of chargers namely single rate and double rate. As the name suggest, double rate battery chargers charge faster than the single rate battery charger. Double rate battery chargers are a little more expensive than single rate battery chargers

For a standard industrial battery charger, the running time can be calculated as,

(6 - 8-hour discharge rate) X Ampere - hour rating = Average charging time
Charger current rating X 0.66

*Note: The equation is an approximation for calculative purpose only. Please refer to the battery charger specification for details.

Parts of Stacker

Mast is an attachment to the mask/ face of the truck. It's an upright steel assembly of hydraulic cylinders to provide the lifting capability to the reach truck.

Mast have a stationary outside channel and telescopic inner channel that provides high lifting capability and low collapsible height.

    Types of mast
    1. 2 stage mast (1 columns of telescopic mast) Suitable for high lift application where the overall lowered height (mast closed height) is an issue or a critical criterion i.e. places with low ceilings and relatively small sized doors or places where the application is mostly indoor.
      These mast have double acting cylinders and chain reeving to achieve higher heights.
    2. 3 stage mast (2 columns of telescopic mast) Similar to 2 Stage mast but smaller overall lowered height than a 2 Stage mast.
    3. 4 Stage Mast (3 columns of telescopic mast) Similar to 3 Stage mast but smaller overall lowered height than a 3 Stage mast.

Electric Motor: Electric motors have two variants namely AC motors and DC motors.

  • Electric trucks are suitable only for Inside operation
  • Electric trucks require battery charging station

Fork carriage is the assembly to which a fork or any other attachment is connected. Carriage have three different classes, namely Class 1, Class 2, Class 3 which is based on the capacity of the reach truck.

Carriages have mounting holes for interchanging the fork attachment with some other attachment. Its done to maintain the versatility of the forklift.

Forks are the load engagement device i.e. they are the device that come in physical contact of the load to be lifted. Forks are attached to the carriage.

Forks standard dimension is ((1070 - 1200) X (100 - 150)) mm (Length X Width). They are around 40mm thick at the heels or the tip ends.

Overhead guard protects the driver from any falling object. It is considered a mandatory accessory required by OSHA (Occupational Safety and Health Administration).


Load backrest is what the name defines. They are provided atop carriage to avoid load from falling backward when the mast is tilted backward.


Outriggers are a replacement of counterbalance used in a standard forklift truck. The outriggers provide the necessary stability to the truck during lifting and lowering of load.

They are equivalent to the size of forks. Stackers have bigger straddles than the Reach truck because of the fixed mast and absence of pantographic movement present in stacker.


Drive Wheel is located at the back of hydraulic lifts mechanism and or below the battery compartment in battery operated pallet trucks.

Drive wheels come in either polyurethane or nylon wheels. While the polyurethane wheels are more rigid, for epoxy floors nylon wheels are more preferred.

Load rollers are positioned at the open end of the out riggers.

Drive wheel come in either polyurethane or nylon wheels. While the polyurethane wheels are more rigid, for epoxy floors nylon wheels are more preferred.