Guide · Engineering · Updated 7 November 2026
Lifting off-center loads safely
Calculate the tilting moment, find the center of gravity and choose the right lifting aid
By Zeilhofer Handhabungstechnik, manufacturer from Holzkirchen, Germany · more than 2,500 systems delivered since 1999 · ISO 9001 and TISAX Level 2
Short answer
A load is off-center when its center of gravity lies to the side of the gripping or suspension point. This creates a tilting moment: weight force times distance, M = m × g × a. On a crane hook, chain hoist or vacuum tube lifter the load rotates until its center of gravity sits vertically below the suspension point. It hangs at an angle and swings. A lifting aid with rigid load guidance absorbs the moment and holds the part in position. At Zeilhofer these are the ZH90 lifting axis up to 1,200 kg, the articulated arm manipulator up to 800 kg, the ZH90 Flex-Arm up to 200 kg and the Hebelift ZH up to 100 kg.
Key points at a glance
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Off-center means: the center of gravity and the gripping point are not aligned vertically.
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The tilting moment grows with weight and distance. 200 kg with a 300 mm offset results in about 589 Nm.
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The 3D model gives the most accurate center of gravity; alternatively, weigh the part on two scales.
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Cranes, chain hoists and vacuum tube lifters cannot absorb a moment; the load tilts into the vertical.
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Rigid guidance holds the load in position; the operator does not feel the moment.
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Zeilhofer designs the base system and the gripper for weight and center-of-gravity position.
CHAPTER 01
What is an off-center load?
Every part has a center of gravity in which its weight is notionally concentrated. If the gripping or suspension point lies exactly above it, the load hangs steadily. If it lies to the side, the load is off-center. In production this is the rule rather than the exception: a gearbox housing is gripped by its flange, a glass pane is held by suction on one side, a trailer hitch does not have its center of gravity in the middle of the part.
Part-specific grippers on the ZH90 lifting axis: the gripping point rarely sits exactly above the center of gravity.
Center-of-gravity offset
Horizontal distance between the center of gravity and the gripping point, also called lever arm a.
Tilting moment
Turning effect of the load around the gripping point, also called load moment. Unit: Nm.
Eccentric
Technical term for off-center: the load does not act at the center.
Top-heavy
The center of gravity is high or to one side; the part tends to tip when lifted.
Scope: This guide covers the moment created by the weight of a load. The moment a nutrunner generates when tightening is covered in the guide Reaction torque when screwdriving.
CHAPTER 02
How to calculate the tilting moment
The moment of an off-center load is the product of weight force and lever arm. The lever arm is the horizontal distance between the center of gravity and the gripping point.
M = m × g × a
M = tilting moment in Nm · m = mass in kg · g = 9.81 m/s² · a = horizontal distance from center of gravity to gripping point in m
The further the center of gravity is from the gripping point, the larger the moment. Twice the distance means twice the moment.
Example 1
50 kg, center of gravity 400 mm beside the gripping point
≈ 196 Nm
50 × 9.81 × 0.4
Example 2
200 kg, center of gravity 300 mm beside the gripping point
≈ 589 Nm
200 × 9.81 × 0.3
Example 3
800 kg, center of gravity 500 mm beside the gripping point
≈ 3,924 Nm
800 × 9.81 × 0.5
Caution when rotating, tilting and turning: if the part is rotated about a horizontal axis, the center of gravity moves with it and the horizontal distance to the gripping point changes. The position with the greatest distance is decisive. Inertial forces are added when starting and braking. That is why Zeilhofer designs for the least favorable position, including acceleration and safety margins.
CHAPTER 03
Finding the center of gravity: three methods
With irregular parts the center of gravity is often not visible. The German Social Accident Insurance (DGUV) recommends marking it on the part or the packaging. Besides the weight, it is the most important input for designing a lifting aid.
01
From the 3D model
The most accurate method. Every common CAD system outputs weight and center-of-gravity coordinates via its mass properties, provided the materials are assigned correctly.
02
With two scales
Place the part on two supports at distance L, with a scale under each. The center of gravity lies at distance x = L × F2 / (F1 + F2) from support 1.
Example: L = 1,000 mm, F1 = 120 kg, F2 = 80 kg → x = 400 mm
03
By suspension
For flat parts: suspend freely from two points one after the other and mark the vertical each time. The intersection of the lines is the center of gravity.
If you have several part variants, tell us the center of gravity of each one. The gripper is designed for the least favorable variant.
CHAPTER 04
Which lifting technology absorbs the moment
A rope, a chain or a vacuum tube can only pull; it cannot hold a moment. If such a system lifts an off-center load, the load rotates until its center of gravity lies vertically below the suspension point. The part hangs at an angle, keeps swinging and has to be brought into position by hand. When joining, loading a machine or placing the part on a workpiece carrier, this is exactly the critical moment.
Suspended or rigidly guided: only rigid guidance holds a part gripped off-center in position.
Overhead crane and chain hoist
Suspended load, no moment can be absorbed. The load aligns itself with its center of gravity and swings.
Does not absorb the moment
Vacuum tube lifter
Hangs on the tube; the part swings and tilts when held by suction on one side. Drawbacks and alternative
Does not absorb the moment
Rope manipulator
Guided by the center of gravity on a rope, up to 150 kg. Suitable if the gripping point lies above the center of gravity or the gripper adapts to it.
Suitable to a limited extent
Articulated arm manipulator and lifting axis
Rigid load guidance; the moment is taken by the structure. The part stays stable at every height and in every position.
Absorbs the moment
When a crane still makes sense is compared in the guide Manipulator, crane or chain hoist?
CHAPTER 05
Zeilhofer systems for off-center loads
The operator guides the part with little force while the guidance carries the moment. Which system fits depends on weight, center-of-gravity offset and movement.
UP TO 1,200 KG
ZH90 lifting axis
The patented Zeilhofer lifting axis guides the load rigidly in the Z direction and absorbs moments from off-center loads. Torsional stiffness 3,000 Nm at 1,000 mm stroke, positioning to the millimeter. For heavy parts with a large center-of-gravity offset.
UP TO 800 KG
Articulated arm manipulator
The rigid Zeilhofer articulated arm absorbs off-center loads and torques, with a radius of up to 4.5 m. Typical when parts are inserted sideways into machines or fixtures.
UP TO 200 KG
ZH90 Flex-Arm
Lifting axis and articulated arm in one system, up to 4 m radius, optionally with a 48-volt battery. For medium loads with a center-of-gravity offset and an additional swivel range.
UP TO 100 KG
Hebelift ZH
Mobile, with Zeilhofer 48 V battery technology and the lifting axis at its core. Holds lighter off-center parts rigidly in position, even where no ceiling or rail is available.
Not sure which system fits? The product finder leads you to the right lifting aid in about one minute. You can configure the ZH90 lifting axis directly in the ZH90 configurator.
CHAPTER 06
Typical off-center parts from practice
VEHICLE ASSEMBLY
Trailer hitches
Depending on the design, the center of gravity is not in the middle of the part.
CONTROL CABINET CONSTRUCTION
Mounting plates and enclosures
TOOLMAKING
Changing tools
VEHICLE ASSEMBLY
Car doors
GLASS AND WINDOWS
Glass panes
Held by suction or gripped on one side; the position changes when tilting and glazing.
ENGINE AND TRANSMISSION
Joining powertrain units
AGRICULTURAL AND CONSTRUCTION MACHINERY
Gearbox housings and axle parts
MECHANICAL ENGINEERING
Loading workpieces
Guided sideways into the machine; the gripper sits outside while the load projects inside.
FOUNDRY
Ladles and crucibles
When pouring, the center of gravity moves with the fill level. Rigid guidance keeps the ladle in position for controlled pouring.
CHAPTER 07
The gripper makes a difference
How large the moment becomes is determined not only by the part but also by the gripper. Zeilhofer designs it for each part and uses four levers:
Custom grippers from Holzkirchen, Germany: gripping points, rotation axes and variants are designed for each part.
01
Gripping point close to the center of gravity
Where the part geometry allows, the gripper moves closer to the center of gravity. This shortens the lever arm and therefore the moment.
02
Multiple pick-up points
Gripping, suction or a combination of both distribute the load and hold the part securely in position.
03
Rotation axes in the gripper
Rotating, tilting and turning into the installation position without the operator holding the weight. For heavy parts there is the ZH lift-and-rotate unit.
04
Variants in one gripper
Several part types with different centers of gravity in one gripper, designed for the least favorable variant.
CHAPTER 08
Safety, ergonomics and standards
Ergonomics
Anyone pushing a load that hangs at an angle into position by hand often works with a twisted torso and far from the body. This feeds into the risk assessment under the German Manual Handling of Loads Ordinance (LasthandhabV). Limits and the key indicator method
Risk assessment
Tipping and falling of the load belong in the risk assessment according to EN ISO 12100. The basis is the Machinery Directive and, from 20 January 2027, the EU Machinery Regulation. What changes in 2027
Load handling attachments
Non-fixed load lifting attachments such as grippers and suction pads fall under EN 13155. Zeilhofer designs them for weight and center-of-gravity position and supplies them CE-compliant.
In-service inspection
In Germany, lifting aids are inspected annually according to DGUV Regulation 54. As the manufacturer, Zeilhofer carries out this statutory inspection. To the annual inspection
CHAPTER 09
Checklist: the information needed for the design
With this information Zeilhofer designs the base system and gripper for your off-center part. A drawing or 3D model speeds up the design.
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Weight of the part; for variants, the heaviest
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Center-of-gravity position, ideally from the 3D model
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Possible gripping and suction surfaces
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Pick-up and set-down position: does the part need to be rotated, tilted or turned?
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Movement: stroke, reach, lateral insertion
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Workstation: ceiling, rail or floor, available installation space
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Cycle time and number of part variants
FAQ / Q&A
Frequently asked questions about off-center loads
01 What is an off-center load?
A load is off-center when its center of gravity lies to the side of the gripping or suspension point. This creates a tilting moment that the lifting aid has to absorb.
02 How do you calculate the moment of an off-center load?
Mass times 9.81 times the distance between center of gravity and gripping point: M = m × g × a. 200 kg with a 300 mm offset results in about 589 Nm.
03 How do you find the center of gravity of a part?
Most accurately from the 3D model. Alternatively with two scales under two supports: x = L × F2 / (F1 + F2). Flat parts can be suspended from two points.
04 Why does an off-center load tilt on a crane?
Ropes and chains cannot hold a moment. The load rotates until its center of gravity lies vertically below the hook and then hangs at an angle.
05 Which lifting aid is suitable for off-center loads?
Systems with rigid load guidance: at Zeilhofer the ZH90 lifting axis up to 1,200 kg, the articulated arm manipulator up to 800 kg, the ZH90 Flex-Arm up to 200 kg and the Hebelift ZH up to 100 kg.
06 Can a rope manipulator or vacuum tube lifter lift off-center loads?
A vacuum tube lifter cannot; the part tilts. The Zeilhofer rope manipulator (up to 150 kg) only if the gripping point lies above the center of gravity or the gripper adapts.
07 Does the operator feel the moment when guiding the load?
No. With a Zeilhofer lifting aid with rigid guidance, the moment is taken by the structure. The operator guides the part with little force.
08 What is the difference between load moment and reaction torque?
The load moment results from the weight of an off-center load. The reaction torque results from the tightening torque of the tool during screwdriving.
09 How far may the center of gravity be from the gripping point?
That depends on weight, system and gripper. Zeilhofer designs guidance and gripper for the calculated moment in the least favorable position.
10 What information does Zeilhofer need for the design?
Weight, center-of-gravity position, gripping surfaces, pick-up and set-down position, movement and workstation. Zeilhofer answers inquiries within 24 hours on working days.
READ MORE
Related guides
SELECTION
Choosing a lifting axis
ENGINEERING
Reaction torque when screwdriving
COMPARISON
Articulated arm or rope manipulator?
NEXT STEP
Inquire about your off-center part
Tell us the weight, center-of-gravity position and workstation, ideally with a drawing or 3D model. Zeilhofer designs the lifting aid and gripper for your part. We answer inquiries within 24 hours on working days.
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