What is Center of Gravity

The center of gravity (or center of mass) of an object is the average location of the weight (or mass) of an object in space. An object suspended from its center of gravity in space will be perfectly balanced. A force applied to the center of gravity causes pure translation. A force not applied through the center of gravity makes the object rotate about its center of gravity. When it comes to design of aircraft, spacecraft and even automobiles, calculating the center of gravity is an important part of the process.

Why does one need to find the Center of Gravity?

Controlling the flight of an object necessitates good knowledge of its center of gravity location. For example, aligning the direction of thrust of a rocket motor so that it pushes exactly through the center of gravity of the rocket is essential to achieving a straight flight. This could make a huge difference for the stability of the aircraft as well as its fuel efficiency as it travels from one point to another.

In automotible design, the lower the center of gravity, the greater the stability of the car or truck. This explains why trucks & SUVs have more rollover issues than cars, because they are higher off the road so their center of gravity is higher. Race cars always have a very low center of gravity to avoid rollovers at high speed turns.

It is quite clear that calculating the center of gravity is a critical part of the design process. The question then is how best to do this?

How to calculate the Center of Gravity of an object?
Center of Gravity CG Scale

The center of gravity of an object can be calculated by placing an object on a multiple sensor scale - typically done with a four load cell scale or three load cell scale.  The object is placed at the center of the scale platform. The weight of the object is measured at the four corners individually and the location of the four load cells with respect to the origin is used to compute the sum of the moments and this sum is divided by the total weight to calculate the locations of its x and y position.

X = (W1*X1 + W2*X2 + W3*X3 + W4*X4)/(W1+W2+W3+W4)
And
Y = (W1*Y1 + W2*Y2 + W3*Y3 + W4*Y4)/(W1+W2+W3+W4)

The object can be rotated by 90 degrees and the same process repeated to calculate the center of gravity in the other plane.

Highlights of our Center of Gravity Solution

  • Platform Scale with four USB Load Cells
  • Power & Data via USB port
  • Easy to use LV-4000CG Software
  • Calibration to NIST Standards with certificate
  • Calibration stored in sensor
  • Software compatible with Win 8/10
  • Data updated at up to 150 Hz
  • Display, Log & Plot data in a user friendly GUI interface
  • Accuracy of each load cell is of the order of +/- 0.25% of full scale 
  • Accuracy of scale overall is around +/- 1% of capacity
  • See Center of Gravity in real time with live tracking
  • Store data in a CSV file and open in Excel, Matlab etc.
  • Just place on your desk or floor & level the scale before use
  • Made using light weight Aluminum material with etched grid

How it Works

  • The scale is built using four load cells installed at the four corners of a platform built using stiff aluminum framing. The platform has etched grid on the surface to locate CG.
Center of Gravity CG Scale Top
CG Scale Top with Grid Marks
Center of Gravity CG Scale Bottom with Senors
CG Scale Bottom with Sensors

The scale is built using four iLoad Pro load cells installed at the four corners of a platform built using aluminum framing and one four port USB Hub.

The max update rate from the sensor is 150 Hz.  But if needed, we can provide a max data update of up to 500 Hz.

The location of the Center of Gravity is calculated using the simple formula:

X = (W1*X1 + W2*X2 + W3*X3 + W4*X4)/(W1+W2+W3+W4)
And
Y = (W1*Y1 + W2*Y2 + W3*Y3 + W4*Y4)/(W1+W2+W3+W4)

You can compute the CG of an object in 3D by calculating the CG in two dimensions first and then tilting the platform by a known angle and then measuring the new CG again and figuring out the CG in 3D using transformations.  We do not offer a 3D solution yet as a standard product but could offer a solution to interested customers in the future. Please contact us for your custom CG scale needs.

Center of Gravity CG Scale with Weights
CG Scale Shown with Weights
Center of Gravity CG Scale Software Screen
CG Scale Software

The LoadVUE Pro Center of Gravity software is to be used with the CG Scale to compute and display the Center of gravity of objects in two dimensions.  The individual weights or forces on each load cell is displayed as well as the CG of the object in 2D space is shown as a dot whose diameter varies with the total weight of force of the object.

This can be used to monitor static as well as dynamic change of the CG in real time in order to study the weight and balance distribution of human beings or animals.  The size of the scale as well as the capacity of the scale can be changed to meet your needs. A few standard configurations are available for purchase. Please contact us for your custom CG scale needs.

Watch and Learn

Build Your Own Center of Gravity Scale

If the standard options we offer as Center of Gravity Scales do not meet your needs, you can build your own using our digital USB load cell kit! You just have to build a rigid frame first and mount the four load cells at the four corners of the frame. You can then create a platform (add a grid for easy location and to define a coordinate system) where you can place the objects you want to measure. Use the included load buttons (leveling feet) to level the scale before zeroing it out and using it.

Build Your Own Center of Gravity CG Scale Kit
What's Included in the CG Scale Kit?

The CG Scale kit includes, Four iLoad Pro Load Cells, adjustable feet (load buttons) for leveling of the platform, one 4-Port USB Hub, and LV-4000CG software provided on a USB Drive or as a downloadable link. Calibration certificates for each load cell are included showing traceability to NIST standards. You just need to build your platform and frame and get a PC with Win 8/10 operating system, 8 GB RAM and enough disk space to capture data (500 GB should be more than enough).

Do you need a center of gravity scale custom built to your specs?