How to measure the Center of Gravity of your car!

How to Determine the Center of Gravity (CG) of Your Car

Introduction to CG Calculation

• Understanding the center of gravity (CG) is crucial for car suspension calculations. This video provides a concise method for determining the CG location in any vehicle.

• The focus will be on measuring CG in both longitudinal (X) and vertical (Z) directions, while the Y direction can generally be assumed as centered unless precision is required.

Longitudinal CG Measurement

• The drivetrain layout significantly influences CG placement; front-engine, front-wheel-drive cars typically have a forward-located CG compared to mid or rear-engine configurations.

• For an FR car like the modified BMW E36, weight distribution tends towards the front due to modifications that lighten the rear. This affects where you expect the CG to be located.

Required Measurements

• Key measurements include wheelbase (distance between front and rear axles) and axle weights, which can often be found online or measured directly if modifications are made.

• Professional corner scales provide accurate weight measurements but alternatives include using truck scales at junkyards or home scales with proper weight distribution techniques. Ensure weighing occurs on level ground for accuracy.

Calculating Longitudinal Distance to CG

• The formula used involves multiplying the mass of one axle by the wheelbase and dividing by total axle masses, allowing calculation of distance from either axle to the CG based on available data.

• For example, in this case, it was determined that the distance from the front axle to the CG is 1.264 meters, confirming expectations based on weight distribution analysis.

Vertical Height of CG Measurement

• To find vertical height (Z), one axle must be lifted while weighing; this requires careful measurement of incline angle for accuracy—greater angles yield better results. A lift or forklift may assist in achieving necessary elevation levels during measurement processes.

• It's important to note that lifting alters weight distribution across axles; stiff springs may minimize effects but preventing suspension droop is recommended for precise results—PVC pipes can serve as effective replacements for springs during measurement setups.

Calculating Vertical Height

• The equation used incorporates tangent values from incline measurements along with longitudinal distances and mass distributions among axles; adjustments are needed depending on which axle is lifted during measurement sessions. After inserting all relevant data into this equation, you can derive your vehicle's center of gravity height accurately.

Understanding Car Suspension Metrics

Calculating Center of Gravity (CG) Height

• The speaker calculated the center of gravity (CG) height for their car, determining it to be approximately 55 cm from the ground. This measurement aligns with expectations based on stock ride height.

• The CG height was confirmed through a website that conducted suspension analysis on an E36 model, providing additional validation for the calculated value. A link to this resource will be included in the video description for further reference.

Additional Resources and Further Learning

• A link to an informative article by Suspension Secrets is mentioned, which offers a different perspective and more detailed explanations regarding suspension metrics and calculations. This could serve as a valuable resource for viewers seeking deeper understanding.

• The speaker invites viewers to express interest in a more comprehensive video if they desire further explanation about the equations used in this discussion, indicating openness to audience engagement and feedback.

Viewer Engagement and Closing Remarks

• Viewers are encouraged to post any questions they may have in the comments section, with the speaker committing to respond as best as possible, fostering community interaction around the topic discussed.

• The speaker thanks viewers for watching and suggests liking or subscribing if they found the content useful, promoting ongoing engagement with future videos. They express appreciation once again before concluding the session.