Center of Gravity Height Question.... 2

[MaxVQ]

Is 22" reasonable estimate for a center of gravity height on a 4 door sedan (like a 1995 Nissan Maxima)

I understand if I jack up my car a few feet, I can calculate my actual cgh, but I don't have wheel scales, or a jack that can lift that high?

I thought I read in the Bosch Handbook that you can take 1/3 of the vehicle height as a close estimation.
(in my example 55.7" * .333 = 18.54&quot

Any realword examples someone can share?

Thanks.

 

[c2s]

The CG height on a sedan is typically around 20-21 inches. A rule of thumb is the bumper height.
As for jacking the car to get the CG, you have to do it more than a few feet because of the cos error at small angles.
There is also a paper on measured vehicles. It contains a table about 1/4 of the way thru it. Link:

http://www-nrd.nhtsa.dot.gov/vrtc/ca/capubs\sae1999-01-1336.pdf

Hope this helps
Kevin

 

[MaxVQ]

Thank you! That is a great document.

 

[mikikanazawa]

I seem to remember reading somewhere that the height of the camshafts on OHC cars is also a good approximation of the CG height.

 

[BillyShope]

In a tube frame race car, the camshaft height of a pushrod engine is commonly used, but that's a very rough estimate. If you differentiate the equations used in the "jacking" method, you'll find that a very, very small measurement error will result in a significant CG height error.

For a tube frame race car, I prefer to use the "tabulation" method, where heights, weights, and height-weight products are tabulated for as many components and structural pieces as possible. If this is carried far enough, the height of the remaining weight becomes inconsequential (i.e., you can use a very rough estimate for its height) and the calculated CG height will be sufficiently accurate. Unfortunately, for a passenger car, it's much more difficult to identify significant structural components.