## Centre of gravity of a car

Hi, hope someone can help. I need to find the centre of gravity of a car (x,y and Z). I know the length of the car (5.390m) the distance between the axils (3.116m) and the height of the car (1.515m) I also no the loading on the fronat axil (151.5 N) and the rear axil (111.9 N) and the total mass of the car is (263.5 N). Any suggestions?

Thanks
James
 PhysOrg.com science news on PhysOrg.com >> Ants and carnivorous plants conspire for mutualistic feeding>> Forecast for Titan: Wild weather could be ahead>> Researchers stitch defects into the world's thinnest semiconductor

Mentor
 Quote by jamesd2008 Hi, hope someone can help. I need to find the centre of gravity of a car (x,y and Z). I know the length of the car (5.390m) the distance between the axils (3.116m) and the height of the car (1.515m) I also no the loading on the fronat axil (151.5 N) and the rear axil (111.9 N) and the total mass of the car is (263.5 N). Any suggestions? Thanks James
Welcome to the PF, James. Seems like you need more information in order to get the z part of the CG. What is the application?
 Hi, thanks for your reply i also have the width if the axil at 1.602m. I'm trying to calculate the Breaking forces on a double wishbone suspension system. Have all the retardation acceleration information as well. But think i need to know the centre of gravity of the mass car? Thanks

Mentor

## Centre of gravity of a car

Can you measure the weight shift with the car tilted in either axis? That will help you figure out the z component of the CG. Don't know any other way to do it easily...
 Sorry no all i know is the gross mass of the car and mass distribution over each axil.
 One way that people do is to raise one end of the car. The procedure is explained at this site: http://www.longacreracing.com/articles/art.asp?ARTID=22
 nucleus, thanks for the link very interesting. James

 Quote by jamesd2008 Hi, hope someone can help. I need to find the centre of gravity of a car (x,y and Z). I know the length of the car (5.390m) the distance between the axils (3.116m) and the height of the car (1.515m) I also no the loading on the fronat axil (151.5 N) and the rear axil (111.9 N) and the total mass of the car is (263.5 N). Any suggestions? Thanks James
Thought you might want to check your numbers a little. You have a load of 151.5N on the front axle and 111.9N on the rear axle, which means the car's weight (not mass) is actually 263.4N (a rounding error, but let's take 263.5N as the actual weight). This means that your car, which is 5.4m long, 1.5m high and 1.6m wide only has a mass of about 27kg!

Ok, now once you have the actual forces, do a moment calculation about the centre of mass. ie Load on front axle*distance from front axle to cm=load on rear axle*distance from rear axle to cm. Here you have two unknowns and one equation, so you need another equation: you know that distance from front axle to cm + distance from rear axle to cm = distance between axles. Solve simulataneously and voila, cm position in terms of front or rear axle. It is true that there is not enough info to calculate the z co-ordinate of your cm, actually, you can only calculate the x co-ordinate (and the y co-ordinate, if you assume symmetry about the z axis.)
 Thanks for your replies has been of a great help. Thanks for your time James
 Hi, is there any way to find out CG height i.e z coordinate without actually raising the vehicle??? please reply

 Quote by relish_menace Hi, is there any way to find out CG height i.e z coordinate without actually raising the vehicle??? please reply
No. All you can do is get a rough estimate. For example, a rule of thumb for old V8-powered american car was that the CG height was at the height of the camshaft.

You can also use this calculator for a good estimation (look for h/L).
 Recognitions: Gold Member Science Advisor correct..you will be close to actual if you use cam location height
 Hello everyone, this is my very first post and is related to the topic at hand. This is a virtual car that i'm creating for several simulation such as rfactor and Live for Speed and GTR 2...The length of my car is 170.70 inches, now along the length of car at 32.56 is where the front track of the car starts and at 141.08 inches is where the rear track is located...I've determined the center or gravity of the car by using the calculator suggested by nucleus on post #6. That would be CG is at 16.23 inches and CG of Axle height at 3.53 inches by raising the front axle... My question is, How do i determine the weight of front and rear tracks and find the Center of Gravity? I'm willing to pay for a video tutorial, if any one is from NYC i'm in Richmond Hill Queens...

 Quote by El1iP3S01D Hello everyone, this is my very first post and is related to the topic at hand. This is a virtual car that i'm creating for several simulation such as rfactor and Live for Speed and GTR 2...The length of my car is 170.70 inches, now along the length of car at 32.56 is where the front track of the car starts and at 141.08 inches is where the rear track is located...I've determined the center or gravity of the car by using the calculator suggested by nucleus on post #6. That would be CG is at 16.23 inches and CG of Axle height at 3.53 inches by raising the front axle... My question is, How do i determine the weight of front and rear tracks and find the Center of Gravity? I'm willing to pay for a video tutorial, if any one is from NYC i'm in Richmond Hill Queens...
I'm not sure of your question, but I think this will help:

http://www.team.net/TR8/tr8cca/wedge...ef/CG_def.html
 @jack action, let me see if this will help...
 hello i am new to the forum, i came across this thread and have been trying to figure out the derivation to this formula CGH=(Wb x Fwc)/(Tw x Tanθ), but i havent had any luck. could someone please explain where this furmula came from and how to derive it. Thanks