How to find the center of gravity?

[jk5blazer]

I've heard its from the ground to the bottom of the bell housing, and I've also heard its from the ground to the middle bolt of the bell housing. Is the a correct way to get the CG. If it matters, its an 84 blazer 4 inch lift, 39.5 TSL's.

 

[George_Pimpdaddy]

i dotn thik its that easy and im sure all rigs would be slightly different due to tire size and suspension and different combos.

 

[blowedupmotor87]

i dotn thik its that easy and im sure all rigs would be slightly different due to tire size and suspension and different combos.

BINGO! Heck, ya get into top on or top off, engine/tranny/t-case, what axles, what tires, what wheels, how much lift, everything can effect it! You might could figurer up an okay estimate but, anything at all exact would be very hard to figure out!

 

[sloth]

A detailed procedure for determining COG is outlined here:
http://www.jeepaholics.com/tech/cog/

Hope that helps,
Mike

 

[Hogback Fabrication]

To measure it via the method you are thinking is to measure the distance from the ground to the top bolt on the bellhousing (probably around 40" for your truck).

Again, this is just a guess. It all depends on the body, drivetrain, etc.

 

[jk5blazer]

thanks guys.

 

[BGKYK5]

For the COG procedure Sloth posted to work in the normal (static) sense of the term, you will need to prevent the axles from moving. Any droop or compression of the leaf springs will tweak your measurement. If the axles aren't in their normal level ride height positions, it can make a big difference in the result when you do the trig. Wheels, tires, axles, etc, can be 1500lbs.

 

[6.2Blazer]

Really no easy way to calculate the vertical CG (how high up from the ground it is) at home. We do this type of test at work all of the time and it involves knowing the exact front and rear axle weights, and then lifting one of the axles up with load cells attached to continuosly measure the weight on that axle. You then compare data points of the weight versus height (angle) of the vehicle and calculate it from there. It's about a $2,500 test.

 

[BGKYK5]

I think you could get pretty close with a good scale, a way to lift one end of the truck, a way to prevent suspension movement (solid bars in place of shocks?), high tire pressures, and some trig.

 

[Cowboy_80]

Horizontal COG is determined by:

W1 = front axle weight
W2 = rear axle weight
D1 = distance from front bumper to center of front axle in inches
D2 = distance from front bumper to rear axle in inches

(W1 x D1) + (W2 x D2) = some big number

Divide that number by the gross vehicle weight

that final number is the center of balance in inches from the front bumper.

I say front bumper, but it's the farthest point forward on the vehicle. For us it was the D-rings on the HMMWV's.

I don't know how to tell you how high it is though.

 

[BGKYK5]

You are right about the horizontal location. The vertical location is the tricky one.