Want the CG of the 451

[skiptamm]

Help!! We have a 2008 451 Passion that I am designing a flat turntable for mounting the Smart on the back of a Volvo Semi truck. I need the Center of Gravity info to position it directly over the pivot point on the turntable. Daimler seems to be confused when one asks such questions (standard Engineering design criteria) PLEASE HELP!! Someone! Thanks, Skip

[forestacademy]

Ask these guys
Smart Trailer USA-Home
They built the trailer to balance the smart, so they should know where it is.

[sdixon747]

Skiptamm

Go to a truck stop and get the axle weights. Then ask Mark (DIYGuy) or Henry (hjsdds) for the formula to calculate it. I think I know what the formula is, but I can't remember it for sure and don't want to give you bad info. (It's at home and I'm not) I know they know it. I'm watching your turntable project with interest, as I may do the same thing.

Steve
'09 smart on a Volvo 660

[skiptamm]

Originally Posted by sdixon747

Skiptamm

Go to a truck stop and get the axle weights. Then ask Mark (DIYGuy) or Henry (hjsdds) for the formula to calculate it. I think I know what the formula is, but I can't remember it for sure and don't want to give you bad info. (It's at home and I'm not) I know they know it. I'm watching your turntable project with interest, as I may do the same thing.

Steve
'09 smart on a Volvo 660

Steve,

Thanks. As soon as I get CG I can have welder begin project. I cannot believe that Daimler does not readily have this info.

Will keep posting details as project proceeds on HDT forum.

[sdixon747]

I'll be watching!

[JPaul]

If it helps in any way:

Originally Posted by Bum-bling-B

Well, I've done it. I finally did a Center of Balance. Now last time I weighed my car it chimed in at 80 pounds less! This time the gross weight is 1840. Now my front axle weight was 760 and the rear axle weight was 1080.

After I did the math the C/B was 58 inches. For those who need the center of balance for whatever reason, putting a Smart on a trailer etc. 58 inches is just a hair behind the end of the grab handle/door pull in the interior.

Disclaimer: Your center of balance calculations may vary, but I bet they're pretty close to this one.
...

And surrounding posts...

[Kermit]

Sorry I didn't catch this thread earlier today. If you didn't do it already then here is a picture with the Center of Balance. The vertical portion of the "T" in the duct tape represents where the CB is.

Now for the formula if you didn't get it already:

(D1 x W1) + (D2 x W2)

-----------------------
GVW

Key:
D1= Distance from the front of the car to the center of the front axle
D2= Distance from the front of the car to the center of the rear axle
W1= Weight of the front axle
W2= Weight of the rear axle
GVW = Gross Vehicle Weight
CB= Center of Balance

This was one of the first things I did when I got my car, figure out the CB. I'm weird that way. I teach a class about once or twice a week where I have to explain the CB formula. That explains my enthusiasm.

[Kermit]

BLAST JPaul! You beat me to it while I was typing all of the previous post! Too funny, the original post was mine anyway dug up from the archives.

[Old smart]

The method of locating the longitudinal center of gravity is easy if you know the weights bearing on the front wheels, and the weights bearing on the rear wheels. The LCG is found by a mensuration of “moments” – the products of weights and distances from a common point.

A workable common point could be 1” ahead the front axle (you can’t use the front axle itself because a real distance must be involved). The smart’s wheelbase is 73.5”, so the front axle is 1" behind the common point, while the rear is 74.5" behind. The curb weight of a smart coupe is 1808 lbs.

Just for argument, let us say that the smart has a 45/55 front-to-rear weight distribution, thus there is 813.6 lbs on the front and 994.4 lbs on the rear. Proceed thusly:

Front moment = 813.6# x 1” = 813.6
Rear moment = 994.4# x 74.5” = 74,082.8
Add the moments – 813.6 + 74,082.8 = 74,896.4
Divide that sum by the total curb weight – 74,896.4/1808# = 41.425
The LCG is located at 41.425” behind the common point, or, 40.425” behind the front axle.

[JPaul]

First and foremost, pardon my ignorance. Here it is: where is the center of gravity. Is it, as I suspect, on the vertical plane of the center of balance, but where? More towards the driver's side (because of the instrument panel and steering system)? Or is this somehow balanced by the weight of the engine, the tank, etc...
I vaguely remember someone posting about the weight distribution by wheel, vs. by axle, but I cannot find it. And it said that each wheel showed a different number.