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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
 

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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
 

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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.
 

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If it helps in any way:
Well, I've done it.:D 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... :wink:
 

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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. :eek: I'm weird that way. I teach a class about once or twice a week where I have to explain the CB formula. :rolleyes: That explains my enthusiasm.

 

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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. :)
 

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LCG

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.
 

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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.
 

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The process is the same for the transverse CG, except then you would need the combined weight on the two left wheels and the combined weight on the two rights. Finding the vertical CG is also the same process, but much more complex. Each CG - LCG, TCG and VCG exists separately.
 

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Here is what I found:
The scales I used are a track set that sat on the shop floor and could be off on the total a bit we did level and zero would bet the relationships are good.
LF 390 RF 404
LR 529 RR 525

1848 lbs. wet without driver, I can see an 88 lbs difference with all the options. There have to be others that have access to scales...:D
you can clearly see how she carries her weight
karl
 

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From left to right - right to left center (human terminology as to not confuse anyone with acronyms most normal humans don't understand :confused: ) the Smart is pretty much balanced directly down the exact center.
 

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Discussion Starter #14
Thanks All!!

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.

Thanks to all for your help. Seems like the techies can get ansers faster than the mfg. Many thanks. Watch Escapees HDT forum for more on my long Smart loader for legal carry.

Thanks again.
 

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Skiptamm

Go to a truck stop and get the axle weights.
Steve
'09 smart on a Volvo 660
Hi Steve,
FWIW= Found out you can't weigh the Smart at the CAT Scales by itself. CAT Scales require a minimum of 2000lbs to activate the scale.
I know this for fact as when I went to weigh mine
this info came out. Had to get a buddy to put his truck on the scale and make two weighs and subtract the difference for the Smarts weight.
Actual weight of the Smart w/full tank of fuel was 1880lbs, note mine is a Cabrio.
This is how we carry our's.



Later
Rich :smartje:
 

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The process is the same for the transverse CG, except then you would need the combined weight on the two left wheels and the combined weight on the two rights. Finding the vertical CG is also the same process, but much more complex. Each CG - LCG, TCG and VCG exists separately.
It was my understanding that there was a single CG that has an x, y, and z component...:confused: I spent about 30 minutes 15 years ago explaining how a bit bucket had no impact on the cg of a shelter I was designing a computer system for :rolleyes:
 

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It was my understanding that there was a single CG that has an x, y, and z component...:confused: I spent about 30 minutes 15 years ago explaining how a bit bucket had no impact on the cg of a shelter I was designing a computer system for :rolleyes:
Well, yes there is, but it is really only useful for a static object - then it is Center of Mass. When you think of dynamic forces on a smart that make it yaw, pitch or heel, the xyz components have to be considered separately.
 

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Does anyone have the manufacturer's specs for weight by year and model?
I have a 2015 Pure and only place I found a curb weight figure was Wikipedia, which says the 451 Coupe is 750–795 kg (1,653–1,753 lb)
 
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