Center of Gravity

Raindem

True Classic
Where do you suppose the center of gravity is?

I'm going to be putting my car on a full-rise scissors lift. The lift manual says the CoG for front-engine RWD cars is through the center of the front seat and front engine FWD vehicles is just in front of the front seat. But it says nothing about mid-engine vehicles.
 
I have a guess

I don't have a precise answer, but there is a jack tube under the doors on each side. That jack point will lift both wheels off the ground on whichever side you are lifting on. Seems like that would be pretty close to the CoG.
 
With a wheel base of 220 cm and a stated weight distribution of 41% (front) / 59% (rear), the center of gravity will be 90 cm (~35.5") forward of the center of the rear wheel. This puts it within a (somewhat generous) inch of the side jack points as stated by Jim and Dan.
 
Thanks. Didn't even occur to me to consider the jack point. I was hung up on the Lift manual's method for determining CoG on the other vehicles.
 
There is a very good reason why the CG is located here on the exxe chassis. The Coccyx-lower back is where the human body's sense of balance is located. By locating a chassis at this area the chassis provides an extension to the driver a similar sense of balance. This is one of the reasons why driving an exxe feels they way it does.

http://www.wisegeekhealth.com/what-is-the-coccyx.htm

Virtually every good race car chassis and good production chassis is designed this way. For drivers with sensitivity to this, it makes all the difference between good or bad feed back from the chassis.

This is one of the lesser known and appreciated aspects of the exxe chassis that makes it special. Also, note how low the weight of driver & passenger is relative to the floor pan and overall chassis. This is another aspect of the exxe chassis that makes a difference in dynamic performance.


Bernice


With a wheel base of 220 cm and a stated weight distribution of 41% (front) / 59% (rear), the center of gravity will be 90 cm (~35.5") forward of the center of the rear wheel. This puts it within a (somewhat generous) inch of the side jack points as stated by Jim and Dan.
 
Bernice, this is the interesting fact of the week

It would seem to be the cause of some bragging rights for the X 1/9. It certainly does explain a lot about the driver's experience in the X 1/9 compared to about every other car that I have driven. But before I start bragging, what other vehicles have this characteristic?
 
But before I start bragging, what other vehicles have this characteristic?

It's a well-known fact (I read it in the Onion) that the ferrari 308 was designed to align the center of gravity with the driver's wallet... And in the classic Italian driving position that's pretty close to the exxie's ideal CG location.

OK, seriously, kidding aside...
I'd expect that many mid-engine designs come pretty close to the ideal. But where else are you going to find it in a 2000-pound package with a four-digit price tag?
 
Near 50-50 weight distribution does not assure CG location near the hip. The Miata NA-NB, has a CG at the steering wheel with a CG height about 17".

SAAB 900, NG900, 9000 has CG near the driver's hip.

It would be interesting to compile a list of various cars, their CG location and height relative to road level.


Bernice
 
Near 50-50 weight distribution does not assure CG location near the hip. The Miata NA-NB, has a CG at the steering wheel with a CG height about 17".


Bernice

Which explains why I find driving the Miata at speed somewhat disconcerting, the motions I feel as the car starts to step out are just out of sync with the inputs I am making.

When I recently drove my X (from one storage place to the next) on 25 year old tires on a wet day the car was a bit wooly, but the feeling was great and eminently controllable. When we bought our Miata it had a set of tires apparently no less old, when driven I always felt like I was behind the car and experiencing centripetal force rather then rotating with the car. The M has new tires with nice high limits and capabilities but feels no less discomfiting as the limits are probed.
 
Whoa Larry... I bet this fact gets the MIFY this year!

I must say I always thought the Trans-Derm Cocaine Infusion (TDCI) from the factory steering wheels was the primary reason we got a "thrill" out of driving these cars and why we just keep them forever.

I never thought about the driver (and passenger) actually contributing to the CG aspects and how much that issue would contribute to our driving pleasure! If we have a 2200 pound car and a driver weighing 220 pounds, the driver actually contributes 10% to the CG equation. Soooo... the more you weigh, the more you impact the equation and the overall drive-ability of the car, and the more pleasure you get!

(I must say now that there are some detriments to the mechanicals and tire wear... as well as one's health, but that's little to pay for the knowledge that you are doing your part in increasing the overall performance.)

WOW!

This fact gets my vote for THE MOST INTERESTING FACT of the YEAR award, (MIFY) when it comes up for review next December. Admins, please take note!
 
Stuff like this related to chassis design interest me FAR more than how much energy is available from the power train, how quickly the motor vehicle can accelerate and all that simple minded marketing stuff.

More stuff on hips, center of gravity and sense of balance.
http://runninginsystems.com/2014/09...he-reference-point-for-the-center-of-gravity/

Motor vehicles should be designed for human beings that drive and occupy them along with each and every aspect of human limitations and abilities.
http://www.slideshare.net/sudhavel/basic-ergonomics-in-automotive-design


Overview of chassis-suspension design.
http://www.rqriley.com/suspensn.htm

Does the experience of driving a motor vehicle come from being taken for a ride by the motor vehicle or being an integral part of and in total control of the motor vehicle ?



Bernice
 
Which is why no matter how much marketing hype, market popularity, media rave and .... The NA-NB Miata never appealed to me and never will for this and other technical reasons.

We have an NA that has been chassis optimized between a track day car and performance street car, none of the changes to the suspension, set up and more altered the designed in CG and feel of this chassis.

If one were to de-focus from the competitive aspects of motor vehicles (I'm faster than YOU) and re-focus purely on the individual driving experience, motor vehicle expectations from the driver-owners-fans could be different.. Other major influences on this has much to do with driver points of reference. Some will be intensely focused on what makes a good and proper driving experience based in their historic points of reference of what chassis excellence should be, while others new to this game might never care about these aspects of motor vehicle design.



Bernice



Which explains why I find driving the Miata at speed somewhat disconcerting, the motions I feel as the car starts to step out are just out of sync with the inputs I am making.
 
Bernice, this is getting interesting.

Papa Tony, I agree, this is rising to the top of my "new concepts of the year" list. I feel as though we are probing at the underlying basis of the X 1/9 that we have all been unconsciously following without knowing what it was. The brute acceleration and power part of the automotive experience has dominated the equation in most of the automotive world critiques. But what if the human-machine interaction part were better appreciated by the masses?

It would be interesting to plot out the vehicle-human CG separation on a variety of vehicle, from pick-ups to exotics and a variety of racing cars. I have not seen such a diagram. It might be revealing. Maybe a three-axis diagram, with power-to-weight being one of the other factors. I will bet there is a clustering in two separate domains.
 
I vote for the latter!

You seem to be finally putting into WORDS what it is that we have only described as WOW heretofore.

And additionally, the WHY we feel that way. GREAT post, thanks!
 
My center of gravity is shifting to better enhance the driving experience in the x1/9. Or that is what I tell my self anyway.
 
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