Source for CG Height of a 2012 Car?
Source for CG Height of a 2012 Car?
(OP)
Hi guys!
Well, I'm an autocrosser - with an open wheel purpose-built car - but this January my local region has an event that sounds like a GREAT time to bring out my new ride, a 2012 Nissan Juke, for a spin. And what class is it in? Well, ah, no class, apparently. Yet.
It seems to be (appears to be) a bit tall for its width. A little monster of a car - AWD, CVT, four cylinder turbo/intercooled/direct fuel injection, force vectored AWD (the rear axles each have an electro-mechanical clutch which under certain conditions moves most or even all rear HP to the outer rear tire (fronts kinda being left to fend for themselves. . .)). With (it appears) ABS BY THE WHEEL. Almost unheard of in a street car. A sweet, tight little AWD car. But. . .
It has not been classed yet. Though it is a 2012 version of a 2011 car. A BIT too tall for a bit too narrow car. Too low a "Static Stability Factor" is assumed. Too tall for too narrow a track. But there is no number available on the interweb. . . If I could prove a number I could likely autocross, I think. If I can't, it becomes opinion for local events, and illegal for higher events (which I am uninterested in, in this car).
So. The calculation requires the "CG Height" of the car. I could measure the weight of the front axle tires. Then the rear axle tires. Then jack up one axle at least 10 inches and measure the lower axle weight and jacked-up height (jacked up wheels supported on something). Which will provide a number. Below this, low chance of approval. Above this, certain approval.
Does anyone have access to CG Height values for this car? I could likely do this on truck scales in 30 minutes, but that must be kinda pricy. The NHTSA has no rating for the car, rollover-wise. The IIHS lists the car as a "top safety pick," but it notes a particularly strong roof and traction control, which may mitigate a tendency to roll over.
Chris
Well, I'm an autocrosser - with an open wheel purpose-built car - but this January my local region has an event that sounds like a GREAT time to bring out my new ride, a 2012 Nissan Juke, for a spin. And what class is it in? Well, ah, no class, apparently. Yet.
It seems to be (appears to be) a bit tall for its width. A little monster of a car - AWD, CVT, four cylinder turbo/intercooled/direct fuel injection, force vectored AWD (the rear axles each have an electro-mechanical clutch which under certain conditions moves most or even all rear HP to the outer rear tire (fronts kinda being left to fend for themselves. . .)). With (it appears) ABS BY THE WHEEL. Almost unheard of in a street car. A sweet, tight little AWD car. But. . .
It has not been classed yet. Though it is a 2012 version of a 2011 car. A BIT too tall for a bit too narrow car. Too low a "Static Stability Factor" is assumed. Too tall for too narrow a track. But there is no number available on the interweb. . . If I could prove a number I could likely autocross, I think. If I can't, it becomes opinion for local events, and illegal for higher events (which I am uninterested in, in this car).
So. The calculation requires the "CG Height" of the car. I could measure the weight of the front axle tires. Then the rear axle tires. Then jack up one axle at least 10 inches and measure the lower axle weight and jacked-up height (jacked up wheels supported on something). Which will provide a number. Below this, low chance of approval. Above this, certain approval.
Does anyone have access to CG Height values for this car? I could likely do this on truck scales in 30 minutes, but that must be kinda pricy. The NHTSA has no rating for the car, rollover-wise. The IIHS lists the car as a "top safety pick," but it notes a particularly strong roof and traction control, which may mitigate a tendency to roll over.
Chris





RE: Source for CG Height of a 2012 Car?
As to CG heights the only web source I know is the NHTSA one.
Cheers
Greg Locock
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RE: Source for CG Height of a 2012 Car?
I think I paid $7 for a single weighing of a car on truck scales once, and got separate axle weights.
Norm
RE: Source for CG Height of a 2012 Car?
Actually you could pull it from the side until the wheels came off one side. With a little math, this might get you close enough.
RE: Source for CG Height of a 2012 Car?
Now $7/weigh for three weighs (front tire, rear, front with rears up on ramps or some such) is in the neighborhood. But of course 20-30 pounds off might mean a bogus test, I agree. . . But then of course there's a 50% chance of an error in my favor!
I have emailed Nissan but expect no response.
This debate is spreading through both the Juke and autocrossing communities.
Chris
RE: Source for CG Height of a 2012 Car?
RE: Source for CG Height of a 2012 Car?
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Source for CG Height of a 2012 Car?
I think tipping it would give the best solution.
RE: Source for CG Height of a 2012 Car?
RE: Source for CG Height of a 2012 Car?
Either way, you do have to "tip" it, and if the car was set up to behave in true accordance with rigid body theory it shouldn't make any difference if the tipping were to be in the pitch or the roll direction.
In a tested-as-is scenario, suspensions have ride and roll stiffnesses and tires have width and are non-rigid, so their effects will vary depending on which way you choose to tip the car.
Norm
RE: Source for CG Height of a 2012 Car?
Regards
Pat
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RE: Source for CG Height of a 2012 Car?
RE: Source for CG Height of a 2012 Car?
Norm
RE: Source for CG Height of a 2012 Car?
Norm, I think your correct re the reason for the OP. Hardly work related engineering I think.
Regards
Pat
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RE: Source for CG Height of a 2012 Car?
Yes, yes, I'm in the future too, now.
So, a call to CAT Scales just now and a VERY helpful gentleman gently asked if my weights could be taken with the front wheels on one pad and the rear wheels on the other.
Sadly, my ramps only go up six inches, but I can use a floor jack to lift the rear of the car and slip something 10 inches tall under the wheels, and lower the car onto that. Since I will be in no way no how UNDER the car, I'm actually considering a couple of cinder blocks. . . But am not sure that I can lift 16 inches (must be more than 10) plus wheel droop, even with a spacer between the jack pad and the car lift point. Though perhaps with the two tires-to-be-lifted starting on the ramps. . . But that's a solvable problem! (with the tires-to-be lifted almost certainly the fronts, since the parking brake locks those, and I'm not sure how my CVT transmission "parks.")
Oh, and $9.50 for the first weigh, and since it will be within 24 hours, second weigh for just $1.00! This coming weekend!
Chris
RE: Source for CG Height of a 2012 Car?
Rod
RE: Source for CG Height of a 2012 Car?
From your comments you are in west virginia. Here are some of the airports: Raleigh County Memorial Airport at Beckley, the Yeager Airport at Charleston, the Harrison-Marion Regional Airport at Clarksburg, the Tri-State Airport at Huntington, the Greenbrier Valley Airport at Lewisburg, the Morgantown Municipal Airport and the Mid-Ohio Valley Regional Airport at Parkersburg.
One of these has to be close to you. Go out and ask the aircraft maintenance guys, what they would charge you to do a weight and balance on your car. Most aircraft scales will do about 1500 lbs per wheel, some are bigger.
B.E.
The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor
RE: Source for CG Height of a 2012 Car?
FWIW if you are in Morgantown, I can probably find someone local who has corner weighing scales for you. I have been meaning to build myself a set, but time is tight for me lately.
RE: Source for CG Height of a 2012 Car?
RE: Source for CG Height of a 2012 Car?
RE: Source for CG Height of a 2012 Car?