Place to measure center of gravity height

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Eric Wong
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Place to measure center of gravity height

Postby Eric Wong » Fri Jul 28, 2017 10:18 am

Hello, I'd like to find a place in SoCal (preferably Los Angeles) which can do center of gravity height measurements to calculate the Static Stability Factor (SSF) as described in:
https://dk1xgl0d43mu1.cloudfront.net/us ... s-1-12.pdf
This is for my Chevy Bolt EV, which fails the 1:1 track width:height relationship, but has a floor-mounted battery weighing over 900 lbs (like a Tesla Model S/X/3). For the Model S, it's only 18", so I think the Bolt would be similar.

I've never competed in anything before, and the Bolt is the only car I'd compete in, but it's ineligible unless I can get an independently verified SSF and submit it to SEB. I haven't seen the exact measurement posted on any websites, and I don't think it's been disclosed by GM.

So, is there an independent shop/lab which can do this? Thanks.

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Bill Martin
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Re: Place to measure center of gravity height

Postby Bill Martin » Sat Jul 29, 2017 11:19 am

Here's how it's done with race scales:
http://www.longacreracing.com/technical ... item=42586

Eric Wong
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Re: Place to measure center of gravity height

Postby Eric Wong » Sat Jul 29, 2017 8:02 pm

Yes, it requires scales, a tall lift and solid shock links; so probably not a lot of places have these. I don't even have the tools or skills to replace MacPherson struts, myself.

The center-of-gravity-height will also be different with windows rolled down, and I noticed most folks had both front windows down today, some only had the driver side down; but most had rear windows up. I suppose the front being down is for safety and driver extraction and the rest of the windows were up for aerodynamics?

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KJ Christopher
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Re: Place to measure center of gravity height

Postby KJ Christopher » Sun Jul 30, 2017 6:19 am

Eric Wong wrote: I suppose the front being down is for safety and driver extraction and the rest of the windows were up for aerodynamics?


I'd posit no where near that much thought went into their window positioning.
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Eric Wong
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Re: Place to measure center of gravity height

Postby Eric Wong » Wed Nov 01, 2017 12:19 am

It looks like GM published the center-of-gravity height as 20.7" at some point on their media site:

http://media.chevrolet.com/media/us/en/ ... .tab1.html

It wasn't in an earlier copy from 2016, and archive.org has not crawled it this year so I'm not sure when it appeared:

https://web.archive.org/web/20161214162 ... .tab1.html

Nor is it on chevrolet.com without "media".

The 20.7" center-of-gravity and 59.1" track width gives the SSF as: 59.1 / (2 * 20.7) = 1.4275; more than the 1.3 required.

Somebody else also submitted this info to SEB already, so it should be classed in the December Fastrack (out Nov 20) and I should be able to finally run my Bolt at the December events.


I was going to wait for the NHTSA to test the car and then submit an FOIA request to get the raw data with the SSF, but now I won't have to wait as long :)
Somebody else also went this route with the Nissan Leaf to get it classed.

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Quoc-Viet Dang
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Re: Place to measure center of gravity height

Postby Quoc-Viet Dang » Fri Nov 03, 2017 12:48 pm

Eric Wong wrote:It looks like GM published the center-of-gravity height as 20.7" at some point on their media site:

http://media.chevrolet.com/media/us/en/ ... .tab1.html

It wasn't in an earlier copy from 2016, and archive.org has not crawled it this year so I'm not sure when it appeared:

https://web.archive.org/web/20161214162 ... .tab1.html

Nor is it on chevrolet.com without "media".

The 20.7" center-of-gravity and 59.1" track width gives the SSF as: 59.1 / (2 * 20.7) = 1.4275; more than the 1.3 required.

Somebody else also submitted this info to SEB already, so it should be classed in the December Fastrack (out Nov 20) and I should be able to finally run my Bolt at the December events.


I was going to wait for the NHTSA to test the car and then submit an FOIA request to get the raw data with the SSF, but now I won't have to wait as long :)
Somebody else also went this route with the Nissan Leaf to get it classed.


That's awesome Eric, I'm glad you were able to follow through with this! I hope they class it asap.


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