How to Calculate Your Jeeps Center of Gravity and Rollover Angles

[Daless2]

How to Calculate Your Jeeps Center of Gravity and Rollover Angles


Good morning folks,

A few months back I did a write-up to assist anyone in determining, with a reasonable degree of accuracy, where the Center of Gravity is located on their own Jeep, and what the actual roll over angle would be for their Jeep.

I will not bore everyone by posting the write-up here, but if you have an interest it can be read on-line at this link.

http://www.jeepaholics.com/tech/cog/#_Toc535118730


If you would like a copy of this write-up (in MS Word Format) you can download it from my rudimentary web site at

http://home.att.net/~email.id/wsb/html/view.cgi-home.html-.html


Please note, there is an Excel Spreadsheet that goes along with this write-up. You can download the spreadsheet from the above site as well.

Hope some find this useful,
(But what do I know? I am just a newbie! :) )

Frank

[Mo]

Not nearly as fun as determining the 'pucker rate' though.

[Keith Strong]

I prefer the "Awwwww Shit....we are goin over!" method of telling :rolleyes:

[Hardly Givashit]

Better yet, have a couple jeeps winch you to your rollover point while your sitting in the jeep to get a "Feel" for just how far you can go before things get real tippy. ;)

http://community.webshots.com/storage/1/v0/1/5/38/35810538nGdSLW_ph

We had this set-up as a demonstration for Jamboree participants last summer.

http://community.webshots.com/storage/1/v0/1/5/23/35810523MPQExF_ph

<edit photo size> :D

[Daless2]

Hi Mo,

I have to say, you definitely have a point with the "pucker rate".

Perhaps we can meld the two together and build a scale or index. Instead of degrees needed to roll (ROA) perhaps it could be pucker factor in pounds (PFP)! :)

On a serious side , the process I have outlined should be accurate to within about 1/2 degree for ROA and CoG's should be accurate to less the + or - 1/8 inch.

This process and formulas used have been validated by several friends including one mathematics professor and one physics professor at the University of Kentucky, one honest to goodness rocket scientist, and four mechanical engineers and myself a newbie.

If you have a desire to tune the location of your CoG or alter the Rollover Angles you might want to plan your actions out first.

If you know where your CoG and ROA are to start with, (even by pucker rate) you can be fairly accurate and predictive as to the effects of any changes you might make.

These changes can involve any number of things you wish to do, add or remove weight, change spring rates, lengthen or shorten wheelbase/track, ect.

This info can also help you factor in the effects of changing sprung vs unsprung weight. (i.e. migrating from a D-35 to a D-60 and understanding what to expect in addition to bigger everything) or tuning the effects of a Currie AR bar on your Jeep.

BJOTF,

Thanks for the great pictures. I used a similar method to validate my CoG and ROA formulas. Went over to an industrial supply house, owned by a friend, and barrowed a hugh forklift to do the same thing!

That was an experience! :rolleyes:

Any chance I can ask you to make the pictures a bit smaller? They take a long time to load on this end. Thanks!


I realize some folks would have no desire or need to determine this information out for their own Jeep. Yet I also realize many people do have the desire but just haven't had the means to do so in a relatively easy way.

As a part of this write-up I provide a spreadsheet to use in calculating your own numbers. I have also asked folks to send me a copy of the spread sheet once completed, so I could add their Jeep's CoG and ROA information into my data base.

Since January, 2002 I have received 627 completed spreadsheets. My target is 1,000.

I plan to build a database and make it available on-line so that others can access the information and see how other jeeps are set up, configured and built and what they might expect for CoG and ROA should they elect to go the same route.


Keith,

I have done it the way you described myself. Did not like it!

Have a great day folks,

Frank

[doctor_G]

Got rolling over down to a science don't you. Eh?
Thanks for the write up. :D

[Honkylips]

On a serious side , the process I have outlined should be accurate to within about 1/2 degree for ROA and CoG's should be accurate to less the + or - 1/8 inch. This process and formulas used have been validated by several friends including one mathematics professor and one physics professor at the University of Kentucky, one honest to goodness rocket scientist, and four mechanical engineers and myself a newbie.

That seems like a fairly reliable formula you've worked out. However, to be REALLY accurate, here is my formula:

1- Take one can of Coors beer
2- Drink two good swigs of beer and place can in center console cupholder (real rigs have cupholders)
3- Drive rig on slowly increasing sidehill
4- When the beer spills out of the can, you are at your rollover point.

My process and formula has been validated by several boozehounds, one drunk hitchhiker, and many other such fine charachters.:D

Seriously though, my hats off to you for having the time and brainpower to come up with that stuff. And here I never thought I'd see a practical application of all that boring math we had to sit through.