View Full Version : Does 1g = 1g = 1g?
03-05-2010, 10:43 PM
I have some data that shows I pulled 1g during a sweeping turn at the last autocross.
I was wondering if the radial acceleration is affected at all by any specific details about the body in motion such as weight or is it purely determined by speed and turn radius?
In other words, do a 250 lb man and a 125 woman experience 1g if they both follow the exact same trajectory at the same speed?
03-05-2010, 11:43 PM
1g = 1g = 1g
03-06-2010, 12:17 AM
03-06-2010, 06:06 PM
if they both follow the exact same trajectory at the same speed?
Indeed they would but it would take different amounts of force in order to make both follow the same trajectory and speed.
In order to generate gee force you need to generate acceleration. This acceleration needs a driving force. The acceleration of an object is based off of its change on velocity versus time. It would require more force to make a heavier object accelerate at the same rate as an object that's not as heavy.
03-07-2010, 02:20 AM
being a dynamics student i am obligated to contribute. Force= Mass x Accel
so the 250 lb man and the 125lb woman will experience the same accel but will experience the "force" differently.
03-07-2010, 04:42 AM
We are talking about centrifugal force. 1g for a 250 lbs man is 250 lbs. 1g for 125 lbs woman is 125 lbs. The 1 g would occur with the same trajectory and speed.
03-07-2010, 11:54 AM
A “G” is no different than HP or PSI, it is just a measurement, and will always be the same. However, there can be variables in what you may have seen, and just like with reading HP the equipment makes a difference.
A spike in your G trace over the course of a turn can simply be a bump in the track surface. Only pay attention to sustained numbers, a brief spike does not mean your car can generate those numbers. A cheap G meter, one that works only via accelerometers can be easily fooled; body roll will make it read artificially high. A GPS only meter can also be off, as the inexpensive ones refresh too slowly to get an accurate number. The best type of meter is one that combines accelerometers and GPS with a 5hz or more sampling rate, 10hz is better. The two measurements keep each other in check, and the software will generate the number based on the data from both sources.
Also keep in mind the lot in Fontana is not flat, so you will see numbers that are better in one direction. El Toro is a much better place for testing and getting this type of data.
Don’t get hung up on achieving a high G number, that is like bench racing dyno numbers, it may look cool on paper but does not mean you have a fast car.
03-08-2010, 01:21 AM
As Jason noted above, it could be a spike. BUT, I just read that part of the manual last night, and will get an average sustained G number for ya, Long ;)
And the instrumentation I'm using is sampling at 5hz (sorry! i have a tight budget)
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