[lurk mode = off]
This has been an interesting, and for the most part healthy,
discussion on course speeds. The only thing I have some heartburn
with is the claimed g-levels for cornering. I have been in the
business of measuring this with laboratory grade equipment for close
to 30 years and can tell you that there are a lot of exaggerated
claims out there.
One point is that most of the kit used to measure lateral
acceleration is not lab grade, so things like bias, drift,
temperature compensation and cross-axis (lateral versus vertical or
fore-aft) are definitely not corrected. These sensors are typically
have a variation between 5 and 15%. Some of the newer GPS based
systems that calculate the lat accel of the antenna are the closest
to providing a decent measurement for reasonably low cost.
Another point is most of these sensors are not corrected for roll
angle or the roll correction algorithm is not very robust as roll
angle needs to be measured. Not correcting for roll inflates the lat
accel measurement by about 6%.
It is also important to know that there are both steady state limits
and dynamic peak metrics that are used to characterize max lateral
acceleration and they are very different. A high performance vehicle
that can pull 1 g on a steady-state skid pad test can typically
generate peak values 20% greater than the steady-state.
We've measured some of the full-zoot SS type cars with a competition
set-up on R compound tires (basically the fastest of the stock class
cars) and see steady state values of ~1.1g. This means dynamic peaks
that are about 25% higher. For purposes of course speed
calculations, I would use the steady state numbers because that is
what the vehicle an sustain.
Hope this helps.
John Carriere
Vehicle Dynamics Group
one of the Big 3 car companies
[lurk mode = on]
At 03:28 PM 2/21/2006, Mark Andy wrote:
>My old DS (then) neon would pull 1.2 g's on G-Forces. What does a built
>to the hilt ASP car pull?
>
>Here's a question for the math wizzes... Assuming a car that pulls 1.1 or
>1.2 g or so, what's the spacing on a slalom that can be taken at 45mph
>max?
JACircuits Autocross Timing Systems
http://www.jacircuits.com
- Timing the SCCA Solo II Nationals since 1985
***********
|