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I tried a similar calculation using the formula from "A Practical Guide to Race Car Data Analysis" by Bob Knox, pp65:
My big question is; why do I need to scale the channel by 2.5X? Did I make a mistake on the math channel?
Thanks,
Greg
I know John Block says it takes a little fiddling with the scaling number to make it work out. Your visualization looks good to me!
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Any comments on using a combination of gyros and gps to calculate understeer/oversteer? Seems like it might be the best approach of you have the gyro data.
And what's really interesting is at the Glen the car understeers to the right but oversteers to the left.
The first place to look is the crossweight of the car. Sounds like you have uneven cross weight.
Cross-weight Percentage
Cross-weight percentage compares the diagonal weight totals to the car's total weight. To calculate cross-weight percentage, add the RF weight to the LR weight and divide the sum by the total weight of the car. Cross-weight is also called wedge: If the percentage is over 50 percent, the car has wedge; if below 50 percent, the car has reverse wedge.
More wedge means that the car will likely understeer more in a left turn. The advantage to wedge is that the left rear tire carries more load, so the car drives off the turns better. But in a right turn, the opposite occurs and the handling is worse. In almost all cases, the loss of cornering performance in one direction is greater than the gain in the other direction.
On oval track cars, cross-weight is usually used in conjunction with stagger (where the right rear tire is larger in circumference than the left rear tire) to balance handling. More stagger usually loosens the handling in left turns, so more cross-weight is used to tighten it up. But stagger is not a good idea on a road course or autocross either, where the ideal is 50-percent cross-weight and no stagger.
One of the problems with cross-weight is that it will change the handling balance from a left to a right turn. This can make maneuvering in traffic difficult, even dangerous. On a road course, the cross-weight percentage should be very close to 50 percent, within a half-degree either way, to keep the handling balance similar in a right-hand turn compared to a left-hand turn. In the example at the beginning of the article, this was the problem: a cross-weight percentage that was less than 50 percent, and probably off by at least two percent.
One of the keys to obtaining a good setup is using the correct procedure to weigh your race car.
So both my cup cars (one of them just sold to a rennlister) have steering angle sensors and Motec pro logging. What is the best formula? Sorry for asking for free information from professionals!!
Gregtureks data are interesting...My 996 cup car had some inherent U/S at those same turns but nothing at 13. U/S was also on throttle.. I figured that its got to with rake-angle which can be affected by too much wing in the rest at the high speeds I guess.
I think one explanation for this i that WGI right handers have varying (sometimes substantial) degrees of Camber and the few left handers little or now camber. The one major exception being T6 which you need to take just right to catch the camber.
Originally Posted by 2BWise
And what's really interesting is at the Glen the car understeers to the right but oversteers to the left.
Recently installed an MXS to replace a CDS system that i had for years...really liked the data presentation that used the track map as the X axis in signal plots, like the one in TPA:
There is no easy way to make that map. You can do rainbow maps with the gps map. It will be the actual line you drove cored according to to the measure you select. You can also do a sector map with channel tags it, though I find the gps map most helpful.
Recently installed an MXS to replace a CDS system that i had for years...really liked the data presentation that used the track map as the X axis in signal plots, like the one in TPA:
Is there a way to do this in RS2?[/QUOTE]
No. Not in RSA or i2.
The TrackMaster (CDS) visualization is really good, though.
thanks for the replies, Matt and Peter. The CDS/TM visualization has always been a great feature, easy to interpret between sessions. I'm surprised no one has figured out a way to do it with AIM.
Wow. The depth of knowledge in this forum never ceases to amaze. I was doing some shower thinking about this exact thing after seeing how the track precision app shows over/understeer.
I was looking at the AiM math channel manual (http://www.aim-sportline.com/downloa...ls_101_eng.pdf) and saw that it has a calculation for under/oversteer.
Has anybody used that, and how does it compare to the eqn posted in the first post? They look similar, but the AiM eqn seems to be set up w/ metric units so the constants are all different.
More specifically, what data is your steering sensor giving you as opposed to what you were trying to get? e.g. Steering wheel angle, angle of front wheels relative to the vehicle CL etc.
That’s one of the issues. Steering Angle (at the control input) is different from Steered Angle (front wheels from C/L)
To explore this fully, the three resources I recommend are John Block’s Auto-Ware AiM webinars (may be in the advanced offering, have to look at my notes, his series is starting ANY DAY now), Bob Knox’s book Practical Data Analysis for Race Cars and Jorge Segers’ book published by the Society of Automotive Engineers. This CAN be done in AiM, but you’ll need some good measures from the car (break out the turn plates and double check your dimensional measures).
From John Block: Hey Racers,
I'm getting ready to kick off a new round of AiM data acquisition webinars next week. If you have already been though these courses please sound-off and let others know what you thought of them. If you have never been through these classes you will be amazed at what you can discover about your race car with data acq. So, come join the fun at www.auto-ware.com/webinar_home.html
Thread from the grave ....
Question for the group - recommendations on formula for car setup to detect understeer when steering angle is not available?
09-06-2017, 04:48 PM
