Performance Tech News            from Auto-Ware
July 2010
Let me know what you are doing by making me a friend on facebook.  It's fast and fun. 
Find me on Facebook
News -  Set-up Management

It's amazing how people will be careful and orderly in one place (such as work) and lazy and sloppy in another (racing). I've seen full time racers just as guilty as weekenders, too. Keeping track of where you are and what you are doing with a race car is not something you can do in your head or on scattered note pads.

Race car set-up and changes are very entangled. This is further complicated by human nature and inherent variation in doing specific tasks. So, even if you have good records, there is a very good possibility the car is not set up exactly like you think.

One method to combat this situation is to use a Set-up/run sheet before and while running the car and then perform a "set-down" at the end of the day (or back in the shop if necessary). A set-down is just the process of measuring ride heights, angles, etc., and recording the race car's current configuration (be sure to check those springs, too).
The Set-up/run sheets are designed to contain the vast majority of set-up parameters and have a place to record lap times and observations on the track such as "traffic" or "off line." Begin the process by filling in the set-up portion at the top of the first sheet. Then, on subsequent runs, record only the changes to the set-up in the appropriate boxes and the associated lap times. This provides a good record of changes (preventing forgotten changes) and/or helps prevent trying to decipher cryptic notes, later.
At the end of the day, transfer all of the changes or unchanged original settings to a final sheet. Once the set-down is complete (and recorded) compare this to your final set-up sheet. Don't be shocked when the two do not match! It happens often as things vibrate, loosen, shift, or were not properly changed on the race car. The bottom line is you now have a neat and orderly process to control set-up. This prevents those times when you chase your tail trying to "figure out what the hell is going on with this dumb car" because the actual set-up is different than what you have in your head.
Tech Tips -  Tire Indexing 
tire mark
Preparation is a major key to success in racing. Part of your prep should be to help diagnose whatever comes your way.
From time to time the driver may report a vibration on the track. Of course, your first response is to ask "Did you feel it in the seat or steering wheel?" This may help you eliminate one end of the car over the other, but you still don't have an answer to the exact problem.
As part of your race prep, take 5 minutes and mark your tires and wheels with a "paint pen" as shown in the photo. If you have not done this before you will be surprised how much the tire will "clock" or rotate on the wheel. This can cause the tire/wheel to be out of balance and/or eccentric.
If you make it a habit of checking the marks after every run, chances are you will know ahead of time what to change or where to further investigate the next time you get a vibration report.
Equation of the Month - Ackerman Angle

This month's equation can be used to identify how many degrees the tires need to turn (steer) for a given radius corner (identified in last month's equation).

Aa = ATAN((Wb/12)/R) Where Aa is the Ackerman angle, Wb is the car's wheelbase (inches) and R is the corner radius the car is traveling along (feet).

For those of you with data acquisition, you can use this month's equation as a simple "Math Channel."  If you calibrate your steering channel with alignment turn plates (rather than an angle finder on the steering wheel), you can compare this new math channel to your steering channel and you will have measure of over/understeer.  Technically, if the steering channel value is greater than the Ackerman math channel value, the car is understeering.  However, if the value is between 0 and 1 degree (or so) the driver may not be able to sense the understeer and report a numb feel or a neutral handling car.
Please feel free to pass this newsletter to your friends and tell them to drop me an email so they can get the Performance Tech News, too.
Forward to a Friend 
John Block