Roger,

Thanks for writing. I do think you need to just come out and say what you think! I agree with some of what you present, but not all of it. I don’t really think of myself as arrogant, but I’m opinionated about certain things. There is a difference.

In my three plus years of travel, I’ve had the unique opportunity to view the actions of lots of racers, young included. In my Q&A I never said all young drivers were whiney, pouty, big mouths, but from what I’ve seen, a few are. It was that group that I was referring to. I think the drivers can figure out who it pertains to easily enough.

When I addressed “you young racers,” I was asking them how they wanted to be remembered so that when and if the situation came up whereby they got angry with something that happened on the racetrack, they could be aware that how they react might just stick with them forever. I don’t apologize for that.

I’m sorry you took offense to the content and you obviously see a lot of good, responsible, young racers where ever you watch races. I do too. If I can help one or more drivers to rethink how they act, including the NASCAR drivers, one of whom I was in part referring to, then I will have done my job here at CT. Thanks again for your input.

Physics of Fast School Project

My 11-year-old daughter, Maddi Jo, decided to use front end geometry for her science fair project. She titled her project, “The Physics of Fast.” She made a wood model of a chassis and used nails to show different moment center locations. She used a fish scale to show force required to make the chassis roll.

Using an angle finder, she would pull the chassis from the varying moment center locations and measure the amount of force required to make the chassis model roll to 20 degrees. She graphed the results and was able to show that a longer moment arm required less force to roll the chassis 20 degrees, thus allowing the chassis to roll over more easily.

She then made an illustration showing how changing the control arm angles can move the moment center location. She won First Place in the science fair and her teacher said that it was one of the most unique projects she had ever had. Thanks for providing such good information.

-- Greg Williams; Ft. Gibson, OK

Greg,

Thanks so much sharing your daughter’s story. I have so many people I talk to who read our magazine and try to understand the technology that have a hard time understanding some of it. And here, Maddi Jo, at 11 years old, has understood the concepts so well. And it’s amazing that she has an interest in the physics of racing.

I think this should give incentive to many of the racers who think this stuff is too difficult to master. Hey, Maddi Jo did it, you can too. A lot of this stuff is just common sense. Helping the chassis to have what it wants is all it is. Understanding what the chassis wants is the first step in creating the right setup that accomplishes that.

In order to solve a problem, we must first understand what causes that problem. The concept of moment arms and moment centers is central to understanding what the front end, or any double A-arm suspension, does and needs. Thanks again for writing.

Moment Center for Street Stock

We run at Nash Speedway on the quarter-mile flat track. I would like for you to give me a few suggestions on moment center for this type of track. We are running a 3,400-pound mid-’80s model Caprice. I have a set of talk spindles on it and we are allowed to run aftermarket A-arms on the top.

What would be some good angles for the upper and lower A-arms to get the moment center close to where it will work well? I can measure for moment center but I don’t have a program to calculate it for me and no one is willing to let me use ones they have. Any help would be greatly appreciated.

Thanks,
-- Andy Ford

Andy,

I can only give you general suggestions. As you know, I always recommend using software to calculate the moment center mostly because we are interested in the dynamic MC location, the one where it moves to after the chassis dives and rolls. Using software is the only way to know that location. That being said, here are some suggestions.

Generally speaking, we want less of an angle in the lower control arms, and we want more of an angle in the uppers for a stock chassis. For a lower banked racetrack, we usually want more of an angle in the left upper control arm than the right upper. This moves the MC more to the left and left of centerline a bit. Don’t overdo the difference in angles since that might move the MC too far left, and that is not good either. A difference of 5 to 8 degrees should be sufficient. The work you are doing will make a huge difference in how the car turns, which is the primary problem with how those cars work. The cars that have this worked out usually dominate their class.

Weight Vs. Rear Percent

As a longtime follower of your columns, thanks for your insight into the dynamics of race cars. I have a theoretical question for you. Given that you are racing on dirt in an entry-level class with no weight limit (weight jacks legal), would it be more beneficial to run as light as possible, sacrificing some rear percentage or stack the weight on to achieve what is perceived to be the ideal rear percentage?

More specifically, would having the car weigh 2,800 pounds with 50 percent rear percentage be better than a weight of 3,200 pounds with 53-54 percent rear percentage? And another passing thought: NASCAR wants to make racing more exciting. Imagine a night race with magnesium splitters. Hmmm.

-- Ron Miller

Ron,

I just saw a Sprint Car race where the cars were bottoming out and throwing sparks and it was admittedly cool to watch. As long as one of those burning pieces of magnesium doesn’t get in someone’s eye, I’m for it.

As for the weights, I personally would rather run 400 pounds lighter with the 50-50 front to rear percent. Rear weight doesn’t necessarily provide rear bite. It does create an unbalanced polar moment that wants to swing the rear end out through the turns.

In any case, on dry and slick tracks, move what weight you can to the right side of the car. This loads the right-side tires more and helps to bite through the dust on the dry track and promotes grip and side bite.

Distinguishable Race Cars

Current models are great. I think that they don’t have to be current as long as they can be distinguished from one another. As you can see the Northwest Early Stocks provide great racing and cars that stand out with their individuality. Race cars are cool! Let’s keep them appealing.
Thanks,

-- Gil Rapp

Gil,
That’s exactly what I saw running at State Line Speedway in northwestern Idaho. Three nostalgia racing organizations combined their numbers to race there recently. And I agree, the cars stood out and were recognizable from one another. And the fans loved it.

Tap-Out
The following was copied from the Slinger Speedway website and was written by Dan Margetta. It describes an incident that happened in the August 11th Super Late Model race with two drivers battling for the lead. It demonstrates not only a great rule, but a driver with the honesty and integrity to apply it to himself. It reads:

“The caution flag waved again on lap 33…Church chose the inside lane for the restart with Bennett alongside and Bennett gained momentum exiting turn two to clear Church for the lead entering turn three. As Bennett moved into the lower groove, contact with Church’s car sent his machine looping around. Bennett was allowed to keep his spot on the track after Church used the new “tap-out” gentleman’s rule claiming responsibility for the incident.”