In looking at and thinking about our current situation with short track racing, I have come upon a view of the situation that might make perfect sense. As with most things, it’s like when we get lost in the woods. For some unknown reason, we always seem to end up returning to the point where we first got lost. I think our sport is about to do just that.

I’m old enough to remember how it was, and lived some of it, back in the 1960s. Racers then built their own motors, constructed their own cars, welded the rollcage to the chassis, and did all of the maintenance themselves.

There were no turnkey cars or professionally built $30,000 motors or paid consultants back in the day. Why do you think Smokey Yunick was so popular? He spoke directly to, and was one of, those same constructors.

What we did have was a lot of interest in racing, sometimes huge car counts and legions of fans in the grandstands. What we have now, after “getting lost in the woods” is low car counts and nearly empty grandstands.

Maybe the answer is to get back to that time when you purchased separately all of the parts for the motor, carefully assembled it checking all of the clearances, and then torqued all of the bolts yourself. When you got done, installed it in the car, wired it up and cranked it for the first time, it was truly something special.

When you do it all yourself, you know everything about it, and you take a lot of pride in knowing it was your hard work and attention to details that made it run so well. And when you beat the competition, it becomes even sweeter.

It’s the same for the chassis. There were no chassis gurus back in the day, only innovation and hard work. Teams tried anything and everything to try to gain an edge on the other teams. We came out of all of that with new products and new technology.

What I’m afraid of is that our society has evolved in a similar fashion to the sport of racing. We have come to expect having things handed to us and the only sweat equity we have in our racing anymore is a signature on a check or a credit card receipt.

Maybe what we need are kit cars. I came across this very idea recently while looking through the first issue of Circle Track magazine printed sometime in 1982. The title was “Chrysler Kit Cars—The Short Track Stocker That Comes in a Box.”

The kits came, as described in a caption of a photo showing all of the parts laid out, “Pre-engineered and ready to race, every last detail of a Kit Car’s construction has been executed in hardware.” And there was even a kit car motor talked about in that article.

Right now you can buy a Ford Cobra kit car, a dune buggy kit, and more. Why not a race car kit car? It’s because nobody has taken the time to assemble the parts list and make it available. I think there are still many teams out there that can and want to build their own cars and motors from scratch.

The staff here at CT will be discussing just this topic in the coming weeks and it would be interesting to put our own motor together using a parts list we develop. We need to do this build ourselves and document all of the steps and procedures to demonstrate that this is either very possible, or not. And we’ll compile a price list covering all of the components to document exactly how much the build will cost.

What the industry has available today as far as the quality of parts is unbelievable. The CNC revolution and other machinery innovations have provided us with more exact dimensioning for our parts like never before. Again, back in the day, you really had to measure the crank journals, pistons and bores carefully and they didn’t always measure up.

In today’s world, I bet the tolerances are much tighter to being what is needed and so the parts go together much better. It would be much more appropriate now to attempt building your own motor than it was back then. It was a necessity in 1965, it would be cheaper and more fun to do a build today, even if money was no object.

I need to know your thoughts on this. Please email or mail me your ideas. There’s no need to put your name on your correspondence if you don’t want to, but don’t hold back your opinion. Are there still mechanically minded racers out there who would love to turn their garage into a mini-motor plant? I’m betting my piston rings there are.

If you have comments or questions about this or anything racing related, send them to my email address: Bob.Bolles@sorc.com, or mail can be sent to Circle Track, Senior Tech Editor, 9036 Brittany Way, Tampa, FL 33619.

Reverse Rotation Motors

On the mind at the moment is engine rotation and how the chassis reacts planting the tires and maintaining the traction. Clockwise verses reverse rotation engines. Would you guys be involving anything like this in an article in the future?
—Unsigned

Dear Unsigned,
Smokey tried a little of that at some point in time. What happens now with the torque of the motor is that the engine tries to rotate the rearend in a counter clockwise direction when you face toward the front of the car. This loads the left rear tire upon acceleration. I know this because I put a car on scales, loaded the axle and watched the LR scale weight go up.

Because acceleration takes away some of the available grip from the rear tires, we need more grip to control the wheelspin. With this rotation of the rearend and the resulting loading of the LR tire, we also see a rise in the crossweight which tightens the car as well as providing a more even loading of the rear tires which produces more overall traction for that pair.

If we reversed the rotation of the engine, the opposite would occur and the car would become very loose off the corners. It would be better to leave things alone in that department.

Gear Ratio Information

I have a question pertaining to the gear ratios in a rearend. I somewhat understand it from the article “Rearend Gear Guide—Gear Ratio Rationale” (April ’09) but I’m still not sure of what I need.

I’m looking for the best rearend gear ratio for the best cornering performance. Which direction should I go, higher or lower (which way is which on the numerical scale)? I think I should go lower, but I’m just getting into all of the gearing and ratio stuff so I need some schooling on it.
—Unsigned

Dear Unsigned,
First off, a higher gear relates to a lower gear ratio number. I think higher used to refer to a higher speed with the same engine rpm. A lower gear is a higher ratio number and therefore a higher rpm for the same speed.

Gear ratio has nothing to do with cornering performance. It has everything to do with getting off the corners. Choosing a gear ratio really depends on your goals. On dirt, if we are continually spinning our tires, we might need a higher gear to reduce the rpms and torque to the rear wheels to stop the wheelspin.

If we have plenty of bite, we might want a lower gear to provide a higher rpm and more torque to help accelerate the car off the corner. The downside might be that we run out of rpm in our powerband somewhere before we have to lift for the next corner.

There is a gear ratio for every application and racetrack that will produce the quickest lap time and you need to experiment to find it. Knowing your car’s powerband—where it begins making good power and where it falls off in the upper rpm range—can help you determine which gear would be best.

Roll Center/Moment Center Question

Could you please email me a moment-center-for-dummies rundown as I’m not an expert setup guy? I simply don’t understand it. It’s an imaginary position that has real effects on handling? Please help me out if you can.

Thanks,
—Karmen Parks

Karmen,
Moment center (or roll center) is an imaginary point that acts just like a bolt through the chassis. And it does have a real effect on the handling, more so than just about any other component on our race car. But it’s an imaginary point that is dictated by the very real components, such as the upper and lower control arms, and their location on our car. To learn more about it, I suggest you go online to www.circletrack.com and search our extensive article archives. There you’ll find numerous articles that explain what the moment center is and what it does. The most recent being run in the Nov. ’12 issue and one prior in the Dec. ’11 issue. Over time, we have discovered much more about this design feature than was known back 20 years ago. Not only that, but we have also refined our view of where the MC should be designed to be for different race cars.

Third Link Angles Discussion

I look forward every month to reading “Track Tech Q&A.” You answer a lot of interesting and good questions. One answer you gave in the Nov. ’12 issue I have to question and at the same time give us all something to think about.

The question was, Long or Short Third Link?, from Matt in Canada. Your answer was that you did not know of any ratio between the trailing arm length and third link. Well, there is a ratio to keep in mind if you really want to cut hairs.

If you want to keep the pinion angle as close to the static set degrees as to the dynamic, the lower control arms and the third link must all be the same length. If the third link is of different length, the arc that the rearend takes in compression will change the pinion angle from the static setup. It will not raise and lower, instead maintaining the same pre-set angle.

Now in the same November Q&A you answered a question about Rear Trailing Arm Angles and Pinion Angles from Unsigned, I assume in Orlando. Keeping the pinion angle the same and opposite direction as the driveshaft to the tranny angle is what you try to do. I agree 100 percent.

Now give this some thought. We’re all concerned with pinion angle, with good reason. Have we ever given thought to what is happening to the lateral pinion angle when we set up a car to rear steer? I know it never crossed my mind before I started thinking about writing this response to you. Some of the Late Model dirt cars change their left to right wheel bass lengths 6 to 10 inches. That is one hell of an angle being put on the rear U-joint especially if you’re on a short track with long sweeping corners. So should we give pinion angle a bit more breathing room?

Something to think about,
—Phil Tomeo

Phil, you are correct that with a shorter third link, the pinion angle will increase as the rear squats on acceleration. So, a team would be advised to check and set the pinion angle with the rear of the car in a lowered position to simulate the height coming off the corners. That way, under full torque and loading, the pinion angle will be optimum.

The problem with most race cars is that there is no room to put in a third link that is as long as the lower links. And, a shorter link provides more opportunity to increase the angle allowing for more antisquat leverage.

As to rear steer and its influence on the top view pinion angle, I have some thoughts. If the left rear wheel moved 4 inches forward and the right rear wheel remained stationary, then an angle of about 3.5 degrees would result for a 66-inch track width.

A Dirt Late Model or Modified set up that way might well carry that attitude most of the way down the straight and the top view pinion angle would remain 3 to 3.5 degrees in relation to the driveshaft. So, if I were looking for equal and opposite U-joint angles at each end of the driveshaft, I might run zero side view angle and the engine at 3 degrees of top view angle with the rear left from the front.

Finding Moment Center Without Software

I have a quick question. (I’m sure you’ve never heard that one before!). I’m racing a Dirt Modified and have read and re-read all the information you present in your book as well as the articles you have written for Circle Track relating to roll centers and moment arms. I’ve even attempted to diagram this out on my garage wall, a frustrating and non-productive exercise to say the least.

Is there an easy way to know that I’m in the ballpark without investing in the software necessary to get this information? I have typically put the right lower A-arm pivot point a 1/4- to a 1/2-inch lower than the lower right ball joint pivot point and have set the right height on the left level or a little lower with me in the car.

If I had you standing in my shop (an open invitation to spend a race weekend with us in West Texas/Southern New Mexico by the way) to set up the front end without the use of above mentioned software, what would you do?

Also, I’m paying attention to how much movement I’m getting from my shock grommets to make a decision on spring rates. The front end appears to be working well with a 650-pound on the RF and a 600-pound on the LF. How would you determine what are the proper rates for the rear of the car, specifically the right rear?

The car is a metric stub car with the original metric lower A-arms, so it’s a little narrower than what appears to be popular right now. The car is also approximately 20 years old and I take a certain amount of pride in competing with and occasionally beating those that are spending a significant amount more than I to be fast.

Thanks for your time and advice. The invitation is sincere. We have two tracks locally that are being run by the same two guys that happen to be racers. They have put a lot of effort in providing great racing facilities and I believe have found a way to actually turn a profit doing it. It might make for some good copy for the magazine.

Hope all is well and I appreciate your time,
—Tom Georges

Tom, there is no quick answer to your questions. The geometry of the front end is complicated, believe me, I have tried to make it simple, but it’s not. Unfortunately, the only way to accurately find the dynamic roll center location is to find it with software. Anyone can draw the car out as it sits statically, but when the chassis pickup points and ball joints move through dive and roll, it’s almost impossible to draw out.

There are some general truths that I have discovered from working with lots of cars. Generally, the lower control arms need to be less than three degrees and the right lower arm needs to be half, or so, less than the left lower arm in angle, all with the chassis points lower than the ball joints.

The upper arm angles need to be such that the left upper arm is more angle than the right upper arm. The right upper often has an ideal angle of between 12 and 16 degrees and the left upper arm needs to be 4 to 6 degrees more than the right upper arm angle.

When I say angle, I mean the angle of a line drawn through the ball joint’s center of rotation to the chassis mount center of rotation. The angle of the tubing that connects the two is not accurate and is almost never the same angle.

The spring rates can’t be guessed at. Every car is different in the weights and locations of roll centers, and so on. You want to keep the LF on the track most of the time, and put more loading on it for tacky conditions than with dry slick. Increasing the RR spring rate will put more load on the LF, and decreasing it will take load off the LF, just to give you some idea.

  • «
  • |
  • 1
  • |
  • 2
  • |
  • View Full Article