The NASCAR Car of Tomorrow (COT) is an interesting concept and one that rekindles our interest in Nextel Cup for several reasons. This magazine has, as a policy, refrained from either reporting on or covering NASCAR Nextel Cup racing because historically very little of the technology developed there pertained to the short-track racer. That has all changed with the COT.
With the changes made for...
With the changes made for the COT concept, NASCAR teams have suddenly found themselves searching for usable chassis setup technology to replace aero manipulation.
The NASCAR inspectors have...
The NASCAR inspectors have a tool that goes over the entire body to check for compliance to the strict rules governing the shape of the fenders, hood, roof, and such. There is no manipulation allowed to any part of the spec body.
The rear wing on the COT is...
The rear wing on the COT is closely related to the Grand Am Daytona Prototype rear wing. It's no secret that NASCAR and Grand Am are related. This wing can produce a lot of rear downforce. It's mostly unwanted at this time until the teams figure out how to make the front ends turn. In order for a wing to function correctly, the air must flow over and under it unrestricted. Note that the underside of the wing is close to the trunk lid. This makes it more of a spoiler than a wing at the center of the car.
Before you start writing that letter to the editor, let me stress that we have not strayed in our direction here at CT by taking this look inside the COT. Rather, we see where that series is coming about full circle, back to many of the same issues that confront the average Saturday night racer. That's worth taking a closer look.
For the past eight or nine years, teams in what is often referred to as the "top stock car class" have concentrated on aerodynamic technology. They have spent hundreds of expensive hours in wind tunnels and invested thousands of manpower hours in tweaking the metal bodies into shapes that would produce more aero downforce. It was expensive and restrictive for teams just starting out with no history of aero research.
All of that has come to a grinding halt with the unveiling and implementation of the Car of Tomorrow. With the testing and racing in select events in 2007, the teams and NASCAR have decided to go full-time with the COT for the '08 season. What is the COT and how has it changed the way NASCAR teams prepare for competition? Here is a look inside the COT and an explanation of how the teams are affected, from a technical standpoint.
NO MORE AERO MANIPULATION
The COT has, by rule, a well-defined body shape and the chassis is also specified as to the exact construction layout with certain leeway for front geometry. Basically, the COT lost about 600 pounds of downforce in the front and about 300 pounds in the back of the car over the earlier model Cup car. So, it's comparatively unbalanced downforce-wise when compared with the old design.
Then, NASCAR mandated a rear wing in place of the old spoiler that's similar to the Grand Am Daytona Prototype road-racing wing. Any aero engineer worth his/her salt will tell you the spoiler produces more drag than downforce. The wing, on the other hand, produces tons of downforce and a lot less drag. The wing is adjustable within strict tolerances as to angle of attack, so the actual downforce can be adjusted somewhat.
TALLER BODY WITH A HIGHER CG
The whole COT is 2 inches taller than the old car, which raises the center of gravity. The car is wider by 4 inches, but as we discovered, the driver is not significantly closer to the centerline as previously advertised. The driver's compartment is 11/44 inch wider, which doesn't provide the opportunity to move the seat in by much.
We were told that the individual parts and pieces are heavy and the car now weighs close to the limit once completed with all of the components installed. Some teams did not have to add ballast at a recent race using the COT.
ADDED SAFETY FEATURES
A few additions were added to help protect the drivers. The left-side framerail is doubled on the COT. The floor is heavier with a choice of steel plating or honeycomb aluminum installed under the driver's seat.
The car has a driveshaft tunnel that must be installed to the specs. It is heavy gauge steel and has heavy steel strap assemblies at the front and rear. This tunnel fully encloses the driveshaft and nearly eliminates the danger of a loose shaft. It also adds a lot of weight to the car.
As for the construction of the cars, each team and/or car builder must build the chassis/rollcage assembly and submit it to a NASCAR facility, where the location of each joint, component, and measurement is recorded and a data sheet is produced by what is called a coordinate measuring system. If the car is not within a certain tolerance, it is rejected until it's brought within the specifications.
Every joint and mating of...
Every joint and mating of the rollcage and other components must be placed within strict tolerances according to construction plans developed by NASCAR. Once the teams figure out what is expected of them and have properly jigged their build plates, the process should improve production.
A steel tunnel encloses the...
A steel tunnel encloses the driveshaft, and heavy strap assemblies serve to contain a driveshaft that breaks free of either the transmission or rearend. This is a heavy piece and adds a lot of weight to the car. Note that the front "strap" becomes a part of the crossmember.
A set of construction plans...
A set of construction plans is provided by NASCAR so each car builder can see the dimensioning. The tolerances are not too strict in most cases, with plus or minus 0.250 inch allowed. That's a half-inch allowable variation. If you're out of a specific range, the car must be changed to bring it into compliance.
This process can take as few as two or three passes through the gauntlet or as many as nine for one team. Teams must follow a set of construction plans to build the car, as well as a whole section in the rule book explaining the process. The base frame/rollcage cost of the COT is higher because of this process. One car builder told us it used to cost about $8,500, and it now costs around $18,000 for a bare frame and rollcage with some sheetmetal.
THE PROBLEMS CREATED BY THE COT
Most top teams had the older car figured out so that it turned well and was fast and consistent. With the COT, most teams are lost. With a loss of 300 pounds more downforce at the front than at the rear of the cars, drivers complain that the cars won't turn. Gee, we wonder where we've heard that before.
With the addition of a rear wing capable of producing loads of, well, added load, we have a car that's seriously front-grip deficient. So teams are looking at making changes to the front geometry, rear wing angle, and other factors to help get the cars to a neutral handling status again.
Since the rear wing is mostly exaggerating the problem, many teams have learned they need to adjust it to maximum angle of attack and in effect stall the wing so it produces less downforce. With the problems they have with less front grip, the last thing they need is a wing that can add rear grip.
BACK TO THE FUTURE
In reality, the COT handles much like the Street Stock cars we are all familiar with-they lack front grip. Observing the cars on TV tells the tale. We see where the car is either pushing up the track, or if the crew has loosened it sufficiently, it's tight/loose, but either way it's slow.
One driver reported that each time he entered a certain turn, the car behaved differently. One time it pushed and then snapped loose on exit (the old tight/loose syndrome) and the next time it turned well and was loose all the way around the turn. It's this uncertainty that unnerves many drivers.
In the past, the teams have put a significant portion of their resources into aero technology and will now have to rethink how they engineer their cars. The chassis dynamicist will now be in demand and the aero engineers can either find another genre or try to get up to speed on their dynamics lessons. Mechanical engineers will be in demand and any new technology that leans in that direction will need to be utilized.
It's an exciting time for all of circle track racing. Maybe now we can finally find common ground with the top levels of stock car racing by virtue of having common goals and experiencing common problems. We'll be here to report on how the top teams in Nextel (soon to be Sprint) Cup handle this new set of complications and how they utilize their technical know-how in solving the handling problems with the COT.
As we continue with this story in coming issues, don't look for results of the NASCAR Nextel Cup Series races or interviews with drivers about how a race went for them and their sponsors. We are still, and will always be, a technical source for the racers, be they short track or Nextel Cup. We're still with ya, man.
There is a thick section in...
There is a thick section in the NASCAR Nextel Cup rule book on the COT. This defines each and every aspect of the car and what is and is not allowable as to modifications.
The car chassis and rollcage...
The car chassis and rollcage assembly comes as a precut kit and is tack welded together so that it meets the dimensioning guidelines of NASCAR rules. Front framerail heights and control-arm angles are not regulated. This provides the teams with some leverage in the front-end design.
The front nose of the COT...
The front nose of the COT is a special design that limits downforce. A carbon-fiber splitter is incorporated at the bottom and is adjustable within a certain range. With the loss of some 600 pounds of downforce at the front reported by some teams, it's hard to make the car turn.