When it experienced trouble with clutch failures, Earnhardt Childress Racing Engines turned to Quarter Master® to help create a clutch package that breaks through the boundaries of what had previously been possible.

There’s a reason why you always find some manufacturers in the automotive performance market involved in racing. And that’s because you won’t find anyone, anywhere that can abuse stuff and generally push every component on a car to its absolute mechanical limit like a race car driver. If a part or a component is good enough to win races, a racer will use it. And if it isn’t, he or she will cast it aside unapologetically and find something that works. That’s also why there are some manufacturers you will never find in racing – they don’t want to be exposed in the harsh light of competition.

Quarter Master® has been in racing for years, producing high-performance clutches and driveline components for all types of competition. And with that history comes an understanding that its products must continually evolve and improve as race teams find new and inventive ways to push their equipment beyond its limits in the search for speed.

So it didn’t come as a big surprise when the engineers at Earnhardt Childress Racing contacted Quarter Master® because its NASCAR Sprint Cup Engines were exceeding the power limits of the clutches it was using. As the horsepower and torque levels rose, as well as the RPM limits, teams were discovering cracked clutch discs, warped flywheels and other problems. Sometimes the clutches weren’t even surviving a single race weekend; teams were even having to replace components after practice and before the actual race had even started.

“Unfortunately, the solution isn’t as simple as beefing up the clutch and flywheel components,” explains ECR’s Paul Bolton, who serves as an Engine Design Engineer. “The number-one priority, as always, is winning races. And in order to make the most speed you want to transmit every bit of torque possible from the engine to the rear wheels. A heavier clutch assembly has a higher moment of inertia, which means it’s absorbing some of that torque every time the driver is trying to accelerate out of the turns. It’s easy to make something strong by adding mass, but that wasn’t an answer that we could accept.

“So it’s always a fight between absolute stiffness in the driveline for durability and getting the lightest weight possible for a low moment of inertia.”

So the Quarter Master® engineering staff, including Jeff Neal, began working with ECR in its search for a solution. The existing clutch used three disks that were 7.25 inches in diameter with a six-leg “basket.” For years it has been a dependable design, and its light weight made it a favorite among race teams looking to get every ounce of power to the rear wheels.

“At ECR, we’re really believe that having open working relationship with our technical partners helps us win races,” says lead engine builder Rick Mann. “And the results Quarter Master® brought back after we told them what we were dealing with, really proves how important a good working relationship with the right manufacturers can be. The new design they came up with not only cures the durability issues we were having, it also gives up very little in terms of weight.”

Instead of simply beefing up the existing clutch design, Neal and the engineers at Quarter Master® went back to the drawing board. Most notably, the six legs of the clutch were replaced with eight slightly smaller legs. By redistributing the loading across the circumference of the clutch basket, they were able to increase the clamping load by 25 percent while only increasing the overall weight by just a half of a pound.

“The new clutch has been a real success,” Bolton adds. “Even with the added rigidity, the increase in moment of inertia with the new system is less than 10 percent. By reducing the pressure plate movement we’re able to increase the efficiency of the drivetrain. We not only fixed a durability problem, we’ve helped the teams go faster.”

While they were at it, the Quarter Master® engineers also redesigned the bellhousing to increase the stiffness there as well. The upgraded bellhousing keeps the transmission from moving, which reduces wear of the transmission gears and the pilot bearing.

Now, Mann says, the Nextel Sprint Cup teams running ECR’s engines can go up to three races reliably with the new clutch system, while they were often going through two clutches in a single weekend before. When you consider all the practice laps a team will make before both qualifying and the actual race, that’s as many as 3,000 miles! You can expect Quarter Master® to take the lessons learned from creating this next-generation racing clutch and use them to make lighter, more dependable clutches for other high-horsepower applications. It’s one of the advantages that comes with the commitment required to race – and win – on the highest level.

Any clutch has a tremendously difficult job. It must transmit all the torque created by the engine to the transmission using only pressure and friction. The demands are even greater in performance applications like NASCAR Sprint Cup Series racing because the power reaches tremendous levels while weight must be kept to an absolute minimum. That’s why Quarter Master® considers this a great test bed for ideas that may eventually find themselves in other applications.

Chevrolet’s new R07 engine was designed expressly for NASCAR Sprint Cup competition and includes several innovations, but in a nod to tradition the bellhousing bolt pattern is classic small block Chevy. It’s always good to remember your roots.

The foundation of the new system designed by Quarter Master® is the eight leg clutch with three 7.25 inch disks. By carefully directing where the loads are placed, this new design can handle the increased torque levels of Earnhardt-Childress Racing’s engines with an increase in overall weight of just one half of a pound. Incredibly, after 3,000 miles of competition, this clutch will exhibit less than 0.003 of an inch of runout.

The ultra-light flywheel includes the ring gear. By efficiently dispersing the forces a clutch must withstand, the Quarter Master® design can use some surprisingly lightweight components. For example, those are ¼ inch studs used to bolt the clutch to the flywheel.

ECR uses a special tool to keep the clutch centered over the hub. Everything is balanced to eliminate power-robbing vibrations, so both the clutch and flywheel are marked for correct orientation with each other.

Here, you can see the 7.25 inch pressure plates aligned and in place.

Not everything in a Cup shop is high tech. Here, you can see the short piece of one-inch square tubing that keeps the flywheel from turning while the fasteners holding the clutch in place are torqued.

This may be one of the most highly engineered bellhousings in the world. The ribs are precisely placed to maximize strength while keeping the overall weight as low as possible. Even in aluminum, notice how much effort has been made to carve away every bit of extra material possible on the transmission side of the bellhousing.

Another interesting problem ECR’s race teams were having that the new Quarter Master® system solved was starter failures. When the Car of Tomorrow was introduced, part of the mandated design was to reverse the starter orientation. In order to create more header clearance (among other things), it was flipped as you see here. At first, excessive vibrations were killing starters, but the stiffer bellhousing and beefed up starter components now keep the starters working dependably.