Setting the template for the foreseeable future?
By Bertie S. Brown:
Lighter and stronger than conventional driveshafts, the unorthodox carbon fiber units fulfill an even more important role: they are at the heart of traction, attempting to deter any disruption of the tire’s contact patch. They are, in fact, a milestone in drivetrain innovation and efficiency.
In the U.S., it was around 2014 when their reputation began to flourish on the short track dirt ovals and their innovative advancements quickly penetrated the drag racing and high-performance street car arenas.
In addition to lightness and strength, carbon fiber driveshafts demonstrate torsional compliance. Torsional compliance is the capacity to control twisting force. In contrast, the conventional tubular metal driveshaft is rigid; it exhibits minimal torsional compliance—much less give. Oddly, the word compliance when linked to the term carbon fiber seems inconsistent. Isn’t carbon fiber brittle? Not when torsional force is applied apparently.
In fact, when you watch video evidence of three degrees of torsional compliance—twisting from natural form to three degrees and back again—the miraculous mental image will endure. And in severe operation, it is this yielding quality that softens the torque spikes when cycling the throttle—on and off the pedal—and changing gears both of which cause stress reversals.
Thus, the presence of carbon fiber compliance means less tire spin. It also lessens the shock introduced to the tire’s contact patch when compared to shafts made of aluminum or steel, implying superior traction during launch.
Defining a new design direction
The ultimate strength of the carbon fiber driveshaft is determined by its end fittings, or at least this is the formula applied by the Minnesota manufacturer QA1. The tube and its vigorous bond to the yokes far exceed even the strongest universal joints available. Typically, a slip joint connects the leading end of the driveshaft to the transmission and the rear end connection is made by a u-joint assembly. U-joints are either of the 1310 series using a 3.250in cross joint or the 1350 series with a 3.625in cross joint. Due to their greater power output and harsher launches, most drag racing cars employ the latter.
But how is driveshaft size determined? To establish the size or series of shaft, QA1 requires details of the vehicle’s use, its drivetrain and its torque characteristics under load.
To increase or decrease the torsional strength, they may alter the carbon fiber tube diameter or the wall thickness or the angle of the weave or the type of filament—even the application of different resins is considered. These parameters vary depending upon whether the shaft is being used for drag racing or circle track racing.
On first acquaintance, you might wonder if the properties of the composite driveshaft continually deflect in this manner will the weave strength eventually degrade. “No, it doesn’t,” says QA1’s Dan Voight, “carbon fiber structures have impressive resilience and memory.” These are unfamiliar characteristics of the old world and one can only conclude that we do, indeed, live in fascinating times, as they say.
Half the weight of a DOM steel shaft, the carbon fiber counterpart provides excellent strength. Indeed, it’s worth noting that the fibers must be laid in the correct direction and at the correct angle to maximize strength and stiffness as well as minimizing weight for ideal performance. So, what is the distinction between strength and stiffness?
“Strength,” says Dan Voight, “refers to the amount of power the driveshaft can transmit. Stiffness relates to the amount the driveshaft twists under a given load.”
This manufacturer applies a further hallmark that contributes significantly to the merits of their carbon fiber driveshafts. They collaborate with 3M. A leading aerospace corporation and possibly the most influential resin developer in the country, 3M is conveniently located just down the road from QA1’s manufacturing base.
Evidenced by three years of hard competition, carbon fiber driveshafts are now available for a wide range of drag racing categories, some capable of transmitting over 3,000 hp. Uniformly consistent, QA1 specializes in tailoring these assemblies for specific applications, including high-performance street vehicles.
QA1 Precision Products Inc.
21730 Hanover Avenue
Lakeville, MN 55044