To address the issue of rapid clamp load drop-off with clutch disc wear, Cusco uses a special diaphragm spring in the pressure plate. Using a special coating, material and geometry, the Cusco spring can maintain a consistent clamp load even when the discs wear quite a bit. Cusco benchmarked their twin-disc against others, and found that their springs maintained the clamp load over nearly twice the wear distance.
To make the clutch have a longer engagement travel, allowing it to be smoothly driven off the line, the fulcrum of the pressure plate's diaphragm spring, located on top of the pressure ring, is a flat spring with give in it. This additional spring action gives more pedal travel to the stroke of the pressure ring as the clutch is being engaged. The fulcrum also works at a reduced leverage ratio, further increasing pedal engagement travel and reducing pedal effort needed to disengage the clutch. The result is a lot of room in the pedal travel, right as the clutch starts to grab giving an initial feel close to that of a factory clutch combined with a light, non leg busting pedal effort.
To cushion the drivetrain, make for a smoother engagement and to reduce drivetrain noise both of the clutch discs use a sprung hub. This is an unusual concession to streetabilty in a twin-disc. The discs' friction material is full metal, usually the best for burst resistance, torque capacity and heat resistance but the worst for niceness on the street. Cusco has perfected the material's characteristics so that the material has the good attributes of metal but still allows a fairly smooth engagement. This is a major feat as anyone who has daily driven a metal disc clutch on the street can attest too.
The floater plate between the two discs has some unique features as well. First, it is fairly thick and has a ventilated center to help pump cooling air into the heart of the clutch. Flat leaf springs help keep the floater actively centered and under tension when the clutch disengages, reducing the annoying chingging noise that all twin-discs are affected with. Twin-disc clutches tend to wear the pressure plate side disc faster as well as its gap tends to close first as the clutch is engaged. The centering springs keep the gap, and thus wear characteristics, consistent between the discs.
The pressure plate cover is machined out of billet aluminum giving it both lightness and stiffness compared to the stamped steel that most clutches use. The flywheel of the clutch assembly is forged steel with a lightweight thin cross section. The support pillars for the clutch are also steel which is an advantage. Many twin-discs have support columns made of aluminum for lightness. The trouble is that on a streetcar, the frequent use causes the drive tangs of the clutch floater plates to wear grooves into the pillars. The floaters get stuck in the grooves causing sticking and inconsistent clutch action. In this case the harder steel is the superior material.
All of these technical features make for an amazing clutch. It takes the punishment of AWD drag launches and will hold all of the power that the engine mods we will make in the future will produce. Although it is not perfectly silky smooth like a stock clutch, the Cusco twin-disc is still the smoothest engaging, least chattery and quietest twin-disc we have ever driven. Short of an ultra expensive exotic carbon/carbon clutch, we have never experienced a twin-disc so smooth and it's the smoothest easiest to drive all-metal disc clutch we have ever used, period.