Clutch Action
Clutch Action
A clutch's main purpose in life is to smoothly transfer power from the engine to the wheels. It does no one any good have 500 horsepower at the engine if you can not get that power to the wheels. Automotive clutch systems are basically made up of three parts: the pressure plate (clutch cover), the clutch disc, and the flywheel. The pressure plate is bolted to the flywheel which in turn is bolted to the crankshaft. The clutch disc is attached to the transmission thru a hole in its center. When the clutch is engaged the disc is squeezed against the flywheel by the pressure plate, and when the clutch pedal is pushed to the floor the disc is spinning freely between the pressure plate and flywheel.
The amount of torque or power the clutch can transfer from the engine to the wheels depends on how hard the pressure plate squeezes the disc, how big is the disc, how sticky is the disc, how sticky is the flywheel, and how many discs are being used. The larger the disc, the more power it can transfer. Unfortunately most of today's cars have very small transmissions and very little room to make the disc bigger around. Increasing the clamping force of the pressure plate is a great way to increase a clutch's torque capacity.
There are a number of ways to do this including moving the fulcrum or pivot point that the diaphragm spring rides against. This method is used when you only need a small increase in pressure to give a modest increase in holding power. (Fig. A)
Another good way to increase torque capacity is to replace the diaphragm spring with a stronger unit. RPS uses their patented (#5,769,973) technology to increase the strength of the existing spring while erasing any memory of the stock spring. RPS also uses their unique proportional dual diaphragm pressure plate technology that allows them to set the clamp force to any desired pressure within 100 lb increments. (Fig. B) ACT replaces their springs with thicker one piece units.
Stickier clutch discs are another way to hold more power. There are many different materials to choose from, but the most important thing to consider is the balance between good holding power, drivability, and clutch life. As a rule of thumb full face organic discs provide the smoothest engagement and the longest life. Puck style discs hold more power that street discs and can take more slippage and heat generated by harder driving. The fewer the pucks the more power the disc can hold. Four puck discs can hold more than six puck disc, but because they have less material a four puck disc will wear out faster than a six puck. Since puck style discs are stickier than organic disc, they are usually less driver friendly. One way to improve the drivability is to make sure to use a sprung hub puck discs. Solid hub discs are strictly for racing (less weight) and are not fun on the street. Puck style clutches are also harder on their opposing surfaces, like the flywheel and pressure plate casting. One novel way to address this problem is RPS's CYN-R-G
Segmented Flywheel (Fig. D) and Pro MAX pressure plate (Fig. C). Both of these use a unique segmented heat shield system that allows for better heat transfer and replaceable parts for the life of the car. As most drag racers know, they have to replace their pressure plate every time they replace their puck style disc because the disc has worn a groove to large to machine out. The Pro MAX pressure plate uses steel pucks that are more wear resistant than standard cast or ductile iron unit and they are replaceable.
Because of the rapid advancements in horsepower numbers, tire combinations and suspension systems, there has been an equally rapid demand for better and better clutch systems. One company, RPS feels they are leading the way with their Turboclutch Carbon (Fig. E) and Ti Carbon (Fig. F) line of ultra performance clutches. Carbon-carbon is used in Formula One for their brake and clutch systems. It is also used by Top Fuel, Funny Car and Pro Import racing for their brake systems. The advantages of carbon-carbon are many, including smooth engagement, high heat capacity, light weight discs, and long life.
