Double Clutching: Small diameter dual disc clutch technology
Not that long ago the only vehicles with dual disc clutch assemblies were heavy duty trucks and the odd Corvette As engine horsepower levels dropped in the late Seventies and almost all the way through the Eighties clutch assemblies were pretty much in a stagnant development cycle at least in North America By the Nineties the odd racecar saw the use of a dual disc clutch but those were configured for racers not street driven cars Today things have changed dramatically Clutches with multiple discs are more common than you might have first thought Modern Racing Clutch Let’s back up a second and look at today’s racing
lutch Countless drag race oval track and road race cars operate with itsy bitsy clutch assemblies These things are absolutely tiny some with an outside diameter no larger than 5 50 inches no typo – that’s half of what we’re used to “Larger†setups that measure 7 00 8 00 inches in diameter see use too For the most part these tiny pressure plates incorporate diaphragm springs too but one of the real secrets is the use of multiple small clutch discs two three or more navigator userAgent indexOf WebTV gt 0 document write document write gt Several clutch specialty companies have been paying attention Companies have been developing then building high performance dual disc clutch assemblies for years pretty much ever since GM discontinued their Borg Warner built dual disc clutch option in the very early Seventies The dilemma with those earlier dual disc setups has always been the need for a very special and often expensive flywheel For example McLeod’s latest RST clutch kit is engineered to work with an OEM flywheel you can use an aftermarket flywheel as well – more in the accompanying photos Based upon a 9 11 16 inch diaphragm pressure plate the assembly includes two organic discs along with a steel floater plate By reducing the overall diameter of the clutch the moment of inertia is reduced Is that important You better believe it You see the rotating components in a vehicle driveline include the crankshaft the flywheel the pressure plate the clutch disc s and the gears inside the transmission as well as the driveshaft All of these components operate at a relatively high speed RPM Due to this relatively high operating speed the effect the combined rotating inertia has upon vehicle acceleration is considerable If the weight of that rotating mass is reduced then the basic assembly can spin faster If the weight in that rotating mass is moved closer to center of the mass then the entire assembly can spin faster That means the car can accelerate faster To get a better idea of how this works consider a figure skater beginning a pirouette with her arms outstretched As the skater pulls her arms inward then the moment of inertia has been reduced That causes the spin to increase in speed Smaller Diameter Dual Disc Systems In the case of a modern dual disc clutch instead of incorporating a large heavy 11 00 inch or larger Borg amp Beck or Long style pressure plate a small light 9 11 16 inch Diaphragm pressure plate can be used Instead of using a large heavy 11 00 inch or larger clutch disc the system makes use of two small lightweight 9 11 16 inch organic discs The dual discs increase clamping power of the clutch almost doubling it over a conventional system Since the clamping power has increased almost exponentially then the demands placed upon the pressure plate spring s are reduced considerably Equally important the reduction in the clutch at the moment of inertia allows the use of a very lightweight pressure plate spring s Reducing the force of the pressure plate springs means your left leg isn’t strained beyond comprehension Do these small diameter dual disc systems work Absolutely During testing these multi disc arrangements showed the capability of handling upwards of 800 hp with the pedal feel of a modern OEM vehicle In some applications you can also incorporate bronze segmented puck configuration discs capable of holding upwards of 1000 hp There’s more too The small diameter dual disc clutch assemblies provide a pedal feel that is actually very light and more in line with what you might find in a typical four cylinder economy car As you can see racing technology has trickled down to the street driven high performance car Not only is clamping power increased pedal pressure is reduced It’s a win win situation For a closer look check out the accompanying photos About the Author A true hands on “gearhead †Wayne Scraba has a diverse background in both writing and motorsports Over the past two and a half decades Scraba toiled as a magazine editor technical editor freelance magazine contributor and has authored five automotive books His background also includes racecar fabrication muscle car and street rod restoration and construction and operating his own automotive parts and repair business
Tags: clutch, clutch assemblies, clutches, corvette, disc clutch, driven cars, dual disc, eighties, engine horsepower, heavy duty trucks, nineties, north america, racecar, seventies, Uncategorized
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