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The chief advantage of an aluminum high performance flywheel is weight saving. In weight saving, aluminum is the most potent medium we have available in flywheel manufacture. Using aluminum sheds 10-15lb from the rotating assembly of a conventional steel flywheel, but it is the effect the weight loss has on the moment of inertia—the measure of an object's resistance to changes to its rotation—that contributes the real gains. The lower moment of inertia in the aluminum flywheel provokes an instant response, delivering not only faster acceleration and faster deceleration but also suppressing wheel spin. In addition the component is not very expensive and the installation process not very laborious.
Ram Clutches, a competition clutch and flywheel manufacturer since the early 1970s, designs their aluminum flywheels as re-buildable units. Moreover they feature a thick ¼-inch mild steel friction insert to dissipate heat faster, maintain a flat friction surface, and reduce the likelihood of distortion. Thinner, un-ground inserts have a tendency to buckle under the severe heat of hard clutch duty. Though replacement inserts can be renewed by the factory, rarely do the flywheels require them. Typically they are resurfaced on a Blanchard grinder when wear exceeds 0.015in, and this resurfacing process could be applied several times over if necessary.

“You may not think there is much difference between a 3/16in thick steel insert and a 1/4in thick insert, but the difference is huge,” insists Ram’s technical director Pat Norcia. “The 1/4in thick material with 33 percent more metal to dissipate the heat ensures clutch engagement remains smooth. A common problem with thinner 3/16in inserts is that they don’t always remain flat. As the heat builds, distortion occurs and the lighter plate lifts between the rivets. This leads to reduced clearance of the clutch disc. Also if the surface doesn’t remain flat, a smooth clutch engagement is compromised. Clutch chatter will occur if one area is high, which makes the clutch grab unevenly and chatter follows.”
Aluminum flywheel blanks are derived from 6061 material with a T6 temper, and they arrive at Ram’s facility in Columbia, SC in a variety of thicknesses and diameters from 12.5 to 15 inches. They are classified by their diameter and by the number of teeth on the starter ring gear that encircles them. The most popular blanks are 13.5 and 14 inches. The smallest of these suit the 2300/2000 Ford (135 teeth) and the largest are used on the big-block Fords (184 teeth). The most popular flywheel for a Chevrolet carries a 168-tooth ring gear and is produced from a 13.5in blank as is a Ford with a164-tooth gear. The Chrysler unit usually features a 143-tooth ring gear and is machined from a 13.750in blank.

Flywheels provide 50 percent of the friction surface to which the clutch disc mates; therefore, they contribute half of the holding power of the clutch system. Premium flywheels possess four essential elements: a proper friction surface finish, a perfectly flat friction surface, a friction surface parallel to the crankshaft flange, and a fine balance. Approximately 1 in 20 flywheels is endowed with perfect balance; the remaining 19 will display drilled balance holes. Ram’s Pat Norcia reports they balance their units to within half-oz/inch. “To provide a proper friction surface and to ensure the flywheel is parallel to the crankshaft flange,” says Norcia, “we use a Blanchard grinder that enables us to grind the flywheels flat to within 0.001in.” A Blanchard grinder not only spins its grinding head but also its table with the flywheel attached. By rotating the flywheel and the grinding stone in two different directions, a perfect mating surface is achieved. With a 36-grit grinding stone this device provides a true surface, hence smoother clutch engagement and greater clutch longevity.

On the edge of the flywheel a groove is machined to accept a starter ring gear and on its back face three button-head securing screws are installed after the ring gear is heat-expanded then shrunk in place. The securing screws offer a safety margin on competition cars by keeping the ring gear from rotating on the flywheel. “If for some reason,” comments Norcia, “the flywheel is exposed to excessive heat, perhaps through severe clutch slippage, the ring gear could become loose as the cooling rates of the steel ring gear and the aluminum flywheel differ. For this reason Ram fits retaining screws.” He added that on billet competition drag racing clutches, were slipping is normal practice, retaining screws are essential.

The principal failings on aftermarket high-performance aluminum flywheels are often a steel friction insert of inadequate thickness (usually 3/16in), the omission of a properly ground surface on the friction insert, and the lack of balancing. To survive these hazards here in this series of pictures is how Ram Clutches makes their high-performance lightweight flywheels.

Source:
Ram Clutches
www.RamClutches.com