Adhesive keeps the weights on

Toledo, OH -A new bonding system from Dana Corp.'s Spicer Driveshaft Div. joins counterweights to driveshafts, replacing a heat welding process that can distort a shaft's thin-walled aluminum or steel tubes.

Called UV FlexBond, the patented system relies on a multi-cured urethane adhesive from Dymax (Torrington, CT) to join the balance weights to the outside of the shaft-near its tube yoke. UV FlexBond employs two curing methods: A 10-sec UV cure of the adhesive around the weight's perimeter fixes the weight in place during assembly and shipping. A second chemical cure of the adhesive under the weight creates a permanent bond. The resulting bond strength is more than enough to hold a 1-oz weight to a 4-inch driveshaft spinning at 7,000 rpm, reports Jim Duggan, the division's chief engineer for advanced design.

UV FlexBond also goes hand in hand with a change in the weight material from steel to the flexible lead. Duggan explains that torque tends to change the shape of shaft tubes, and flexible lead's ability to conform to the changing shapes reduces the amount of stress that has to be taken up by the adhesive. "Steel weights would pop right off," he says.

So far, Dana has supplied about 200 of the UV FlexBond driveshafts-mostly for NASCAR use. The company will soon ramp up production to supply these driveshafts commercially.