Focus on Lubrication: This machine screams for grease

It may be hard to remember, while riding the boomerangs and corkscrew loops of one of North America’s top roller coasters, that all that excitement depends on grease. But John Kuschyk, supervisor of maintenance of the Great American Scream Machine at the Six Flags Great Adventure in Jackson, N.J., never forgets.

That’s because the road wheels on the 1,100-metre-long (3,600 ft) mega-roller coaster need to have the grease in their bearings replenished every seven to 10 days from March to October, which adds up to a lot of grease.

Kuschyk and Six Flags have two priorities for the Scream Machine. First, above all, is public safety. Second is a very fast, smooth ride. Both depend on a grease that will perform across the wide range of temperatures, from chilly spring to the heat of summer, that will allow lubricant to flow easily between the inside and outside bearings, and that will not put a drag on the wheels.

The original specification for the 11-year-old Scream Machine called for the road wheel bearings to be in an oil bath. The problem was that the oil caps sometimes came off unexpectedly and let the oil fly out. Eventually the caps were sealed and the oil replaced with a grease installed with a manual pump or gun under pressure through fittings in the wheels’ hubs.

The system is not closed, however, and after a week or 10 days, fresh grease has to be pumped in to replace that which leaks out. The grease that was being used, according to Kuschyk, was “very expensive.” The mineral-based grease also tended to stiffen in the chilly mornings of the early season, so Kuschyk wanted a grease that was stable over a wider temperature range.

He turned first to a supply partner, Kaman Industrial Technologies of Windsor, Conn. Kaman has supplied bearings for all the roller coasters in the park since the 1980s. Bob Terry of the distributor’s Blackwood, N.J., branch, says, “Six Flags Great Adventure is basically proactive with their maintenance. They can’t afford downtime while the park is open — people expect to ride all the rides when they come. Six Flags relies on Kaman to keep them up-to-date with new products and technologies.”

Terry recommended Dow Corning BG-20 High-Performance Synthetic Grease, which Kaman could supply locally at about one-fifth the price of the mineral-based grease. The product is a polyester grease with lithium complex thickener. It combines the wide temperature range of a silicone grease, estimated at –45C to 180C (–50F to 360F), with the high load-carrying capacity typical of solid lubricant-containing organic greases.

This grease is advantageous in applications that experience high temperatures, extreme pressure or high speed, which pretty well describes the Scream Machine.

Kuschyk phased in the new grease with care, trying it out in one-half of a seven-car train during the 1998 season. When the material performed with no failures and no additional drag on the wheels, he replaced the grease in one complete train with Dow Corning BG-20 High-Performance Synthetic Grease for the 1999 season.

Guests riding the Scream Machine have no idea they are riding on a cost-saving grease. Some people even say the ride is faster than before. But who has time to think about that? They’re all too busy screaming.