Servo Kinetics Inc. (SKI), Ann Arbor, Mich. has had a long-term contract to refurbish the hydraulic rides at Cedar Point, Ohio’s largest amusement park, in Sandusky. The rides are trucked to SKI’s facility during the off season, refurbished back to the original manufacturer’s specifications, and then returned to the park for Cedar Point’s engineers to do their testing to assure that the ride meets their criteria for normal and safe operation in the next season.

Typically, Servo Kinetics rebuilds five rides during a six-month time period from mid-November to Mid-April. This year, in early January, Cedar Point Engineering notified them that they wanted them to do a total refurbishment on the park’s major ride, the Top Thrill Dragster.

 refurbished hydraulic gear motors

A typical roller coaster pulls passenger cars to its highest point by a cable or chain drive, then releases it, and gravity takes over. Instead, Top Thrill Dragster — built by Switzerland’s Intamin and installed in 2003 — accelerates the 6-ton coaster train hydraulically from a standstill at the loading area to 120 mph in about 4 seconds. (This provides the Thrill in the ride’s name.)

A pump and accumulator system supplies 32 Model QXM83 dual-section hydraulic gear motors (which weigh 800 lb each) from Bucher Hydraulics to produce the acceleration. The system runs at 320 bar, and peak power is 10,000 psi. When Cedar Point maintenance people noted that leakage had become excessive over seven years of service, they asked for the rehab work.

amusment rideSKI evaluated all 32 motors. After a warm-up period, each motor was tested for 4 hr at low and high speeds while leakage was monitored. They determined that several motors had severe wear in the gear section, three motors required new shafts, and two were beyond repair and had two be replaced. Servokinetics understood the extreme demands of the thrill ride application and felt that the Bucher motors had done well to survive over so many years of service.

In addition, all motors had large manifolds containing various valves for reversing four of the motors to return the coaster’s drive lug to its passenger-loading platform. (The remaining motors were allowed to free-wheel back to the home position.) SKI also refurbished the manifolds and valving.

Cedar Point happily advised SKI that the Dragster was up and running — and performing as good as new after the refurbished motors and controls were reinstalled.

For more inofrmation, call George P. Kokalis, of Servo Kinetics Inc., at (800) 824-0808, or visit www.servokinetics.com.