New towing Dyno expands test capabilities - Test Equipment - Brief Article

Diesel Progress North American Edition, Feb, 2002

Mack Trucks Vehicle Development Laboratory, Allentown, Pa., has expanded its testing capabilities with the addition of an RS-15K towing dynamometer built by DynoMotve LLC, Manitou Springs, Colo.

Specifically, Mack wanted to use a towing dynamometer to test trucks, both current vehicles and future, higher horsepower models, under differing climatic conditions that could not be duplicated at the facility.

"The requirement from Mack was unique," said DynoMotive's Peter Poirson. "They had exacting requirements and wanted testing under continuous high loads at high altitudes."

Designed to be used for high altitude tests in the Rocky Mountains, as well as at the test track, Mack's requirement was for 750 lip at speeds from 20 mph to 75 mph with altitudes as high as 10,000 ft. Further, Poirson said, this had to be done without stopping to change speed ranges on the dynamometer, which is designed continuously to hold a maximum drawbar power load.

"With low air density and low humidity to dissipate the heat generated by the absorbers, additional absorbers were required," Poirson said. "With so many absorbers installed in a series configuration, specially designer absorber mounts and coupling shafts were designed to eliminate resonant frequencies in the system. The absorbers were also built with special bearings and wiring."

Eddy current absorbers were connected in series to a tandem truck rear axle. An Onan 30 kW diesel generator set is used to supply power to the absorbers and the instrumentation. A two-speed transmission was installed to allow for testing at speeds from 3 to 75 mph and also to disconnect the air-cooled eddy current absorbers when the dynamometer is in transit to a testing area.

With the transmission in low gear, the towing dynamometer can continuously maintain 20,000 lb. of drawbar pull at speeds as low as 3 mph. A load cell, connected to a unique sliding fifth wheel, provides accurate drawbar pull measurements, Poirson said.

Superflow, Corp., Colorado Springs, Colo., provided the control and data acquisition system in a joint design program with DynoMotive. The system is capable of recording up to 76 channels of information.

The controller can be programmed by the operator to perform any type of test from simple constant speed and load tests to slop/grade simulations and preprogrammed actual road simulation tests. Control and tests are controlled through a hand-held control module. A driver's aide display is provided to give the driver input for throttle control.

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