Development of an Updated Brake Chatter Test for Anti-Brake Chatter Transmission/Hydraulic Fluids

The advantages of wet brakes are convincing, nearly all tractors built today are equipped with them, but problems do exist with their use. One of the concerns with oil lubricated (wet) brakes found on off-highway and agricultural equipment is brake chatter caused by stick-slip phenomenon (rapid fluctuations in friction coefficient) in the friction couplings. Rapid changes in brake torque can cause noise and vibration in the vehicle. A major factor in the amount of brake chatter in a wet brake system is the oil used to lubricate and cool the brakes. To develop oils with properties that control brake chatter, a test is needed to measure performance. The testing of Tractor Hydraulic Fluids (THF) for brake chatter performance has been performed for over 20 years. This paper describes the efforts to develop a test utilizing a new type of brake system. The brake system was instrumented to record brake torque hydraulic apply pressure, and input speed. A computerized data acquisition system aids in the recording organizing, and summarizing of the large volume of numerical data. One of the parameters measured in this test is the variation of torque level during brake application. Different oils of known performance levels were tested using both old and new brake chatter tests, and a correlation was made.