AGMA 11FTM18 PDF

After a period of operation turbo gears may exhibit a change in the tooth contact pattern, reducing full face width contact, and thereby increasing the risk of tooth distress due to the decreased loaded area of the teeth. The phenomena may or may not occur. In some units the shift is more severe than others and has been observed in cases where there is as little as 50,000 hours of operation. In other cases there is no evidence of any change for units in operation for more than 100,000 hours. This condition has been observed primarily in single helical gears with low helix angles (10-13?). All recorded observations have been with case carburized hardened and ground gear sets. This paper describes the phenomena observed among some of many installed high speed gear units in field operation that have been inspected. The authors have not found any written material describing this behavior and upon further investigation suggest a possible cause. Left unchecked and without corrective action, this occurrence may result in tooth breakage.