Case Study – Helicopter Transmission Ring Gear

Helicopter Transmission’s Ring Gear Carrier

As a premier source for investment cast parts, at Waltek Inc. we have an extensive history of producing complicated shapes and assemblies that exhibit exceptional structural integrity. We manufactured the ring gear carrier highlighted here for use in a helicopter transmission. This part, which functions within the main rotor gearbox, was built to meet a rigorous set of quality criteria to ensure safe and satisfactory performance.

Prior to our involvement in this project, the part was produced at another vendor by means of sand casting. While sand casting is a very effective method for producing quality parts, investment casting is a better alternative for producing complex shapes. The sand cast parts were falling short, mainly with porosity. Class C non-destructive testing revealed unacceptable flaws that could potentially lead to cracks or weakening.

As a respected supplier of high quality investment castings, the client approached us to provide an alternative solution. Our investment casting process, which incorporates reliable process controls, allows us to create strong, accurate parts with consistent repeatability. Using grade A35 aluminum, we were able to cast this dimensionally complex workpiece with extraordinary precision. Once the part was released from the wax casting mold, secondary operations consisted of heat treating, deburring, and tumble blasting to remove all traces of scale and other particulates.

Extensive mechanical testing and Class B NDT inspection ensured the part met all vital quality criteria. Radiographic examination showed no indication of voids or other flaws that would adversely affect the quality of the finished piece. In addition, fluorescent penetrant tests confirmed that there were no surface defects that compromised its integrity.

Finished workpieces measured 12.5” in diameter and 5.0” in height. Manufactured to within 0.005” tolerances, they satisfied AMS2771 requirements for mechanical properties, including a minimum tensile strength of 33 KSI, yield strength at 0.2% offset of 27 KSI, and elongation of 3%.

Our ability to respond quickly and perform a range of secondary operations in-house enabled the client to take delivery of the finished product within a 7-8 week timeframe. They were very impressed with the quality and the small amount of finish machining that was needed. Their feedback indicated that the parts satisfied their rigorous requirements for both structural integrity and appearance.

If you are interested in learning more about this project or our investment casting process, contact us today.

For more information about this project or our investment casting capabilities, contact us today.