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.

Product Description: Helicopter Transmission’s Ring Gear Carrier

Capabilities and Processes Applied: Autoclave
Heat Treat
Mechanical Testing
Non-Destructive Testing (NDT)
Set up
Tumble Blast
Wax injection

Overall Part Diameter: 12.5 in

Overall Part Height: 5 in

Tightest Tolerances (±): 0.005 in

Material: A356 Aluminum

Material Finish: Blasted Surface

Industry Focus: Aerospace

Delivery/Turnaround Time: 7/8 weeks

Delivery Location: Michigan

Standards Met: Class B Non-Destructive Testing (NDT) inspection for Fluorescent Penetrant and Radiograph

Product Name: Bracket Pull Housing
Lens Driver
Retaining Collar

Why did the customer choose you to do this job?: Local vendor
Looking for a supplier to provide parts that pass the Aerospace NDT requirements for porosity and fluorescent testing.
Previous experience in metal fabrication of custom outdoor shelters
Provide full service (design, manufacturing and installation)

What positive feedback did you receive from the client upon completion?: The customer stated the parts machine very well and look great after machining.
The customer was pleased with every aspect of our work and has come back to us for additional project partnerships
We are the customer’s best supplier, we go above and beyond.

What would you like to point out about this piece/process? (Special Features, Processes, Materials): Complete machining capabilities are featured in these products including: Precision CNC Turning, Sinker EDM, Laser drilling, and TIG welding for final assembly
Part is an unconventional size for an aluminum enclosure

Describe the title/role of the employees involved in the project?: Certified Welder
Design Engineer