Forest City Gear Goes World Class

Forest City Gear Goes World Class

Critical winch crown gears machined in titanium alloy for BMW ORACLE Racings Americas Cup entry.

The current America’s Cup competition features “domestic content” rules: All equipment for the yachts must be manufactured in the country that the team represents. BMW ORACLE Racing sails for San Francisco’s Golden Gate Yacht Club, so all on-board equipment must be American-made.

The current America’s Cup competition features “domestic content” rules: All equipment for the yachts must be manufactured in the country that the team represents. BMW ORACLE Racing sails for San Francisco’s Golden Gate Yacht Club, so all on-board equipment must be American-made.


Winches are critical equipment on a racing yacht, and speed, reliability and weight are important factors for determining which winch packages will be selected for use on yachts competing for international glory. This week, the competition for the 33rd America's Cup Match begins — a quadrennial competition to determine the fastest yacht afloat. The event, which is named for the yacht that won the first challenge in 1851, also showcases preeminent sailing skills and, of course, superior craftsmanship in the design of yachts and their equipment.

Forest City Gear, a Roscoe, IL, machine shop, supplied crown gears and splines of special high-strength, lightweight and corrosion-resistant titanium for use in the engine and winch system of the new BMW ORACLE Racing trimaran. BMW ORACLE Racing is one of the two finalist teams now racing in the America’s Cup event underway in Valencia, Spain.

Made from Ti-6-4, a titanium alloy often found in aerospace applications, this material is extremely durable and was determined to be ideal for this project by the Alpha Engineering Consulting designers, Forest City Gear’s customer of Forest City Gear.

The manufacturing process for these gears (and their corresponding spline components) was hobbing and shaping, respectively. The crown radius was the main point, owing to the extreme stress and motion present when such gears are in use.

Jon Williams, a member of BMW ORACLE Racing’s shore team explained: “During the build-up to the previous America’s Cup in Valencia, Spain, we undertook development of our own transmission components for the winch systems on our yachts. After careful study, we had determined this was a critical area for improving our performance on the water.”

BMW ORACLE Racing wanted to reduce the mass and increase the mechanical efficiency of the gear and spline assembly. A prototype project proved successful and the team undertook a complete redesign of the gearboxes for their USA87 and USA98 yachts.

Forest City Gear used a hobbing process to machine these gears in T06-4; the corresponding splines were produced by shaping, also in Ti-6-4. Because of the extreme stress and motion on the assembly, the crown radius was the main point, according to Forest City Gear.
Forest City Gear used a hobbing process to machine these gears in Ti6-4; the corresponding splines were produced by shaping, also in Ti-6-4. Because of the extreme stress and motion on the assembly, the crown radius was the main point, according to Forest City Gear.

The new gearboxes were manufactured in New Zealand, and now onboard the yacht used by BMW ORACLE Racing in this year’s America’s Cup. The current competition sees different rules than previous America’s Cup programs. Among the rules is a regulation that all equipment for the yachts must be constructed in the country the team represents. Because BMW ORACLE Racing sails under the flag of San Francisco’s Golden Gate Yacht Club, all on-board equipment must be American-made.

Williams continues, “The construction of our trimaran was a formidable project and it was clear we needed to utilize a group of vendors with specialist skill and expertise. Our project called for a fairly wide selection of gears, splines and driveshaft components, some of which were non-standard sizes. Two vendors we selected to produce these components were Arrow Gear and Forest City Gear”. For Forest City Gear, Jared Lyford and Tom Christenson ran the project. The gearbox casings and other associated parts were manufactured by RB Enterprises, a custom manufacturer in Everett, Wash. For Arrow Gear, Joe Arvin ran the project to deliver the bevel gears. Final assembly of the gearboxes and their installation occurred at BMW ORACLE Racing’s structural R&D facility in Anacortes, Wash.

After five weeks of intensive testing off Seattle and San Diego, the gearboxes were removed for inspection. The results were impressive: the gears were showing only the first signs of polishing on flanks. They looked new!! It was concluded that the gears were a significant improvement on the New Zealand-sourced gears used by BMW ORALCE Racing in their previous America’s Cup program.

Williams concludes, “Arrow Gear and Forest City Gear have provided the team with a quality product. We would use them again.”

Update: The BMW Oracle team beat the two-time defending champion Alinghi team to win the 33rd America's Cup competition.

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