A 2009 NASA cutaway photo illustrates the contact gears of a helicopter transmission. Photo courtesy of NASA Glenn Research Center
Small, high-tech U.S. businesses have until Feb. 17 to solicit U.S. Army funding to develop and demonstrate a helicopter transmission that does not require physical contact among its gears to convert engine power to rotor thrust for new installations and retrofits.
“Development of a non-contact transmission” is one of 89 topics included in the Army’s solicitation under its fiscal 2016 Small Business Innovation Research program. That program, part of a larger Defense Dept. effort, targets high-tech companies with fewer than 500 employees.
“Highly innovative, game-changing power transfer concepts and configurations will be considered favorably,” said the solicitation for the three-phase transmission research effort. But proposals should aim for “a torque and speed reduction typical of an Army scout helicopter,” i.e. an approximate input of 5,000 to 10,000 rpm and a main mast output of a 15:1 to 20:1 reduction at 500 to 800 hp.
The solicitation laid out a timeline that called for a contract award in June for phase 1, which would “investigate the underlying physical principles” needed to create a non-mechanical contact gearbox and develop a preliminary design for it.
The solicitation noted that mechanical-contact transmissions (in which gears create a torque and speed conversion through their teeth surfaces touching each other) rely on lubrication to protect those surfaces from wear and overheating. Such systems “are vulnerable to loss-of-lubrication events and require regular maintenance for the lubrication system.” The Army wants to reduce or eliminate the reliance on lubrication by doing away with such gear surfaces (as well as the bearings that support rotating components).
The Army observed that “recent efforts to develop non-contact gearboxes have focused on the magnetic planetary configuration,” which are used in wind turbines, marine propulsion and hybrid electric systems. But the service said “new concepts for non-contact transmissions are highly encouraged.” Proposed concepts should be scalable to cover classes of utility, attack or cargo helicopters. The solicitation is available here