Working closely with Barden, Ultra Electronics Precision Air Systems has reduced bearing costs and assembly times by 40-50 per cent on its high-pressure pure-air generator.
The company produces a range of mini-compressors known as Hippag (High Pressure Pure Air Generators).
These are compact, lightweight, electrically powered air compressors that are carried onboard various military platforms.
The Hippag airborne compressor provides a continuous source of high-pressure pure air to cool the infrared seekers of an aircraft's defensive missiles, keeping them ready for action.
Hippag also provides a controllable energy source for the pneumatic ejection of aircraft munitions, while meeting the emerging requirement for launching increased quantities of smaller, smart munitions.
More than 5,600 Hippags have been delivered for defence applications around the world.
Hippag has been developed for the F-35 JSF aircraft and is being supplied for Boeing's Small Diameter Bomb programme, the Eurofighter Typhoon, the US Marine Corps AV-8B Harrier, AH-1W Super Cobra, F/A-18 C/D Hornet and the US Navy F/A-18 E/F Super Hornet aircraft.
At the heart of the Hippag system is a bearing assembly that is based on a swash-plate configuration.
Supplied by Barden, this precision bearing is a custom-designed assembly that comprises a pair of bearings mounted on a cranked shaft with a 15deg offset between axes.
The function of the bearing is to transfer rotary motion into linear motion, enabling the axial motion of the Hippag compressor pistons.
Typically, the bearing assembly will comprise a pair of solid, pre-loaded angular-contact bearings on the swash axis and a second pair of angular-contact bearings for the shaft axis, which are spring preloaded and share a double-row inner ring.
The bearings are made from carbon chrome and use standard steel balls, as the Hippag application speeds are relatively low (less than 700rpm).
These two bearing subassemblies are then mounted onto the offset shaft.
Ultra receives the completed subassembly from Barden and drops itinto its Hippag housing to mate with the brushless DC motor, which sits on one side of the bearings with the compressor on the other side.
Barden's original design was selected because it utilised lower-cost manufacturing methods using existing tooling and a cellular manufacturing approach that also contributed to a lower-cost bearing solution.
The bearing assembly integrates directly with the Hippag unit and is smaller and lighter than the original.
The original flange-mounted assembly has been replaced with a threaded outside diameter that enables through grinding.
According to Hughes, there were several engineering challenges to be overcome.
For Barden, Hippag is a low-speed, high-load application with a life of less than 500 hours.
Barden supplies products to a range of extreme-environment applications, including vacuum pumps and the aerospace industry.
The product range encompasses predominantly radial, single-row, super-precision, angular-contact and deep-groove ball bearings that meet and exceed ABEC 7/9 standards.
Bearings are manufactured and controlled under strict aerospace procedures, providing full traceability, controlled lubrication and complete retention of records.
Manufactured bearing sizes range from 5 to 180mm outside diameter.
The company is capable of manufacturing bearings to a geometric tolerance of P2 or better and envelope dimensions to P4 or better.
Raceway roundness is better than 0.5um, with raceway surface finish better than 0.025um Ra.
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