Antennae test rig

Antennae test rig

Keywords: Military, Rig testing, Aircraft, Hepco Slide Systems

Hepco's ability to supply a complete 6m beam assembly comprising precision base and complementary Heavy Duty Linear Motion System with in-built drive mechanism, won the company an unusual and prestigious order (Plate 6). The assembly was to form an important part of an aircraft antennae test rig destined for the US Air Force. Rigidity of the system is paramount as its function is to transport a radar array to various positions along its length in order that sensitivity can be checked. The weight of this load is about 100 kg which has to be positioned to an accuracy of 0.025mm.

The test rig is used in the world's largest anechoic test chamber - a converted 300m x 200m aircraft hanger at Edwards Air Force Base in California. Anechoic technology absorbs signals from the antenna so no energy is reflected back off the chamber walls to distort test results. The technology creates the effect of being in open air so the antenna responds as if operating on an aircraft in flight. The chamber also prevents unwanted external signals from entering and affecting the test readings.

The USAF rig comprises a "towable" trolley weighing about 2.5 tonnes with a mast which can raise the aircraft radar antennae about 15m off the ground. The standard, 6m long Hepco Heavy Duty Beam is mounted on the mast and uses two ground single-edge "V" slides and Heavy Duty Bearing Blocks. The bearings used are eccentric and concentric allowing easy adjustment and pre-load setting.

Plate 6 Hepco's complete 6m beam assembly, comprising precision base and complementary Heavy Duty Linear Motion System with in-built drive mechanism, won the company an unusal and prestigious order

In operation, the carriage transports the radar array which it positions to an accuracy of 0.025mm. The actuator carriage is raised and lowered using Hepco's rack and pinion drive, which is integrated with the single edge "V"slide. The standard accuracy of this set-up is 0.25mm, but in this application it is enhanced by the inclusion of an encoder.

The test rig was designed and built for the USAF by Machine Technology Inc. of Cartersville, Georgia who completed the project in partnership with the French company, Satimo. For advice on linear motion and the supply of the Heavy Duty System, Machine Technology turned to Blue Ridge Industrial Sales, the local manufacturer's representative for Hepco's US distributor Bishop Wisecarver.

Details from Hepco Slide Systems Ltd. Tel: +44 (0)1884 243400; Fax: +44(0)1884 243399.