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The paper will review existing seals used in off-highway heavy equipment, both radial lip seal applications and face type seal applications in general use on track vehicles. With the trend towards improved reliability and durability, together with the never ending quest for quality and product improvements, the paper will discuss a number of seal development programs which will result in products that meet the new and projected future requirements for seals from the off-highway heavy equipment manufacturers.

This paper describes an IC engine fuel-system conversion to dual-fuel capability, on a carbureted Cessna 150. This conversion differs from others by adding a fuel injector in parallel to the existing carburetor. The fuel injector pump is activated when switching to ethanol. The advantage is conventional take-off and landing on either fuel with mixture full rich. Altitude leaning remains conventional. This is the first conversion to provide smooth in-flight fuel type change-over at cruise power, if the prescribed procedure is followed. This conversion method is applicable to all carbureted or fuel injected aircraft and automotive engines.

In the course of studying the market requirements for seals in large axles and relating this to conventional sealing technology, it became apparent that a fresh approach to sealing was desirable. This paper describes such a development in detail. Centrifugal action is the principle sealing action of the seal. Although this is in itself not new, the method by which it is harnessed makes the design radically different from normal “slinger” seals. Both practical and analytical work are covered in the text.

The truck wheel seal requirements have changed over the past ten years. Some of the critical requirements for a truck wheel seal in today's environment are: the ability to exclude dust, mud, and water over a wide range of operating conditions; the ability of the elastomeric sealing element to tolerate various aggressive lubricants over a wide range of operating conditions; the ability to provide an adequate OD seal when installed in aluminum housings of various surface finishes; and the ability of the seal to be installed with minimal opportunity for installation damage or improper installation. An improved unitized truck wheel seal was developed to accommodate the above requirements. During the development program, it became obvious that an advanced Nitrile rubber (NBR) formulation was necessary to assist the seal design in accommodating the more demanding performance requirements.

A new unitized pinion seal has been developed for use in automotive pinion applications, particularly where the design of the differential can accommodate a yoke-installed unitized seal. The paper reviews a number of existing pinion seal designs and discusses the philosophy behind the new unitized design. The test results presented demonstrate the improved performance of the new unitized design over the conventional non-unitized multi-lip radial lip design commonly used in pinion applications.

The development of the highly saturated nitrile family of polymers has enabled elastomeric compounds to be developed for both rotating and reciprocating seal applications with good high temperature performance combined with the relatively good low temperature performance associated with conventional nitrile compounds. The paper will discuss a number of compound development programs and illustrate results obtained from both laboratory and seal tests making reference to use of the new compounds in pinion, steering gear and engine seal applications.

AEA Technology is carrying out an ongoing programme of lightning simulation testing work on carbon composite ‘T-joints’. These typically represent skin to spar bolted interfaces, and the tests help to determine whether aircraft fuel tanks incorporating such structures are liable to produce sparks during a lightning attachment. For testing, the T-joints are integrated into a complex test rig that is intended to provide representative current flow during the simulation tests. The intention is that the current distribution in the T-joint should be similar to the current distribution on the equivalent part of the aircraft structure during a lightning attachment. A combined experimental testing and computational modelling work programme has been carried out in order to investigate how representative the test-rig current distribution is to that on a real aircraft. In the first part of this study the test rig itself is modelled using the 3D code ELECTRA.