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The objective of this paper is to determine the whirling bending critical speeds of pultruded composite shafts in simply supported boundary conditions. Theoretical studies have been carried using Patran to determine the natural frequencies and the mode shapes for the Jeffcot and Kikuchi rigid rotor models. A tabletop experimental apparatus has been fabricated and the bending critical speeds have been measured for various span lengths between the supports. The results of this study may be useful in identifying whether pultruded composite shafts can be employed as drive shafts in automotive or other industries.

The infernal combustion engine continues to make increasing demands on the valve seat insert as power outputs are increased, the use of alternative fuels proliferated and better fuel economy sought. These demands are being met by the latest developments in sintered powder metal valve seat insert materials and design. The developments described are; the incorporation of a high temperature solid lubricant into a heat and wear resistant sintered alloy steel which is particularly effective in dry running environments; a cobalt free, cost conscious high speed tool steel based sintered alloy possessing excellent thermal conductivity for use in arduous applications including the new alternative fuels (natural gas, L.P.G. etc.) and a design of sintered valve seat insert for use in the inlet position which induces a swirl action into the ingoing fuel/air mixture leading to improved fuel economy.

DEVELOPMENTS IN SINTERED PISTON AND SEALING RINGS. Sintered metal alloys have been used to supply the major proportion of the European requirement for shock absorber sealing rings in recent years, and the inherent self lubricating properties conferred by oil retaining surface porosity has proved to be most beneficial. Sintered sealing ring usage extends into other fields including automatic transmission systems and hydraulics. Production of sintered rings has been developed at Brico to enable such features as chamfers and steps to be incorporated without secondary machining operations. In the field of piston rings, a large number of small non-automotive engines such as lawn mowers, chain saws and outboard marine engines have used sintered alloys for many years, and the powder metallurgy process has proved to be very competitive. Where scuff resistance is a major factor, sintered rings perform well due to their oil retaining surface.

An examination of future trends in lift truck developments suggests a stable product line with a requirement for increased power at a time of escalating fuel costs. Within the time scale of the present survey (up to about the year 2000) only battery/electric and derivatives of conventional reciprocating engines will provide this power. As the turn of the century is approached, a breakthrough in the development of high density, low weight battery systems is forecast, leading to a recovery of lost market share and eventual dominance. In the intervening period gasolene and diesel-derived engines will increase their market penetration, but the opportunity of reducing, or at least containing, operating costs by the introduction of a broad specification fuel oil and injected stratified charge engines will be lost.