Experiments have been carried out using a laboratory test machine with a positive tappet rotation device, to evaluate the influence of such rotation on cam and tappet surface deterioration. Rotating tappets, 300 rev/min, showed a scuffing resistance 80–100 per cent higher than that of stationary tappets. The rotation, however, decreased the pitting resistance which became 20–30 per cent lower: the negative effect of the tappet rotation on pitting has been confirmed on an electrically driven engine.
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