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By Popular demand and to keep the girl's end up here is, hopefully the first of ma,y Technical discussion papers from our secretary
The Camshaft / Valves
The camshaft works by pushing against tappet and push rod in order to activate each valve in turn via the fulcrum action of the rocker. The camshaft itself is driven by either a belt or chain attached to the bottom, or crankshaft pulley of the engine.In an Ottocycle (4 stroke engine, designed by Mr. Otto) you may find either one or twin camshafts. A single cam may operate both exhaust & inlet valves, whilst a twin came may operate either inlet or exhaust.
Hi-Lift cams aid performance at a higher rev.range by creating a better area for the flow of gases in the engine. At lower ranges, performance is rather lumpy hence the Variable Valve Control engines such as Rover's VVC or Ford's Zetec. In such engines a dynamically controlled 'gear' controls the height (angle) of the camshaft to allow for a better spread of power throughout the rev range. During the 1960's an aftermarket 'bolt on gear' was available for your own engine for a similar operation. Nothing is new….!
All engines today however share one problem - valves are operated by springs. Springs cause bounce and thus inefficiency. Desmodrymic vales ( £1 to the person who can spell it correctly) moreover have no springs. Unfortunately the forks which operate the valves instead of springs had a tendency to wear quickly, thus the system was never to be a commercial success.
We could do away with valves completely - In 1959 Felix Wankel (pronounced Vankel) produced a rotary engine based on the principles inspired by James Watt almost 200 years previously. But that's another story……!!
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