Clerk cycle Dugald Clerk

clerk describes experiments brayton engine 1878



the otto cycle patented in 1876, recognised have significant practical value. clerk followed concept of 2 stroke engine of 1880, not infringe otto s patent (being 4 stroke engine).

clerk describes cambell engine using cycle, follows: has 2 cylinders, respectively pump , motor, driven cranks placed @ right angles each other, pump crank leading. pump takes in charge of gas , air, , motor piston overruns port in side of cylinder @ out-end of stroke discharge exhaust gases. when pressure in motor cylinder has fallen atmosphere, pump forces charge cover of motor cylinder through check valve, displacing before products of combustion through exhaust port ; motor piston returns, compressing contents of cylinder compression space. charge fired , piston performs working stroke. clerk cycle.

the clerk engine uses automatic poppet type valves inlet air , gas (one spring assistance, 1 without), , port in cylinder uncovered piston exhaust valve. references clerk engine slide valve may refer earlier experiments lenoir type engine. ignition carrying external flame, using modification of method developed in 1878.

most engine designs pre-dated otto engine (and clerk engine), such of de rivaz, niépce brothers, jean joseph etienne lenoir, samuel morey, , others, did use 2 stroke engines, natural in times of steam engine. clerk s significant contribution introducing otto-styled compression 2 stroke engine, bringing efficiency up-to-date (for 1880s). several manufacturers adopted clerk cycle in short term, though commercial aspects such patents on 4-stroke cycle part of this. many years later 2-stroke engine large capacity diesels using turbocharger or supercharger has become common, example in ships , railway locomotives. open crankshafts, , advantages of higher power weight ratio, these engines closely aligned dugald clerk s concepts, , clerk cycle.

pumping cylinder vs supercharger

clerk s engine made of 2 cylinders – 1 working cylinder , additional cylinder charge cylinder, expelling exhaust through port uncovered piston. sources consider additional cylinder world s first supercharger. clerk himself states not compressing pump, , not intended compress before introduction motor, merely exercise force enough pass gases through lift valve motor cylinder, , there displace burnt gases, discharging them exhaust pipe. hence sources recognise instead pumping cylinder , pointing out did not compress fuel-air mixture, moved fresh mixture working cylinder force out gasses burnt previously.

clerk s engine vs modern two-stroke engine

clerk s original design did not allow construction of smaller engines, required aforementioned additional pumping cylinder each working cylinder. crucial simplification of concept, made possible small yet powerful 2 stroke engines mass markets, patented joseph day in 1894.

joseph day, design of three-port two-stroke engine
nash, design of two-port two-stroke engine
robson, design of two-stroke engine under-piston scavenge
fielding, design of uniflow two-stroke engine




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