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Forgotten Hero
The man who invented the two-stroke engine
By David Boothroyd
Published April 2001

You would think that the man responsible for a world changing invention would at least have his name in the encyclopedia. In certain areas of motor sport, his invention is so widely used that he would have statues in his honor in every boat club, his picture in every bikers’ bar, and yet I’ll bet you have never heard of him.

Perhaps you have never realized how all pervasive the two-stroke engine is, and what a clever and radical development it was. Here are a few examples. In the motorcycle world all three Grand Prix Classes have been won by two-strokes for as long as most people can remember. Motocross and Trials riders never consider anything else if they are serious about winning. Certainly throughout Europe most people’s first experience of motorcycling is powered by a two-stroke engine, In four wheeled racing, nearly all of our Formula One drivers learned their craft driving two-stroke Karts, and on the water the majority of outboard powered boats and personal water craft are still cruised or raced under two-stroke power.

The earliest internal combustion engine used a system that came to be known as the four-stroke cycle. In engineering circles it is called the Otto Cycle since it was invented by Karl Otto. A four-stroke engine needs to have valves, and a mechanism for opening and closing them at the correct time, and it produces power only once every two rotations of the crank. A well built two-stroke halves the number of components and doubles the power.

Some people reading this will have books on the history of bikes or boats and will be able to explain that the two-stroke engine was invented by Sir Dugald Clark in 1881. Sir Dugald was an interesting character in his own right, but the engine he designed was not the sort of two-stroke that became such a world-beater. An engine operating on the Clark cycle uses valves like a four stroke and requires a compressor to blow air, possibly mixed with fuel, into the cylinder. Some very fine Clark cycle engines were made, by the Detroit Diesel Company for example, but they were for ships or big trucks or locomotives. They never made an impact on the mass market.

The everyday two-stroke, which we find in everything from chainsaws to two hundred horsepower V8 outboards, is a much simpler and cleverer design. It uses the pressure in the crankcase below the piston to force fuel and air into the combustion chamber and simultaneously push out the spent gases. Using only three moving parts, the highest specific power output ever was recorded by a tiny two stroke Suzuki which produced an astonishing 395BHP per liter. Imagine if you had nearly eight hundred horsepower from your two-liter car engine

When I first started researching into the early development of two strokes, I was astounded to discover that not one of the standard works on the subject even gave the name of the inventor of “our” sort of two stroke. Then at last I found a book that stated that the crankcase compression two stroke was invented by “Day”. It was two more years before I found that his first name was Joseph. This is a brief outline of his story.

Joseph Day

Joseph Day was born in London in 1855 and trained as an engineer at the School of Practical Engineering at Crystal Palace in London. On graduation he became a trainee at an engineering firm in Bath. In 1878 he started his own business, an iron foundry making cranes, mortar mills and compressors amongst other things. Interestingly he advertised a new design of “valveless air compressor” which he made on license from the patentee, Edmund Edwards. By 1889, he was working on an engine design that would not infringe the patents that Otto had on the four-stroke. This is what eventually came to be called Valve less Two-Stroke Engine.

In fact there were two flap valves in Joseph Day’s original design, one in the inlet port, where you would probably find a reed valve on a modern two stroke, and one in the crown of the piston, because he did not come up with the idea of the transfer ports until a couple of years later. He made about 250 of these first two-port motors, fitting them to small generating sets, which won a prize at the International Electrical Exhibition in 1892.

It was one of Joseph Day’s workmen, Frederick Cock, who made the modification which allowed the skirt of the piston to control the inlet port and do away with valves altogether, giving rise to the classic piston ported two stroke. Only two of these original engines have survived, one in the Deutsches Museum in Munich, the other in the Science Museum in London.

The first American patent was taken out in 1894, and by 1906, a dozen American companies had taken licenses. One of these, Palmers of Connecticut, had produced over 60000 two-stroke engines before 1912. Many of these early engines found their way into motorcycles, or onto the back of boats.

So what happened to Joseph Day?

His company in Bath was a general engineering one, and his engines were a sideline. Much of his money came from the manufacture of bread making machinery, and the prices of wheat were very turbulent around the turn of the 19^th Century. The profitability of Day’s factory fluctuated just as wildly. These were early days for the idea of the limited company, and shareholders, then as now, could panic and bring down a company that they thought to be under threat. The problem is made worse, (also then as now) by the publication of rumours, or the deliberate orchestration of publicity campaigns in the press.

This happened to Joseph Day, with the result that his firm was driven into bankruptcy. A flurry of lawsuits followed, with Day as both plaintiff and defendant. The Treasury Solicitor even tried to have him extradited from the USA where he had gone to try to sell his US patents in order to raise money. The case was eventually settled when the jury found that Day had no case to answer, but it all came too late, and he went into virtual retirement by the seaside. The development of his engine then passed to his license holders in America, whose royalties restored his finances sufficiently to allow him to launch a spectacular new venture after the First World War.

This new enterprise was the exploration for oil. Unfortunately he was looking for it in Norfolk in the east of England. A second financial disaster was the last straw, and Joseph Day disappeared from public view between 1925 and his death in 1946. His obscurity was so complete that a mere five years after his death, the Science Museum made a public appeal for biographical information about him – with no apparent result.

I hope that everyone who has enjoyed two-stroke power will agree that this is a man who deserves to be famous. He should be in every engineering hall of fame alongside Otto, Diesel and Benz. It’s time to give Joseph Day his place in history.

I am deeply indebted in this article to the research of Hugh Torrens of Keele University, and for anyone wishing to read the full story there is a booklet by Hugh entitled “Joseph Day”  The book is published by and obtainable from the Bath Industrial Heritage Trust.

Dave Boothroyd is a College Lecturer, guitar player, and lifelong two-stroke enthusiast. He writes from the United Kingdom.

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