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The man who
invented the two-stroke engine
By David Boothroyd
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 Ill
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 peoples 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.
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
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.
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
Days 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 Days 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 19th Century. The profitability
of Days 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. Its 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.
is a College Lecturer, guitar player, and
lifelong two-stroke enthusiast. He writes
from the United Kingdom.
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