chapter 2
This page is dedicated to the memory of Pat Braden who died on August 25, 2002.
Chapter 3
Twenties' Technology
I'd like to re-emphasize that the things about the Peugeot which we find
so dramatic today -- the twin cams, desmodromic valve actuation, four
valves per cylinder, hemispheric combustion chambers and twin plugs --
were underutilized in 1914. While the design gave a clear advantage in
volumetric efficiency, the real benefit of the configuration awaited much
higher engine speeds. And engine speeds stayed low because of the poor
metallurgy and fuels of the era. For the effort, twin cams and all didn't
give much more power.
That fact may explain why Merosi failed to use a twin-cam design in any
of his passenger cars. Fusi claims that Jano's greatest single attribute
was his ability to translate racing car designs to passenger car use. The
compliment to Jano is certainly invidious to Merosi. In Merosi's
defense, I think we can say that Jano translated better than Merosi
because the technology had improved enough to make the translation
worthwhile. If you have an engine which goes no faster than 4000 rpm,
then the inertia of pushrods hardly matters. As proof of this point, we
need to remember that Merosi's RL series pushrod engines were
considered very high performance and the RLTF was an outstandingly
successful race car.
Merosi's Grand Prix car and its exploration of the twin-cam layout,
then, has to be seen as a diversion, rather than the first example of a long
line of twin-cam engine designs. So long as Merosi was Alfa's chief
designer, Alfa engines had pushrods. Clearly, Merosi's era bumped up
against material limitations time and time again, mostly in the area of
metallurgy. One of the reasons the engines couldn't go faster was that
the metals weren't strong enough to stand the forces imposed on them:
pistons melted or shattered, rods bent and crankshafts broke.
I've been struck by how closely the development of durable metals
enabled the development of the automobile. Important dates of the metals
industry slightly predate the important dates of automotive history:
generally, cars came along at about the same time that metals were
getting durable. The addition of chromium to iron to increase wear
resistance dates to the early 1870s, and manganese tungsten steel, hard
enough to be used as a cutting tool, was an 1871 discovery by Robert
Mushet. Stainless steel was discovered by H. Brearley in 1913 and the
first wear-resistant aluminum alloy was patented in 1909 as Duralumin.
Before there were aluminum pistons, the skirts of cast iron pistons were
drilled to achieve lightness.
Quite separate from metallurgy is the development of automotive
petrochemicals, notably oil and gasoline, but probably also including
tires. The development of improved lubricants and fuels, of course, was
pushed by the needs of the auto industry and evolved around improved
methods of refining and the addition of chemicals to improve durability
and lubricity in the case of oil and to control rate of burning for gasoline.
In the early engines, compression ratios had to be kept very low (below
5:1), otherwise, the fuel would ignite spontaneously under compression
and knock bad enough to destroy the engine. The goal of
fuel-formulating is to get an even-burning flame front which proceeds
across the top of the piston just rapidly enough to be completely burned
as the exhaust valve begins to open. Thus, improved fuels were slower,
not faster burning, and the biggest advance in that technology was the
addition of tetraethyl lead, but that's a subject more appropriate to a
later chapter.
I think this is the place I need to identify what is probably the biggest
single source of technological advance: war. It seems man is nowhere
more clever nor motivated, nor efficient than in trying to kill his fellow.
The automobile industry has benefited tremendously from the technology
of war: in mass production techniques, improved metallurgy and new
technologies such as solid-state electronics, miniaturization and the
application of computer controls.
The direct link between war and technological advancement is frequently
obvious: Brearley developed stainless steel when he was trying to find
a metal which would be non-corrosive as a rifle barrel. Computers were
first employed to develop ballistic trajectory charts which were used to
aim cannon and large guns. Other links are less obvious: in the early part
of this century, military aeronautics enriched the automobile's
technology and many famous automotive names got their start as aero
engineers. The transfer of aeronautical technology is easy because the
goals of both cars and planes are the same: light, powerful and
aerodynamic. Thus, the efforts expended on airframes and aero engines
also helped make automobiles faster and more reliable.
In very broad strokes, these are the areas of technology which surrounded
the development of the automobile. Within automotive technology itself,
other concerns persisted and were solved only to create new areas of
effort. Looking ahead for just a moment, it is almost intuitive that the
timing of the intake and exhaust valves should correspond exactly to the
up and down motion of the piston. That is true, we learned, only in
normally-aspirated engines turning at relatively slow speeds. As engine
speeds increased and gas dynamics became more significant in the intake
and exhaust passages, it was desirable to open the intake valve earlier
and close the exhaust valve later than top dead center. This technique,
called overlap, may have been employed in the 1912 Peugeot, but that
is not known for certain. There is probably a doctoral dissertation here
for anyone so inclined.
Because some compromise between bore and stroke was always part of
an engine's design, the early designers were fascinated with finding the
"perfect" ratio which would give the greatest power in all applications.
There was great popular interest in every new car's bore and stroke. A
wide variety of designs produced strokes as long as the 250 mm (about
10 inches!) of the 28.4 liter, 300 hp Grand Prix Fiat of 1910. That was
about the time designers concluded that you could go too far with either
bore or stroke. The net result was a consensus that the practical limit of
a single cylinder was 0.5 liter, with a bore and stroke which approaches
"square," i.e., the same dimension of bore as stroke. Notably, the 0.5-liter
limit is a rule still observed in our current 4-cylinder Alfa engine.
As noted above, a large bore created fuel-burning problems. With a large
bore, it was hard to get all the fuel burned before the power cycle was
completed and the exhaust valve opened. So, an engine with an
over-large bore coughed out unburned fuel. On the other hand, if you had
a small bore you needed a long stroke to get the desired displacement.
But the longer the stroke, the faster the piston travels for a given engine
rpm, and the higher the pressures -- and wear -- on piston, rings and
cylinder walls. A long stroke produced a short-lived engine.
These problems, of complete fuel burning, manageable piston speeds and
higher-speed engines, were all solved by the improvements in metallurgy
and petrochemicals I've outlined so briefly above.
KTUD Alfa Romeo main page!
Copyright March, 1996
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