chapter 4
This page is dedicated to the memory of Pat Braden who died on August 25, 2002.
Chapter 5
Mature Merosi
The cars we have talked about so far have been pre-war designs: even
the technology of the
G1 is more tied to the Edwardian cars than proper
post-World War I designs. As a generalization, the post-war cars were
much more tidy and easy to manage than their predecessors. The skill of
making a motor car was becoming an art, nowhere more evident than in
the work of Ettore Bugatti, whom we discussed in the last chapter. One
could regard an engine of the 1920s with the same critical gaze as a
painting or sculpture, and automobiles were certainly much more
integrated in their designs than the bits-and-pieces assemblages which
marked the earliest efforts. The goal of the artists of the 1920s was an
integrated engine with virtually smooth sides and few external
accessories. By this standard, the
RL engine was pretty, indeed.
As suggested in the last installment, the
RL series was inspired by a new
3-liter formula for racing cars which took effect in 1920 and ran until
1922. Merosi was dogged in his allegiance to a single design, and the RL
series cars were simply updates of themes established in the ‘teens:
Merosi kept with pushrods, even though the 1912 Peugeot had
established the potential of a small, high-speed engine with overhead
camshafts.
Post-war metallurgy had improved to allow stronger metals and higher
engine speeds, while fuels were beginning to allow higher compression
ratios which pushed combustion pressures higher. The typical measure
of progress has always been engine speed: by that measure, the RL
turned 3200 rpm compared to the 2200 to 2400 rpm of the first
A.L.F.A.s. In comparison, the 1914 GP engine turned about 3000 rpm.
But there are other measures of progress. One is to measure the pressure
developed in the cylinder, Brake Mean Effective Pressure (BMEP).
Another measure, the median speed of the piston, gives a good measure
of the engine's durability, because higher piston speeds impose
excessive side loads and also exacerbate wear of the piston and rings.
Using those two measures, the original 12 HP A.L.F.A. had a BMEP of
only 3.74 kg/cm2 and a median piston speed of 8.39 meters/second. In
comparison, the 1914 GP had a BMEP of 5.9 kg/cm2 and a mean piston
speed of 14.05 meters/second. The original RL, introduced in 1922,
produced a BMEP of 5.42 kg/cm2 and had a mean piston speed of 11.73
meters/second; the internal cylinder pressures of the passenger car almost
equaled the grand prix design of eight years ago. In fact, the most highly
tuned of the RL series, the RLTF, had a BMEP of 7.14 kg/cm2, well
beyond what was achievable in 1914, while its mean piston speed of
13.94 meters/second reflects a much shorter stroke (110 mm versus 143
mm for the Grand Prix car) at a significantly higher speed (3800 rpm).
In more prosaic terms, the RL was a super-reliable car you could hop in
and go. It was equipped with an electric starter and manual choke so no
special physical prowess was needed to drive it. The spark advance was
still manually adjusted, but a high-output magneto helped assure that the
plugs fired each time. And, once started, it was both durable and fast,
with a top speed just over a mile a minute. Steering was quite light and
the mechanically operated brakes worked on all four wheels.
The RL's pushrods were operated from a camshaft which sat high in the
crankcase. At the RL's engine speeds, there was no concern for valve
float. By this time, the gas dynamics of the engine had been understood
well enough to utilize valve overlap, where the intake and exhaust valves
are open at the same time at the beginning of the intake stroke.
The RL was no alloy wonder: its cylinder block was a single iron
casting, and the cylinder head was another iron casting. The forged
crankshaft was deeply recessed into the crankcase skirt for good lateral
support to the four main bearings, and the wet sump held seven liters of
lubricant. Pistons for the RL produced a compression ratio of 5.2:1.
The crankshaft and rod bearings for all these engines were poured, as
opposed to the precision inserts we have today. A poured bearing is thick
and individually cast, then hand-formed by scraping to fit the crankshaft
journal. Prussian blue is used to mark the high points of the bearing and
these points are then carefully scraped away by the technician until at
least a 40% contact surface is achieved. After the engine is assembled,
it is run at light speeds (broken in) to allow the bearings to wear into a
proper fit with the crankshaft journal.
Though a poured bearing has limited load-carrying properties, it is very
tolerant of dirt in the lubricant. These old engines ingested a lot of dirt,
since there were neither oil nor air filters and roads were typically
unpaved: a coarse screen covered the carburetor intake if one wanted to
keep rocks out of the engine. Small pieces of metal simply bury
themselves in the bearing material without harm to the crankshaft journal.
Non-detergent oil allowed heavier metal particles to settle out into the
sludge in the sump when the engine was turned off.
Another advantage of the poured bearing is that it is renewable. Usually,
for the original pouring process, a few shims were added between the
bearing cap so that, if the bearing became loose, removal of one shim
and careful rescraping would give a new running surface. The oil
pressure required to support a plain-metal bearing was remarkably low:
my 6C1750 carried a normal pressure of seven pounds. The actual
pressures at the rod bearings were higher because of centrifugation.
The only alternative to the poured metal bearing was a roller bearing,
which required virtually no oil pressure and offered lower frictional
losses than the poured bearing. But a roller-bearing engine required an
inconvenient warm-up period before it could carry a load. Driving off
with a cold roller-bearing engine was a good way to break a crankshaft.
Ball and roller bearings were ideal in a race-car and were used on most
of the early sporting Bugattis, most notably the Type 35.
The RL's suspension was essentially ox-cart, with semi-elliptic springs
front and back for the solid axles. The ride quality of such a car can be
improved considerably by keeping the chassis long and flexible. That is,
the chassis is the main suspension member. With such a chassis, stiff
springs are essential to provide control over rough roads. The proper
driving technique is to grasp the wheel only lightly on the straight, letting
it work in your hands. The front wheels' caster will take care of
returning the car to straight-ahead after a bump. A firm grip on the wheel
is needed only for turns, and trying to fight the car as it wanders down
the road only produces a series of drunken swerves. The modern driver
would find the multiple-disc clutch brutal, and the non-synchronized
gearbox taxing, but these were both standard features of the era.
For those accustomed to thinking of the Giulietta or Milano as a
standard-size Alfa, The RL was a large car, much more akin to the 164
in size and luxurious intent. The Alfa museum at Arese contains an
RLSS which was owned by a Maharajah, giving some idea of the
elegance these models could achieve.
The
RL Normale was the first in the RL series,
and one of only a few
Alfas to own the title Normale (there is no such thing as a Giulietta
Normale, thanks). During this era, Alfa released cars in series, and the
RL saw five such, with the first and second being released during
1922-23, the third and fourth in 1924 and the fifth series in 1925. Only
nominal changes differentiated the series, typically, and the differences
are largely lost to us today, though I think Peter Hull could probably
recite the differences from memory.
For the sixth and seventh series RL (1925-1927), the Normale appellation
was changed to Turismo, and engine capacity was enlarged from 2916
cc to 2994 cc, while horsepower rose to 61 at 3200 rpm, giving a top
speed of 115 km/h. The same larger displacement also was available as
RL Sport, with 71 hp and
RL Super Sport with 83 hp. The most popular
of the RL series, of course, was the RL Super Sport, or RLSS, and it is
this model which has been cherished -- and survived -- in greatest
numbers.
For 1923, Merosi prepared a group of 88-hp, 2994 cc RL cars for the
Targa Florio, and two which carried 3154 cc engines producing 95 hp.
The Alfas took 1st, 2nd and 4th overall. Spurred by the success, for 1924
Merosi redesigned the engine and crankcase to give seven-main-bearing
support to 3620 cc. Output was increased to 125 hp (BMEP was 8.18
kg/cm2). These RLTF Targa Florio cars are the
most desirable of the RL
series, and several of them are still raced in vintage events. The RLTF
is Merosi's greatest race car.
Between 1923 and 1925, a four-cylinder version of the RL was produced,
called the RM. It developed 40 hp from 1944 cc (total production was
only 131). A higher-compression (6.0:1) version, the RM Sport, gave 44
hp while a 1996 cc long-wheelbase version called the RM Unificato
developed 48 hp.
In 1920, a Milanese financier, Niccola Romeo, made a large investment
in the company and attached his name to it: thus, the name Alfa Romeo
was born. Romeo was not a car enthusiast, and his impact on the
company was much more financial than technical. Romeo's stewardship
of Alfa continued until its control was turned over to the government
during the depression.
KTUD Alfa Romeo main page!
Copyright March, 1996
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