Backbones

["John Hertzman" <johnhertzman@domain.elided>]

Will Owen, amiably disputing w/George Graves about backbones, monocoques and
degrees of integration thereof on Loti, wrote "There have been many times I've
wished it had inspired the designers of the 116 chassis, who also had an older
prototype of their own (the article I have calls it a Disco Volante, but J.
Hertzman told me otherwise ...John?) with a backbone frame and deDion axle."

The Disco Volante story is curious and imprecise, elastic anyhow, as the name
was inspired by the form of the striking body, with an ogival cross-section,
which Touring built for the 1900 C 52 -2000 and 1900 C 52 3000 cars, the first
of several sports-competition variants based on components of the
four-cylinder two-liter 1900 berlinas ("the family car that wins races") which
in turn had an engine based on the six cylinder three liter 6C 3000 Berlina
prototype of 1948 which never reached production, although one engine had run
in the Mille Miglia in an earlier chassis as the 6C 3000 C50.

"Disco Volante" was the Italian term for the extraterrestrial spacecraft,
frequently seen in those days, which Americans called Flying Saucers, and both
the dramatic form of the originals and the otherworldly name were
quintessential vintage Touring; both Touring and Alfa appreciated the PR value
of the name applied in the popular press. The only one of the 1900 C 52 cars
which enjoyed any competition success, however, was a narrow-sided version,
(which Fusi calls the Disco Volante a fianchi stretti) which represented an
abandonment of the Touring form which had been the source of the name.

The next variant is the one Will refers to, the 6C 3000 CM, with much the same
front suspension and steering (but with wide four-leading-shoe drum brakes,
two sets of two leading shoe brakes side by side in each drum) and a 3.5 liter
six in a backbone chassis with a De Dion rear axle and inboard brakes, bodied
by Colli. They were great cars, arguably the last and greatest Alfa expression
of the classic front-engined supercar, but with barely the thinnest possible
link, if that, to Touring's concept of an aerodynamic design.

Two noteworthy disco descendants followed - a slightly smaller three-liter,
the 6C 3000 PR, which was unfortunately destroyed during its first testing,
and the Sportiva, which returned to the two liter four cylinder and a
perimeter spaceframe (the antecedent of the TZ's chassis) with the dimensions
of the 3000 PR.

There can be no question that the 1900 C 52, 6C 3000 CM, 6C 3000 PR, and 2000
Sportiva were a succession of closely related cars. The distinctive body of
the 1900 C 52 was properly called the Disco Volante, and in popular use the
name became attached to the chassis, and to some extent remained with it when
the chassis was radically redesigned and fitted with very different bodies. I
won't fight over it; call any what you please. But where would one draw the
line? If the 6C 3000 CM chassis is a Disco Volante, then Pininfarina's
"Superflow" show cars on that chassis were Disco Volantes, and if the
Superflow is a Disco then the production rehash of its styling as the Duetto
is a Disco Volante. Anybody's choice, but I prefer to limit the name to the
few cars which had the Touring body.

Back to the backbone frame. It has a very long history, for very good reasons.
The largest limitation it has for competition sports cars today, at least in
its pure form, is that the driver and passenger are sitting on outriggers hung
on either side of the main structure of the car. If you want a rollbar too,
and a hoop at the knees, and anything in the way of intrusion protection, you
arrive at a rollcage which by itself can do most of the work of the backbone.

The shift-linkage problem Will mentioned has been solved in some cases by
having a rigid backbone tying the (front) engine to the (rear) final drive. I
can't dangle that without mentioning the tipo 160 GP design study which never
got built, apart from the engine. It was a flat twelve four-wheel-drive car,
with inboard drum brakes on both ends, and the entire chassis structure was
the engine, rear transmission, and a looong bellhousing connecting the two.
I'm not sure how comfortable it would have been for the driver, who sat behind
the rear differential with his thighs between the transmission and the rear
brakes, but it is a fascinating design, worth looking up in Fusi, p.499-502.

Cheers

John H.
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