Torque tubes and torque tubes (and giunti, etc.)

["John Hertzman" <johnhertzman@xxxxxxxxxxxxx>]

George Graves comments on relative demerits of torque tubes and giubos,
questioning "why they didn't use the old tried-and-true Hotchkiss arrangement
with a universal joint in the drive line and a sliding spline drive shaft
instead of the giubos."

Without picking diminutive nits, I hope, I will mention that there is an older
and more widely recognized meaning of 'torque tube', meaning the system used
by every Ford before 1949 and every Alfa before 1935; what Fusi describes as a
"cardano unico -albero racchiuso nel tubo centrale ponte". A single universal
joint, with the driveshaft enclosed in a tube attached inflexibly to the rear
axle, that tube taking the torque. There is also a distinctly different and
well-established understanding of "the old tried-and-true Hotchkiss
arrangement"; it is the use of two semi-elliptic springs to take the torque.
Pomeroy, in his magisterial "The Grand Prix Car", writes that "The 1905
Hotchkiss is also worthy of mention, as on this car a live rear axle was
located by semi-elliptic springs which were also used to drive the car, an
arrangement copied by Hola and Peugeot, and which has since been followed on
racing cars and has become almost universal on production models." He
subsequently used the term "hotchkiss drive" in every example of a car with
live axle and semi-elliptics, but never on cars with live axles and other
spring systems such as the Bugatti's quarter elliptics.

In 1935 with the 6C 2300 B, and from then until the 1900, Alfa went to 'giu'
without the 'bo'; before the engineer Boschi (the 'bo') patented his bonded
rubber giunti Alfa used what Fusi describes as an "albero non-oscillante, con
tre giunti elastici" - a non-oscillating driveshaft with three elastic
joints." With the 1900 Alfa adopted a two-section driveshaft with three joints
in various arrangements, but always at least one cardan (or Hooke) universal
and at least one giubo, which trickled down to the Giulietta and Giulia. There
was one exception, perhaps more, to the use of flex joints, but not in Alfa's
most glorious products; the Disco Volante had a single driveshaft with two
Hooke joints and presumably a sliding spline.

Why giubos? The usual understanding is that it was an NVH issue, possibly
compounded by Alfa's love of what worked in the past. There is nothing to stop
George, or anyone else, from fabricating a two-section driveshaft with three
conventional universals and a sliding joint for a GTV6, Milano, or other
Alfetta-based car.

George mentions how the torque-tube system (in his understanding of the term)
"just makes changing the clutch a costly maintenance nightmare." I'm not sure
that it would need to, with a well-detailed design, but I can't say about
Ferraris. In Peter Hull's monograph on the Type B P3 there is a photo (p.135)
of mechanics changing the gearbox on a P3 between a heat and the final at
Dieppe in 1934. It looks no more difficult than similar operations I did on my
A-V8 fifty-five years ago; disconnect brake lines, spring U-bolts, the
universal, slide the rear axle back, and remove transmission.

I have a nagging suspicion that giubo failure has a lot to do with driving
style; every Alfa I've owned had at least one giubo, and haven't blown one
yet, which may be just luck. Wish I could ask Fred how many he blew- he drove
fast but drove smooth, and enjoyed demonstrating no-clutch shifting with two
fingers on the shift lever. Not intended as criticism of other driving styles;
YMMV, and enjoy it.

John H.
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