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

["John Hertzman" <johnhertzman@xxxxxxxxxxxxx>]

Minor quibble, George misread the NVH in my recent post as NIH, Not Invented
Here, understandable enough (enuf?) given established digest spelling
precedents, but I did really mean NVH, which is Noise, Vibration and Harshness
in conventional industry shorthand. (George knows that, but was tweaking the
pedants.)

While most versions of the 1900 had at least one giubo, per Fusi the 1900
Sprint (1951-53, not to be confused with the 1954-58 Super Sprint) had three
cardan (or Hooke) joints and no giubo, from which I assume that the 1900, like
the Giulietta, had sliding splines as well as a giubo.

George's reference to "there must be something to take-up the torque of that
long, whippy shaft -especially when starting from rest, or else the drive
shaft could snap" puzzles; the prewar cars had small-diameter driveshafts,
presumably solid, which should behave like torsion bars, while the 1900 and
later cars had relatively large diameter tube driveshafts, which I can't
imagine snapping. Perhaps it was the cushioning of the 'torsion bar'
driveshaft which saved the earlier style flex joints from giuboesque failure?

My idle speculation. Enjoy yours,

John H.

  ----- Original Message -----
  From: George Graves
  To: John Hertzman
  Cc: alfa-digest@domain.elided
  Sent: Thursday, June 12, 2003 7:59 PM
  Subject: Re: Torque tubes and torque tubes (and giunti, etc.)


  First off. let me state that I enjoyed reading your reply immensely. The
historical context was, as always interesting and informative.

  I was using the term 'torque-tube' in its most modern (I hope) context, I.E,
a method of supporting a drive shaft so the the shaft itself is relieved of
the chore of having to adapt to the relative (and non-relative) movements of
the front and the back of the car. The main reason for universal joints, be
they the twin-pivot type or giubos, is to allow the rear
axle/differential/gearbox of a car to dance around with respect to the engine
and chassis without making the drive shaft move in any direction that is
likely to damage it. Therefore, that the shaft be somewhat flexible with
regard to the X. Y, and Z axis is desirable in the extreme. Most cars do this
with twin-pivot, two axes universal joints, for X and Y, and a sliding spline
for Z. If one uses a hollow pipe hard bolted to both the back of the engine
and the front of the transaxle or differential, then there is no independent,
relative motion between the engine and the transaxle and the drive shaft,
turning inside of that pipe cannot move in ANY axis except to spin, and
therefore needs no universal joints of any kind.

  When I spoke of maintenance, I was referring to the fact that the drive
shaft MUST come loose from the clutch plate in order to replace that assembly.
Unless the shaft is splined so that it can be compressed several inches, there
is no way to detach it from the clutch without removing (or loosening) either
the engine or the transaxle. Just unbolting the torque-tube from either end
still leaves an unmoving drive shaft connected to both the engine and the
transaxle, whether the clutch is at the engine end or at the transaxle end.
One must be able to move the shaft back to disconnect it from the clutch plate
somehow, and this usually requires moving either the engine or the transaxle
itself to accomplish this. On the Ferrari 275 GTB and I believe , the Daytona,
for instance, to change the clutch (located on the engine flywheel) It
requires that one disconnect the drive shaft from the transaxle input shaft
(after disconnecting the torque-tube from both), and drop the nose of the
transaxle. This affords enough clearance to pull the solid drive shaft and
it's sheath (the torque-tube) back, clear of the clutch assembly at the engine
end.

  Of course, anyone can, if they have the time, money, and ambition, replace
the giubos in an Alfetta with twin-pivot U-joints and a splined shaft, but the
question is why didn't Alfa do it that way, and John answered that question in
part, I think, when he said NIH (not invented here). But I also think that
there may be a more practical reason too. The shaft on an Alfetta is turning
all the time that the engine is running, not just when the clutch is engaged.
Therefore, when a gear is selected and the clutch engaged, there must be
something to take-up the torque of that long, whippy shaft -especially when
starting from rest, or else the drive shaft could snap. The giubos would seem
to allow for some torsional wind-up that would cushion this action.

  George Graves
  '86 GTV-6 3.0S

  On Thursday, June 12, 2003, at 02:52 PM, John Hertzman wrote:


    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 Bugattis 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 Alfas 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 Alfas 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. Im not
sure that it would need to, with a well-detailed design, but I cant say about
Ferraris. In Peter Hulls 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 Ive owned had at least one giubo, and havent 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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