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

[George Graves <gmgraves@xxxxxxxxxxx>]

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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