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

[George Graves <gmgraves@xxxxxxxxxxx>]

On Thursday, June 12, 2003, at 07:32 PM, John Hertzman wrote:

> 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.)

Whoops, mea culpa!
>
> 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?

I think it depends upon where the clutch is located. If it's in-unit
with the engine, the short 'pilot shaft' betwixt engine and clutch is
not long enough to have any support problems or torsional rigidity
problems (as torsional rigidity, all things being equal, can be
calculated as a product of length vs cross-sectional diameter for any
given Rockwell number in metals.), but with the clutch in-unit with the
transaxle at the back of the engine (ala 116 Alfettas) the entire
engine torque is carried by the drive shaft before (not after) the
clutch is engaged and disengaged. When the clutch is engaged, and
bites, it's bound to twist the drive shaft more than it would were the
shaft on the output side of the clutch rather than on the input side.
As you say, its all speculation and mine is based on ancient, barely
remembered college physics.



>
> 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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