Re: Giubo bolts

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

Dana, responding to Jon Pike's flippant suggestion that ease of drawing might
have accounted for parts-manual bolt orientation, writes "People who are
certain that cars were assembled at Arese using whatever parts Luigi happend
to pull out of the bin after a few shots of grappa may find it hard to
believe, but Alfa Romeo's factory parts manuals are actually a reliable guide
to the way the cars were assembled.  The drawings show the driveshaft bolts
from various angles, but the orientation of the bolts and nuts is always
consistent."

Have to agree with Dana and unfortunately disagree with Henrik Hasager
Johansen who had suggested "The guibo bolts are supposed to be mounted 3
having the nut pointing to the rear of the car and 3 having the nut pointing
to the front of the car." It is true for some models, but not for any 105/115
that I have information on, and I am reasonably sure that the variations
followed an engineer's perceived logic and sensibilities (whether for
manufacture, assembly, service, or operation) rather than an assembler's whim,
sobriety, or chance.

Proper Giubos (as distinct from the 6C's earlier type of flex joints) made
their debut on the 1900, with two joints on the 1900, 1900 T.I., and 1900
Super, and one on the 1900 T.I. Super and 1900 C Super Sprint. As far as I can
tell from parts books and shop manuals all of these had the bolt heads against
the flange, with the washers, nuts, and/or locknuts against the unflanged
segment of the Giubos. Everything I can find on the 102 2000 and the Giulietta
indicates the same orientation: head end of bolt through the flange, threaded
end and nut at the unflanged segment.

On the 105 cars the very precise drawing at the head of the "Propeller Shaft"
section of shop manual #1222 shows the same thing that all of the other
illustrations, and all the parts books, show: the heads of the flex-joint
bolts are toward the transmission, the nuts and lock nuts to the rear (or
center) of the car.

The Alfa Sei, the first step toward the De Dion era (but still with front
transmission) has a two-Giubo driveshaft (no center joint) which reverses the
105 orientation at both ends: all bolt heads toward the middle of the car, all
nuts toward the transmission and the differential regardless of flanges.

Fifteen of the Alfetta Giubo bolts follow the form of wheel studs: splined
bolts with circular heads at the flanges, washers and elastic stopnuts on the
open sectors of the Giubos, but three unsplined hex-head bolts attach the rear
Giubo to the transmission input flange, nuts to the rear of the flange.

Haven't crawled under the Milano to check, but I assume that it and the GTV-6
follow the Alfetta layout. (Don't have a parts book for either, or a fiche
reader, nor useful shop manuals for the driveshaft of either.)

So- as far as I can tell from the material I have, all 105/115 cars had the
heads toward the transmission and the nuts toward the rear, but no other Alfas
did. Why this would be so is another question; unlike the Alfettas they are
all identical unsplined hex-headed bolts. It is quite possible that the reason
is no more than that it satisfied the sensibilities of the engineer who made
the decision. Engineering often transcends into architecture (and occasionally
the reverse happens) and often in architecture (or engineering) there will be
two or more 'reasons' for a particular decision, a good reason and the real
reason. It is all part of what makes Alfas (and Italian culture more
generally) endlessly interesting to people of certain dispositions.

Enjoy yours,

John H.
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