Sliding blocks, etc.

[Will Owen <nashwill@xxxxxxxxx>]

In v.7, #393, Richard Welty wrote:

"the Alfetta/GTV-6/Milano watts linkage is actually not a "correct"
implementation; it works pretty well, but the sliding block is actually
a
better way to implement the function centering the rear axle and
controlling the location of the roll center in the rear.

"a "correct" watts linkage in a car would anchor the center link to the
body, and the end links to the axle, which is the opposite of what Alfa
did
in the production cars. the proper implementation is much harder to
manufacture and is not particularly space efficient."

What a sliding block does that that neither a Watts link nor a Panhard
rod can do is restrict the axle's motion to purely vertical. The
center point of the Watts link on the Alfetta/Milano axle describes a
shallow S curve, kinda like the old Studebaker logo; the motion of the
end of a Panhard rod is obviously a shallow arc. In the real world,
these slight deviations from purely straight up-and-down are
inconsequential, and more than compensated for by the high degree of
free articulation given to the axle (in contrast to the earlier
a-bracket, which wouldn't work at all without lots of rubber in the
bushings), and the relative simplicity of the design.

"as i recall, the factory sliding block requires a lot of maintenence,
which
is why it's not on the street cars."

It also concentrates a lot of cornering forces into a very small area,
and a lot of noise and vibration as well. 

Okay...now that I've gone and pontificated probably well over my head,
would someone with some direct experience with the sliding-block axle
like to comment?

Will Owen



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